Im wondering if I have a bad wheel bearing and/or axle, or ifmy trans just needs servicing. When I drive it, Im hearing a rhythmic thumping. The shifter is very difficult to get into and out of gear, but once in gear it runs great and shifts great, just makes that terrible rhythmic sound. I have a 98 XJR with about 76k miles. Please tell me it sounds like servicing the trans should fix the problem. PLEASE!

 

Anyone?

 

Well, I suppose your subject line scares people away!
I can emphatically say that changing the fluid will not fix your thumping noise.
And as to "servicing the transmission", then if that is where the noise is coming from, "servicing" it will fix it, but that may well be a complete overhaul.

 

I would look into why the shifter is stiff, if you can do the work yourself then all good - the car is fitted with a Mercedes gearbox and generally bombproof, so I'd be inclided to suspect the diff. Does it thump while stationary or only when moving? Have you listened around the car with th bonnet up, got your head under the car? You need to locate it before we can suggest a fix, you see it could be an engine issue also...

 

+1

Look at the shifter issue forst, it might lead you to the problem. I would also lift the car and look at the cable routing/driveshaft for clues.

 

It only thumps when on the move, not at a standstill.

 

You might be due for a wheel bearing. Can you tell if it's coming from the front or rear ? I had one go bad and it sounded like a helicopter was flying overhead. Rhythmic with speed. You could try jacking it up and wobbling the wheels. There's a post on what a 3 and 9 wobble is or a 6 and 12, but I can't remember which was caused by what, but any play is not good.

 

What does the transmission dipstick say the level is?
Check the rearend fluid level.
Jack each corner of the car up, then grab the wheel and try to rock it from side to side to see if a wheel bearing is bad. Turn the wheel while in the air, see if you can hear anything dragging.

Check this TSB out 206-07 DATE 04/98
A/T Selector Lever - Difficult to Shift From PARK

 

Has anyone mentioned the jurid coupling and center bearing yet? Either one could result in a thump.

 

mustangtyson:
If your car has a transmission dipstick, it is an aftermarket item!

 

You may want to watch this video:

 

We just drove 4550km and I had a slight thump sound and a shake, Car had an alignment and a tire balance and rotate before we left ... thankful I took it in today and found out the problem, was only a bad rear passenger tire .

 

Ok, lets get back to basics. You know there is an issue with the shifter assembly. Check the cable under the car, check the shifter assembly (mine was bad at 84k, dealer I bought from replaced it), and resolve this first. With any car, resolve any known faults first, then try to diagnose the unknown. Eliminate as many variables as possible.

For the transmission, check the fluid level and condition. These Mercedes gearboxes are stout, but not immortal. If the fluid looks ok and is at a decent level, it could still have issues, but I'd look at other areas before going down that road; eliminating variables...

Check wheel bearings, tires, u-joints and couplings, alignment, etc. Make sure that the drivetrain and suspension outside of the transmission is solid and not the issue or contributing. Only after a very good look elsewhere would I go down the road of a possible gearbox issue. A rhythmic pulse but excellent performance from the gearbox may very well be some sort of rotating drivetrain component out of balance, damaged or failing.

Also, when I was learning how to rebuild auto boxes; the advice I got from a long time transmission shop owner was, the time to change transmission fluid is almost always *before* there is an issue, and trying to resolve slipping or thunking with fluid changes or flushes usually shortens the remaining life rather than extends it.