another transaxle question

John · 02-13-04, 09:56 AM

Hello again everybody!

Well, I've been using the search function and the FAQ to learn more info about building a GT40 and have found tons of great information! Great site!

I have come across one question that I haven't yet been able to find an answer to. Maybe I'm not searching for the proper terms and if this has been covered over and over again I apologize. I see that transmission questions are pretty frequently raised.

So, background to my question then is this...

When I build a GT40, I of course want a stout transmission that can handle some power (nothing outragous, just a trans that I don't have to worry about grenading every time I let the clutch out quickly). I also want a transmission with a fairly short first gear with an effective ratio of around 10:1 so I don't have to slip the clutch so much to get moving. Finally, I would like a very highway-friendly top gear so that I can comfortably cruise at 65-70 at a relatively low rpm (2000-2500rpm perhaps?).

So, I have found great posts outlining gear ratios for various transmissions. The G50/50, several other of the "G" boxes, RBT, and a few other boxes look like they offer great ratios and fit the bill.

So, finally, the question that I have is this...

Among all the posts I can't seem to find many people asking "which of these transmissions will fit?" So, I don't yet have a GT40 kit to build... and I suppose part of my consideration of which I will buy would be which transmission will fit the car (and how much that trans will cost).

So, can anyone help out with information about which boxes fit which kits?

Thanks a bunch. Sorry for the post being long, just wanted to lay out all of the facts so you know where I'm coming from.

John

jimbo · 02-13-04, 10:47 AM

The best way to find out what fits is to ask the manufacturers of the various cars what they recommend..having said that, here's what I know:
ERA use ZF boxes. Period. I have never heard of them using anything else unless they may have used a T44 for the few Mark II cars they built..but T44s would cost about the same if they were made of gold. [img]/ubbthreads/images/graemlins/grin.gif[/img]
RF cars I believe use Renault boxes, or Audi/Porsche boxes. So do CAV. The cars which were formerly called GT40NZ (kind of like 'the artist formerly known as Prince') used Renault boxes when I was looking at them.
Either of these types of units can be set up to work well in GT40s. The one thing we don't seem to see is a lot of complaints about transmission failures, and given that a lot of the cars are raced, this seems to be a good thing to me. The UK guys, especially Frank Catt and Martin and Malcolm, are running the Renault and Audi/Porsche boxes, I think, and know a lot about setting them up and getting them to live without turning into metal paste.
The ZF units are robust and can be had in a variety of ratios- essentially what you do is call RBT and order what you need. There are also a limited number of BMW M1 units available, and they are good, but the cost is higher than from RBT and you have to have them converted to RHD. Now, for a car which was LHD, the M1 unit might be a good alternative.
One of the quirks of GT40 ownership is that if you wish to use a ZF box, the transmission will probably cost you a lot more than the engine. I don't think RBTs prices are at all out of line for what you get- these units are rare and parts are not cheap. Every small-block GT40 that finished LeMans used a ZF box, albeit with an oil pump and separate cooler, so to say they are durable understates the case. If properly cared for, they are very very tough.
I don't know much about the Quaife units. They cost a LOT, they are all new, and they are probably terrific. Are they worth 1.5 or 2.0 ZFs? Not to me.
Oh, and an aside...a few years ago I talked with Harley Cluxton, who bought 1075 from the Gulf Oil Co and owned it for a while before selling it. I asked him what it was like to drive..Harley had owned several GT40s and I thought he would have an interesting comparative view of it. He said 1075 had the smoothest shifting ZF box he'd ever driven in a GT40. I know it had several engines, all race cars do, but I have often wondered if 1075 won TWO 24hr races using the same ZF transmission. I hope they changed the fluid at least [img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img]

Ron Earp · 02-13-04, 11:25 AM

Here are combinations that I've read about:

ERA - ZF
RF - Audi/Getrag, ZF, RBT
DRB - Porsche
GT40 NZ - Audi/Getrag
CAV - Audi/Getrag, ZF, RBT I think Gary has
GTD - Everything and then some

But, basically any unit can be used in any car. When you call the company they'll just ask you which you want to use.

