How much to pay for new gear synchronizers?
#31
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Greg,
If it turns out that my transmission does need to be replaced, (fluid, clutch adjustments do not work), do you recommend I go with the rebuilt tranny for my 83 ("08"), or upgrade to the "13" as a previous poster mentioned? If so, what are the downsides? Extra parts, modifications?
Thanks!
Just in case, I have added a rebuilt tranny from 928 Intl to my wish list.
Bradster928
If it turns out that my transmission does need to be replaced, (fluid, clutch adjustments do not work), do you recommend I go with the rebuilt tranny for my 83 ("08"), or upgrade to the "13" as a previous poster mentioned? If so, what are the downsides? Extra parts, modifications?
Thanks!
Just in case, I have added a rebuilt tranny from 928 Intl to my wish list.
Bradster928
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...
#32
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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
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
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#33
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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.
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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
Thanks again Greg, and everyone else, for your sound advice.
Bradster
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Yes...no....well, it depends.
New syncros, with a new shifting sleeve (the part that goes over the top of the syncro and engages the gear), will take some time to break-in. The first 10 or so engagements can seem like a bad joke...or like someone screwed up. This can be a very, very stiff and slow engagement.
New syncros, with a worn out shifting sleeve, will shift very easily....and might even still "grind" when they are put into gear.
Many times, people just drop in new syncros without paying any attention to the shifting sleeve and then wonder why their transmission still grinds, with new syncros. I've frequently taken apart transmisison with brand new syncros that grind like crazy, because the shifting sleeve/sleeves are worn out. The shift sleeve is a wear surface, too. They do wear slower than the syncros, but they wear, regardless. This needs to be inspected and shift sleeves need to be replaced, frequently. On the "early" early gearboxes, the shift sleeve for 1st and reverse has engaging teeth cut on both sides of the sleeve. Since reverse has no syncro, the teeth will have never "touched" a syncro (unless someone has been inside the gearbox before you and has "flipped" this sleeve over). This "virgin" sleeve side can be used to gauge how much wear the other sleeves have on them, by setting each side of each sleeve on top of each installed syncro and comparing how far the sleeve sits down on the syncro, compared to the "virgin" side of the 1st and 2nd slider.
As you can imagine, the "tightness" of the new syncro and how hard it is to engage is completely dependant on how much wear there is, inside each shifting sleeve. I frequently "flip" 1st and reverse over on these early transmissions to use the "virgin surface. That makes them darn stiff going into 1st gear....but if all the other sleeves are used, the rest of the gears will be easier to engage.
Make sense?
Pictures might help, if you don't understand.
New syncros, with a new shifting sleeve (the part that goes over the top of the syncro and engages the gear), will take some time to break-in. The first 10 or so engagements can seem like a bad joke...or like someone screwed up. This can be a very, very stiff and slow engagement.
New syncros, with a worn out shifting sleeve, will shift very easily....and might even still "grind" when they are put into gear.
Many times, people just drop in new syncros without paying any attention to the shifting sleeve and then wonder why their transmission still grinds, with new syncros. I've frequently taken apart transmisison with brand new syncros that grind like crazy, because the shifting sleeve/sleeves are worn out. The shift sleeve is a wear surface, too. They do wear slower than the syncros, but they wear, regardless. This needs to be inspected and shift sleeves need to be replaced, frequently. On the "early" early gearboxes, the shift sleeve for 1st and reverse has engaging teeth cut on both sides of the sleeve. Since reverse has no syncro, the teeth will have never "touched" a syncro (unless someone has been inside the gearbox before you and has "flipped" this sleeve over). This "virgin" sleeve side can be used to gauge how much wear the other sleeves have on them, by setting each side of each sleeve on top of each installed syncro and comparing how far the sleeve sits down on the syncro, compared to the "virgin" side of the 1st and 2nd slider.
As you can imagine, the "tightness" of the new syncro and how hard it is to engage is completely dependant on how much wear there is, inside each shifting sleeve. I frequently "flip" 1st and reverse over on these early transmissions to use the "virgin surface. That makes them darn stiff going into 1st gear....but if all the other sleeves are used, the rest of the gears will be easier to engage.
Make sense?
Pictures might help, if you don't understand.
It really helps, like the ones you posted on the LSD build.
#37
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"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.
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.
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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
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
#39
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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...
I do hope that he is already knowledgeable...
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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.
Just as a point of reference, Porsche switched to the single disc clutch because the factory trained dealer mechanics had trouble adjusting them.
#41
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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.
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.
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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
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
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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
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
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.