Important News TT on the 85,86 MY!
08-04-2004, 01:39 PM
#1
Burning Brakes
Thread Starter
Important News TT on the 85,86 MY!
OK,
Thanx to all the great advice I got here on Rennlist and John Pirtle in particular, my shark is back to normal.
I thought this deserved a separate thread for future search considerations.
After much searching and reading, I decided to go ahead and check for preload on my flexplate.
Now from what I have seen, there has never been direct reference to the 85, 86 model years when discussing thrust bearing failure? Everything that I was able to find referred to S4 and newer 928's. Because of this, I had never checked for this preload before. My shark is not a daily driver so I haven't put mega miles on it but there is definately enough mileage since I bought the car to be concerned that I may have preload on the flexplate.
When I laid a flat edge across my flexplate, I was surprised to find that there was a small amount of preload on the plate. I never measured but I guessed it was less than half a milimeter. So I released the tension and the flexplate shifted a small amount back into position.
Once I started the car after the work was done, I now had a rattle coming from my torque tube. I was totally pissed thinking that I was now in need of a new TT because this one may have fallen victim to some sort of wear due to the pressure on the flexplate. This turned out NOT to be the case.
Through some awesome advice from Rennlist posters John and Greg, I discovered last night that my rear pinch bolt was not torqued properly! I actually got over a half turn of the pinchbolt before the torque wrench clicked off at 66flbs (90 nm). I started the car again and voila, the noise was gone.
Thank you guys a helluvalot for the great advice
I want to make a couple of observations here.
1) These checks CAN be done with the exhaust in place. At least for the 85,86 cars. I am not certain of the exhaust routing for the S4 and up cars.
2) I believe that this inspection is AS important a check for buying a used 928 as the timing belt. Checking the flexplate preload and the crank endplay could save you thousands of dollars in repairs and may even save you the price of the car!!
3) I had a thought this morning. I wonder how many torque tubes have been replaced over the years at repair costs of thousands and thousands of dollars, simply because the pinch bolts were not torqued correctly?
Make this an important part of any PPI that you are having done. All in all, it took me a little over an hour to complete this.
Cheers
Thanx to all the great advice I got here on Rennlist and John Pirtle in particular, my shark is back to normal.
I thought this deserved a separate thread for future search considerations.
After much searching and reading, I decided to go ahead and check for preload on my flexplate.
Now from what I have seen, there has never been direct reference to the 85, 86 model years when discussing thrust bearing failure? Everything that I was able to find referred to S4 and newer 928's. Because of this, I had never checked for this preload before. My shark is not a daily driver so I haven't put mega miles on it but there is definately enough mileage since I bought the car to be concerned that I may have preload on the flexplate.
When I laid a flat edge across my flexplate, I was surprised to find that there was a small amount of preload on the plate. I never measured but I guessed it was less than half a milimeter. So I released the tension and the flexplate shifted a small amount back into position.
Once I started the car after the work was done, I now had a rattle coming from my torque tube. I was totally pissed thinking that I was now in need of a new TT because this one may have fallen victim to some sort of wear due to the pressure on the flexplate. This turned out NOT to be the case.
Through some awesome advice from Rennlist posters John and Greg, I discovered last night that my rear pinch bolt was not torqued properly! I actually got over a half turn of the pinchbolt before the torque wrench clicked off at 66flbs (90 nm). I started the car again and voila, the noise was gone.
Thank you guys a helluvalot for the great advice
I want to make a couple of observations here.
1) These checks CAN be done with the exhaust in place. At least for the 85,86 cars. I am not certain of the exhaust routing for the S4 and up cars.
2) I believe that this inspection is AS important a check for buying a used 928 as the timing belt. Checking the flexplate preload and the crank endplay could save you thousands of dollars in repairs and may even save you the price of the car!!
3) I had a thought this morning. I wonder how many torque tubes have been replaced over the years at repair costs of thousands and thousands of dollars, simply because the pinch bolts were not torqued correctly?
Make this an important part of any PPI that you are having done. All in all, it took me a little over an hour to complete this.
Cheers
08-04-2004, 06:06 PM
#3
Burning Brakes
Thread Starter
Hi Nicole,
Thanx a bunch.
I just wanted to make sure that this thread referenced DIRECTLY to the 85, 86 cars to help keep my fellow MY guys out of trouble.
The front pinchbolt has been documented a number of times but not the rear (that I have found?). The first thing to do is unscrew the heatshield that covers the resonators towards the back of the car. You can't get the shield out but you can shift it around enough to give you some extra clearance. There is a black rubber plug in the bottom of the TT at the rear that you pull out to gain access to the rear pinchbolt. I used a 27mm on a breakbar to rotate my crank until the pinch bolt was visable in the hole. The only way to get a 1/2" 8mm hexkey in there is to be certain that the pinchbolt is as far over the right (looking from rear to front of the car) of the access hole as possible. This allowed just enough space for me to get the 2" long 8mm hexkey onto the bolt. With enough space left over to get my torque wrench in. It will become more clear once you are under there looking at it. The worst thing is that you might have to drop the rear of the exhaust to access the bolt but that only requires maybe an extra 20 minutes or so of work. I just wanted to do this and show it as a very simple task in order to motivate more people into checking it.
Cheers
Thanx a bunch.
I just wanted to make sure that this thread referenced DIRECTLY to the 85, 86 cars to help keep my fellow MY guys out of trouble.
The front pinchbolt has been documented a number of times but not the rear (that I have found?). The first thing to do is unscrew the heatshield that covers the resonators towards the back of the car. You can't get the shield out but you can shift it around enough to give you some extra clearance. There is a black rubber plug in the bottom of the TT at the rear that you pull out to gain access to the rear pinchbolt. I used a 27mm on a breakbar to rotate my crank until the pinch bolt was visable in the hole. The only way to get a 1/2" 8mm hexkey in there is to be certain that the pinchbolt is as far over the right (looking from rear to front of the car) of the access hole as possible. This allowed just enough space for me to get the 2" long 8mm hexkey onto the bolt. With enough space left over to get my torque wrench in. It will become more clear once you are under there looking at it. The worst thing is that you might have to drop the rear of the exhaust to access the bolt but that only requires maybe an extra 20 minutes or so of work. I just wanted to do this and show it as a very simple task in order to motivate more people into checking it.
Cheers
08-04-2004, 09:08 PM
#4
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This is great additional information, Bernie!
Most of us have never looked into accessing this bolt, now it is documented for when we need it.
Most of us have never looked into accessing this bolt, now it is documented for when we need it.
08-05-2004, 12:34 AM
#5
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Bernie,
as the bolt was loose it may have stretched re tensioning an already fatigued bolt mat cause some problems in the future, the bolts are cheap and worth every penny for the peace of mind.
Mike
as the bolt was loose it may have stretched re tensioning an already fatigued bolt mat cause some problems in the future, the bolts are cheap and worth every penny for the peace of mind.
Mike