Help ! Sudden No Auto Gear Shift
10-15-2012, 04:48 PM
#61
Nordschleife Master
Thread Starter
Thanks Malcolm.
The torque for these bolts are 46 Nm ?
From looking at the task, looks like going to be a PITA, but then again what isn't ?
I have a feeling this won't be 'it'.
The torque for these bolts are 46 Nm ?
From looking at the task, looks like going to be a PITA, but then again what isn't ?
I have a feeling this won't be 'it'.
10-15-2012, 04:51 PM
#62
Seems to me that you could look through the opening in the bottom of the converter housing and see the torque converter rotate as you rotate the engine at the crankshaft to verify that the flex plate is connected to the torque converter.
10-15-2012, 04:53 PM
#63
Nordschleife Master
Thread Starter
Yes, I can see that it is, but I will check the torques nonetheless. This problem is confounding.
Last edited by MainePorsche; 10-15-2012 at 05:58 PM.
10-15-2012, 05:45 PM
#64
Here's what the WSM says......
This new thread explains how to check the modulating pressure:
https://rennlist.com/forums/928-foru...nsmission.html
Condition: Transmission slips in all selector lever positions
Correction: 1. Check modulating pressure, adjusting if necessary. If not adjustable, check movement of modulating pressure control valve. Clean modulating pressure safety valve in shift valve housing upper section.
2. Check whether vacuum line from intake branch to vacuum box is plugged. If yes, replace.
3. Check operating pressure. If too low or not available:
a) Disassemble and clean shift valve housing. and service operating pressure control valve.
b) Remove and inspect primary pump, replacing if necessary.
Correction: 1. Check modulating pressure, adjusting if necessary. If not adjustable, check movement of modulating pressure control valve. Clean modulating pressure safety valve in shift valve housing upper section.
2. Check whether vacuum line from intake branch to vacuum box is plugged. If yes, replace.
3. Check operating pressure. If too low or not available:
a) Disassemble and clean shift valve housing. and service operating pressure control valve.
b) Remove and inspect primary pump, replacing if necessary.
https://rennlist.com/forums/928-foru...nsmission.html
10-15-2012, 06:22 PM
#65
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Does the fluid level go down in the tranny fluid reservoir when you have the engine running? If not, the primary pump has failed. Odd but technically possible.
10-15-2012, 06:29 PM
#66
Rennlist
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Here's what the WSM says......
This new thread explains how to check the modulating pressure:
https://rennlist.com/forums/928-foru...nsmission.html
This new thread explains how to check the modulating pressure:
https://rennlist.com/forums/928-foru...nsmission.html
It doesn't "slip"....it doesn't move.
__________________
greg brown
714 879 9072
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Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
10-15-2012, 06:33 PM
#67
Rennlist
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There's a main pressure relief valve, for the pump pressure that can fail....also obscure.
It's almost to the point where I am starting to think that the "reverse" clutches got so thin that the spring retainer blew off and did enough damage to take out 2nd gear, also. I've seem this happen, a couple of times. It's a real mess.
10-15-2012, 07:31 PM
#68
Nordschleife Master
Thread Starter
10-15-2012, 08:17 PM
#70
Rennlist Member
I've got to admit this is a bizar problem.
To mee it seems as though it is most likely that either the shifting mechanism inside the trans has failed or there is some problem inside the diff. In order for park not to function either the parking paw is disengages or damaged or the link between the park mechanism and the rear wheels. my first guess is that the shifting mechanism has failed. my rational for this is that it happened when he went from park to drive to leave the parking lot. everything functioned normally leading up to him getting ready to pull out. he observed no abnormal noise or motion, the car just failed to engine any gear. the other possibility seems to be the differential but if it were to fail you would think there would be some noise or jerkiness to it.
don't know the best way to diagnose this though. one thing to maybe check would be to see if the selector lever in the trans isstill secure, or can you pull it out of the trtans. if the inner shift linkage is loose you may have extra in/out motiion on the shift shaft going into the trans.
have you drained the diff fluid to se how it looks? also you may be able to peer in through the drain/fill holes to se if there is anything visible that doesn't look right.
To mee it seems as though it is most likely that either the shifting mechanism inside the trans has failed or there is some problem inside the diff. In order for park not to function either the parking paw is disengages or damaged or the link between the park mechanism and the rear wheels. my first guess is that the shifting mechanism has failed. my rational for this is that it happened when he went from park to drive to leave the parking lot. everything functioned normally leading up to him getting ready to pull out. he observed no abnormal noise or motion, the car just failed to engine any gear. the other possibility seems to be the differential but if it were to fail you would think there would be some noise or jerkiness to it.
don't know the best way to diagnose this though. one thing to maybe check would be to see if the selector lever in the trans isstill secure, or can you pull it out of the trtans. if the inner shift linkage is loose you may have extra in/out motiion on the shift shaft going into the trans.
have you drained the diff fluid to se how it looks? also you may be able to peer in through the drain/fill holes to se if there is anything visible that doesn't look right.
10-15-2012, 08:19 PM
#71
Rennlist Member
I generally agree with looking at the last thing touched, but the modulator and any issues with fluid level or even any brake bands in the trans shouldn't effect the park position function.
10-15-2012, 08:22 PM
#72
Rennlist
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10-15-2012, 08:23 PM
#73
Nordschleife Master
Thread Starter
Simon,
The union of the selector arm to the trans. unit appears very much intact.
I haven't inspected the diff. fluid yet. I changed it out last year. I just think it odd that the wheels turn by hand as I described previously - in P and N but not in R,D,2,and 3.
The union of the selector arm to the trans. unit appears very much intact.
I haven't inspected the diff. fluid yet. I changed it out last year. I just think it odd that the wheels turn by hand as I described previously - in P and N but not in R,D,2,and 3.
10-15-2012, 08:26 PM
#74
Nordschleife Master
Thread Starter
Greg,
When the event first occurred I had just started the car up to pull away. Obvious it wouldn't go into Drive. I then put it into Park and I began to roll forward on the slight grade I was on. Attempted to back up - nothing. Had to use the E brake to keep from moving.
When the event first occurred I had just started the car up to pull away. Obvious it wouldn't go into Drive. I then put it into Park and I began to roll forward on the slight grade I was on. Attempted to back up - nothing. Had to use the E brake to keep from moving.