5-Speed Candidate Conversion Chart

Picking up on the encouragement of David aka msd1107, I reorganized and expanded the transmission chart I posted in the Elan - Isuzu 5-speed thread.

The chart contains sections for Isuzu, T9, T5, and Alfa Romeo transmissions – all of which were reported to have been adapted for Elan usage in one form or other.

Any corrections and / or additions are welcome.
Transmission-Matrix.xls (110 KB)

Thanks John,

Good spreadsheet!

No wonder my +2 5 speed is so slow off the line…

And here’s me thinking my 100kg was holding it back :smiley:

Take care,
Peter

There are a half a dozen folks that I have talked with that would not give up the ford base ultra close ratio gearbox for anything. That said what people seem to want is a box that can give them 70 mph at 2500 - 3000 rpm. With the tire scituation in the U.S. it is looking more and more that a set of 13 inch tires will soon eat most of a $1000. I am starting to think that a larger diameter will be the only available option. So I am going to make some room in one of my S2 shells to fit them, along with the 3.55 ring and pinion. there will be some clutch slipping to deal with and a change in driving style though 20 mph school zones but I think it is something that I can live with. If I thought I could keep getting 13 inch tires I would get the custom cut Ring and pinion in the 3.1x to 3.2x that I have talked about in the past. This is a cheap (dollar wise) solutution. I really cant see any of these 5 speed conversions costing less that $2000 U.S.D. to get it installed into an Elan. This is not the kind of box that I have at the present, to get the equivalent ratios will be north of $3K and probably closer to or over $4000.

David and John
The xls chart needs something about rear end ratios and tire diameters to make it meaningful.

garyanderson wrote:

If you mean adding calculation capability, I find the XLS program at http://westfield-world.com/gearboxshifts.html helpful. Click on “Gear Ratio Calculator” which will load the program into Excel. After it is loaded, if you want a local copy of the program click on “save as”.

If you are thinking of something else – let me know and I add it.

johnc,

The Westfield calculator has inaccuracies. I wrote them last year.

As Gary requested, I added a sheet to your spreadsheet that could cover what he wants. Really a quick and dirty cut and paste with no user instructions.

Hope this helps.

David
1968 36-7988
20080408 Transmission-Matrix.xls (77 KB)

Since the owners manual for my wife’s toy is sitting right here, I can help on the Alfa end.

For a 1972 Alfa 5 speed the ratios are:
1st 3.30
2nd 1.99
3rd 1.35
4th 1.00
5th 0.79
Rev 3.01

Of course the shift throws are pretty long even if you put a short stick on it like you would need for an Elan, and I haven’t been particularly impressed with the synchros on any of the family Alfa (father-in-law has 2). Ours is worse then most though.

Rob

Hi Rob, this should be a safe place to rip Italian synchros. Can you even imagine what an Alfa trans would do after the third red line shift in an Elan?
Eric

Hey guys, you are downloading too quickly!

Enclosed is an updated spreadsheet from johnc.

Various formatting changes.

Updated the BGH T9 to .82 5th since this produces better ratios in a theoretical sense. Racers can select closer ratios if desired.

Added the 2.75 1st gear set. Mike Ostrov, when he did the T9 conversion for the Elite, chose the 2.75/.82 ratios. If you have ever driven this car, you would agree it is a very nice set. Gary and I would still hold out for a 2.5 1st gear, though.

Added Alfa-Romeo ratio data from my 60s era SCCA specification data book. Don’t even ask why I still have this. It still has all my original notes on gear ratios, drops, optimum selections, etc.

Added Toyota gearbox data for a variety of their rear wheel drive gear boxes.

Added user instructions for the sheet that displays speed vs differential ratio and gear ratio. There are four aspects to this, tire rev/mile, RPM, differential ratio, and gearbox ratio. There are 6 ways to display this information in 2-dimensioal tables. You are getting one, I have a spreadsheet with the others, in case anybody is curious.

David
1968 36/7988
20080408 Transmission-Matrix.xls (111 KB)

I expect to have the engine out of my +2 in the fall and would like to take the opportunity to install a 5 speed. In the US some highway travel ( hours at 75 mph) is largely unavoidable. Besides the T9 conversion any other suggestions for a road car with 1700 cc and a mild sprint cam?
Phil in Tennessee

I’ve used the MT75 from the ‘sulking frog’ Scorpio, the box needs some modification to fit within the chassis rails and the output flange (transit) needs reducing in diameter. The shift is superb, better than a four speed original but its a real pain to fit, fouling the chassis at the top and the exhaust at the bottom, also the starter position is is rotated down wards and fouls the sump. I have used a TC Europa (austin Maxi) pre engaged starter and that fouls the chassis slightly.

