tranny, is this a rebuild or adjustment?

[mr.flat6]

1981 911 sc. Upshifting from 1 to 2 sometimes results in gear grinding. 2 to 3 is good. 3 to 4 is good. 4 to 5 is good.
Downshifting from 5 to 4 is good, 4 to 3 is good, 3 to 2 is good, 2 TO 1 is terrible with grinding and lever will not ingage until car almost comes to a stop. All of this is somewhat intermittent.
So, are there bad syncros or is there some adjustments that I can do?

Thanks to all in advance.
Tx! john

[jwetering]

First thing's first - change your transmission fluid. Spend the extra $10 and put in the SWEPCO goop. It's a heavy equipment fluid that's particularly well suited to the 915 transmission that is in your car. I've heard many a man say that a SWEPCO fill has salvaged an otherwise crappy feeling 915. If that doesn't work...it's probably synchro replacement time. If the grinding happened in other gears aw well as 1-2 I might suspect a clutch adjustment....

[tmctguer]

i'm on the other side of the swepco issue. i'm of the opinion that a fresh change of normal tranny fluid accomplished much, if not all, of what swepco fans claim their product does.

mr. flat six IS on the right track, however. can't hurt changing your tranny oil to WHATEVER to eliminate exhausted oil as the problem.

if you go with swepco, report back to us and let us know if it cures your ills. who knows............you may convert me yet !

[old_skul]

Swepco mops up the competition. A friend "flushed" his tranny with Castrol for a week and then went to Swepco. There's a huge difference.

Six, for your problem, there's several possible problems:

1. Tranny fluid is old. Change it.
2. Transmission and motor mounts are old/broken. R&R.
3. 1st/2nd gear synchros are shot. They share a synchro, actually. Rebuild tranny or swap it out.
4. Shift linkage is old or needs adjustment - shifter itself, ball cup bushing, shift rod front bushing, or coupler bushings are worn. R&R.
5. Clutch needs travel & free play adjustment.
6. Shift fork in transmission is loose (seen this one myself). Open access cover and tighten.

If you cover all of these except #3 (and you should), you need a tranny rebuild. Want the quick answer? Double-clutch down into 1st sometime and see if it goes in without grinding.

[Wayne 962]

I personally don't use Swepco in my Porsches because every single tranny leaks, and I haven't had time to reseal them.

That said, everyone I talk to raves about how Swepco can make an old tranny shift like new. I have to think that all the people (and we do sell a lot of it too) can't be having the placebo effect.

From the advice of my customers, I would say that they are very, very happy with the performance of the Swepco 201 product. We also have this new 212 gear lube, which Warren specifically asked me to carry and stock. He must know something that I'm not aware of?



-Wayne

[Early_S_Man]

Mark is correct in that ALL of the related details need to be taken care of before deciding to rebuild/replace a 915! ESPECIALLY the clutch adjustment, because a dragging clutch disk (too little free play) can cause excessive wear on all of the synchronizer mechanisms, but epecially 1st gear!

However, no synchronizer assemblies are shared ... each of the five assemblies is held captive to each 'free' gear, and actually use five or six moving parts and the non-moving 'dog teeth' part that is pressed onto the gear to replace ONE Balk ring of the Borg-Warner type! The slider (operating sleeve) and spider ARE shared for the paired gears 1-2, 3-4, and 5th-reverse.

Gear oil was changed at the recommended 6000-mile service interval by very few owners over the years, unless the servicing was carried out at dealerships, and I am convinced that neglecting the gear oil was responsible for a majority of complaints (and actual problems) about 915 transaxles! The Porsche-patented synchronizer design is very sensitive to contaminants in the gear oil, and in spite of the praise and good results obtained with Swepco 201 gear oil, keeping clean gear oil in a 915 is more important than the brand of the gear oil!

[rstoll]

You described my tranny exactly. I have done the cheap flush/Swepco thing with some improvement. Recently dropped the Swepco and went to a heavier lube with better results. Still no downshift into first without a little clutching. Syncro time or just work around it. Personally I would just change the lubricant and use something like Valvoline. If you decide to rebuild afterwards you haven't wasted $50 on Swepco.