Have a 1995 XJ6 Vandenplus that has a ridiculous vibration that starts precisely at 30 miles and hour and at Precisely 52 miles and hour it stop's as if something has changed or turned off. First I thought it was a drive line issue, replace entire drive line with rebuilt, didn't change. replace all of the tire with new, didn't change, replace the motor and trans mounts still nothing. I am completely baffled. Could this be an issue with the ABS. that's kind of how the vibration feels, or could it be in the differential? Any suggestions would be greatly appreciated.

 

Vibrations can be very tricky and frustrating

Do you feel this more thru the steering wheel? Or more thru the seat and/or body of the car?

Was the driveline correctly aligned when replaced?

Does switching tires front-back change anything?

Is the vibration 100% road speed related or is it also engine RPM related?

Cheers
DD

 

I changes the drive line, I wasn;t aware of any alignment, How is that done?

 

Vibration is throught the car and it seems to be speed related

 

I have read this carefully and follow Dougs comments.

The alignment of the tailshaft at the centre bearing mounting plate is "adjustable" for driveline vibration. Same centre bearing arrangement as the early saloons, and we oldies know only too well the headaches that sucker caused over the years.

SOME people have reported the big nut that holds the diff pinion flange in place has come loose, and a bad vibration is real.

The actual transmission torque convertor is also a vibration source. Not a cheap item to replace. Sometimes a simple transmission fluid change will reduce or sort that item, sometimes not. Mine had a shudder at 80kph (50mph) and after a few trans fluid drop and refills it is as sweet as ever, so maybe I was/am lucky.

Engine mount alignment is also a requirement if and when they are disturbed/replaced.

 

Here is the procedure for aligning the propshaft. I haven't done this yet but it's on my list for the winter.

If you try it first and post pics and any extra "how to" tips that would be great

 

Good suggestions so far. If the driveshaft alignment isn't the culprit, then there are a few other things to check.

When dealing with vibrations, the trick is to isolate as many variables as possible. To add to Doug's line of questions:

1) Is this vibration accompanied by any sort of noise? A bad wheel bearing will cause vibrations and are often accompanied by a low, dull roar that can initially be hard to hear if you're not listening for it. Jack the car up so that the wheels are off the ground and try pushing and pulling on each wheel. If there's any freeplay, then you've got a bad wheel bearing. Have you noticed any banging or clunking sounds recently?

2) I'm curious to know if swapping the tires from front to rear made any noticeable difference. The vibration would still be present, but you'd be able to tell if the source had changed position.

3) Changing the car's dynamics up can also give a clue as to what the problem is. Does the vibration occur while the car is coasting in Neutral? Is it more/less noticeable under braking? How about when turning?

4) I know that you say the vibration runs throughout the car, but there's got to be a localized source for it. Have someone ride with you and have them sit in the front and back seat to see if it's more noticeable in the front/rear or left/right of the car.