Help, I keep breaking flex plates!
05-11-2010, 12:09 AM
#76
Jerry,
I conceed, "Checkmate"!
Change the word "wobble" to "be canted" or "offset".
Best of luck Troy and we look forward to what you ultimately find the correction specifics.
Tails 1990 928S4 Auto
I conceed, "Checkmate"!
Change the word "wobble" to "be canted" or "offset".
Best of luck Troy and we look forward to what you ultimately find the correction specifics.
Tails 1990 928S4 Auto
05-11-2010, 11:16 AM
#78
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To all,
I am overwhelmed and so thankful for all the concern and advice on this thread...THANK YOU!.
To update: there seems to be no bend in the TT shaft, for when I rotate it there is no wobble or out of true aspect to it. This may be a crude test but I clamped a needle nose vise-grip on to the bell housing approximately 1\16" gap from the TT...I noticed no variation in that gap as I spun the TT. As I mentioned before, the bearing distance from the front of the tube was 11", which seems acceptable. I hope to have a couple other rennlisters (Hans & Kurt) put another set of eyes on the situation Wednesday. Kurt also has a dial indicator to check my crank end play...I will keep you all posted and thanks again!
Kind regards,
Troy
I am overwhelmed and so thankful for all the concern and advice on this thread...THANK YOU!.
To update: there seems to be no bend in the TT shaft, for when I rotate it there is no wobble or out of true aspect to it. This may be a crude test but I clamped a needle nose vise-grip on to the bell housing approximately 1\16" gap from the TT...I noticed no variation in that gap as I spun the TT. As I mentioned before, the bearing distance from the front of the tube was 11", which seems acceptable. I hope to have a couple other rennlisters (Hans & Kurt) put another set of eyes on the situation Wednesday. Kurt also has a dial indicator to check my crank end play...I will keep you all posted and thanks again!
Kind regards,
Troy
05-11-2010, 11:44 AM
#79
Rennlist Member
Hi Troy. I am curious to know if it is the torque tube you are spinning or the drive shaft? I think it is the Torque Tube that you need to spin around the drive shaft to see if the torque tube is bent, not the drive shaft. If it is the torque tube you are actually spinning I will be at a loss to suggest how you find the misalignment. Jerry
05-11-2010, 11:32 PM
#80
Drifting
Hi Troy,
I'm not sure I can make it to your house tomorrow evening. I have the dial indicators in my truck if you want to swing by my office on your way to work (in Castleton). Or give me a call and we can come up with plan B
I'm not sure I can make it to your house tomorrow evening. I have the dial indicators in my truck if you want to swing by my office on your way to work (in Castleton). Or give me a call and we can come up with plan B
05-12-2010, 12:26 AM
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Hello all,
Here is the latest...
After speaking to Constantine on the phone tonight (for almost an hour and oh what a great guy...thanks Constantine!) we came up with an alignment issue with my TT mating to the flex plate. I also had another fellow rennlister, Hans (quite a clever fellow I might add, see his water pump delete thread) put a second set of eyes on my situation and without being to long-winded we came to the conclusion that my TT housing is most likely bowed or bent which James, Jerry, Karl, and Nicole nailed earlier on this thread.
You see, when I had previously installed the flex plates I would have to put a tremendous amount of upward pressure on the TT shaft to get the flex plate to mate up to the holes in the flywheel. With the TT being bowed upward it would cause the shaft in turn to point downwards which in turn would cause fatigue and stress on the flex plate.
Another possible cause we came up with could be pointed to the bell housing. It seems it could be tweaked or bowed causing the misalignment, or the combination of both TT and bell housing.
Tomorrow, with a little help from my friends, we will drop the TT out of the car to fully inspect...I have a sneaking suspicion we will find it bent.
I will keep you all posted with our findings, and again thank you to everyone that has contributed to this thread and my odd situation...It truly amazes me all the support and wealth of information on this forum!
Cheers to all!
Troy
Here is the latest...
After speaking to Constantine on the phone tonight (for almost an hour and oh what a great guy...thanks Constantine!) we came up with an alignment issue with my TT mating to the flex plate. I also had another fellow rennlister, Hans (quite a clever fellow I might add, see his water pump delete thread) put a second set of eyes on my situation and without being to long-winded we came to the conclusion that my TT housing is most likely bowed or bent which James, Jerry, Karl, and Nicole nailed earlier on this thread.
You see, when I had previously installed the flex plates I would have to put a tremendous amount of upward pressure on the TT shaft to get the flex plate to mate up to the holes in the flywheel. With the TT being bowed upward it would cause the shaft in turn to point downwards which in turn would cause fatigue and stress on the flex plate.
Another possible cause we came up with could be pointed to the bell housing. It seems it could be tweaked or bowed causing the misalignment, or the combination of both TT and bell housing.
