GregBBRD

I, personally, like the "early" transmissions and would always prefer to drive one of these, instead of the Borg Warner design transmissions.

I'm certainly in the minority regarding this....most people like the easier shifting Borg Warner boxes.

I've been doing this for a long time and I drove 901 and 915 gearboxes for many years...both on the street and on the race track. I got used to the "feel" of these transmissions and like the feedback that this style syncro gives me. The "early" 928 gearboxes, with the "Porsche design" syncros are the same design as these gearboxes, so it's no surprise that I enjoy them.

I rebuilt a '83 for my son and gave him the choice of which gearbox he wanted in the car. Interestingly enough, he too likes the stock gearbox from the '83. He says that he likes the feeling of knowing that he is in a gear that this transmission provides.

If your transmission has relatively low mileage on it, I'd encourage you to have your own gearbox rebuilt and not "buy someone else's problems". Sometimes a "known" piece of equipment is better than something that is put together from pieces...

Andre Hedrick

Greg,

As an extra data point, the G28/08 I had before drinking the Borg Warner Kool-Aid was actually fantastic, and I only let it go when I got the G28/13 because I need the cash for other things. Now that I have another one (cause my new 12 is actually an 08), I plan on sending to you in a year (need more money) to have it rebuilt as my spare. Please check you PM's and reply.

Also in my first 928, which I put a rebuilt 05 in it, it was completely solid, and had a fantastic firm shift.

I have bank rolled about $12K in gearbox's of two cars during the past 11 years, and if I had it to do all over again, I wish I had met you earlier and my lessons would not be so expensive

GregBBRD

Yes, unfortunately, it happens.

The actual disassembly and reassembly of a transmission is fairly straight forward. Get a shop manual and follow the instructions....don't even need very many special tools.

The trick to them is knowing what wears and when it is bad. The shop manual doesn't give you many clues about this....they give you a syncro wear limit number. This takes years and years of looking at pieces and knowing what will work and what is going to not work. Keep in mind that I've done literally thousands of Porsche transmissions, in the 40 years that I've been doing this. No one in my shop, besides me, rebuilds transmissions....there is simply no way for me to pass on enough information to make that a wise thing to do. I take them apart, I clean the pieces so that I can inspect each piece, and I put them back together. Personally.

I don't cut corners. Never have and never will. When I put a part back into a gearbox, I "require" that each part, if treated reasonably, will last many more miles. I'm not the guy to take apart and "repair" a transmission for the used car lot....thankfully.

I can take apart an engine and actually tell you very little about the driving habits of the owner....unless he is a complete idiot. However, I can take apart a transmission and tell you volumes about how the owner drives.

No one told me how to check how much wear is inside a shift sleeve. I've never had a single minute of "transmission instruction" by another person. I had to learn this stuff myself....and that means that I put a few gearboxes together that shifted like crap, worked like crap, or were noisy and I "got" to take them back apart and study what wasn't correct.

Doesn't happen much, anymore.

I'm not unhappy about that.

GregBBRD

So you need pictures...

You know what that means, right?

Bradster928

Thanks Greg. I'll know more after I meet with my local guy on Feb. 3. Frankly, I don't see how tranny fluid and clutch adjustments will fix this issue, but I remain cautiously optimistic. This is my daily driver so I need it to be right/solid and I am willing to do whatever it takes. I really love this car even more than my 79.

Thanks again Greg, and everyone else, for your sound advice.

Bradster

blown 87

Yes, that helps Greg, and of course we would love to have any pictures that you wanted to post.
It really helps, like the ones you posted on the LSD build.

WallyP

"I'll know more after I meet with my local guy on Feb. 3. Frankly, I don't see how tranny fluid and clutch adjustments will fix this issue, but I remain cautiously optimistic."

Not to belabor the point, but you will probably find out more about your local guy's 928 knowledge than about the clutch/transmission problems.

Bradster928

Wally,

No doubt about that. I very much respect your opinion now and from my earlier 1979 928 days. (You were very helpful with an alternator charging issue.)

Anyway, I plan to print this post and take it to my apppointment so that he can have the benefit of the great information provided here. I have great confidence in this shop and, if successful, will make it known for any other Central Virginia 928 folks.

