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Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Mon Dec 28, 2009 8:16 pm
by msd1107

Good suggestion to have the lower 4 gears correspond to the current 4-speed with the top 2 ratios being OD's.

The 6-speed thread (elan-f15/speed-gearbox-for-the-elan-t18541.html) had just that suggestion by Bill (bill308).

For anyone interested (and who have not read the thread), it is worth while spending the time to read some of the opinions expressed and technical issues raised.

1968 36/7988

Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Tue Dec 29, 2009 10:52 am
by worzel

Some interesting ideas on this one have ben thrown up.

I can only speak for UK owners since they've easy access to T9 boxes- apologies to US owners!

I'll try and cover some of the points that seem of concern and see if this helps others to "have a go" themselves.

When I converted my car in 1999 I was lucky enough to get hold of the matching bellhousing for around ?110 (this is the alloy Rocket to BDA item)- basically a replica of the cast iron 4 speed one but with the fixing pattern for a T9 so eliminating a sandwich plate.

These are very probably still out there in old Ford Rally shops but locating them might be more problematic. A cheaper way (cheaper than the BurtonPower units) might be to get hold of a RS2000 alloy one, cut off the unwanted starter housing and modify it to take a hydraulic clutch unit. One of these was up on e-bay recently for ?100 or so.

A suitable clutch disc is not a problem- if you're a cheapskate a std Sierra item will work fine but might not take too kindly to 6500 rpm drop starts. A racing MGB item from Demontweeks costs around ?90. If anybody is interested I'll dig out the ref number.

Gearlever location- options- there seem to be various ways of doing this- more now than when I last wrote about this. Personally I don't see the need for a custom tailhousing- nice though it might be- it's not going to work any better than a cut/welded one which in any case can be very neatly finished.

The main issue seems to be how far owners want to go. My own car has the simplest conversion (simpler = fewer problems?). The lever is not quite in the "correct" position but the extra short distance can be achieved by a short extension to the gearlever base. Other conversions put the lever pretty much as per the 4 speeder but need a lot more machining etc. I can put owners' minds at rest about future repairs to modded boxes- generally conversion doesn't affect the actual gearsets, only the linkages. Some require a modified/new 5th selector fork but any competent foundry can cast one of these for around ?35 even as a one-off (I had one done about 2 years ago).

As for ratios, these seem to be causing agonies for owners. I can only give my own opinion based on my own experience. My car uses a box from a 2.8 Sierra with a 3.35 1st. Previously I had a 4 speed box with a higher 1st. In practice I've never really noticed much difference (yes I know there is one) but in the real world I don't do rev limit starts and find the lower 1st permits hillstarts with virtually no clutch slip needed. The intermediates are higher so it's swings and roundabouts.

If such things really bother you can get the 2.97 1st set from BurtonPower.



Re: Voight's T9 centre plate mods

PostPosted: Wed Dec 30, 2009 9:14 pm
by msd1107

I didn't look at my Voight brochure, but Gary posted one here: elan-f14/voights-gearbox-conversions-t19741.html

Quoting from the brochure "Based on Sierra type 9 with new aluminum tail extension, centre plate and bellhousing in LM25 aluminum ... "

1968 36/7988

Re: Voight's T9 centre plate mods

PostPosted: Thu Dec 31, 2009 12:59 pm
by CBUEB1771
msd1107 wrote:Quoting from the brochure "Based on Sierra type 9 with new aluminum tail extension, centre plate and bellhousing in LM25 aluminum ... "

David, Clearly you are correct here but the standard T9 also has a light alloy center plate between the iron main case and the tail housing. Some day I might actually receive my Voights/Esposito T9 conversion and I can figure out why Mr. Voights has made a new center plate.

Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Thu Dec 31, 2009 1:55 pm
by garyeanderson
These pictures were in the For Sale section at one time. I think John Worzel was selling the box and posted the photos so I copied them. This is the down and dirty way that has been done to move the gear lever forward on the Type 9. I asked Bill Gavin to see if he could get some real copies of the info on the paper, I guess the person that bought the box from John (I may have the sellers name wrong but I don't think so) also got the directions and he was going to get the info scanned some time and send it to Bill. Well time went by and so did the idea of scanning the "plans" with the relivant dimensions. It probably doesn't matter much as some bright spark of a person could look at the photos and see how the gear lever was moved forward and a hollow tube with a new "comb" welded to it was made and the opening for the shift rod was enlarged for the tube with the new "comb" slid through and pinned to a modified 5th gear shft fork. Hopefully someone will take the bit in the mouth and go with it, I don't wan't to do any projects at the moment as it leads to other work that costs money and takes food out of Beauregard mouth. He is not happy when he misses a meal so to trade a t9 5 speed conversion for a hungry hound is not anything I need at the moment. I plan to keep the T9 I have for the mk1 Cortina if that project ever get my attention, if not it will be sold to someone at a later date for them to keep around. I wish that the original documents could be found and posted for all but it wasn't to be unless someone reads this and has the ability to scan what they bought 3 years ago when I copied these photos here.

