Twin-Cam to T5 Bellhousing Anyone?

[johnc]

In a previous message I said

The rear mark labeled 'S10' is the location is the S10 shift lever location again assuming a stock Elan bellhousing and no adapter plate. It is located 1" and 1 3/4" behind the center of the Elan gear shift opening with an Elan and Mustang 2.3L bellhousing respectively.

I met to say: The rear mark labeled 'S10' is the location of the S10 shift lever. It is located 1" and 1 3/4" behind the center of the Elan gear shift opening with an Elan and a Mustang 2.3L bellhousing respectively.

[garyeanderson]

I did a little bit more measuring this morning. The Spyder dimentions between the two verticle square tubes actually are not parallell do to the mathamatics of geometry. At the top of the frame where the body mounts are for the dashboard bracket, it measures ~7 1/4 inches. At the bottom of the chassis tubes it is very close to 8 inches. This will not be a easy thing to deal with, either the T 5 gearbox will need a little massaging or the verticle tubes will need to be worked on. I do not think that most people will want to grind away a portion of one or both tubes and plate the opened up tube(s). The Spyder chassis may not be suitable for a T 5 swap and may be better off using the T 9. There is a verticle bellhousing that is being poduced by 105speed.com and costs ?225.

Gary

[garyeanderson]

Here are a couple of photos that I found of the new T 9 bell, I am not certain that this is the bell from 105speed.com but I really can't imagine that there are two being produced in England. I found these photos on the LCR web site, they were posted by "Joners" and he may be involved with 105speed, but I do not know for certain. I believe this bell is a direct swap for the Twin Cam Bell (105e) except that is uses the later 2000e starter with the 3 mounting bolts. I believe that both 2 ear and 3 ear starters used the same PCD and should not be an issue. Other than cost, this seems to be a better alternative to using a modified bell from the U.S. delivered Merkurs or the earlier bellhousings that were installed on the U.S. delivered Pintos (the Car) equipped with 2 liter pinto engines and German 4 speed gearboxes. Both of the U.S. available bellhousings will need, new starters, flywheels, slave cylinders and associated hardware and you still end up with the gearbox tilted several degrees.

[CBUEB1771]

Gary,
I measured the width of the T-5 where it bolts to the tail housing when I was looking at the brand new one at Forte's Parts Connection. I got 7.5" wide at the top. It narrows quite a bit working down from the top cover. Mike Forte showed me where a lot of installers lop metal off of the main case to fit tight tunnels. To be fair, I performed just a quick a quick tape measure job with the tail housing in place. My measurement is therefore not terribly accurate. We still need to fit up a junk yard T-5 in a couple of chassis before declaring victory or retreat.

[CBUEB1771]

It is also getting close to March 1st, the time when Alan Voights told me to call to see if he is back in production.

[johnc]

I found the following picture on www.mustang59magazine.com with the following caption:

If you have an '05-'06 V-6 Mustang and are looking for a new or spare gearbox, D&D has a limited supply of take-out S197 T5s for only $799. Go ahead-price one from your Ford dealer.On the S197 V-6 version, you can see the basic shape of a T5 in the main case, but the tailhousing features a radically different shifter tower for the new Mustang's set-back shifter location and a harmonic damper on the output shaft.

Looks like it might make an interesting alternative to the S10 tail housing. Also it appears as if the harmonic damper is secured to the tail shaft with a nut.

It appears the price may have been reduced to $499 -- see bottom of page at:
http://www.ddperformance.com/T-5%20Transmissions.htm

[johnc]

Would someone please post an accurate measurement of the T9 transmission case length (i.e. from front face to rear face) -- Thank you.

[msd1107]

For a Merkur T9 (I don't have my SPC T9 here, they should be the same)

Transmission housing - 8 1/2" long, 5 3/4" wide
Transmission housing including 5th gear sandwich housing - 9 1/2"
Tailhousing - 14 1/8"
Rear of tailhousing to front of bellhousing - 31"

[worzel]

Hi

Just some info you might find useful.

I converted my sprint 10 years ago to a Type 9- back then I used a "Rocket to BDA" bellhousing which in effect is a carbon copy of the original 4 speed cast iron item but mates to the Type 9 box. Doesn't require a sandwich plate. I bought it 2nd hand for around ?110.

There is/was an alternative that is much cheaper and is still available today (at least in the UK)- the Ford RS2000 had an alloy bellhousing that again is virtually a carbon copy of the 4 speed item but this uses a cable clutch release mechanism. However, it wouldn't really be too much of a problem to modify it to take a hydraulic release. It at least has the advantage of dropping straight in to the std Lotus chassis without cutting any of the chassis. Being light, transport costs might make it feasible to transport to the US, modify it and still work out less/better than some of the suggestions on the forum.

Ford RS2000's were made in considerable numbers so locating one of these bellhousings via say the RS owners club shouldn't be too problematic.

Regards

John

[CBUEB1771]

Would someone please post an accurate measurement of the T9 transmission case length (i.e. from front face to rear face) -- Thank you.

