Bill W.

On my new-to-me 88' the Getrag tranny does not shift between 1st and 2nd and to a lesser degree 2nd to 3rd as easily as I think it should (and other 911's I've driven did). I suspect the syncros are in need of replacement but I'm not ready to do that at this time, (read $$).

On the BMW K12 motorcycles they use Getrag trannies (I know they're not the same.) and originally BMW said not to use Synth. Gear Oil, then BMW came out and recommended Synth. and the bike went from shifting moderately smoothly to shifting silky smooth, a night and day diff. This was not just my opinion, it's been extoled on several lists I monitor.

My thought is to change the tranny gear oil to Valvoline 75w90 Synth. gear oil and see if that buys me some time before I have to have the syncros replaced. I've seen no mention of synthetic gear oil in a 911 mentioned anywhere.
What are the thoughts of the folks here on this idea? Any other suggestions?

Bill W.

Geoffrey

I switched from Swepco to Redline synthetic in my G50/50 and noticed little difference. If you do change the trans oil, be sure you get the right oil or additives if you have a LSD. I called Redline directly and they recommended a blend of their products for me since the G50/50 has an LSD.

Steve Weiner-Rennsport Systems

Hi Bill:

All things being equal, the G-50 transmissions shift better with a good synthetic over a dino oil.

We've had great luck with Mobil 1 synthetic gear lube, 75W-90. Just be gentle until you overhaul that thing,....

Dave Thomas

My '88 Carrera had fresh 90w gear oil in it when I bought it, and it shifted great; of course part of that is the low milkeage (61K miles). I later changed to Mobil 1 75W-90 and it shifted essentially the same. With the arrival of colder weather I feel that it's probably shifting a little better when cold than it would be with the dino oil, but that's just a guess. Overall I'd say there's little difference in performance, but I would expect that the sunthetic is protecting things better.

Bill W.

Thanks for the replies. If I can find one of the premium Synth. 75w90's I will use that otherwise it will be the Valvoline or Mobil 1 brands.

Hopefully I'll get it overhauled before spring.

Thanks again,
Bill

ron mcatee

I used Valvoline and Redline in my 88 Carrera G-50 and shifting was OK. I read on one of the threads about Mobil 1 working better in the G-50 and tried it. Remarkable change. Shifts very smoothly and goes into 1st easily from 0-10 mph.

Spider911
88 Carrera

Bill W.

Will be picking up 4 qts. of Mobil 1 Gear Oil on my next stop at the auto parts store. Thanks again for the advice.

Bill W.

Biotron

Ditto,
Thanks Spider911. I just put in redline and did not notice the difference I expected. Hard to go into first gear when its cold. I already use Mobile One in the 3.2 and love it. I'll give it a try and post the results.

Galen

Bill W.

I replaced the tranny gear oil w/ Mobile 1 75w90 and it seems to shift much better even in our cooler weather, thanks for the tip.

Reading the 101 Projects Book (what a great marketing idea) I found the Shifter Bushing Kit replacement and will tackle that next.

As a diagnostic tip, the tranny shifts from 1st to 2nd MUCH better when RPM's are kept under 2.5k than it does at 4k RPM or higher. My instinct tells me this may be indicative of either a tranny/motor mount problem or the shifter bushings, does this make sense?

Thanks again,
Bill W.