Happy New Year and may we all have a much better year in 2010 that most of us did in 2009








Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Thu Dec 31, 2009 5:48 pm
by curly type 26
Great job Gary, you have certainly helped to clear the muddy water (well for me anyway) Hope old Beau dosen't have to go without his supper that would never do! All the best for 2010 Curly :D

Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Sun Jan 03, 2010 12:38 am
by msd1107
A previous post on the 6-speed thread had a comparison of the various ratios available for the MX-5 gearbox, plus the Lotus 4-speeds. A private communication expanded that to include many of the ratios available for the T9 gearbox. Now that this thread is active again, the most suitable ratios for the T5 are included. There are over 200 T5 gearbox part numbers. Many of them are duplicate ratio sets, and many are much too low geared to be of interest. For instance, a 1st gear ratio of 4.03 wouldn?t be very satisfactory. The highest geared 1st speed is 2.95, not very close. It is available with several 5th gear ratios. The next best 1st gear is 3.35, not very suitable, again with several intermediate and 5th gear ratios.

For each gearbox, the information extracted is as follows: "Gb ratio" is the gearbox ratio, in 1st through top from top to bottom. "% diff" is the percentage difference between the current gear and the next gear. "speed" is the speed achieved at 6,500 rpm. "diff" is the difference in speeds achieved in the current gear and the next higher gear. "err" is the error term for this gear and the next gear when the program calculates the Figure of Merit (FoM). Zero is best, low single digit figures OK, larger figures not OK. The math is simple, the results illuminating. "FoM" is the Figure of Merit. This is a mathematical calculation as to how well the gear ratios are staged. The maximum is 100, and there theoretically is no minimum. You will perceive a gearbox with a FoM above 80 as being a well-staged set of gears. By the time the FoM gets down to 0, there will be awkward gaps between one of more ratios and either too wide or too narrow a gap.

Now, let?s take a pretend drive in 19 cars with these 19 different gearboxes. Back-to-back drives allow for the evaluation of subtle differences between gearboxes that appear to be close together and that might not be so noticeable individually. But the wide range of gearboxes makes differences quite noticeable. I will proceed from the highest geared 1st speed to the lowest geared 1st speed. All the data assumes a car with 155-13 tires, 3.55 differential ratio, and 6,500 rpm. If you want to see results for other configurations, download the spreadsheet (20080411z.xls) at the bottom of the first page of posts at viewtopic.php?t=16413&view=next .

Lotus CR 2.51 1st, 4th direct.

Gb ratio % diff speed...diff...err....FoM=99.8
2.510....53.4...047.9...25.6...00.0...51.9 at 7,000

On startup, the acceleration feels soft due to the high gearing (50+ if you go to 7000). 1st to 2nd feels medium close, basically because the gearing is high (in many cars, this is similar to 2nd). 2nd to 3rd feels a little closer, and 3rd to 4th feels closer still. Looking at the speed difference between gears shows why. The speed difference decreases for each gear, giving the impression of closer gearing. Notice the FoM of 99.8, as close to perfect as you are likely to see.

Bill?s hypothetical 2.65 1st, 4th direct, OD on 5th, 6th.