(I was going to wait until Feb 3 for my state inspection/appointment, but I will probably up the date to as soon as possible. As the weather has become frigid, the tranny is almost impossible to shift into second without grinding. Of course, I imagine the cold weather does not help the situation.)

In the meantime, take care all.

Bradster928

WallyP

If your guy is going to work on the clutch, I would suggest spending some time with search, and printing out several posts on adjusting the dual-disk clutch. If you you do end up having to pay for his training on your car, at least you can give him as much info as possible.

I do hope that he is already knowledgeable...

danglerb

If he is knowledgeable, somebody on Rennlist will know about them, so why not just post the shop name?

Just as a point of reference, Porsche switched to the single disc clutch because the factory trained dealer mechanics had trouble adjusting them.

GregBBRD

Bradster928:

There's not a much mystery to the dual disc clutch as this thread would lead you to believe. Once the clutches functtion, they usually work fine. It's mainly the installation process that makes people (and me) nuts. I've installed these things and had them not release, taken them out, looked at them, changed nothing, put them back in, re-adjusted the "H" stops and had them work perfectly. Obviously, something was wrong...but I had and still have no clue what that was.

The "visual test" to see if the clutch works is uber simple. Put the car in the air, with someone sitting inside. Remove the plug that allow access to the rear pinch bolt [find the torque tube....huge round tube....follow to the rear. Where the torque tube ends (black painted steel) and the transmission starts (aluminum) is where this plug is located....one straight edge touches the torque tube and the curved portion fits inside the transmission.] Have someone start the car. (Leave the clutch out, in nuetral.) Look up into that hole where the plug was and see the shaft spin. Have the person inside depress the clutch. The shaft should immediately (within a couple seconds) slow down and stop completely.

If this works, check the torque on the pinch bolt (62 ft lbs.), reinstall the rubber plug, and forget about the clutch.

There's also a quicker, non visual test.....

Your transmission has no syncro in reverse.

If you can push down the clutch pedal and put the car into reverse immediately, the clutch is releasing fine. If it is really cold outside and the transmission is also cold, you might have to wait a couple of seconds to be able to engage reverse.

These transmissions were very sensitive to the thickness of the gear oil. In the very early cars, the syncros worked so poorly when they were cold, that Porsche authorized the dealers to put ATF in them, instead of gear oil. Back in the late '70's and early '80's, the thinnest gear oil one could easily find was straight 90 weight "dyno" oil. This stuff was pretty thick. I eventually found a 85/90 Kendall gear oil that worked great in these transmission and used it for about 20 years. When that gear oil got impossible to find, I switched to Mobil One LS 75/90 and I've used that for the past ten years. I hand write tags for my rebuilt gearboxes and attach them to the transmissions telling people to use this gear oil when they do their first fill. Auto Zone stocks this gear oil. Ecconomical. Works great. Easy on the gears, easy on the syncros, and works great with the limited slips.

Change the gear oil and drive the car for a few days to see if the gear oil fixes your problem.

Bradster928

Thanks again Greg! I will make sure the shop uses the Mobil LS 75/90. I appreciate the time taken to explain the clutch adjustment.

Bradster928

Bradster928

Greg,

Maybe it is the clutch after all. My car just failed the immediately into reverse test described in your post above. After being fully warmed up, it take two to three seconds for me to shift into reverse without grinding.

Hope springs eternal. We'll see.

Bradster928

GregBBRD

Think about what is still spinning, once the clutch is depressed.

Those two clutch disc are still spinning, from inertia. The entire shaft inside the torque tube and virtually the entire transmission is still spinning (5th gear is made right on that input shaft, which spins the countershaft and all the gears on the pinion shaft....there's a whole bunch of gears spinning around in there.

That's a whole bunch of inertia. Thicker gear oil actually slows down the gears inside the gearbox and decreases the effects of inertia, but makes the syncros "gummy".

Because of the "lack" of a syncro in reverse inside these gearboxes, I frequently will engage a forward gear to stop the transmission from spinning, before I shift into reverse. People tear the leading edge of the teeth off of these reverse gears, on a frequent basis.

Have your mechanic do the "visual check". Many times, the shaft will only slow and not stop, on its own. Like I said, if the shaft stops in 3 seconds or so, things are fine.

blown 87

Sure sounds like your clutch is not adjusted correctly.