5-Speed Candidate Conversion Chart

[msd1107]

Tom,

Is it possible to use the .78 5th gear from the 1352-116 or 1352-168 (SVO Mustang)? Mathematically, the ratios are better with this setup. You might notice that the drop from 4th to 5th feels a little wider with your current ratio set than with the SVO set.

Even after all these years, I can't look at a set of ratios and tell a whole lot about them. For this, I use a spreadsheet, which does all the calculations and generates all the tables and charts.

In a vehicle, I can tell the difference that changing one gear by one tooth makes, although looking at the ratio numbers would not give me a clue. I suspect that in the T5, both gears in the 5th ratio are different by one tooth between .73 and .78.

Like I said, I use a spreadsheet to do the analysis. However, this is so large (10+mb) it cannot be distributed. So I deleted everything in it that I could, bringing its size down, but it is stil, at 1.8mb, too large. So I ZIPped it, bringing the size down to 349kb. But LotusElan.net does not accept .ZIP files, so I renamed it back to a .XLS extension that is accepted.

After you download the file, rename it back to its .ZIP extension, then unZIP it. Then load it into Excel or whatever you use to display spreadsheets. It was saved in '97 format, so every body should be able to use it.

It may take awhile to get familiar with all the data and concepts. But there is a comprehensive help text that explains what all the fields are, and a lot of the theory and formulas used. I think that if someone is skilled enough to swap in, or want to swap in, a foreign transmission, they are skilled enough to understand the numbers in the spreadsheet, and will enjoy their motoring experience more understanding what is happening.

Have fun!

David
1968 36/7988

[mikealdren]

David,
I'm intrigued by your concept of a ?universal? set of ratios for road cars, I think it?s a good idea. You could then use diff ratios and tyre sizes to give the required overall gearing for optimum acceleration, top speed or low cruising revs.

It?s quite amazing how manufacturers get things ?wrong? but they also have ridiculous speed related considerations imposed on them by marketing and regulators which can lead to different ratios at the cost of drivability. You get cars set to avoid gear changes to optimise headline 0-60 times or minimise statutory fuel consumption and emissions. The result is a car that looks good on paper but isn?t great to drive,

My daily car is an Alfa 166, with a 3 litre V6, it has loads of torque over a wide band. It also has a 6 speed box with a top ratio of about 21 mph/1000 revs. I suspect it?s geared for max acceleration but I almost never use 5th gear. As a user, I would much prefer a really tall 6th gear for motorway cruising and would be happy if it pulled max speed in 5th.

Of course this has nothing to do with Elans, most of the constraints here are to do with boxes optimised for other car?s foibles.
Mike

[msd1107]

Mike,

Thanks for the kind comments.

My and Gary's admiration for the CR gear set is not to try to promulgate a specific set of ratios. These ratios happen to have certain mathematical properties (I mean, who ever heard of generating gear ratios with number sequences?), that are of little relevance in the real world.

However, the basic principals still hold. An engineer can sit down at the terminal (using the big 10mb package) and come up with a set of ratios that can be presented to management as being optimum in the current space-time continum.

This thread illustrates that a wide range of transmissions "could" be adapted to the Elan. However, these are sedan based, with ratios not really suited for our cars.

What I had hoped to accomplish was to find a gearbox relatively easy to adapt to the Elan, and even more importantly, a friendly gear cutter who can cut us sets of ratios at a price that the community could afford. (Well, there are some who want the conversion to be relative cost free. That is not going to happen.)

Since I am sort of un-retired (was retired for some years, but was "coerced" to help in a startup), I have the flexibility to meet with people who have the ability to move this project forward, and am certainly willing to expend what ever effort is necessary.

David
1968 36/7988

[bill308]

This is a very interesting thread.

I recently took delivery of a Voights T9 conversion kit and a hard to read set of instructions (hand printing - sketch - light copy).

John Esposito of Quantum Mechanics was kind enough to let me piggyback Voights conversion on one of his pallet shipments from the UK to the USA. Thank you John.

I plan to fit this gearbox to a 1966, S2, SE, RHD, (chassis #5327). The goal is a very capable road car and occasional track use like maybe time trials. Medium distance, 80 mph cruising is a must.

The gear ratios in the Voights box are, as you know, pretty disappointing. BGH Geartech makes several suitable gearsets, ranging in price from 235-999 GBP.

