Transmission woes
#106
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Greg,
I saw this first hand. I went to the Transmission shop and he had the flexplate in a vice. He said the only way you would be able to feel it moving was to press it out of the bell housing and put it in the vice. He had a pair of vice grips attached and told me to grab them and see if I felt anything. I felt a wobble as if there was a 1/2mm or so of play. Apparently that's enough to make that god forsaken rattle sound.
I can tell you now that it does not make a peep. It feels like a totally different vehicle with the rebuilt/new transmission and correctly oriented throttle cable.
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I saw this first hand. I went to the Transmission shop and he had the flexplate in a vice. He said the only way you would be able to feel it moving was to press it out of the bell housing and put it in the vice. He had a pair of vice grips attached and told me to grab them and see if I felt anything. I felt a wobble as if there was a 1/2mm or so of play. Apparently that's enough to make that god forsaken rattle sound.
I can tell you now that it does not make a peep. It feels like a totally different vehicle with the rebuilt/new transmission and correctly oriented throttle cable.
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I'm trying to figure out if there are specific years that I need to keep my eyes open, for this problem, or if it is systemic to all the years.
Can you look in your door jamb and tell us your production date?
#107
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#108
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I actually feel a bit left out....
For all of the vehicles I've had apart and for all of the transmissions I've rebuilt....I've never seen one of these flex plates with the rivets loose. Never. Ever.
The technical bulletin for this problem is dated December 16, 1986 and says that it covers 1985 through 1987 models. Yet, Porsche continued to rivet the flexplates all the way through the entire 928 model line. It would not be like Porsche to keep installing a weak part, which required a repair a couple of years after production. So it would seem that they must have "solved" this problem after the December 16, 1986 date?
So are we to assume that this "rivet problem" was for a "short run" of flexplates and the problem got solved after this date?
Anyone know?
What is the date of manufacture on the OP's vehicle?
For all of the vehicles I've had apart and for all of the transmissions I've rebuilt....I've never seen one of these flex plates with the rivets loose. Never. Ever.
The technical bulletin for this problem is dated December 16, 1986 and says that it covers 1985 through 1987 models. Yet, Porsche continued to rivet the flexplates all the way through the entire 928 model line. It would not be like Porsche to keep installing a weak part, which required a repair a couple of years after production. So it would seem that they must have "solved" this problem after the December 16, 1986 date?
So are we to assume that this "rivet problem" was for a "short run" of flexplates and the problem got solved after this date?
Anyone know?
What is the date of manufacture on the OP's vehicle?
Rivets in this application are generally acceptable and the fact that they continued to use this fastening method would indicate that their testing showed it was good enough. Many flex plates are done this way. In fact, all of the ones I have ever seen have been done this way.
#109
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I can tell you that without it being removed from the car, the deficiency is virtually undetectable other than the annoying noise it makes when the car is at idol. The recommendation is to replace the rivets with new ones so they think the method is appropriate. Unfortunately they don't seem to hold.
#110
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For those playing along at home, are these the rivets?
https://rennlist.com/forums/8084134-post3.html
https://rennlist.com/forums/8084134-post3.html
#111
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I'd be interested if anyone past the 12/86 build date has had this problem.
#112
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Rattle started a few thousand miles after the TT was rebuilt and TC bearings were replaced. I anticipate yanking the trans and fixing it in a month or so.
#113
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I have a MY 87, and will check my build date and report back later. I would be very surprised if I do not have this problem- I have the rattle at idle and everything else has been checked/replaced except for that. Sound is coming from the TC area.
Rattle started a few thousand miles after the TT was rebuilt and TC bearings were replaced. I anticipate yanking the trans and fixing it in a month or so.
Rattle started a few thousand miles after the TT was rebuilt and TC bearings were replaced. I anticipate yanking the trans and fixing it in a month or so.
Funny think is I never had this in the 9 years before the work mentioned above and can't help to notice that you had the same thing happen after your replacement of the TT, TC bearings!
#114
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I've got two pre-December 1986 transmissions apart. Both flexplates seemed tight, when I applied torque to them, holding them in a vice. One has no signs of anything migrating out of the rivets. The other had some dark streaks...almost looked like lubricant "slinging" off the rivets and across the flexplate. This one I took apart. The rivets seemed very tight and there was no sign of any wear on the sides of the rivets, however there was definite metal fretting between the shaft and the flexplate....it has been moving.
I will disassemble the other one and report back.
I sure like the idea of the rivets more than bolts. The bolts have threads, where they pass through the assembly, whereas the rivets are solid and exactly the right size. Seems like the bolts would be more prone to allowing movement than the rivets.
I will disassemble the other one and report back.
I sure like the idea of the rivets more than bolts. The bolts have threads, where they pass through the assembly, whereas the rivets are solid and exactly the right size. Seems like the bolts would be more prone to allowing movement than the rivets.
#115
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My humble offering (speaking as barely-fledged noob, FWIW), the loose rivet rattle at idle was plain, (a light chatter more reminiscent of a cracked flexplate in a conventional North 'Murican car) in a low serial number '92 968 Tip that I learned up on before the current puzzle. A Different Beast, to be sure, with dramatically different 4 cyl. torsional driveline behaviour, but torque tube shaft nonetheless...and yes, the rivets were fretted and slightly rusty, play was easily felt after disassembly. The light chatter would disappear above idle w/ trans in drive....and this chuckle/rattle began 12 mos after replacing the rotted rubber flywheel damper. Wish I'd had the stones to drill them out and bolt up instead of buying new Porsche part with rivets. If you are wondering, yes; I don't get out much, lol. And, yes, it's reasonable to assume that factory
Was sourcing both 928/968 model line parts from the same jobber, I think. FWIW.
Was sourcing both 928/968 model line parts from the same jobber, I think. FWIW.
#116
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I lived in Mexico for about 8 years and street raced the car on a 1/2 - 3/4 mile straight road and having the mentality of that experience I was trying to modify the car to get off the line faster. Now with the problems in Mexico I am not returning to enjoy that party any more so I really have no need for the modified converter at this point.
#118
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Hi,This is my first post as I have recently acquired a RHD 1985 928 S2 which needs a bit of restoration. The engine is out at the moment (able to source lots of pricey bits) but am having trouble getting a transmission oil pipe return line part number 960.307.029.02. It's the one that connects from the bottom connector on the little oil cooler right back to the one that connects to the transmission assembly (part no. 960.307.039.00)The metal pipe on the old one is very corroded although the rubber parts seem ok. Can anyone suggest a workaround. I see stainless steel transmission cooler hose for Chevrolet for sale on ebay. Could something like that be used on my 928. Can anyone offer me some advice.
PS. I also need and cant get two little bonded rubber mountings part of the fuel injection system(part no. 999.689 001.00)
Any alternative suggestions would be appreciated.
Many thanks, John. (I'm Irish)
PS. I also need and cant get two little bonded rubber mountings part of the fuel injection system(part no. 999.689 001.00)
Any alternative suggestions would be appreciated.
Many thanks, John. (I'm Irish)