Front end vibration ... suggestions?

[Black Magic]

I am having a hard time tracking this problem down.

I have not got a lift on her, but I have changed to an 89 RR Classic U-jointed shaft in the rear - and replaced both U-joints in that.

There is a vibration that seems to start @ 45 mph, goes away about 60mph, and comes back really bad at 70 mph. It is reduced in it severity by either accelerating, or slowing down - basically it is worst at a neutral throttle setting.

It seems to be coming from the front end, but is not transmitted into the steering wheel - its the body/frame that gets shaken so I am tending to say that its not wheel balance problems.

I have jacked up the front end and turned the wheels. I couldn't disern noise, clunks, or loosness in the front driveshaft - but the backlash in the diff had a barely discernable "two stage" feel to it that the rear diff doesn't (It has a straight, limit to limit feel, with no "bump" in when it gets to the limit)

My rear shocks need replaced and I am guessing that the front probably does too.

Now to my question ... does it sound like a problem in the diff? I had thought it was a U-joint - but they SEEM OK.

[Rovin4life]

ITs do difficult to say what it is.

if your feeling it thru the body its most likely a driveline issue.

Could it be the RR driveshaft. Perhaps, You might want to re index the drive shaft to see if it works.

Have it checked out if your not really sure.

Have the driveshafts checked for balance as well.

Send it to a driveshaft shop nearby if you have one in your area.

[01001010]

seems like ive mentioned this quite a few times but I'm gonna have to go with RotoFlex again..lol

Do you still have one? Your rotoflex is located on your rear driveshaft where it meets with the rear diff. Its a rubber coupling. If this is damaged or if it even has some small cracks in it, these could be the culprit of your driveline vibrations. I know mine is damaged for sure and by working the throttle while on the highway, i can make the vibrations go away for a bit but there's no getting rid of them after 80..mine start after 60.

[frickjp]

Originally Posted by Black Magic

I am having a hard time tracking this problem down.

I have not got a lift on her, but I have changed to an 89 RR Classic U-jointed shaft in the rear - and replaced both U-joints in that.

You need to pull the safts, lock the box and see where your vibration is. The rear diff is pointing upward to accomodate the rotoflex. With 2 u-joints, you need to angle it down. The pinion should be on the same plane as the x-fer box output shaft. You can spacer the links rearward by adding some washers between the mount and the end of the arm.

[Funrover]

Are the driveshafts still balanced? CARIDJAN JOINT....that's all I am gonna say!!!

[01001010]

Originally Posted by Black Magic

I have not got a lift on her, but I have changed to an 89 RR Classic U-jointed shaft in the rear - and replaced both U-joints in that.

Woops, missed that part...nevermind my post then..lol

[pavel]

Black magic - did you have this vibration before you changed the driveshaft & U joints? I'm assuming that the vibration was the reason you made the change/repair.....

[Black Magic]

I had a vibration - I had put it down to it being the hairy rotoflex. It did seem that the rear diff flange and pinion were loose and wobbling a fair bit when I was working on the swap. I need to recheck that when dropping the rear shaft.

I have so many issues on this vehicle its hard to know where to start. Working on the major mechanicals first. I do have what I feel is excessive play in the drivetrain - picking its the transfer case (or is it transmission) splines fretting.

[DISCO INCUBUS]

Try taking off the rear driveshaft and lock the difflock and drive it to see if the vibration was from the shaft. You can try the front aswell to try to isolate the
problem.