Gb ratio % diff speed..diff..err...gears..FoM=94.2

Startup is easier, due to the lower 2.65 1st. 1st to 2nd and 2nd to 3rd feel quite similar, because the mph drops between gears are quite similar. 3rd to 4th feels a little wider, since the CR has a decreasing mph gap between gears and this gearbox has a constant gap. 4th to 5th feels the same, and a car with the proper differential ratio and engine tune should be able to pull max revs in 5th. 5th to 6th feels the same drop, and 6th is a true overdrive. Many of you are running around 4800 rpm at 80 mph. This setup shows just over 3000 rpm

Well, it is not too likely we will get a new gear set cut, and even less likely re-engineer the shift linkage for 4th direct. So I generated a new gearbox with the same overall ratio between 1st and 6th, but with 5th direct. This came out with 3.205, 2.042, 1.528, 1.208, 1.000, and 0.855 ratios and a FoM of 94.2. Using a pinion and ring gear of 11:33 produces speeds in gear very close to the previous gear set and a 9:32 3.55 differential. 10:32 would be equivalent to a 3.77, and 10:33 would be equivalent to 3.90.

BGH E7 2.66 1st, 0.82 5th

Gb ratio % diff speed...diff...err..FoM=72.8

The BGH E7 looks quite similar to Bill?s proposed set in 1st through 5th. The differences are primarily in 2nd and 3rd, and although appearing minor, result in a decrease in the FoM from 90+ to 70+. If you drove these two gearboxes back to back, you would be able to sense the differences as you shifted up through 1st through 4th.

The following T5 gearboxes, the Lotus ?Mid-close?, and the BGH E2 have virtually the same 1st gear ratio. However, the intermediate gears and, where present, 5th gear provide different driving experiences.

T5 1352-184 1988 Sierra 2L Turbo 2.95 1st, .80 5th.

Gb ratio % diff speed...diff...err..FoM=28.0

The first 4 ratios produce a FoM of 67.1, so 5th gear is not optimal but would work well on the road. In comparison with the Lotus ?mid-close? and the BGH E2, the slightly greater 1st-2nd drop and slightly closer 3rd-4th drop would feel better on the road.

T5 1352-028 1983 Camaro/Firebird 5L V8 2.95 1st, .73 5th.

Gb ratio % diff speed...diff...err..FoM=-23.1

Changing 5th gear from 0.80 to 0.73 decreases the FoM from 28.0 to ?23.1, passing the optimum 5th gear ratio for the FoM of 0.77. On the road, you would notice the wider ratio drop when shifting into 5th.

T5 1352-065 1984 Mustang/Capri 5L V8 2.95 1st, .63 5th.

Gb ratio % diff speed...diff...err..FoM=-1241.2

Changing 5th gear from 0.80 to 0.63 decreases the FoM from 28.0 to ?1241.2, passing the optimum 5th gear ratio for the FoM of 0.77. On the road, you would notice the much wider ratio drop when shifting into 5th. The only reason to choose this ratio set is if you want a very tall OD 5th for relaxed cruising, but the TC probably cannot pull this gear. Note that there is 1352-115 for the Ford SVO 5L V8 with a 0.68 5th gear ratio. Neither of these 5th gear ratios is very suitable for our cars.

Lotus ?Mid-close? ratio 2.97 1st, 4th direct.

Gb ratio % diff speed...diff...err..FoM=97.5

The so-called ?mid-close? ratio is actually a sedan ratio set. Startup is much easier in 1st since the Elan is quite a bit lighter than the corresponding sedan. 1st to 2nd feels closer than the Lotus CR and Bills hypothetical 6-speed gear sets. It is in an absolute sense (% drop of 47.9% vs 56.9% and 53.4%) but the speeds are lower, so the mph difference is less also (19.5 mph vs 25.8 and 25.6). 2nd to 3rd feels a little wider (26.3 mph difference vs 24.6 and 24.2). The 3rd to 4th shift feels quite wide, both percentage wise (39.7% vs 26.5% and 23.1%) and speed difference (34.2 mph vs 25.2 and 22.6). The FoM is an excellent 97.5.

BGH E2 2.98 1st, .82 5th.

Gb ratio % diff speed...diff...err..FoM=-169.0

The first 4 ratios look quite similar to the Lotus mid-close ratio set and the T5 gear sets. But driving the ratio sets back to back would show the BGH set a little better in driveability compared to the Lotus mid-close ratio set, and not quite as good as the T5. 2nd and 3rd are a little further from 1st and closer to 4th, which gives a better on road experience. The 5th gear ratio of .82 is too low, contributing to the FoM of -169. A 5th gear of 0.76 would give a FoM of 99.6 or 2nd gear of 1.795, a 3rd gear of 1.285 would give a correspondingly high FoM, and the first 4 ratios have a FoM of 99.8. These also look similar to the 2.95 1st gear T5 ratio sets, but the T5, with its slightly greater 1st-2nd drop and closer 3rd-4th drop, would feel better on the road.