Tomorrow, with a little help from my friends, we will drop the TT out of the car to fully inspect...I have a sneaking suspicion we will find it bent.
I will keep you all posted with our findings, and again thank you to everyone that has contributed to this thread and my odd situation...It truly amazes me all the support and wealth of information on this forum!
Cheers to all!
Troy
Last edited by troy928; 05-12-2010 at 01:27 AM.
05-12-2010, 01:26 AM
#82
Team Owner
if you dont find the TT bent then drop the engine bell housing and connect it to the the TT to examine
05-13-2010, 02:07 AM
#84
Rennlist Member
The bellhousing won't bend much before it snaps. When we were swapping parts out on Kibort's car at Sharktoberfest I found a bend in his TT using a tape measure. You can do this by just dropping the exhaust and heat shields, then measuring the distance between front and rear flanges at all 4 corners. You can also measure between the rear flange on the TT and the front flange on either side of the upper bellhousing, but that will only tell you if it is bent sideways.
11-22-2010, 06:16 PM
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Long over due update...
The underlying problem was the tourqe tube bearings and carriers were worn out.
If you have any play in the tt shaft (up or down, side to side movemet) time for a new tt or a rebuild.
Any play will cause a whipping action with the tt shaft at hard acceleratin and boom, another f-p cracked.
This was what was causing all the damage to the previous flex-plates.
I rebuilt my TT about 2 months ago (1500 miles) and no problems what so ever!
Thanks to all for their help and support on this thread and I hope this helps for any future Rennlister who my have a similar problem.
Cheers,
Troy
The underlying problem was the tourqe tube bearings and carriers were worn out.
If you have any play in the tt shaft (up or down, side to side movemet) time for a new tt or a rebuild.
Any play will cause a whipping action with the tt shaft at hard acceleratin and boom, another f-p cracked.
This was what was causing all the damage to the previous flex-plates.
I rebuilt my TT about 2 months ago (1500 miles) and no problems what so ever!
Thanks to all for their help and support on this thread and I hope this helps for any future Rennlister who my have a similar problem.
Cheers,
Troy
Last edited by troy928; 11-23-2010 at 05:30 PM. Reason: spelling
475hp/460lb.ft
11-23-2010, 05:29 PM
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Thanks Dan...
Troy,
11-23-2010, 09:19 PM
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Hi Troy,
Still doubt the migrated bearings were the root cause of the flex plates breaking. The migrated bearings would only have caused vibrations while under operation which would have been felt while driving.
When you explained the fact that it was hard to mate up the flex plate holes to the flywheel holes, a condition which I have never seen to your extent, and the damage to your TT flange (IIRC) which had been previously repaired, I still believe that previous damage and subsequent mis-alignment was the root cause of your problems.
For the vibrations to have caused flex plate fracturing, they would have made the 928 very unpleasent to drive and other problems would have surfaced along with cracked flex plates.
This from talking to and helping my fare share of owners with migrated TT bearings and vibrations in their drive line.
Cheers,
Still doubt the migrated bearings were the root cause of the flex plates breaking. The migrated bearings would only have caused vibrations while under operation which would have been felt while driving.
When you explained the fact that it was hard to mate up the flex plate holes to the flywheel holes, a condition which I have never seen to your extent, and the damage to your TT flange (IIRC) which had been previously repaired, I still believe that previous damage and subsequent mis-alignment was the root cause of your problems.
For the vibrations to have caused flex plate fracturing, they would have made the 928 very unpleasent to drive and other problems would have surfaced along with cracked flex plates.
This from talking to and helping my fare share of owners with migrated TT bearings and vibrations in their drive line.
Cheers,
02-18-2011, 10:36 AM
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My 1987 is doing the exact same thing now. Broke one flex plate and recently replaced it. When we did the drive shaft had to be pulled downward to line back up with the flex plate. We did not like the situation but I need the car to get to work. Lucky for me I am only .6 miles from home.
Weird part is that when we removed the cracked plate the shaft did not seem to drop downward (IE no tension on the plate.)
Note the position of the shaft indicated, to me, that it was not bent. When rotated it always remained skewed downward. It did not walk up and down in the torque tube.
Could it be misaligned some where in the back, or am I looking at a rebuild?
Oh and the transmission shifts quite hard when at part throttle... it is better then throttle at least 1/2 open. (not sure that has anything to do with it but figured I would add it for conversation)
Thanks
Eric
Weird part is that when we removed the cracked plate the shaft did not seem to drop downward (IE no tension on the plate.)
Note the position of the shaft indicated, to me, that it was not bent. When rotated it always remained skewed downward. It did not walk up and down in the torque tube.
Could it be misaligned some where in the back, or am I looking at a rebuild?
Oh and the transmission shifts quite hard when at part throttle... it is better then throttle at least 1/2 open. (not sure that has anything to do with it but figured I would add it for conversation)
Thanks
Eric
