86 w124 300D Auto: Heavy Thud noise from rear axle

[penderb]

I have an 86 W124 300D Auto with circa 330, 000 miles on the engine. Autobox was fully re conditioned last January. So far, I'm happy with box. But recently when box is changing up,there is a loud sudden "thud" from what appears to be the rear axle. It happens only on the actual change of a gear, up or down. I've grave worries it's diff related!!! or something to do with the drive shaft going into back axle!!
Can anyone shed some light?

Any info greatly appreciated

Billy

 

[spannerman]

Hi Billy,


It's more than likely it's a flexydisc coupling on the drive shaft, which is far enough back to make it sound like it's coming from the diff. It's not a major deal but it sounds as if it has ruptured, and needs to be replaced asap.


Donie

 

[tom7035]

I think what spannerman means is the rear rubber 'doughnut' on the propshaft, with which I would agree. (The driveshafts have all-metal CV joints).
Cheers, Tom.

 

[Bolide]

Clonking gearchanges

Billy


As others have said, it'll be the front or rear prop doughnut. Or it'll be the rubber mounts for the diff. Or it'll be backlash in the diff. Or the auto box

Or all of them...

One way to check is to put it on a ramp with a mechanic underneath. Sit in the car with the handbrake off and the footbrake on. Shift between Reverse and Drive - that'll show up where the loose bits are

If the rear wheels move a lot front to rear then the rear tie rod things that set the tracking have worn rubber bushes

At 330k I think you can expect some wear, but it's all fixable


Nick Froome
www.w124.co.uk

 

[penderb]

Apologies for lateness of reply, been busy with work!
I'll go with Nick on this one and get her onto the ramp. As least now I have a good idea what's wrong and more importantly, how to go about investigating it, as previously ,I had no idea where to start.

Many thanks Guys

Billy