Otto Mechanic

I've been able to put a few miles on my recently restored '89 S2 and I've noticed it's very stiff going into 2nd from either direction. The transaxle was pretty much completely rebuilt during the 2 years I've been restoring the car, with the addition of a re-built ZF LSD, "short" 5th gear and transaxle oil cooler. While the gearbox was apart it was inspected by someone I consider to be the foremost expert on them in the SF Bay Area and I don't have any complaints about it other than this one. I also installed an Only944 short shift kit, could this be a known characteristic of that kit? I know there are two possible configurations for the kit, with use of the top slot in the linkage recommended to reduce side to side motion by 30% and wonder if that may be a factor? I did follow the recommendation.

I'd like to know if others might consider the 1st to 2nd and 3rd to 2nd transitions slow on their gearboxes? Mine is the AOS box. I don't have any prior experience with it, so I'm sort of blind, but it seems stiff.

Are there any thing's I should be looking into that could explain it? I'd like to make shifts into 2nd faster if I can.

Thanks,

thomasmryan

how is it when the oil/case gets up to temperature? does double clutching help? the syncros rely on friction so oil too thick or too thin doesn't help match the speed of the three parts that are meshing.

of course, a decrease in throw lessens your mechanical advantage.

Otto Mechanic

Thanks for your reply Thomas.

I haven't noticed a difference between a hot and cold transaxle. The linkage is stiff when I drive it from the shop to the street, and equally stiff driving back to the shop after a two hour spirited drive over the CA Central Coast range between Cambria and El Paso de Robles. I did the last test on a day that was over 104F ambient and from a starting temperature of less than 90F ambient (shop temp on that day), so I'm inclined to think it isn't temperature related unless the transaxle cooler is much more effective than I thought?

It sounds as if I might consider moving the linkage to the lower position to increase my mechanical advantage, but I don't understand why 2nd would be different from 3rd, 4th and 5th in performance? Those shifts are quick and positive.

PS: to put it in terms almost everyone can relate to, shifting from first to second, or from third to second, feels just like shifting from second to first when the RPMs are too high to engage. It's as if I don't have a synchro on that shift. Is that normal on an upshift?

PPS: No, I haven't attempted double clutching since it was my understanding the AOS box has 2nd gear synchros? If not, I don't see double clutching as a technique that would improve shift speed. It's not that it doesn't shift, or that it makes bad noises, it just feels like shifting in liquid metal.

PPPS: I'm using 90 weight gear oil in the gearbox, fresh from the re-build less than 500 miles ago. It's what I believe to be the Porsche recommendation but I can verify the brand if that might make a difference?

Regards,

Otto Mechanic

The more I think about this, the more I suspect the AOS box doesn't support 2nd gear synchro? The alternative seems to be that the synchromesh for that gear has failed. The response to the problem is very different so it would really help if someone could validate one or maybe provide a conclusive test for the other?

Otto Mechanic

OK. I suppose I'm facing reality. My AOS box needs a new 2nd gear synchro. Oh well.

harveyf

Scott, I would at least try a selection of different tranny oils. Offers a cheap set of experiments. Redline comes to mind but there are others. I would also try putting in the OEM shifter, if you still have the parts. I have one of Lizard short shift kits on my 928, installed by the PO, and I have never been totally in love with it.

Jfrahm

Concur on putting in the OEM shifter. If it's not clunking/grinding I would not suspect the synchro. A worn synchro would have been replaced, should have been evident. Plus it'd make for slower, deliberate shifts to avoid a little grind and not (in my experience) more difficulty moving the shift lever.

Before draining out all that gear oil maybe try shifting it at the trans end, see if you can see/feel the shifter binding. It looks pretty unforgiving.

951and944S

It's possible that the synchro is new and/or of passing the manual gap clearance spec and it's doing the best it can because

a) some other component clearance is too tight, keeping the shaft synched partially to an opposing speed
b) clutch not disengaging fully and allowing input speed to main shaft to slow.

a) to test synchro, with parking brake set, engine idling smoothly, watch tachometer closely and listen carefully to engine tone.
without touching clutch pedal, move shifter in position to ready 2nd gear
pull first slightly, then incremental increasing pressure to engage 2nd
engine note should change and possibly a drop of a couple hundred rpm

b) Get a helper that you trust to work the pedal with engine running and rear of car raised.
Remove large rubber inspection plug at rear mounting flange
Note how quickly shaft/coupling stops turning when command to press clutch pedal is given

T

marc abrams

Scott, I'm in agreement with Harvey on the oils too. BTW I'm using Redline MT-90. The shorter shifter handle don't help matters ether.

Otto Mechanic

I wish I had more experience with the OEM shifter, I should have thought of this before the restore. I drove the car from my house in Jackson WY to the WYDOT to get it registered right after I brought it in from Florida, all of maybe 6 blocks, before putting it in the shop for two years.

I do know the OEM shifter needs a rebuild, ala Michael's "Transaxle linkage rebuild project" (https://rennlist.com/forums/924-931-...d-project.html), but I'd decided to just replace rather than rebuild at the time. I did keep all the parts naturally so I can still go back and rebuild it, though it would take some time.

I'll try T's experiment first as soon as I get back to the car. I'm up in Santa Cruz this week getting ready to move another batch of equipment from the old shop to the new, as well as rebuilding the smog pump on my 928 while I'm here, so it'll be a few days before I can try it. After that, an oil change, then the OEM linkage replacement.

Thanks for all the ideas. Lot's of new things to look at,

Tom M'Guinn

First to second is stiff in my car too, and has been on three different transaxles, including my current Kevin Gross-rebuild with "S" hardened gears. Wish I could tell you why...

PaulD_944S2

Scott, what shape is the linkage on the trans in? You might want to consider cleaning and lubing it. It's out there in the dirty underside of the car!

Otto Mechanic

Good to know Tom, maybe Kevin will chime in, I hadn't thought to ask him personally. The fellow who did my rebuild is local but he's known to be an expert on Audi transmissions, his shop is in San Jose CA, Sprint Auto Works, a fellow named James Osborne. I haven't been able to take the car over to him since it's in Paso Robles now and he isn't

What version of transmission are you using? Mine's the AOS that came stock on the '89 S2, only changes have been to add the ZF LSD, short ratio 5th gear, and the trans oil cooler. Kevin helped with the cooler installation by sending me the gaskets I needed.

Otto Mechanic

Hey Paul -

Clean as a whistle. The shift linkage itself is new, that's the Only944 short kit, but the whole transmission was degreased and power washed before I took it in to the shop for the re-build.

I guess you didn't have a chance to get down under the car and look since we were mostly checking out the new body work.

jhowell371

Hey Scott, looks like you got your wrong key problem fixed. My S2's 1st to second shift is also stiff, slow or whatever. It never grinds but it doesn't shift as slick as 2nd to 3rd on up. I usually never floor mine in first gear because you wind thru it in the blink of an eye and face that slow shift to second. I just get it rolling in first and shift into second and floor it and let the 3 liter's torque go to work First gear is like a granny gear in an S2, almost unneeded. These things don't seem to like being speed shifted like an old Muncie 4 speed. Fifty years ago I used to shift my 4 speed 396 Chevy with my right foot jammed to floor. Still have a toothless input gear from such shenanigans kicking around somewhere, it made a good clutch alignment tool over the years for those 1 hour clutch changes, best record was 45 minutes