Hey everyone,

I've searched through some other threads and I haven't found a definitive answer for my problem. I've had a high-speed rear vibration for some time now and I just assumed that is was something to do with the drive shaft (u-joints or a dent in it). I finally got around to pulling it out and having it checked and it was in fact out of balance. I had a new yoke welded to it because it was broken, and a whole new sheath put on the outside to correct an out-of-round issue. I also replaced the u-joint even though they didn't appear to be that bad. I though I all this was my problem for sure, however, I still have the same problem.

I have a 95 2WD, long bed, std cab (one-piece drive shaft), 5.8L, E4OD auto and everything is stock. All four ball joints, outer tie rods and radius arm bushings were done little over a year ago (about 10,000 miles ago).

The issue is, right after about 70mph the whole cab starts to shake but dies out after I slow back down. Also around 50-55mph it shakes even worse, especially when maintaining that speed or decelerating without pushing the brakes (while accelerating I don't notice it much). I've checked the tire balance a few times and rotated my tires around to see if the vibration moved at all but nothing changed. I double checked the tires for being out-of-round and they look good to as they are only 3 year old.

In any case, I'm stumped as to what is causing this. Could it be the rear shocks? They look like they haven't been replaced in a while. Or maybe a pivot bushing for the front I-beams? I also though it might be the front wheel bearings as I recently detected a very small amount of play in them. I think the problem is coming from the rear but I guess it could be anywhere as the whole truck shakes up and down!

Sorry for the long post but I will appreciate any help with this. My wife is pregnant and wants me to get rid of my truck for a smaller car because it is to "rough" for her. I want to fix this so I can keep both of them!

Thanks,
Tony

 

Check your wheel weights. you may have lost a weight and caused a tire to be out of balance.

 

Our Afro-american friend's refer to rear vibration as,"Junk inda Trunk!" (Supposed to be a good thing)

 

The weld would have to be top dead center w/ no excess lag. When rpm's of something heavy gets into the hundreds & more, tolerances/angles/weight distrubution, become critial. Sometimes if you have a chase vehicle traveling with you, observing at different angles, you can see what's out of whack. It will stand out.

 

Ghostman - I've checked the wheel balance a few times as I have easy access to tire machines and wheel balancers. When I returned from a test drive, and it was still shaking, I checked again and the wheels were still in balance. I even went so far as to break the tires down and rotate them on the wheels and re-balance - no change.

ymeski - I had all the work done by a reputable heavy truck machine shop and the welds looked very clean and straight, in fact, I couldn't even tell where it began or ended; just one fluid circle around the new yoke! I haven't explicitly checked like you stated but since doing all of that work to the drive shaft and experiencing absolutely no change in the vibration, I was thinking that it was safe to rule out the drive shaft. I'm not a mechanic though, so I could be wrong!

I'm quite baffled by this but I have learned to deal with it. After all, it is a 15 year old truck! I just don't like that my wife has to endure the discomfort whenever she is in my truck.

 

I understand. I bought a new dodge 3500 in 04. it had the same issue. it was in the shop at least 6 times. two different shops. they were replacing everything even the rear end. I am a mechanic also. we could not find it. It ended up being the Front Drive shaft on mine. There are so many things that could be causing it.

 

Try the chase vehicle thing. A different perspective while the vibration is occurring.

 

Indeed, that's what I'm afraid of! I can start replacing a bunch of parts but I was hoping to narrow it down a little because I don't have a whole lot of excess cash!

Thanks man

 

Have a very similar issue with mine. I finally took cover off the rear end and discovered my spider gears and pinion shaft are worn quite a bit. The rear end grease was also way too thin. (like 20wt) I can't get new parts till next week, so I refilled with Lucas gear oil. (140wt) this alone made a huge difference.
Mine looks like someone ran it with two very different size tires on rear or was stuck and spinning one wheel a LONG time.

Just a thought....easy to check.

 

After re reading your post, it sounds like a tierod bushing, but you say they're fairly new. Does a particular road condition set it off? Any lane search? If you had another set of tires & rims you could put on temporarily to rule those out. Not beig there to eperience it, it's even harder to fugure out. It's not an engine rpm/load hamonic balancer type vibration?