Burton Power offers a T9 with 2.98 first gear for 895 GBP. The gearset costs 300 GPB with a layshaft cluster in return. You see, Burton Power machines off and replaces first gear on the cluster and adds a new mainshaft first gear. This begs the question if first gear on the cluster can be replaced, why not the others? I don't know if this is possible, at an economical cost, but it might be considered. This path would seem to allow changes and customization if you don't get it right the first time.

The other issue I have with the T9 setup is that it is not exactly light weight. I haven't weighed it yet or compared it to my 4-speed, but moving it around the garage and basement needs to be done with care. An alloy case would save a few pounds and is available for about 550 GPB.

When John Esposito called to tell me the setup was in, he commented to me something along the lines that "Voights did a really nice job on the tailshaft assembly". John would like to work with BGH and Voights to offer a gearbox solution to US customers but Voights and BGH don't seem to be interested and without email are difficult to have a dialogue with.

Bill

[msd1107]

Bill,

Interesting comments re your Voights kit documentation. I received my SPC gearbox (which Quaife resells) with absolutely zilch. And a call (they have no web site or email) got zilch. So much for customer support. And the documentation that came with the Spyder chassis might be useful if I had already done the job.

It is not difficult to produce an acceptable user manual. (Of course, I say that since I have done user manuals, just like some in the group feel it is not difficult dealing with the mechanical issues of the gearbox conversion while I have no clue)

You are right, the standard ratios in the Voights kit are not good. The BGH E7/E8 with 2.75/.82 is a good set of ratios to install in your box.

The SPC T9 I had weighed 58 lbs. The Merkur XR4ti with gearstick, shield, and bellhousing is 82 lbs. Quaife has an aluminum case and top cover for the T9. However, since the US sales have been taken over by Autotech, the prices have increased considerably.

When you consider the cost of the Voights box, a Quaife aluminum case, a BGH gearset, the cost starts to build up. We could do better ourselves by getting a gearset made with proper ratios, TC compatible splines, a gearcase cast with 2000E bolt pattern and Elan frame mounting. That reduces the conversion to repositioning the gearstick, which has been discussed on the forum. (worzel can give detailed instructions on at least 3 ways to do this, all of them different than the Voights method).

You are correct about the situation with Alan and BGH. BGH is too busy to consider a lowly Elan project. So unless you order an off the shelf BGH gearset, nada. And Alan will not sell his tailhousing separately, either. There is more that goes into his conversion than meets the eye. There is a new sandwich plate, new shift fork, and changes in the main case.

So unless we do the job ourselves, a properly engineeered T9 is not going to happen.

David
1968 36/7988

[redskatejbf]

bill308 I freely admit I know little or nothing about 4 /5 gearbox ratios ,but follow the comments but I can`t recall anyone suggesting with the Voight 5 speed box using a 3.54 ratio diff to `lift` the first gear.
Is this a non-starter? does it make 5th. gear too high. If I was to fit a 5 speed I would have to go for the Voight g/box as I do not have the expertise to build / modify any other /box .
Regards, John.

[msd1107]

John,

You could use a 3.54 differential ratio to "lift" 1st gear. All ratios would be "lifted" in proportion. You would still be left with the wide ratio drop between 1st and 2nd.

Consider whether your car can pull the 5th gear to peak power RPM in 5th (one way to determine gearing). Generally speaking, a FHC with engine modifications should. A DHC probably can't. The average driver doesn't care, they are looking to reduce RPMs on the highway.

An earlier post on April 12, 6:25am, has a downloadable spreadsheet that allows you to input your car's tire size, target RPM, gearbox ratios and see speeds for a variety of differential ratios.

And a post on April 12, 12:18pm, has a downloadable spreadsheet that has more comprehensive tables and charts. It also has comprehensive documentation so you might come to understand some of these issues.

Admittidly, most people do not sweat the details, and drive what they have. I always thought Elan owners were more technically oriented, and would be interested in reading about some of these things.

David
1968 36/7988

[RotoFlexible]

Consider whether your car can pull the 5th gear to peak power RPM in 5th (one way to determine gearing). Generally speaking, a FHC with engine modifications should. A DHC probably can't. The average driver doesn't care, they are looking to reduce RPMs on the highway.

I am very much the "average driver" you describe. My new engine would be very happy at 70mpn/3000 RPM instead of the 4000 it turns now. I don't care too much about the 4th-5th gap, so a .75 5th, and something like the CR 1-4 ratios I am so used to, would do nicely. It would be interesting to see what speed the car could do in 5th but it's not something I'd do every day.