John,
The Ford drawing I have shows the main case as 212.0 +/- 0.08 mm (8.346 +/- 0.003 inches) long. The overall length of the main case, 5th gear extension and tailhousing is 595.0 mm (23.425 inches). Unfortunately this drawing does not provide enough information to infer the length of the fifth gear extension itself.

[johnc]

I put together an estimate of the dimensions of the Alan Voigts 5-speed conversion kit based on the 8.346" case dimension posted by Russ. The estimates were done by loading the brochure obtained by Gary Anderson into a CAD program. The estimates appear to reasonably consistent in spite of inherent parallax errors. All estimates are rounded to the nearest 0.1".

Bell housing length -- 6.7?
Transmission case ? 8.35? (per drawing)
Bulk head gear plate ? 1.0?
Tail housing ? 13.0?
Rear transmission case to shifter ? 2.5 / 2.6?
Diameter shifter base ? 1.6?

Dimensions per Tremec Diagram:

A = 10.9 / 11.0?
B =
C =
D =
E = 22.4?
F = 14.0?
G =
H = 2.1?

Conclusions:

Alan Voigts shifter location may be approximate 1/4? rearward of the stock Elan. The small diameter of the shifter base (1.6?) compared to the 3.25? transmission tunnel shifter hole should provide sufficient latitude for any inaccuracy in measurement estimates or in situ variations.

One observation: It is unclear whether or not the stock shift lever rubber gather will fit Alan's shift lever. If not, it should be straight forward to fit a leather gather by adding a rim to the center console opening.

[johnc]

Gary Anderson wrote:

I did a little bit more measuring this morning. The Spyder dimentions between the two verticle square tubes actually are not parallell do to the mathamatics of geometry. At the top of the frame where the body mounts are for the dashboard bracket, it measures ~7 1/4 inches. At the bottom of the chassis tubes it is very close to 8 inches. This will not be a easy thing to deal with, either the T 5 gearbox will need a little massaging or the verticle tubes will need to be worked on.

In the last few days I went to a couple of pick-n-pulls frankly looking for an Isuzu transmission, but did find any. However, I did source a S-10 tailhousing, shift lever, and cover plate.

Attached is an outline of the S-10 tailhousing where it mates with the gearbox. It looks like one should be able to trim the width at this point down to about 7 3/8" and maybe little a bit more -- perhaps 1/8" per side. Because the attachment means is an external flange arrangement the width forward and aft of this interface can be reduced substantially more with one exception being along the sides of the top cover.

[garyeanderson]

To me, it looks like it should fit. Whether the gearbox vibrates or rattles agains the Spyder chassis remains to be seen. It may need a degree or two rotation to the right and some machining to make the clearences a little greater to prevent interference when running and driving.

Gary

[johnc]

The following gearbox photos in combination with the T5 tailhousing template I posted above should give one a good idea of where the castings can be trimmed.

[msd1107]

Considerations for adapting a 5-speed transmission to the Elan.

Ever since LotusElan.net started, and before, there has been discussion about adapting 5-speed transmissions to the Elan.

It strikes me that if there were a checklist of interface issues, that it would be possible to more easily examine the issues involved in a possible adaptation. Bear in mind that given enough effort, practically any conversion can be accomplished. But what we seek is the minimal effort to accomplish the conversion and to allow this to be done by the largest audience.

So here are some things to look out for. Experience will cause this list to be expanded, contracted, or modified.

Input shaft length. If the input shaft is too long, it has to be shortened. Too short is too bad. Complications are the depth of the 5-speed bell housing versus the TC bell housing and/or whether an adapter plate is used.

Input shaft diameter. The TC is .59 (15mm) or .67 (17mm). Probably 15mm should be used, since there are pilot bearings to fit the less common (I think) 17mm crankshaft hole. If the input shaft is different, it has to be machined down to 15mm if larger, or bushings provided to fit the larger TC crankshaft hole.

Input shaft spline diameter and number. If the donor gearbox input spline is different from the TC, a different clutch is needed at a minimum. There can be other problems also.

Gearbox to bell housing mounting bolt pattern. It would be nice if the gearbox just bolted up to the bell housing. If it doesn?t, there are four options.

First, there may already exist a conversion bell housing. If so, use it. There may be issues with clutch actuation which have to be resolved. Also to be considered is the starter motor mounting, its position, compatibility with the existing flywheel, and possible interference issues with the frame. In the worst case, a new flywheel and ring gear will be needed.

Second, an adapter plate could be machined. This will push the rear of the tail housing and shift lever position back, complicating fitting the transmission within the length of the original transmission. Also, it complicates positioning the gear lever appropriately.

Third, if material exists at the correct positions, the existing bolt holes (on the transmission, but maybe on the existing bell housing) could be filled in and new bolt holes drilled.

Last, a new bell housing would have to be designed, cast, and machined. If this is required, we should look at all the cities where we have members to try to locate a ?friendly? pattern shop who would be amenable to doing the job without charging normal commercial rates, which we cannot afford. A possible advantage here would be if the bell housing is cast in aluminum, saving weight over the stock iron bell housing.

Moving to the rear of the transmission.