After all of this effort the car still isn’t finished so I can’t comment on how the conversion has worked, I do know that 1st is very short but 5th(most real world driving is done in 3rd to 5th, 1st and 2nd for pulling away/around town. I intend to use my car for everything…trips to town, b road blats and long runs on motorways, so I think the benifits will out weigh the short comings. Worse case scenario the four speed can go back in!

If you want some pics of the install i can email them to you.

regards

Mark

Update for the 5-speed candidate conversion spreadsheet.

Updated Elan ratios using actual tooth counts. Included 3rd party gearsets.

Improved formatting for Toyota section.

Added a section for Datsun transmissions. There are sure a lot.

Should we include any other manufacturers or transmissions?

David
1968 36/7988
20080408 Transmission-Matrix.xls (116 KB)

Attached is the list of MT75 ratios at least for Scorpio Applications

Gerry
mt75 ratios.xls (37 KB)

Updated spreadsheet including Gerry’s MT75 ratios.

I took Gary’s comments about not giving up the close ratio transmission to heart, as I feel the same way. When my first Elan was consumed by fire, I bought back the pile of pieces to retrieve the CR box.

Interestingly, the general set of ratios in that box has been used through the years and across many manufacturers. It may be close to the “perfect” 4-speed ratio set.

There are some interesting mathematical properties in the ratios. The 1st to 2nd ratio spread is 50% (in round terms) which seems to be a good compromise, not too wide, not too close. Numerologically, it is a 3/2 ratio.

The speed gaps between ratios are relatively constant, which seems to produce a good feeling staging of ratios. So, if it gets 100 mph in top, the speeds in gear are 40, 60, 80, and 100 for a constant 20 mph gap.

Again bringing forth numerology, the gearbox ratios can be generated with a number sequence. In this case, the sequence 5/2, 5/3, 5/4, and 5/5 generates the ratios 2.50, 1.67, 1.25, and 1.00.

This can be extended to produce 5 ratios, 5/2, 5/3, 5/4, 5/5, and 5/6 for 2.50, 1.67, 1.25, 1.00, and .83 for an overdrive 5th. Or 6/2, 6/3, 6/4, 6/5, and 6/6 for 3.00, 2.00, 1.50, 1.20, and 1.00 for direct top.

The corresponding 6-speed would be 6/2, 6/3, 6/4, 6/5, 6/6, and 6/7 for 3.00, 2.00, 1.50, 1.20, 1.00, and .86.

Looking at the canditate 5-speeds in the spreadsheet produces a sinking feeling in me. First gear ratios of 3.3, 3.5 or lower just don’t work well in our light weight cars. In essence, this provides four speeds with a startup gear. As Gary said, it would be better to use a higher diff ratio and retain the benefits of the 4-speed ratios, at a lower cost. The spreadsheet has another sheet with differential ratio possibilities for different ring and pinion teeth, including such possibilities as 36/11 (3.27), 32/10 (3.20), 35/11 (3.182), 31/10 (3.10) and so on.

The other approach would be to cut a new set of gears for the candidate geabox. Several of us have a spreadsheet that can provide optimum tooth numbers closely approximating the 2.50, 1.67, 1.25, 1.00, .83 sequence that would be a logical extension to the current CR 4-speed. It would seem that a shop that can cut gears could take the shafts and gears from a donor gearbox, and cut a new set to our tooth specifications without a lot of agony. This is not rocket science, or the development of a new gearbox.

I will donate the software and time to come up with appropriate tooth counts for a candidate gearbox, and possibly the costs for the prototype gearset. There a several of us here in SoCa who really want a 5-speed but are rather put off with the cost of a Voight-BGH combination. I had been working with a shop which cuts gears for vintage cars, but it looks like they got too busy and the quote they came back with was several times the original estimate so it doesn’t pencil out.

Well, back into my ivory tower.

David
1968 36/7988
20080408 Transmission-Matrix.xls (116 KB)

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.

Tom

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
20080411zGearRatios.xls (349 KB)

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

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

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

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

bill308 I freely admit I know little or nothing about 4 /5 gearbox ratios ,but follow the comments but I cant 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.