High torque transaxles....

Has anyone had luck purchasing a high torque rated transaxle for under $10k?? I can not understand why we are unable to purchase transaxles such as RBT, Quaife, etc. for under $10k.

I realize the G50 is an option, but the gear ratios that I have seen are not really optimal. The first gear that I have seen works out to over 13:1 and the top gear works out to 2.58:1 overall ratios. I would like to have ~10-11:1 first and ~2:1 top gear. It would work if you could change the final drive a bit (shift things down), but all that appears to be available in the aftermarket are different gear ratios (1st through 5th) and not the final drive (stock is 3.44:1). You could change all five gear sets I guess, but the cost would be high I would expect.

For example, G-force can make a magnesium cased transmisson capable of taking 1400 hp for just over $6k. And if you have seen Warren Johnson launch off the line you know it will take some serious abuse. This transmisson is way stronger then any of the above mentioned transaxles. So I add a diff to the case (aka T44) and to cost should jump to $16k to $20k?

Sorry just venting a bit.....

How about a refurbished (to as-new specs) ZF for less than $9,000 from Lloyd Butfoy?

That is not a bad option. What I do not like is that the bigest spread you can get for a ZF 5 is 3.47 first gear to last gear. I think for a engine with lots of torque a spread of ~5 to 1 is optimal. With a 3.2:1 diff ratio you get 7.1:1 (fairly tall) and a 2.05 top gear (nice cruise RPM on highway and nice top speed for the track). If you use a 3.7:1 diff ratio you get a good launch first gear and a bit high winding top gear.

My 0.02 anyway.
Thanks
Gary

Some G60 ratios:

993 Turbo (3.44 final)
3.82 2.15 1.56 1.21 0.97 0.75

996 Turbo (3.44 final)
3.82 2.05 1.41 1.12 0.92 0.75

996 Coupe (3.44 final)
3.82 2.20 1.52 1.22 1.02 0.84

And I dug up for G50/50 (3.44 final)
2.69 2.00 1.53 1.18 0.92

Ian

Thanks for the info. The numbers that I have for the G50/50 are different. they are:

3.154 1.789 1.269 0.967 0.756

I wonder which are correct.

Gary,

3.154/1.789/1.269/0.967/0.756....3.44:1 F/D,
are the correct numbers for the G50/50.
That's straight from the Porsche Factory
Tech Manual.
There are factory and aftermarket individual
gear ratios and ring/pinion sets available,
so the options are not as limited as you
might think.
I have thrown everything but the kitchen
sink at my 1987 G50 (Quaife ATB LSD)(500+ft/lbs of torque), without so much as a burp from it. I will be installing a stronger clutch disc and upgraded pressure plate sometime soon, but the gearbox itself, is very strong.
By the way, I would do some VERY careful measuring, before deciding on a G60. The extra gear(6th) means extra length, and clearance will be VERY close, if not non-existent.

Bill

[ April 24, 2003: Message edited by: Bill Bayard ]

You guys are correct. I think I pulled by
G50-50 numbers off of a quaife related
site - so it was probably some custom gearset.

Yeah, the G60 is a tad longer, though some
G50-50s and G50-52s are longer than a G50.
I also am not fond of how close the ratios are
on the G60.

Ian

Ian,

The typical rear mount on the G50 series gearboxes(late 1987 and newer) is a doughnut style mount, which needs to be exchanged for the older style(shorter/early 1987 and older) rear cover in order to fit into a 40. I'm not sure if the old style cover will fit the 993/996 gearbox. The doughnut mount can be machined off, if necessary, but it doesn't look too pretty. The difference between the G50 and G60 is about 1 1/2", which might as well be a mile, if there's only 1 1/4" of clearance!

Bill

Just got back from a fellows house in the area who owns a GTD with a G50/50. Nice setup. He has the older cover and cable shift, etc. Kennedy engineering adapters, etc. VERY stiff single disk clutch.

392 CI 351W making 440 RWHP. Has had the trans for about 25k miles including a good bit of road race track time. Has had no problems with G50. Only trouble was with CV and half shafts. He subsequently has gone to the 930 heavy duty units and has had no problems. He has even made quite a few on track sub 12 second quarter mile runs (best of 11.4 at 122 MPH). The street tires will not take full throttle until third gear.

I have taken a few photos and will put them up on my site this weekend.

G.

[ April 24, 2003: Message edited by: Gary Gibbs ]

FWIW I'm using a Renault box with the Derek Bell/Quaiffe internals and a Quaiffe LSD.

The same set-up is used in a couple of cars making over 500 bhp with no problems to date.

There are no chassis mods necessary on the GTD & it's much lighter and smaller than the G50 and ZF.

Apparentley the input shaft on the Bell/Quaiffe kit is actually larger than the G50 input shaft.

Full details at http://www.bell-performance.co.uk/

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Originally posted by Bill Bayard:
Gary,

There are factory and aftermarket individual
gear ratios and ring/pinion sets available,
so the options are not as limited as you
might think.
<HR></BLOCKQUOTE>
Bill, I have spoke a bit with Powerhaus II and they do not offer any other ring and pinion sets for the G50 (they do offer a great deal of gear sets though). Do you know specific vendors that might offer different ring and pinion ratios?

Gary,

During my research phase, I spoke to a half dozen or more G50 experts. One of them told me of two different ring and pinion sets,
other than the stock set. It's been two years+, so I'll have to dig in my files to see who it was, what the ratios were, and where to order them. I'll let you know ASAP. That's if I can find a record of it in my files. Keep your fingers crossed!.......
After digging through reams of paper, I found the culprit, sort of. I still don't know who told me about this, but Porsche
built 7:37 & 7:33 R&P sets for racing, but only in limited quantities. I'm still looking...........

Regards,

Bill

[ April 25, 2003: Message edited by: Bill Bayard ]

I have never installed a G50-50. However if the car you just saw was red and from Virginia Beach, take a good look at the effort that went into the installation. Some major metal cutting went on to make it fit. It is a nice set up and very strong. Just make sure you know how much work is envolved in the install!!

Bud, maybe you can talk Rick into joining
the board? I know I've tossd his name about
a few times, and it looks like Gary has seen
his car

Ian

I should have mentioned the board to him the yesterday. I will. Concerning the install, I have not seen the very back of a GTD for comparison, but would not be surprised that there was some cutting and rewelding, etc. On the CAV's the back section bolts on and would make alterations a bit easier. In his car the back section is part of the frame. He also lowered the engine about three inches and moved the engine as far forward as possible. His shaft angles are nearly perfect. Front to back he is dead in line with the wheels and top to bottom the shafts slope down toward the hubs a very small amount.

Bill,
I think what I would be interested in ring and pinion would be something like 2.75:1. I would guess they would not make something so tall (for the 911 racing crowd). The reason I asked is that the 2.75 would bring down first gear a bit and give a little lower cruise RPM with the stock G50 ratios. You can get close with the ratios offered by Powerhaus II for the 1st through 5th gears, but unfortunately would have to change 5 gears versus the ring and pinion only. Don't get me wrong the stock ratios look pretty darn good as is.

[ April 25, 2003: Message edited by: Gary Gibbs ]

In a bit of a different direction, the M1 ZF is a pretty tough piece...