bilwilli

I have had this rattle noise like a loose heat shield in the driver train of my 87 928 for about 40,000 miles, so I thought is was time to tackle the problem. I removed the drive train and found a bearing in the tt was trashed so I rebuilt the tt with Super Bearings and replaced the TC bearings and new seals, figure I cover all the bases. I put it all back together feeling I corrected the problem. I fired her up and it sounded the same as before. Not really looking to pull the transmission again. I turned the drive shaft and it felt good. Any suggestions would be appreciated.
Regards Bill

NC928S4

I have what appears to be the same problem. I replaced TT, Torque Converter bearing and seal, re-torqued flex plates and more. No change - driving me crazy. Noise sounds like a geiger counter and only heard when no load is on drive train. Put it in park and geiger goes off. Noise happens after car is turned off too.

I hunted with mechanics stethoscope but noise seems to come from no where in particular.

I gave up looking for the problem. When it breaks, whatever it is I'll fix it. Not the best solution but I ran out of options.

bilwilli

This has been going on for years. Loudest when you turn off motor and doesn't really change when given gas.

Chalkboss

One thing to look at is where the flexplate rivets to the spline. On an 87 (maybe other years), these rivets may become loose over time, leading to a rattle when at idle, in park or neutral. Had this problem on mine, and it was not obvious (to me) that they were loose by inspecting it. Had Greg fix it- he machines the existing holes in the two pieces (as a unit) and uses nice hardware and shoulder bolts. Noise gone.

I don't know why they did the riveting on some years and not others...

Chalkboss

Here is the repaired part- note the bolts.

bilwilli

That's what I am thinking. I checked the flexplate and it appeared to be in good shape...maybe not.

GregBBRD

Look for red corrosion around the rivet/running out in lines from rivets. Loose steel/iron pieces always make metal dust, which rusts almost instantly.

bilwilli

Would they fail at 50-60 thousand miles. I have had noise for a long time and it never seemed to get any worse.

ppv3

1991 964 C2 rattle/whining noise at 1800 RPM --- went up on the rack---tightened all lose connections--to no avail--checked muffler, heat shields etc to no avail

Then dismantled the Fan assembly---the bearing was worn--new bearing and hums like new!!!!!