TRD 33030-SE100 3.106 1st, 0.869 6th.

Gb ratio % diff speed..diff..err..FoM=-21.9

1st is lower than the ?mid-close? and BGH E2 sets. Running up and down through the gears you will get the feeling that 1st to 2nd and 5th to 6th are slightly closer than the other ratios and 3rd to 4th is slightly wider. See this in the speed difference column where 1st to 2nd and 5th to 6th are less than the other ratio differences and 3rd to 4th is greater. See this also in the ?err? column, where the high error figure accurately predicts problem in the staging of that ratio pair. Also, the FoM of ?21.9 indicates problems in the staging of the ratios.

The following T5 gearboxes and the T9 2.8L gearbox have the same 1st gear ratio. However, the intermediate gears and 5th gear provide different driving experiences. The 3.35 1st gear is lower enough from the TRD or higher than the S15 1st gear to be noticeable.

T9 2.8 3.35 1st, .82 5th,

Gb ratio % diff speed...diff...err..FoM=-257.8

A big problem is in the very wide 85.1% drop between 1st and 2nd and the smaller speed gap between 3rd and 4th . See this in the %diff column and speed diff column. The large figures in the FoM err column also accurately predict problems with these ratios and lead to the ?257.8 FoM.

T5 1352-126 1985 Mustang/Capri 5L V8 3.35 1st, .80 5th and others

Gb ratio % diff speed...diff...err..FoM=27.8

The slightly lower 2nd and 3rd gear ratios produce a better FoM of 27.8. The 1st to 2nd % difference is still very wide at 73.6% but would still feel better shifting through the gears. Alternative 5th gear ratios of 0.71 (producing a FoM of ?533.3) and 0.68 (producing a FoM of ?941.8 ) are too tall to consider for our TCs. On the road, you would notice the wider ratio drop when shifting into 5th.

T5 1352-199 1990 Mustang 5L V8 3.35 1st, .83 5th

Gb ratio % diff speed...diff...err..FoM=-80.6

This gearbox again has slightly lower 2nd and 3rd gear ratios. The gap between 1st and 2nd gear narrows slightly to 68.3%, almost acceptable. Considering only 1st-4th gears, the FoM is 27.5 (and would increase to 90+ with one tooth more on 3rd gear main shaft). 5th gear ratio at 0.83 is too low, a figure of 0.78 would be optimum. On the road, and using 1st-4th, you would notice a slightly larger perceived gap between 2nd and 3rd than between the other two shifts.

T5 1352-047 1984 Nissan 280ZX 2.8 Turbo 3.35 1st, .75 5th

Gb ratio % diff speed...diff...err..FoM=87.7

This gearbox again has slightly lower 2nd and 3rd gear ratios. The gap between 1st and 2nd gear narrows slightly to 61.1%, almost acceptable. Shifting up through the gears, you would get the impression of wider gaps as you go up the gears. See this in that the mph gaps between gears increases by almost 6 mph between each gear. What you are seeing is the tradeoff between minimizing the ratio gap between 1st and 2nd and minimizing the ratio gap on the top gears. A 1st gear of 3.35 is just too much to get suitable ratios and gaps in four speeds. The FoM of 87.7 is excellent. There is another 5th gear of 0.78 available (1352-080). The FoM is not as good, but the on-road experience is probably good.

S15 3.626 1st, 0.767 6th.

Gb ratio % diff speed..diff..err..FoM=-308.6
If 5-6 is not included in FoM calculation, FoM improves to 72.8.

The 3.626 1st gear is markedly lower than the previous gear sets and is hardly more than a startup gear, getting only to 33.2 mph. The 5th to 6th ratio gap is very wide for the top gear pair. This is responsible for the FoM of ?308.6. Considering only the first five ratios produces a FoM of 72.8 and feels pretty good. A 0.85 OD 6th gear would produce a FoM of 85.1

T9 1.6 3.65 1st, .815 5th,

Gb ratio % diff speed...diff...err..FoM=-11.3

The 3.65 1st gear is almost the same as the S15 3.626 and noticeably higher than the MX5 1st gear. However, there is a large ratio drop between 1st and 2nd, a small speed gap between 2nd and 3rd, and a large speed gap between 3rd and 4th. This is seen in the speed diff column and the FoM error column.

