The Trooper has 204k miles and has developed a vibration which is felt from ~ 78 to ~ 82 mph. The vibration is primarily felt in the seat and transfer case lever more than throguh the steering wheel.

The vibration occurs at the same level in both 3rd and 4th gear so I do not believe it is an engine balance issue.

I have replaced all of the u joints and also had the driveshafts balanced. I've swapped a set of wheels and tires from another Trooper as well as having the tires on this truck balanced and rotated with no change.

My most recent attempt at resolution was to replace the front rotors and repack the front wheel bearings. The rotors felt a bit warped so I decided to just replace them at the same time. This seems to have changed the vibration in that previously the vibration occured regardless of if the truck was accelerating from 78-82mph or if it was slowing down from 82-78mph and now the vibration does not occur during deceleration.

I tried adjusting the bearings to the lightest suggested tension of ~ 3 lbs and then again to ~ 4lbs with no difference in the two settings. The bearings were not obviously bad but they do have 204k miles on them and no telling if they were ever serviced before I cleaned them up. Changing them wouldnt be expensive at under 200.00 but it is a hassle and I'm not sure where to get the proper bearing driver to install the races so I repacked them and put it back together.

I'm stumped for an explanation as to how this change could have had the impact it had (stopping the vibration on deceleration) as well as being stumped as to how to proceed on trying to fix it.

I'd sure appreciate any suggestions as to how I should proceed or even ideas as to what the problem might be.

Mark

I have noticed the same thing in my 93 Trooper. My friend at school had the same problem with his 93 Trooper as well (We had the same model,same options and everything, just opposite color schemes). We used to have the same size tires which 245's, but I've gone up to a 265 now and I noticed a decrease in the amount of vibration I get when I'm decelerating from the same speeds. Maybe by putting the larger size on it absorbs the vibration more, I don't know <img src="/forums/images/graemlins/confused.gif" alt="" />. I'd like to know what causes this as well. The only thing that I can think of is that the trooper is so dang heavy that when it slows down at such high speeds,strains the tranny. My .02, I'm probably way off the mark, but gotta toss an idea out there <img src="/forums/images/graemlins/shiner.gif" alt="" />

So yours only does it on deceleration? Mine always does it accelerating through that range but on decelerating it is different. If I decelerate slowly like by lifting a wee bit on the throttle it will get through that range with no issue but if I lift completely off the throttle it vibrates just as much as if I were accelerating. I figure it has to be driveline related somewhere but I don't know what else to check.

The larger tires are on my agenda. Current is 245/75 and I plan to go to at least 265/75 which if nothing else will raise the actual speed at which it happens.

It's a funny deal. My 1996 5 speed Troop doesnt do it and the tires on that truck are puny little original size ones.

My 95 5speed vibrates from about 76-81mph most of the time. Sometimes it will do it from 80-85mph. I am wondering if the U-Joints on the driveshaft are going bad. A friend of mine said that they weld wights on the driveshaft to balance them. I wonder if one of those might have come off?


michael

Mike,

That's what they do, weld small tabs of metal to the shaft, normally at the ends. I would think any which had come off would show up as rough spots on the shaft where the welds were broken as well as leaving spots where the paint on the driveshaft was "different" looking. Other than scraping them on a rock or something I dont see how the weights would ever come off though.

Mine were obviously bad. You might get under the truck and twist the driveshaft by hand while looking at the yolks. if you can see any movement between the u joints and the caps that go into the shaft or yolks the joints need swapped.

I tried doing them myself but never have I seen ujoints so tough to remove. I took both the front and rear shafts and new joints to a driveshaft shop. They swapped and balanced both shafts for 60.00.

In my truck it made no difference in the vibration but they did need changed.