DHC6

I just recently installed a 951 transmission into my S2 (blew the diff in my S2, thought it was better to just change the transmission). I know of course that the 951 transmission comes with an LSD, and oil cooler (basically the reason why I chose it over an S2 transmission), but is there a difference between the gear ratio's? if so which one do you guys prefer?

docwyte

Yes, you'll notice that the 951 has much taller gearing. At 80mph you'll turn 3100 rpm vs the 3600 rpm the S2 trans does.

This will give you better gas mileage at the expense of acceleration, particularly since you're car doesn't have the power and torque that the turbo cars do.

Also, not all 951 transmissions are equipped with lsd and coolers, so you better check...

JET951

As docwyte has mentioned , the diff ratio is quite a bit higher on the 951 transmission than a S2 , we recently fitted a spare 951 transmission to a customers 944S2 to keep his S2 mobile while we repair his S2 transmission , it really made the S2 feel quite sluggish , around town it felt like it had lost a lot more pickup than the percentage of difference in ratio would suggest , put it another way , I would not contemplate fitting the 951 trans as a permanent thing in a S2

Regards
Bruce Buchanan

DHC6

ah, crap, really? not happy about that now. Kinda stuck with it now. Well at least I know for sure that it has an LSD and oil cooler on it saw it before it went in. I haven't really had a good drive it in since I installed it, but I thought it felt a little different, a little less snappy... shoot. Of course now that I won't cry if it fails, it will last 20 years... Nothing I can do now, except for figuring out how to get more power...

alxdgr8

Love my LSD S2 trans in my 951. Not sure how it would be the other way around...Spencer has a 951 trans in his n/a 944 and says it's not too bad.

Definitely check to make sure you do in fact have an LSD though. LSD was optional for 951 trans, and you could get them with coolers w/o LSD's too. Jack up the rear and if both tires spin in both directions you do in fact have LSD.

Buckaroo Banzi

Just a thought why not remove the ring and pinion from the S2 and install it in the 951 transaxle? check search it has been done before.

-BB

DHC6

hmmm, that might be an idea. thanks. wasn't sure I could do that.

333pg333

You know what you could do though? You could transfer the ring and pinion from your S2 into your 951 tranny and that would effectively bring it down to very similar to your old ratios...but you would lose a bit of outright top speed. We have done this on our 951s and it really brings them to life. Of course this would depend on the condition of your S2 r&p, but well worth considering.

cb944

Slightly OT, but what sort of acceleration advantage do you get by swapping in the S2 ring and pinion on a 951? Do you lose much top speed?

dykaar

Here is a link to a transmission ratio comparison.:

www.924.org/techsection/PorscheTrans1.PDF

I haven't heard much about mixing and matching ratios, other than a small final drive pinion can shear off teeth (catastrophic failure).

Regards,

doug
Waterloo, Ontario Canada, eh


86 951 (http://www.pcaucr.org/index.php/visu...egory&catid=61)
01 E320 (W210) 4matic Wagon (http://www.benzworld.org/forums/w210...body-do-2.html)
00 540i-6 (http:// http://www.trillium-bmwclub.ca/forum...sp?postid=1916)
94 855 turbo Wagon (sold in 09)
85 535i-5 (sold in 07)
76 300D (sold in 92)
83 944 (sold in 86)
I apparently only buy cars designated by numbers

docwyte

Yes, you lose top speed with the S2 trans. If my memory is correct, the S2 trans in a 951 tops out at 155mph, the stock trans yields 180mph (if you have the power to pull it, which nobody does)

Oddjob

The S2 R/P can be installed in the turbo gearbox, but needs to be done by an experienced shop and may be price prohibitive (will be at least $1k and maybe closer to $1500). Anyone quoting much cheaper than that, does not know what they are doing and is not including proper setup/shimming of the backlash, depth and preload on the diff and pinion bearings.

The S2 trans R/P is approx 15% shorter than the Turbo 3.375 R/P. So at a given rpm the motor is transmitting 15% more torque to the rear wheels, 1st - 4th gear. That is what improves acceleration. The stock S2 trans has a taller 5th gear, .778 instead of the turbo .829 5th. So the S2 final drive in 5th gear is only about 7% shorter than the Turbo.

Speed at 6500 rpm in 5th with stock diameter tires is about 171 mph with the turbo trans, 158 with the S2 trans, and 149 with the S2 trans w/ short Turbo 5th.

harrisonrick

Oddjob knows his stuff. +1

I'd look into a 944S2 MAXHP chip by Russell Berry...it would definitely improve the slight lag you may feel in the low end....claim is 8-10 rwhp gains on the dyno.

I think Lindsey sells his chips too IIRC.

The 944S chip certainly smoothed out the "flat" spot in the S's low end torque curve on my car with 4-6 rwhp gains. (3000-3750 RPM area)

Oddjob

Of course, no AOS or AOT S2 transaxles came with the short 5th. They all came with the .778 5th gear. The 2.5 16V S used the .829 Turbo 5th.