MX-5 ?99 on 3.76 1st, 0.843 6th

Gb ratio % diff speed..diff..err..FoM=68.5

1st is even lower than the S15 gear set, getting only to 32.0 mph. The situation is even worse if the differential ratio is a more common 3.77 or 3.90. You would hardly ever use 1st gear after startup. Second gear is not that different from the Lotus CR 1st gear. Shifting up and down, what is noticed is that 2nd to 3rd seems slightly closer and 5th to 6th seems slightly wider than the other gears. See this in the speed difference column, and also in the FoM err column.

RX-8 3.76 1st, 0.843 6th

Gb ratio % diff speed..diff..err..FoM=-156.7

1st, 2nd, 3rd, 5th, and 6th are the same as the MX-5. 1st again is only a startup gear. Just changing 4th brings the FoM down from 68.5 to ?156.7, indicating some kind of problem in the staging of the ratios. See it in the speed difference column where 3rd to 4th is wide at 28.2 mph, and 4th to 5th is close at 18.9 mph. I wonder why they did this.

SXE-10 3.874 1st, 0.869 6th

Gb ratio % diff speed..diff..err..FoM=-51.6

Here 1st feels even lower and more useless, getting only to 31.0 mph. To compound the problem, the 1st to 2nd percentage drop of 78.1% is extremely wide. Shifting from 1st to 2nd bogs the engine unless you rev the h... out of the engine in 1st gear. In addition, the 3rd to 4th and 5th to 6th feel closer than the other shifts, which is reflected in the speed difference column and also the FoM error column and also reflected in the FoM of ?51.6.

So there it is, guys. We use an off the shelf sedan gear set and we suffer the consequences. Bolt up an optimum set, the installation goes more smoothly since the shafts hook up to our existing clutch and driveshaft and the driving experience is more pleasurable. For those who are doubtful as to being able to detect these differences, you only need to do a back-to-back once to be convinced. But, hey, it is your car, and your money.

So what is a person to do? As usual, there is no perfect solution. If you can cope with 1st gear startup and do not do long distances on the freeway, then the Lotus CR is as good as you are likely to get, and it is completely standard. The Esposito/Voight/BGH E7/Quaife 5-speed is a possible candidate, provided John can get production quantities and assuming you can stand the price. Although John is in the US, the gearbox can be delivered worldwide. For a DIY ?solution? in the US, a T5 1352-184 1988 Sierra 2L Turbo 2.95 1st, .80 5th would work well, although you suffer a considerable weight penalty and can't use a Spyder chassis. The 6-speed solution being developed by Vincent still needs engineering development to make it competitive with the T9. As usual, your particular situation will determine what solution you choose.

1968 36/7988

Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Sun Jan 03, 2010 1:14 am
by TomR
Thought the T5 was lighter than the Lotus 4-speeds.

Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Sun Jan 03, 2010 1:31 am
by msd1107

Russ Newton wrote
Tremec T-5 gearboxes weigh 75 lb without bellhousing

Gary Anderson wrote
I have hefted T5's T9's and elan 4speeds, I think they are all heavy.
The 4 speed is close 70 lbs with the Iron bell, I think the T9 is around 85 and the t5 95 to 105.

Russ has emailed me (about my bad memory) that his Plus2 stock gearbox with iron bell and the rest of the components is 80 pounds, The T5 is 75 pounds as claimed in all of the online info that Russ and I could find. That would be no bell ,stick, or fluids. If you used the stock twin cam bell housing at 18 pounds and another couple of pounds for the concentric throw out bearing and adapter plate you may well end up only 20 to 25 pounds over the stock box.

msd1107 (David Harralson) wrote
My T9 (SPC version, should be the same weight as a regular T9) - no bell, stick, or fluids - was 58/59 lbs on the FedEx scale.

Rohan reported a weight of 24.4kg/53.8lbs for a TC gearbox viewtopic.php?t=15794

1968 36/7988

Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Sun Jan 03, 2010 12:00 pm
by garyeanderson
TomR wrote:Thought the T5 was lighter than the Lotus 4-speeds.

Hi Tom

How have you been, good to see there is still an interest in this topic by others. I trawled through some posts and even the same posts as david looked at and here is my cut at it.

The figures below are for gearboxes that were just removed or ready to be installed, they may be off by 2 to 5 pounds in either direction but as I said before the number is Beer and french fries territory as I said before.
All of this weight stuff was discussed and I believe the consensus was that for all intents that the T5 the T9 and the STOCK iron 4 speed are close enough for us to say it doesn?t matter much. A lot as the weight is low in the chassis and central to the frame.

