Big D

The previous owner put Mobil 1 75W90 in the transmission of my 84 Carrera. I have the "usual" trouble getting into 1st and 2nd gears. It's not bad, just takes two tries with a little more force about every other time I shift. I'm wondering if switching to Swepco 201 would help the synchros in this 915 transmission slip into gear a little more easily.

Thanks,

Big D

fixnprsh

Mobil 1 gear oil is top grade, overkill IMO as I used to put it in all the GT3 cup cars............but its synthetic and from what I hear it is not good for a 915. I have used swepco in 915s and never had an issue when the owner knows how to drive.

It might be in there already from the previous owner to try to cure a problem as I know its not cheap. So I dont think there would be much differance in switching now to Swepco as the damage could be done already

Edward

Hi BigD,

From what I've read regarding 915s vs G50s, the former is better suited to dino oil because of the differences in synchros (though I don't know if it's due to synchro design or material). Apparently, synth in the pre-G50s is "too slippery" and thus doesn't let allow the synchros to do their job as effectively while the G50 is designed from the get-go with synthetic as factory fill.

Now as for my SC's 915, it shifts perfectly with Swepco201 with absolutely no bind or hesitation into 1st/2nd, but I have never tried anything other gear oil to compare it to. Likewise, my 993 shifts perfectly and it has had only Mobil1 for most likely all of it's 96k miles. If I were you, I'd most definitely put the Swepco in your Carrera. The Mobil1 is NOT an upgrade if one's tranny isn't designed for it. If your problem doesn't improve, you may want to check all the linkages to make sure they're not sloppy or out of adjustment. Hope this helps.

Edward

Brian_77_3.6

I had Swepco put in my 915 gearbox about a year ago when I had similar problems to what you describe. I think the shop had put Red Line in previously. The Swepco was the cure. Shifts Great and I can even get into 1st gear while rolling at a pretty good clip.

84_Carrera

PO had Mobil in there, I swapped out to Swepco, no real difference in the 1-2 shift after ~5 mo. & 3k miles or so. In my case, looks like a rebuild someday.

Gost

I had the same experience as Fred. No big difference yet in a month and about 500 miles. Perhaps a bit more drive time may help. The new shift cup bushing I installed last week made a nice difference!!

Steve Weiner-Rennsport Systems

Big D:

Swepco is the preferred lubricant for the 901-915-930 transmissions due to their baulk-ring type syncromesh. Synthetics are too slippery and will accelerate wear.

Mobil 1 (or other good synthetics) are better suited to the G-50's Borg-Warner type syncromesh,......

All Porsche gearboxes require a GL-5 type lubricant (Swepco & Mobil 1) to protect the extreme hypoid angle, highly stressed ring & pinions.

Hope this clarifies things a bit.

bbh03

Is it worth putting synthetic into a rebult 915? I don't know if replacement synchros are better suited to it than the originals or if they are the same material/manufacturing process...

JackOlsen

They are the same. Use Swepco.