New Diff Ratios available for OI6

Lynn Larsen

Lynn Larsen

It'd have to be rear engine if he wants a 4 wheel drive GT40. The $64K question is if the R&P can be flipped in the Audi to get proper half shaft rotation. He will then have to deal with what ever the resultant rotation of the torque tube going to the front would be. I assume this would be taken care of by the front diff. This isn't going to be a trivial undertaking if, indeed, it is even possible.

If this is really what is desired, I think the better approach would be a Porsche C4 drive train. No need to change anything, just adapt your engine to the transaxle. Oh and adjust the length of the torque tube.

Thanks Lynn

Now that I think about it, I think you're right.
What do you call those V-8 Fieros that run the engine/transaxle tranversely in the rear?


Lynn Larsen

Lynn Larsen

Bye the way, while the Porsche drive train would be infinitely easier to engineer, good luck getting a rear engine setup under the rear deck of a GT40 body. But, I guess you never said it was a GT40 you were building; we all just assumed.

So, what is it, exactly, you are trying to build??

Thanks guys for your replys, unfortunatley its not a GT40, its a Lamborghini Countach shell, with no chassis ,at the time i bought the body shell many years ago nobody here made a decent GT40 Shell, or they would only sell me a turn key,and i had not won the lottery,
I did mean to say mid engine, so far i have a lexus 1uzfe 4l v8, i have had an adaptor plate and flywheel etc made up to suit the 016 box, i have collected several 2wd and a 4wd box,so could use either, then i thought 4wd might be possiable, i have wrecked a 91 Soarer for all the parts, and have modified the front uprights, by taking out the front bearing i can install a Supra Rear upright bearing assembly, and end up with a 4wd front hub.I have worked out i can get a drive shaft up the side of the v8 and up the centre tunnel to a diff,just gotta work out a right angle drive chain/transfer case to run from the Audi 4wd rear flange, but before i go down a 4wd path im trying to find out how the audi box works, does the power from the engine go to the centre diff and then on to the main diff, the engine in stock from produces 250hp don't want to break the centre diff any thoughts, or sugestions

Lynn Larsen

Lynn Larsen
Well, Mike I was wrong and you were right! Mike is also right in that a number of transverse drive transaxles use a chain drive to take the power down to the the diff and/or tranny/diff depending on the design. At least the ones I am thinking of look like they have a chain drive housing. This is something you might want to look into Graeme. To be honest though, I am not sure that driving the front wheels is going to buy you much over a mid engine/rear wheel drive. A mid engine just hooks up so much better than a front engine or rear engine design. But you would certainly have a one of a kind! I don't recall any other mid engine 4 wheel drive vehicle.

Since the Audi, apparently, doesnt use a transfer case, I would imagine that the aft facing flange is connected to the same shaft that the pinion gear is (would this be the secondary shaft?? I don't know the proper termninology). When I say transfer case, I am thinking of a classic 4-wheel drive where the output of the transmission goes to a transfer case (could be mechanical or viscous) and then propeller shafts go from the transfer case to the front and rear diffs.

I am just guessing and thinking out loud. I don't have any direct knowledge on this, so I suppose I'll just say good luck and let someone who KNOWS help you out.

That does sound like an interesting combination, but the front drive shaft will be very long and probably go through part of the passenger compartment.

My best advice is to get the matching Audi rear differential for the front. I think that is your best chance of getting all of the wheels to spin at the same rate.

An interesting thing for you to look at would be the Diablo VT setup. Seeing how Lamborgini did it will probably give you a few ideas.

I think you may discover that simplicity is a virtue and the road less traveled is often a dead end.

Ian Anderson

Lifetime Supporter
Only car I have heard of being mid engine 4 wheel drive was the Metro 6R4 rally car.

If memory serves me right they took the front drive back through the gearbos - back through the engine sump then onwards to the front wheels.

Never got to look at the mechanicals but saw then at rally cross and accelleration was incredible - something like 0-100 in 10 secs on dirt!


Robert Logan

Defunct Manufactuer - Old RF Company
Well therices are out !!

The cost of a complete Ring and Pinion (including pinion shaft) is US$ 1800 a set and this is if I order TEN.

They are not cheap but this is at MY price and does not allow for R&D that I have had to do. I will be ordering a couple for myself so another 8 needed. Please contact me as soon as posible.