So lets ball the stock iron cased 4 speed with all components 82 pounds

The T9 is a bit more from the Murker (again with all components) 87 pounds

I don?t have a number for the T5 with all components but my gut feeling is that 95 pounds
(this is a guess, I don?t know and until someone pulled one out of a car and puts it on a scale I can only speculate) This is the claimed weight from the web pages where it is advertised plus 20 pounds for the bell, throw out bearing clutch fork, companion flange, etc.
here is all of the topics I found with some relavent info

Engine/Transmission weight


John King Wrote in

Now that I've got my engine out I've had a chance to put it on the bathroom scale and check its weight. Here is what I found:

Engine (with oil but without the parts listed below) ----- 242 lbs
Transmission (with oil) ------------------------------------------ 82 lbs
Generator (with mounting bracket) -------------------------- 12 lbs
Starter -------------------------------------------------------------- 9 lbs
Carburettors (2 Webers - no air box) ----------------------- 10 lbs
Exhaust headers ------------------------------------------------- 6 lbs

The accuracy of the scale is somewhat suspect especially since I got on it and it read what I thought was quite high. But maybe that's just wishful thinking.
John '63 S1

David Harralson wrote in the same topic

Does the transmission weight include the bell housing?

I weighed a T9 recently, which is supposed to be heavier than the Lotus transmission. The T9 weighed 68 lbs without bell housing or oil.

1968 36/7988

Gary Anderson wrote

the stock 105E bellhousing weighs 15 lbs. without bolts, fork, slave cylinder or starter cover. my guess is that the 82 lbs includes all of the above. UPS will ship them so I dont think there that heavy.


and John King responded with

Hi David
Yes, that included the bell housing.
I should have listed it as Transmission/Bell housing. I did neglect to weigh the Engine-to-Bell housing Backing Plate but I don't think that would have even registered on the scale that I used
John '63 S1

Twin-Cam to T5 Bellhousing Anyone?
Page 2

Gary Anderson wrote

Your alternative is great but its expensive. Both options (T9 and 4 speed) in aluminum or magnesium will be lighter by some amount if you cary either to the extream. My alloy bell, gear case and tailshaft for the 4 speed cost $1500 10 years ago. Probably double now. Lets stop all this which is better stuff and see what it will take to make 10 or so kits. Do a proto with junkyard parts for a proof of concept and see what the costs end up being. If its cheap enough who cars about 15 or 20 pounds, If your that concerned about it, it can be lost else where.

p.s. - My Murkur box is 87 pounds with everything as it cam out. The T9 included alloy bell, shifter, fork, bearing, companion flange and very little fluid.


I believe that David posted a link to this page before but to me these sets of ratios raises my preferance of the T5 over the T9 by a lot.
Gearboxman T5 gearkits

After waiting ten years in the vain hope that someone would develop a gearset suitable for the Borg-Warner T5 gearbox, capable of handling the "big grunt" engines, we gave up.... waiting, that is!

The T5 has always had the potential to be an ideal "clubman" gearbox. It just needed some fine tuning.

We have, over time, seen just about all that is imperfect with a stock T5, first-hand. With that in mind, we have come up with a gearset that should address any inherent weaknesses of this transmission.

Short or Long?
Did I say "a gearset"? We have actually come up with two. The first, our wide ratio kit, has the ratios of the standard Sierra Cosworth gearbox: many clients run wide power band engines, and felt that close-ratio would not be a benefit to them.

The second gearset is close-ratio (pictured). This will suit high output normally aspirated, or generally narrow power band engine applications.

See the info box on the right for these ratios and more information.

We can supply this kit fitted to a gearbox on an exchange or outright-buy basis, fit it to your 'box, or just supply the kit - contact us for more information.

Uprated selector forks
In addition to the gearsets, we have identified a weakness in the standard selector forks.

t5 selector:
If they don't break, they wear out the selector tips on a regular basis, so we're making selector fork kits as well.

We've done away with the nasty hook-in finger that is used on the 1st/2nd and 3rd/4th forks to come up with single piece selectors.

