Vibration at highway speeds

[GeosTalon]

Okay, so I get a nasty oscillation from 70 and up. I feel it a bit around 45 MPH, but at 70 or up it is really bad. It is speed related as clutch in, clutch out, engine on or off makes no difference..

Here are some facts:

The vibration started this week.

I've done the following items on the car in the past few weeks:
Did new front CV axles
Did new u-joints and carrier bearings
Drained and refilled fluid from transmission and rear diff

As of today:
Got two new front tires, all four wheels were balanced today. The wheels are a bit bent, nothing major though (been that way since when I got the car 1 month ago and it was fine up until sometime in the past week)
Changed transfer case fluid tonight.
Checked driveshaft, no loose bolts and the u-joints feel tight.
The rear diff has a drip to it, leaks a bit when parked for awhile, puddle the size of a quarter maybe a bit more.
The rear diff fluid did have some metal particles in it, not sure how to quantify it.
The car has a welded center diffential (going to dump that once I find a new 5 spd).

Should I be suspecting the rear differential? I changed the fluid in it last week with some Redline MTL synthetic as I was doing the transmission. I put the rear diff in the air today and it does seem to have a good inch of rotation before the other wheels starts moving.

Thanks for any thoughts.

-George

BTW, if anyone is going to be changing their drivetrain fluid, get yourself a "marine lower unit pump". You can find them at Murray's or most boating stores. They are less than $10, they screw right into the top of a bottle of gear lube, and you can pump the fluid in fast with minimal mess. You'll thank me...

 

[Goro21]

I had a very similar vibration that i fought with for MONTHS. I had the driveshaft and T-case completely rebuilt.. had both front axles replaced.. list goes on and on. None of these things I tried made any difference.

One day when I was changing my oil, I glanced at the lower front motor mount and the bolt holding it in place was completely gone. Not saying this is going to fix your problem, but don't overlook the motor mounts. I put a bolt back where it was supposed to be and my insanely annoying vibration went completely away. Just a thought..

 

[GeosTalon]

I will check all motor mounts this weekend. If you can think of any other thoughts, I'm listening. Thank you for posting.

 

[peckgsx05]

I am currently having the same problem. Please update if/when you fix the problem or find any new information.

 

[fourreGsixty3]

Have you had a 4wheel alignment? If not then thats probably your culprit...and even if you did have it done if you hit any decent size bumps/pot holes its probably out again. Does it shake when you brake? If so does it get worse? Check your rotors, I doubt this is the problem but Im just trowing ideas out there for you to check. If you look at your rotors and there are uneven ware(SP?) marks then they are warped and you may want to replace them, like I said before this is probably not your problem but good thing to check, because my alignment was out and the wheel shoke at 60mph+ and even worse when I hit the brakes, so I fixed the alignment and it went away, but when I hit the brakes at higher speeds the wheel shoke just the same as before so I checked the rotors and they were warped so I figure the shaking should go away soon as I replace them. Good luck with your shaking problem, gets annoying haha.

 

[GeosTalon]

These are all good thoughts. I'm going out to work on the car and try a couple of things. It could be the alignment though. I'll run through the list and post up what I find and what fixes it if applicable.

It doesn't get any better or worse with the brakes. The shaking is far beyond what a rotor with buildup (rotors actually don't warp, the brake pad material actually embeds into the rotor, it's called cementite) but I will check. I don't want to dismiss something just to find out that was the issue.

If anyone else has some suggestions, I'm all ears.

Thanks!

 

[GeosTalon]

Well, I found the issue yesterday.

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It would seem that one of the internal clips wasn't in all the way, and it came out. This allowed for the u-joint to begin to loosen and throw off the balance of the driveshaft.

I also found out that the rear e-brake cable is broken and the driver side caliper is frozen. Wonderful stuff. However the car no longer shakes wildly. The small amount of vibration is from the wheels being bent, which I'll fix at some point.