Best wishes,

I figured up the ratios on
Here is a AFC box (which is the best box you can get in the US and normally has the 3.89 R&P) from a Audi 5000. This is with Roberts new R&P.
Transmission Ratios:
1st: 3.60 2nd: 1.94 3rd: 1.23 4th: 0.90 5th: 0.72

Tire Diameter 1: 26.23 inches
Rear Gear Ratio 1: 3.11:1
RPM 1st 2nd 3rd 4th 5th
1000 7 13 20 28 35
1500 10 19 31 42 52
2000 14 26 41 56 70
2500 17 32 51 70 87
3000 21 39 61 84 105
3500 24 45 71 98 122
4000 28 52 82 112 139
4500 31 58 92 125 157
5000 35 65 102 139 174
5500 38 71 112 153 192
6000 42 78 122 167 209
6500 45 84 133 181 227

Here is a 5N box, which is the most common US box(normally 4:11) with Roberts R&P.
1st: 3.60 2nd: 2.13 3rd: 1.36 4th: 0.97 5th: 0.73

Tire Diameter 1: 26.23 inches
Rear Gear Ratio 1: 3.11:1
RPM 1st 2nd 3rd 4th 5th
1000 7 12 18 26 34
1500 10 18 28 39 52
2000 14 24 37 52 69
2500 17 29 46 65 86
3000 21 35 55 78 103
3500 24 41 65 91 120
4000 28 47 74 103 137
4500 31 53 83 116 155
5000 35 59 92 129 172
5500 38 65 101 142 189
6000 42 71 111 155 206
6500 45 77 120 168 223

Sorry bout the way some of the numbers slide over but hey your getting this info for free !
Some of the tires I looked at for my RF are a shade smaller in Dia. than 26.23, but real close, I went with the same as on Garys chart. From what I understand the 944 turbo 3:37:1 wont fit the 016 box, one of our forum members bought one and tried it. regards, Dan
Gary here is Jim Downard's previous post on this board :
"O.K. guys. Scrap the 944 Turbo S ring and pinoin swap. The bearing cage is larger and won't fit in the transaxle housing"
or Rolf Brunkhorst :
"Just an update on switching the ring and pinion gear from a porsche 944 into the audi 016-it won't work."
Search found these for me, and thanks again guys for the hard ground work. Dan
I don't know if this has been answered before, but I wonder why the 944 parts won't work?

I asume that the ring gear will bolt up, but the pinion does not fit.

So, the question becomes why not have a 944 pinion gear ground to Audi size?

If it's possible, that should cost a lot less than $1,800 and you might be able to find new 944 gears to modify.
Been away for quite a while since my last post, but thought I'd chime in after reading this thread. The 944T R&P would make the 016 into a reasonably well suited trans, ratio wise. I ran the ratios for the 5N with the 3.375 R&P, and they look quite good; better so than the 5U. I've heard mention that Porsche increased the size of the differential bearings to cope with durability issues, but it seems, dare I say, hearsay. As time allows, I'll try digging a bit deeper to see if I can come up with an answer.

Hope the following (useful?) information doesn't get scrambled when posted; for your viewing enjoyment. BTW, I prefer net ratio's, as it is easier to compare against each other, FWIW.

Audi 016-5N w/ 944T 3.375 Diff (the following are net ratios)
1st 12.15
2nd 7.19
3rd 4.59
4th 3.27
5th 2.46

Stock Audi 016 5N 4.11 Diff. (net ratio's)
1st 14.80
2nd 8.75
3rd 5.59
4th 3.99
5th 3.00

Audi 016 3U 3.89 Diff. (net ratio's)
1st 14.00
2nd 7.31
3rd 4.63
4th 3.27
5th 2.49

For comparisson:
Porsche 944 Turbo (T&TS) (net ratio's)
1st 11.81
2nd 6.95
3rd 4.73
4th 3.49
5th 2.79

Corvette Z06 MM6 3.42 Diff. (net ratio's)
1st 9.09
2nd 6.09
3rd 4.45
4th 3.42
5th 2.53
6th 1.71

Porsche 915(late) 3.875 diff. (net ratio's)
1st 12.33
2nd 7.11
3rd 4.89
4th 3.73
5th 2.94

Again, Jim Downard invested hundreds of dollars in the 944 3.375s R&P (and they are hard to find) ,and tried anyway anyone could come up with to make the set work. Jim Please chime in and Rolf since for some reason people dont believe me! /ubbthreads/images/graemlins/mad.gif
What about the other gears that are on the pinion shaft? My overhaul manual says that they are a press, shrink fit and cannot easily be changed. If that is the case that would make it difficult to install the 944 R&P in the 016 box even if the bearing difference could be fixed.
Well, I have never disassembled a 944 trans, but it would seem to me that the gears on the pinion shaft ought to be removeable in order to service the big end pinion bearing. The only gear fixed to the pinion shaft is 5th via a spline.The 1st and 2nd hud is free to slide on the pinion shaft spline. This is what I see in the manual, and is quite similar to many other transmissions, in that regard.

Being an (anal) engineer, I would sure be interested in some real data. Someone telling me "it won't work", or "it won't fit", is just not enough information for us engineering types. :) I Would like to hear details about Jim's experiences.