Lee · 02-13-04, 11:47 AM

I agree with Rons list, except I undertand that NZ is 'usually' Renault.

John · 02-13-04, 12:23 PM

Thanks a bunch for the information guys. That is exactly what I was looking for. [img]/ubbthreads/images/graemlins/smile.gif[/img]

At this early point in my research of kits, the ERA and RF kits appear to be the front runners for potential purchases. I'm not familiar with a few that you mentioned though, so I'll look into those. (GTD, DRB)

Anybody know if the Tornado kit can use pretty much any transmission as well?

I suppose I'll start looking around for prices then and see what I'm in for! [img]/ubbthreads/images/graemlins/tongue.gif[/img]

Thanks again.
John

Bill Bayard · 02-14-04, 09:44 AM

John,

FYI, DRBs are specifically setup for the G50 series Porsche

gearbox. Not cheap, but quite sturdy.

One thing to be aware of, is that different cars and

gearboxes are setup for particular shifter locations and

linkages. Some are rod, some are cable, some

are a combination of both. Then there's the issue of left,

center, or right hand shift. Conversions are always

possible to whatever configuration your heart desires, but

some are far more complex and more expensive than others.

Generally speaking, it's best to stick with whatever box

that the chassis is designed to accept easily.

Bill

Lynn · 02-14-04, 08:44 PM

I know of one guy in Texas that was putting a ZF in a Tornado. If you are fairly mechanical and can use a welder or have a shop that can do it for you just about anything is possible. The one big difference is wether the transaxle is inverted or not. The Porsche and ZF are and this puts the engine lower in the car. A car designed for one of these will probably be easier to change around with. This is not written in stone mind you as RF, as you see, has had a pretty wide variety of gearboxes. The main limiting factor is the length of the transaxle. There are other transaxles that would work, but are just too long to fit. One thing to keep in mind with torque ratings is that few were rated where they were going into a car as light as the GT40. I think this is why the English guys have been so successful using Renault transaxles that don't have near the torque rating of some of the others. Building a midengine car has never been easier, believe it or not, the transaxle choice has always been the crux of the problem and there is more choice now than there ever has been before.

Lynn

Bill Musarra · 02-15-04, 11:49 AM

I think what we need now is an article(s)or responses on:

1. Adapting the various transaxels to the Ford engine.(Whats required and who can do it)

2. Adapting the Ford/Porsche/Whatever starters to this setup, snf why would you do it.

3. Adapting the different clutch/flywheel setups, input shafts, and throwout bearings.

They coiuld be put in the FAQ, or the Articles section. These would be invaluable to all and would straighten out guys with ideas of adapting strange combinations.
I was all hot to give up my 930 for a 996 6 speed (could of been had for about 3K with 1300 miles on it).Then I found out that I could do it but wouldn't have a way to start it. At least that is what the guys from Renegade Hybrids told me. I know they are quite knowlegeable as they do conversions all the time. They also have the setup to flip the ring and pinions on the Porsche setups. Requires some milling and grinding. The info now will save me the questions when I reach that part of the build (which should be in a couple of weeks)
Bill

John · 02-15-04, 08:42 PM

good points! I hadn't thought about the potential problems of fitting a starter motor into the picture with a different type of trans. I also had not taken into account the fact that with such a lighter car the load on the transaxle would be reduced.

Thanks again!

Another question raised though... if certain transmissions requiring different adaptor plates require the engine/trans combination to be mounted slightly differently in the engine bay, does this mean that one has to custom fab their own engine mounts?

I suppose with respect to that question though the same rule applies... certain manufacturer's cars are set up for certain transaxles and the mounts reflect that.

John

Howard Jones · 02-17-04, 02:23 PM

The starter problem can be solved but would require a little, maybe a lot, enginneering. But then the thinking is all the fun anyway. My first idea would be to use a gear reduction starter with the correct throw and gear to match your flywheel and make your own adapter mounting plate.

This whole area of discussion is a prefect example of why these cars are not "K.. C..." As I said a few months ago I will not be using the "K" word anymore.