We've made this kit optional, so leaving it up to you.

part code price
Close ratio gearkit
T5 Borg-Warner, Type 184 (Cosworth) GBMT51C ?895.00
Close ratio gearkit
T5 Borg-Warner, Type 240 (TVR) GBMT51T ?895.00
Wide ratio gearkit
T5 Borg-Warner, Type 184 (Cosworth) GBMT52C ?895.00
Wide ratio gearkit
T5 Borg-Warner, Type 240 (TVR) GBMT52T ?895.00
Selector fork kit
heavy duty allibronze one-piece forks GBMT5FK ?435.00

Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Sun Jan 03, 2010 7:56 pm
by garyeanderson
Well the snow stopped a few minutes ago and I got dug out with the help of a friend with his truck and plow, another 8 inches or so.
I also got the scale out of the shed and weighed up some stock gearboxes. This is the same scale that I weighed the T9 from the Merkur and with the bell, companion flange, clutch fork, gear shifter and knob for a total of 87 pounds. I had the stock Elan box with shifter but not much else it was 62 pounds, when I put a stock 105e iron bell with the closing plate it came up to 79 pounds so John Kings 82 just out of the Elan with every thing is right there. I also had the alloy case and tailshaft gearbox handy so that was easy at 50 pounds but that also had the companion flange and a little oil in it still. Whats it all mean? Not a lot I guess, the tide was full and and all of Beau's tennis balls were burried in the snow, when the tide came in and flooded the yard he couldn't find any of the 10 or so scattered around so he went for a swim and started looking. Eventually he stepped on one and it floated to the surface and all was good again on Kent Steet...





Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Sun Jan 03, 2010 9:17 pm
by msd1107

I had forgotten the Gearboxman kits. Below is the technical information about the ratios, which could be merged with all the data in the post above.

T5 Gearboxman CR

Gb ratio % diff speed...diff...err..FoM=1.0

This is a close ratio gear set (or as I call it, a touring or sporting set) available from . The first 4 ratios appear quite similar to the Lotus CR gear set. Indeed, if 5th gear is excluded from the FoM calculation, the FoM increases to 94.8, indicating 5th gear ratio is not the optimum value, which is around 0.83 giving a FoM of 97.6, a speed in 5th of 148.9 and near constant 25 mph gaps between gears.

The following T5 gearboxes, the Lotus ?Mid-close?, and the BGH E2 have virtually the same 1st gear ratio. However, the intermediate gears and, where present, 5th gear provide different driving experiences.

T5 Gearboxman Wide ratio

Gb ratio % diff speed...diff...err..FoM=14.3

This is a wide ratio gear set available from . This is a rare example of a ratio set than could have the FoM improved with a lower 1st gear with the 1st to 2nd ratio drop still being acceptable. The FoM of 2nd-5th is 100. However, you would find driving this gearbox to quite acceptable, even though the smaller speed increment from 1st-2nd and the higher gears is apparent. Just out of curiosity, the FoM improves with lower 1st gear ratios through a value of 3.48. However, this has an unacceptably wide ratio drop of 80.1%.

If you are looking for a ratio set that corresponds to our beloved 2.51 4-speed, but with a 5th gear, the Gearboxman CR is a valid choice. For street use, raising 5th gear to around 0.83 would be an improvement.

For +2s and those who want a wide ratio gearset, the wide ratio set is a good choice. The 1352-184 gearbox in the 1988 Sierra 2L Turbo is a good choice also if you can find it.

1968 36/7988

Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Sun Jan 03, 2010 9:24 pm
by bigvalvehead
Hi Guys
Popped into the workshop today and put some items on one of the weigh pads from the corner weight gauges.
Results as follows

steel t/c bellhousing 8.5kg
alloy t/c bellhousing 2.5kg
merkur alloy bellhousing 5.0kg
t5 gearbox no stick no belhousing 35.0kg
std gearbox with stick and mount 30kg

This means the T5 with Merkur bellhousing only comes out at approx 1.5 kg over the std setup assuming the S10 rear housing weighs the same as the std one.
The box I have has the .63 top but the engine will be 1953cc all steel injected turbo so should be able to pull as it will also be fitted with 4.4 diff.
Time will tell!!
cheers dave

Re: Twin-Cam to T5 Bellhousing Anyone?

PostPosted: Sun Jan 03, 2010 11:34 pm
by CBUEB1771
bigvalvehead wrote:t5 gearbox no stick no belhousing 35.0kg

That is very close to what Tremec claim for the TVR spec. T-5 in their literature.