Anyway, sign me up as a very interested consumer for this effort.

[garyeanderson]

My old 89 Mustang LX 5.0 would pull a higher top speed in 4th gear that it would in 5th. This was a 140,000 mile car with the Borg Warner T5 that we have been talking about in some of these posts. I think the top speed difference was 10 or 15 mph slower in 5th. Ford, I am sure, did a lot of testing to make sure that they got it right. That said it would do 80 in any of the top 3 gears. Anything that we as owners come up with will have none of that testing. It will be, "I think it will work ok with that .73 overdrive" but until someone puts it in their Elan they won't really know. We have a lot of folks interested in this "multiple 5 speed project", some with bone stock Twin Cams and others with 2 liter Cosworth BD's. I guess what I am saying is its going to work better in some Elans than others. If you did all of the work and spent all of the money and every time you hit a 3 percent grade (3, 4, 5 percent take you choice) you had to drop down to 4th you may be a tad disapointed.

Gary

[msd1107]

Gary,

Very good point. Some manufacturers gear the car for top speed in next to top, and use top for reduced revs when cruising, better fuel economy, better EPA ratings, etc. If the engine is peaky, the driver will have to downshift on an upgrade. But hey, I saw this in my rental car in Europe, where my economy car would hold 140+ km on the straight in 5th, but required a downshift to 4th on any but the most gentle hill.

A previous post http://www.lotuselan.net/forums/viewtopic.php?p=63669 analyzed what potential final ratio might be needed for our Elans in various stages of tune and various tire sizes.

This post http://www.lotuselan.net/forums/viewtopic.php?t=15596 has a spreadsheet that allows the potential top speed of a vehicle to be estimated.

An earlier post in this thread had a downloadable spreadsheet that gave speeds for different differential ratios and gearbox ratios given the cars' tire size and RPM. So, put in a proposed ratio set, scan down the differential ratios to get the closest matching one.

And another post http://www.lotuselan.net/forums/viewtop ... c&start=74 went through some of the issues in converting a foreign transmission for use in the Elan.

But the impression I get is that the majority of people don't care about these details. They want to remove their old transmission, put in the replacement (of course with the aid of a step by step with illustrations installation manual), and have a more relaxing drive down the road.

So when (and if) we get what appears to be an acceptable project defined and bid, we can agree upon a set of ratios. I can create a fitment guide so that the sophisticated user can determine an appropriate differential ratio for their expected useage. During the prototype phase install and take pictures in various car configurations to produce an installation manual.

The impression I get when looking at other cars user groups is that we have better tools to define, model, and evaluate potential solutions. Others seem to take whatever transmission is available in the breakers yard, hack and cut and adapt as necessary to get it to fit and get on with life. Hopefully, we have the capability to get to a technically elegant solution in the philosophy of Chapman.

David
1968 36/7988

[garyeanderson]

Hi David
I should say that all Elans are different, whether delivered from Lotus or modified by one of its many owners. Power being anywhere from 95 bhp (maybe less if it needs work) to over 170. Gearboxes lets call it 4, wide, semi close, ultra close and the 5 speed Maxi box. Differentials from the factory were 3.9, 3.77, 3.55. Various Ford crown wheel and pinions of 4.1, 4.44 maybe some higher too. We have Plus 2's and Elans weighing from 1250 lbs. to over 2000 lbs. coupes, DHC, roadsters, plus 2's chopped plus 2's.

The progression of 1st gear ratios from Ford was something like 3.54 sedans, 2.97 sporting, 2.51 rally or race, some special 2.29 back to shorter 3.65 for nearly every thing. Russ told me once that he didn't want a 1st gear any shorter than a 2.8x for his plus 2. You, Andy, Tim, myself and others would probably not go for anything less than an ultra close with a .8x.
Custom gears are great if we had a one size fits all but that isn't the case. The best we can do (in my lame ass opinion) is to take a box that is relatively common that has good support from the junk yards and aftermarket and get it to fit. A modified T9's certainly fit the bill in England but 1500GBP plus at least a 1st gear swap for 300 or 400 more, installation, then add the shipping to the U.S. and it doesn?t work for many/most Elan owners. The T5 has almost as many issues as do the others (AKA Alfa, Isuzu, Toyota, Ford MT75). This is getting close to dead horse time, unless someone with deep pockets steps up, it is dead.

