are you sure they balanced the tires? Try having them balanced again. That sounds like your issue. They probably only balanced the tires going to the front of the vehicle, which is why you don't feel the vibe coming from the front. Seat vibration indicated the problem is from the rear of the vehicle.

 

FYI spindle bushings will not cause a vibration. Replace your U-joints. They are due anyways. Take your tires somewhere else to have them balanced. I've had places screw mine up multiple times. They usually give that job to the new kid working there and it's more of an art than a science sometimes.

 

Had the 31's balanced twice and this set of 235/75/R15's balanced once. Between the two sets, the vibration stays constant in terms of type and location. Only thing changes is that the vibration is more pronounced with the 31's. Kinda confident that it is not the tires or rims.

By putting the transmission in neutral while coasting through 50-60 MPH, I would think the U-joints are out of the picture as well? I agree that replacing the u-joints is relatively inexpensive, but it just seems like putting unnecessary money/time into the problem. Not that I have not done that before!

 

Thanks for verifying that.

Aaron, does your truck have ADD 4wd? If so, then the CV's do spin. The hubs are always locked in, so to speak.

 

Edit last post..........

I say "truck", but I mean your 4rnr.

 

Yep! ADD indeed. Did not know this was true of ADD. So it could possibly be the CV axle shaft that is causing the vibration given that I have checked the driveline and tires?

 

If it's not the u-joints, bent axle maybe? That could be a reason it's worse with the 31's and although rare, it is possible.

 

Okay, reread the posts......

What makes you think that by having the vehicle in neutral and the vibration is still there that this excludes the drivetrain? The shafts are still spinning. Regardless, I'd think the vibrations would be evident in the shifter. But, yours in the seats.

Did you try dropping the rear shaft and driving in 4wd H? If you did......like you said you would......and the vibrations is still there, then cross the rear shaft out.

I'll admit, I'm at a loss at this point. I'll have to think about it some more.

Oh, is there any chance you have a bent axle or loose bearings in the rear?

 

Haha....you guys are posting faster than I am.

 

Yep...it's true...lol!

I suppose it could be the cause, Aaron. But, I'm honestly not sure because I don't remember having any vibration in my wife's '92 w/ADD when we first got it and the CV's were bad. Didn't drive it much at that point until after I'd change them out.

 

Guess I am going to have to remove the rear shaft and give it a whirl in 4-HI. For some reason (my lack of knowledge), I did not think the drive shaft spun when in neutral. Thought instead that it released. Thinking now that I was wrong

Possible that I have a bad bearing on either side of the rear. Replaced a leaky inner seal and dust cover on the RR side when I was rebuilding the engine. Brakes were soaking wet in fluid. Bad bearing = leaky seal?

 

The driveshaft is still engaged at the differentials via the pinion/companion flange. So, it will still turn, of course. The engine is just "disconnected" at the transmission when in neutral, so no power to the drivetrain.

Leaky seal doesn't necessarily mean bad bearing......just means leaky seal = gear oil from axle/diff leaks out onto the brakes. You may still have a good bearing with grease.

Speaking of diff????!!!! When's the last time you check the fluid level?

 

(Very sorry to be cluttering up your thread with so many posts, Aaron. I can't edit with my computer operating as it is on the only two of three browsers I run that won't crash. Need reformatting!)

Anyway, yeah....try the 4wd H with the DS disconnected. That was a good suggestion early on by the poster.

 

Will do! One question regarding the removal of the driveshaft...I have read a few threads where it was explicit in that the shaft and flange on top or bottom end needs to be marked so they can be re-aligned when installed. Necessary?

 

Um....well, it is recommended, but I have never had any real issues.

I just replaced the rear shaft in my wife's '92 not long ago. It certainly didn't matter if I marked the flanges then. Know what I mean? I just made sure the u-joint's were lined up with each other. Not one vibration. (She did have a vibration, though it was a bad slip joint, which is why I replaced it.)

So, I suppose it's up to you. I guess I would just because there's no real reason not to, in your case.

 

Oh @#$%%! Wait!!!! You have an automatic, right? If so, make sure you have the vehicle in 4wd before you drop the driveline.

 

Curious. Why? Won't ADD engage the front differential otherwise?

 

If you think about, with the automatic you have to step on the brakes before you shift. And, in 2wd with no rear driveshaft connected to the rear axle that would otherwise be locking the drivetrain in a stationary position by the rear brakes, you'd more or less be shifting without having stepped on the brakes first. <<<Grind!!!>>> goes the tranmission.

 

Okay.......on second thought, maybe it won't matter. If you're in P, the driveshaft is out, and you shift from 2wd to 4H, the ADD will engage before you shift into drive. So....whew!

I suppose it's not a totally unneccessary thing to have mentioned it so that you are atleast aware of it, though.

 

It makes no difference if you have it in 4wd or not before dropping the driveshaft. It will not grind or do anything odd... I will stress to make sure that the wheels are blocked, and whatever you do DON't park on a hill without using your parking brake. Once fluid stops flowing (truck off) it will roll (if the incline is enough) Ask me how I know...