First to consider is the length of the bell housing, gear case, and tail shaft. If this is close to the Ford setup, then go to the next section. Otherwise, a new drive shaft of the proper length will need to be patched onto the existing drive shaft. It is probably better to graft on the donor gearbox u-joint rather than use the Ford u-joint and have to cut and weld it onto the donor output.

Output shaft spline diameter and number. If the donor gearbox has a different number and diameter of splines, then it will have to be adapted to the Lotus drive shaft. You could use the Lotus u-joint cut and welded onto the donor gearbox, or use the donor u-joint cut and welded onto the Lotus drive shaft.

Speedometer cable. If the gearbox has the speedometer cable screwed into the side, a 90 deg box will have to be used to allow the speedometer cable to fit within the frame. A proper thread and length need to be sourced.

Gearbox speedometer drive gearing. This establishes the speedometer turns per mile figure. Depending on the source vehicle, the wheel size, tire size, differential ratio, and speedometer turns per mile, figures may be different from the Lotus figures, and produce incorrect odometer/speedometer readings. Also, there is a wide difference in the rev/mile of different tires commonly used (a 15% difference). A previous post http://www.lotuselan.net/forums/viewtopic.php?t=16106 discussed this and provided a spreadsheet so that the tooth figures can be determined. Many gearboxes had a variety of drive/driven gear teeth. These may not be available, or not be the correct ratio. In that case, an external ratio converter is necessary. Some people may go to a mechanical to electronic conversion, and use an electronic speedometer. These often give a fine degree of adaptability, but the typefaces do not give the look of the older Smiths typefaces. In any case, the speedometer may need re-calibration since they are usually inaccurate.

Gearbox to frame mounting bracket. It is highly unlikely that the gearbox will bolt up to the frame. An adapter bracket would be needed. In the worst case, new boss would need to be welded on.

Dimensional problems. If a different bell housing is used, there may be interference issues with the bell housing and the chassis, either the standard Lotus chassis or the Spyder chassis. There may be problems with the starter motor, its position and mounting. This may require a new ring gear and/or flywheel. Hopefully, the starter does not interfere with the chassis. That might require a new starter. The width, height, or depth of the gearbox or the tail shaft may interfere with the Lotus or Spyder chassis (and is particularly severe with the early Spyder chassis).

Now, we come to the gear stick position. Even the original Elan was not perfect, with the early cars being a touch too forward, and the later (anti-sizzle) ones not being quite as precise. But this is dwarfed by the problems with most gearboxes. Usually, the gear stick is much to far to the rear. Some gearboxes have alternative tail housings with alternative gear stick locations. If the distance discrepancy is not too great (a couple of inches or so) you can use a metal plate picking up the gearbox on one end and the remounted gear stick on the other end. Keep in mind the shift geometry changes, with there being an up/down arc in addition to the usual forward/backward movement. This may eventually lead to interference in the frame tunnel or on the gearbox.

This link http://nostalgiacars.co.uk/gearbox.htm shows how one company has approached the problem using a MT75 gear set and custom gear case. One of the ?standard? locations is quite close to the Lotus position.

Lets step back a look a this whole process. Basically, depending on the specific gearbox, we have a new car from engine block to differential, but still with the wide sedan ratios of the donor car. In addition, it requires a substantial amount of mechanical skill and ingenuity, not the remove and replace scenario that could be handled by the usual shop or self mechanic. I am envious of those individuals with the skills and equipment to do this type of conversion, but it limits the number of conversions to a rather small number.

What can be done to resolve this?

Consider a modest proposal, as it were.

Replace the existing gear set with a new gear set. In one fell swoop, this resolves problems with the input shaft length, shaft diameter, input spline diameter and number, output spline number and diameter, u-joint and drive shaft compatibility, as well as inappropriate ratios. Depending on the volume of orders and the flexibility of the machine shop, there can be one compromise ratio set for all users, or a selection of ratio sets.

Note that any sedan gearbox that handled 100 hp or more is a suitable candidate for a conversion, since modern alloys will be reliable under the horsepower outputs of even the strongest TC. These older transmissions often are more compact and lighter than more modern gear boxes dimensioned and stressed for reliability at 200+ hp ratings.

Replace the gearbox case with a new cast aluminum gearbox case. This resolves possible problems with replacement bell housing/adapter plates/new bell housing, starter motor positioning and interface issues, possible flywheel/ring gear incompatibilities, clutch actuation, frame mounting, and speedometer cable mounting. If the original gear case is cast iron, this results in a useful weight reduction.

The gear stick position problem has to be resolved, no matter which type of solution is chosen.

If well designed and executed, the Elan owner now orders and receives a box that they take down to their mechanic, who removes the original transmission, bolts in the new transmission, and the owner drives away with a 5-speed.

This solution requires a substantial amount of up front engineering as well as a commitment for a reasonable number of units. Given the realities of the retail market place (with current complete conversion kits costing from $3K USD with sedan ratios), this probably only makes financial sense if the development, manufacturing, and distribution are all handled within the LotusElan.net user group and other Lotus Elan owners and groups without involving a formal dealer/distribution network.

This concept can work, since an equivalent project put a 5-speed in the Lotus Elite. Those who believed and put their money up got a very nice 5-speed. Those who equivocated lost out.