The custom cut Crown wheel and pinion is the only (semi thrifty) option and its not perfect or anywhere near. No one seems to think much of it so that will be a one off for an individual solution. A 3.10, 3.18 3.25, 3.36, would get most of what folks want and would work with most combinations of 4 speed we currently have and be 1/2 to 1/5 of the cost of some of our current 5 speed options. Your spread sheet gives 60 to 65 mph at 3000 rpm for those ratios with a 165 tire. At the other end in 1st gear (worst case 2.51) 8 to 8.7 mph/1000 rpm, both a little tall but the 3.77 gives 7.2 for the same combo. With a semi-close and 3.77 diff it works out to 6 mph/1000 in 1st and 53.7 at 3000 in 4th. My pockets are inside out for any of it, I am going to go out and drive my Elan this summer. The most I expect to get done is get my ultra-close box reassembled for installation next winter.

[CBUEB1771]

I recently took delivery of a Voights T9 conversion kit and a hard to read set of instructions (hand printing - sketch - light copy).

Your entry is the most interesting in this interesting thread! When did Alan Voights actually agree to sell his T-9 conversion to you? I've had a few telephone conversations with him over the past six months and all I hear is how he will be back in production some day. I too have dangled the option of consolidating the gearbox with a container of other parts so he does not have to worry about packaging for a trans-Atlantic trip. This didn't seem to help either.

[RotoFlexible]

The T5s can easily be built up with any gear set and they are readily available in the US, so the motorsports gears are the normal choice for a rebuilt T5 in performance apps. Mine is 2.95, 1.94, 1.34, 1.0, 0.73 and I'm using it with a 4.11 LSD rear. It is not at all disappointing in a not especially torquey 1.6L BDA conversion.

This gearset sounds like the Holy Grail for my situation - with a 3.9, not the 4.11. 1-4 just slightly wider than my CR (I can live with that, I think) and the all-important 3000rpm highway 5th.

[msd1107]

Hi Gary,

You make a very good point that there a wide range of Elan cars and owners, with different, and opposing, desires.

However, engineering always has to face these issues. And management has to resolve the personel issues. If we engineered a solution that satisfied 3 sigma or 95%, would there be a substantial reduction in demand? Or would this last 5% sign up for the benefits of a properly engineered solution even though they might have to slightly adapt their driving style? Would we care if they didn't?

Since I am mechanically inept, I will shy away from a solution that has me drill, fabricate, cut, weld, machine, mill or any other skills oriented task.

But after reading this thread, I might be tempted to order a Voights kit, call Brian at BGH and order a E6/E7 gearkit, order an aluminum case from Quaife, and get a XR4ti maintenance manual on CD off of ebay (which has 60 odd pages on disassembling/reassembling the gearbox).

Then in theory, it says, I could merge Voights kit with the BGH gearkit in the Quaife case, follow Voights installation instructions and get the kit in the car.

Then I have non-standard components from the engine block to the drive shaft.

The other tack is to machine a gearset to our specifications so we have Lotus shaft lengths and splines, cast a gear case so we have 2000E bolt pattern and frame mounting boss.

The rest, as they say with a casual wave of the hand, is details. It will all plug and play.

The important thing is to get an acceptable quote from a gear cutter for the gearset and a foundry for the gearcase that, in estimated production volumes, pencils out. I had done this earlier, but my contact got sick, the shop got busy, so their written quote came in several times higher than expected. So, on to the next one. Anybody with contacts can help the group effort by getting the gearcutter/foundry and us together to talk and make a deal. Email me with names/phone numbers/email addresses.

I have met with other Elan owners here in SoCalif who have declared they are going to fit a 5-speed come hell or high water. And they have the mechanical skills to do this. So if I can't do the job properly, I may get a hack job and the rest of the Lotus community will lose another opportunity to get a properly engineered 5-speed.

Well, back to work.

David
1968 36/7988

[bill308]

David,

The 2.75/0.82 setup appears really good to me. It's about midway between the close and semi close gear sets. The BGH 2.75 first (there is also a 2.66 available) gear should work well for both the Elan and +2. I can get underway with almost no throttle, just carefully engaging the clutch, with the semi close 2.97, 3.55 rear, and 165x13 on 5.5 inch Panasports. This is particularly useful when on a multilane highway, in barely moving traffic. The state of engine tune was a modest CR, Webers, low inertia flywheel, big valve intakes, degreed in Sprint cams, Port matching to the isolators, detail porting in the valve throat area, and it's path just up stream, but below the guide. The engine had very good driveability and pulled well up to the elevated red line.

Bill