What transmission to use

I'm looking into getting a GT40 kit and was wondering about the transmissions that can be used. I have been reading the forum here and have seen ZF 5 speed(I actually had a new one that I bought from Carrol Shelby in the early 70's for $800 but have since sold)the original transmission, but have also seen Audi, Porsche and Renault used. Of those listed, what are the models used and what are the pro's and con's. Thanks for your help in advance.

This is one of those questions that there is no single "best" answer for.

What I mean by this is that the best transaxle for one person might not be the best choice for you.

Choosing major components such as the engine, trans, and even the car itself,,,, first you need to ask yourself some questions.

#1: what is the primary use for the car?

#2: how concerned am I about "originallity"?

#3: what is my budget?

I'll use my car as an example.
It is to be primarily a street driven car with some occaissonal track use. I am building a mild 302, which should be just under 400hp. I am not concerned with having an "authentic" gearbox, since I am not building a 100 percent "clone" of an original car.

I am using a Renault box, because the gear ratios are favorable for the car. I can install a HD input shaft & drive axle flanges for a durable setup. This box has been proven for many years in other GT40 replicas. The available bellhousing has enough room for a stock sized 10.5 inch ford replacement clutch assembly, which is much more affordable than buying custom clutches needed for other set ups. (I always want my clutch assembly to be the "weakest link" in my drivetrain, since clutches are cheaper than gearboxes.... being able to buy a ford 10.5 inch replacement means they are easy to find and inexpensive.)


I'm not saying the Renault is the best choice for everyone, but I do belive that it will fit my requirements very well.

Now, if I get the chance to build a 500 plus horsepower screamer for my car, I will probably be looking into a more serious transaxle to go along with it.....

...but since I have to repair cars everyday for a living,,,, I am much happier with a dependable "tame" car to play with, than I am with a high strung racing motor on the street. I find that I can spend much more time "driving" and enjoying a car when I'm not always fixing broken parts.

The most important factor in chosing a gearbox is for me would be what final drive ratio is availible. About 3.5 to 1 with a overdriven 5th gear of about .8 or so is just about right for sustained freeway miles. About 70mph I would guess. Now having said that, if these kind of sustained speeds are now how the car will be used and track days, or around town use is you might like a lower final, 3.8 to 1 or so. This is a very important choice to make first before picking a gearbox. Then how much power? 300-375hp of so and the audi, renaults, and lesser porsche's will work fine. If you start getting upwards of 500hp then your are in the ZF, high dollar porsche ballpark. beyond that are full on race boxes 10K and on up and up and up. Finally the different 40 builders more or less use one type or another. The builder you pick out might be able to change gearbox types if ask but I believe this is somewhat rare. The gearbox issue is the central one, you will be served well to completely study the subject before you select a make of car. The more time you spend on this subject the happier you will be in the long run.

Hi and thanks for the feed back, you both make very good points. My plan for the car is to go for nice drives on the weekend. I don't believe that I would need any more than 400 HP to do that and plan on a 289 or 302 as the power plant. Given that, it seems that a Renault, Porsche ot Audi transmission would be fine. I notice you feel that the Renault trans has a better gear ratio spread and I don't doubt that your right. But, I live in southern California and it has been years since I've seen a Renault on the streets. So I have concerns of the availability of the transmission (used rebuilt etc.)and getting parts if needed. I also fear that if I selected a Porsche transmission that it would be very expensive because it says Porsche on it (Porsche getting top dollar for everything they sell, I used to have a 911). So that leaves Audi. Do you know of anyone using an Audi transmission? If so, what year, make model of car did it come out of? Also, I don't want to exclude the Renault or Porsche because I just don't know if my speculations are right. Could be Renault transmissions are plentiful here in CA. I also like the fact that you can use the Ford flywheel, preasure plate and disk (agree with you whole heartedly on that). Sorry to ramble on here, but any more information would be appreciated. What I'm looking for is the specifications on the various transmissions, like - You can use a 1997 Audi 5 speed model C-5 etc. Thanks George

The Audi boxes are plentiful. In the US,
the type 016 came out of the 5000 series.
There are pleny of people using the Audi
box - Roaring Forties uses this as their
recommended basic set up. I'm sure a GTD
can be modified to use one.

The Renault box actually can be taken
from a DeLorean, Lotus Esprit, and, check
this out, the Eagle Premier (so I have
been told). Not easy to find, but not as
difficult as one might think.

(edit - I have gotten conflicting reports about
the '90-'92 Premier's having a Renault R25
transaxle, but the '87-'89 Eagle Medallion
definitely did.)

A Porsche G50 can be had for less money than
you think. Not as cheap as the Audi, but
not nearly the price of a ZF ($8K+ US!).
But, even beefed up Renaults and beefed up
Audis can run pretty high, and if you add
things like LSD, a used G50-50 may be a
bargain.

Again, you need to decide what's best for
your needs and wallet, and then check out
what kits will work.

Ian

[ May 02, 2003: Message edited by: Ian K ]

Pulsar1,

I'd say go with the Audi 016/5N that has 4th and 5th as overdrive. You can tell this one from the rest because the 5N will be stamped on a flat spot on top of the bellhousing.

And welcome to the forum.

Have fun!

John

Pulsar1 - please use the search function. You will find a lot of information under Audi, Porsche, or ZF transmissions. The Audi is also referred to as a Getrag or Gettrag (incorrect) but the info is the same.

Ron

[ May 01, 2003: Message edited by: Ron Earp ]

Ian k - Was the Eagle Premier a four wheel drive vehicle? Thanks. Best regards, Orin Meyer

It was a front drive only vehicle,using the same Renault trans as we all use in the GTD cars ,allbeit a lower spec /weaker version than the Turbo Renault or Turbo Esprit.
I have seen them available in Canada from time to time.

Pulsar1,
Come over to Lancaster and look at my setup.
942-8589
Nathan
427 side oiler
G930 trans

There has been a lot of dicussion about a Audi 6 speed in the works. This just might be the way to go for you. There is nothing wrong with audi's, in fact they are by far the most cost effective way to do this. The lower rear end ratio might not be a problem for you , I just wanted to make you aware how important this issue might be for some people. You also might want to contact the RF guy here in the US,Gordon levy, on the RF suport page on this forum. He know's just about all there is to know about Audi gearboxes and I believe might have some news on a 6 speed audi. Renault's are availible also, a good person to talk to about them would be Mark Sibley, on the GTD page. He can be trusted to give you the straight stuff on these boxes. Good luck, you are doing the right thing sorting out the gearbox issue first. Again, My advice would be to buy the chassis that uses the gearbox you believe would be best for you.

[ May 04, 2003: Message edited by: Howard Jones ]