Reconditioned 915 tran very sticky shift
04-25-2002, 08:48 PM
#1
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Reconditioned 915 tran very sticky shift
911/74
Had trans reconditioned. Test drive shifting was difficult 1st,2nd,3rd. replaced syncros dog teeth
1,2,3. Mech. says there is rubbing on gear shift
rod. Never had problem before. Any Ideas.
Joe russo
Had trans reconditioned. Test drive shifting was difficult 1st,2nd,3rd. replaced syncros dog teeth
1,2,3. Mech. says there is rubbing on gear shift
rod. Never had problem before. Any Ideas.
Joe russo
04-25-2002, 09:44 PM
#2
RL Technical Advisor
Hi Joe:
Sorry to hear of your transmission troubles,.....
There are several things that can affect shifting in a freshly overhauled gearbox:
1) Mix of old and new operating sleeves and dog teeth.
2) Gear oil (Swepco works best)
3) Failure to replace/update all syncro's, op sleeves, dog teeth, anchor blocks, stop blocks, hubs, etc.
3) Bent shift fork(s) or shift shaft.
4) Incorrectly adjusted shift coupler and shifter.
I hope something I've listed here is helpful in diagnosing and resolving your problem. The newest 915 parts from Porsche are not always backwards compatible when installed in older gearboxes, and this creates issues that were not there before.
Frankly, it takes someone who is VERY experienced with these trannys to resolve this.
Sorry to hear of your transmission troubles,.....
There are several things that can affect shifting in a freshly overhauled gearbox:
1) Mix of old and new operating sleeves and dog teeth.
2) Gear oil (Swepco works best)
3) Failure to replace/update all syncro's, op sleeves, dog teeth, anchor blocks, stop blocks, hubs, etc.
3) Bent shift fork(s) or shift shaft.
4) Incorrectly adjusted shift coupler and shifter.
I hope something I've listed here is helpful in diagnosing and resolving your problem. The newest 915 parts from Porsche are not always backwards compatible when installed in older gearboxes, and this creates issues that were not there before.
Frankly, it takes someone who is VERY experienced with these trannys to resolve this.
04-25-2002, 11:49 PM
#3
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Join Date: Apr 2002
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Rubbing on gear shift rod... hmmm??? Did he explain this further?
I took my 915 apart and from what I can remember, ether the trans was put back together all wrong (to the point where its absurd), or you can wish for a misajusted shift coupler as mentionned before. Here's what I propose you do:
1- remove the cover behind the center of the seats. You will see (under rubber boot) your shift coupler.
2-Move the shifter around a bit and look at its behavior : it should turn on the shift rod axis with minimal or no up/down play as you push your shifter right/left. It will move forward/backward as you go up/down into gears with the shifter. If there is loose, suspect worn bushings in shifter assembly (easy and cheap to fix
).
3- You can try your hand at ajusting the coupler. You will need two 13mm wrenches. The procedure is described in many tech articles : basically put yourself in neutral and loosen the bolt that attaches the shift rod to the coupler. Center your shifter and tap the driver side stop (neutral position but alligned with 1st gear).
If you don't center it properly you will not have enough travel left to fully engage into gear.
Turn the coupler (still attached to the trans. side rod, if I remember correctly, you should have 120deg of play - make sure it moves freely) and turn to the furthest clockwise position (looking towards the front of the car from inside). Don't force, it should just rest on the side - and tighten the nut to hold the rod to the coupler. You're done.
If this doesn't do it, your bushing are good and you can't live with the hard 1-2-3 shifting, it's time to pull the engine&trans out again. Who knows what it can be, it's hard to long-distance-diagnose problems like those.
Then again, your synchros might be new& a little big. ? anyway, That was long! GOOD LUCK! - I will pray for you.
I took my 915 apart and from what I can remember, ether the trans was put back together all wrong (to the point where its absurd), or you can wish for a misajusted shift coupler as mentionned before. Here's what I propose you do:
1- remove the cover behind the center of the seats. You will see (under rubber boot) your shift coupler.
2-Move the shifter around a bit and look at its behavior : it should turn on the shift rod axis with minimal or no up/down play as you push your shifter right/left. It will move forward/backward as you go up/down into gears with the shifter. If there is loose, suspect worn bushings in shifter assembly (easy and cheap to fix
).3- You can try your hand at ajusting the coupler. You will need two 13mm wrenches. The procedure is described in many tech articles : basically put yourself in neutral and loosen the bolt that attaches the shift rod to the coupler. Center your shifter and tap the driver side stop (neutral position but alligned with 1st gear).
If you don't center it properly you will not have enough travel left to fully engage into gear.
Turn the coupler (still attached to the trans. side rod, if I remember correctly, you should have 120deg of play - make sure it moves freely) and turn to the furthest clockwise position (looking towards the front of the car from inside). Don't force, it should just rest on the side - and tighten the nut to hold the rod to the coupler. You're done.
If this doesn't do it, your bushing are good and you can't live with the hard 1-2-3 shifting, it's time to pull the engine&trans out again. Who knows what it can be, it's hard to long-distance-diagnose problems like those.
Then again, your synchros might be new& a little big. ? anyway, That was long! GOOD LUCK! - I will pray for you.
04-26-2002, 12:22 PM
#4
this is a very common thing with a rebuilt transmission, in spite of replacing all the parts steve listed. the syncros and shift sleeves need to mate to each other (break in). usually a 15 minute drive with a lot of up and down shifting gets them working smoothly. sometimes it takes longer. it's quite rare to have a perfectly shifting transmission right out of the box. i would suggest giving it a couple of weeks to break in, before worrying too much. in that time, work whichever gear is balky, by repetedly shifting in and out, in and out.
