84 300SD with loud, hard, thump/clank. - PeachParts Mercedes-Benz Forum

Clemson88 · #1 08-17-2014, 10:20 AM

This car spent years with vacuum problems and hard shifting. I've got most of the shift problems solved. Now it's developed a rhythmic scary thump under moderate to hard acceleration from a dead stop. Sometimes it even does it in second gear when accelerating hard.

The sound seems to be located in the middle of the cabin towards the rear seat.

300+ thousand miles on this car and I've owned it for 7 or 8 years. I've done some of the rubber on the front end like engine shocks and mounts but I don't think anyone else ever got under it.

Edit: It's really not a clank it definitely a thump.

snorider · #2 08-17-2014, 10:40 AM

Quote:

Originally Posted by Clemson88

This car spent years with vacuum problems and hard shifting. I've got most of the shift problems solved. Now it's developed a rhythmic scary thump under moderate to hard acceleration from a dead stop. Sometimes it even does it in second gear when accelerating hard.

The sound seems to be located in the middle of the cabin towards the rear seat.

300+ thousand miles on this car and I've owned it for 7 or 8 years. I've done some of the rubber on the front end like engine shocks and mounts but I don't think anyone else ever got under it.

Sounds like it could be your flex disk in your drive shaft? Good Luck

vstech · #3 08-17-2014, 11:35 AM

Center support driveshaft bearing mount. Fairly easy to change. But you may need to change the bearing as well.

Clemson88 · #4 08-17-2014, 12:26 PM

Quote:

Originally Posted by vstech

Center support driveshaft bearing mount. Fairly easy to change. But you may need to change the bearing as well.

Thanks, VStech. I was thinking it's somewhere in that area. I've been reading up on it here and decided if that was the problem I'd replace it and both flex disc too. I've already got the do it yourself on this stuff marked.

Clemson88 · #5 08-17-2014, 01:37 PM

Quote:

Originally Posted by vstech

Center support driveshaft bearing mount. Fairly easy to change. But you may need to change the bearing as well.

Whunter's DYI post on this project shows all this stuff on the bench. Can both drive shafts and center support be removed by just taking out the flex disk and support bolts?

vstech · #6 08-17-2014, 09:35 PM

And the exhaust, and the center heat shield...

The Gears · #7 08-18-2014, 02:42 AM

Quote:

Originally Posted by vstech

And the exhaust, and the center heat shield...

Why remove the exhaust. I have an 84 SD and never had to do that to pull the drive shaft. Drop the diff 6" and slide straight back.

vstech · #8 08-18-2014, 10:11 AM

Hmm... I don't think you can get the center bearing without at least lowering the exhaust. it's pretty well covered.

Clemson88 · #9 08-18-2014, 04:42 PM

Quote:

Originally Posted by vstech

And the exhaust, and the center heat shield...

I'm doing this project in the carport. I've noted that I need to rock the car to let the drive shafts' assemblies settle before locking them in. I also understand that putting the car back on jack stands almost always undoes this. What is the solution to this delimma?

Also, Pelican Parts list a 'Driveshaft Centering Bushing front/rear. Is it common to change this part or is that something unusual?