evsnova74

I got new tires yesterday. On the way to the tire shop there was a bad vibration between 40 and 45mph that felt like you were driving over a rumble strip. I just attributed it to those tires and ignored it. Well on the way back with brand new tires it was doing the exact same thing so to me that rules out a tire balance issue.

A year or 2 ago I replaced the u joints myself, and the first time we drove it it had this same vibration pretty much as soon as you started driving, like 20mph and higher. So I took the drive shaft out to get balanced, no change. I installed a new trans mount, some other things, it's all a bit hazy, all I know for sure is we finally took it somewhere and they put it on a lift and ran it in drive and determined that it was the rear u joint. They said they didn't think it was installed wrong and that sometimes parts are just bad out of the box. Hey whatever, it worked and drove smooth as buttah. Then a month or 2 later the accident happened.

During the weeks that we continued to work out of it while we searched for another van, if this new vibration existed we probably just figured it was from the wreck- the front end was badly out of alignment and was wearing on the inner edges of severely cupped tires (needed shocks but that was the least of our worries at the time).

So idk, now that everything is sorted I have no idea where to start with this. U joints again even though they've been replaced relatively recently? Try to get the driveshaft balanced again? Perhaps look into something in the rear end?

TLDR: got a vibration at 40-45mph and it's not the tires

Triaged

Hold on underneath the van and have someone drive it 40mph while you watch?

Now that almost everyone has a HD video camera in their phone why don't you duct tape a phone or gopro down there and watch the video to see where the vibration is coming from? Or drive it on jack stands.... Or take it to the same shop as last time and have them run it on the lift again?

What kind of accident? Could have bent the axle shaft or drive shaft?

tech2

where do you feel the vibration...steering wheel...body of vehicle?

evsnova74

I do have a gopro now, and considered doing that. The crazy thing was I put it on jack stands last time and it wouldn't do it unless there was load on the drive line I had assumed. Or maybe I just didn't know what to look for. Definitely worth a shot though. The accident was on the front left fender, it didn't seem likely that it would have affected the drive line at all but I'm not gonna rule it out.

evsnova74

I guess it would have to be the body, it feels like a lesser version of veering into the rumble strip on the highway.

William Kisselstein

A bad U-joint where it has slop in it, usually you can feel by letting off on the gas at speed. If you're accelerating it puts a load on it and the vibration goes away. Let off the gas and it's free to vibrate. I don't know if that will help if it's tight and binding somehow.

evsnova74

Well I put the new shocks on it yesterday and drove it for a bit to deliver equipment to my house. It doesn't seem to matter what I do, accelerating, coasting, braking, trans in neutral, even pulled down in 3rd, if it's between 40 and 45mph it's vibrating. On the way back it seemed to be dipping a little under 40 too so may be getting worse.

When I was installing the shocks I rolled under it to check the play in the u joints. They all were solid but there was definitely up and down play between the yoke and the tailhousing of the trans. There may have been side to side play too but I just couldn't put that kind of force on it. It seemed like there was also some play in the carrier bearing but it looked like it must have been replaced too back when I did the u joints so that may just be between the 2 shafts.

I didn't get a chance to gopro it, when I do I'll be focusing on the tailhousing. Any other thoughts?

Gumby22

A little play between the slip yoke and trans output shaft is normal.

I may have missed it but I didn’t read anything about inspecting the rear axle/differential.

Get the rear wheels off the ground and rock the tires top to bottom and side to side to check for bearing play. There shouldn’t be any so replace if necessary.

If no bearing play is present, Drain the differential fluid and look for large metal particles. If the cover has to come off to drain the fluid, support the axle with jack stands and shift it into neutral so you can rotate the carrier to inspect the ring and spider gears.

If it’s a limited slip, you should not be able to hold one wheel and rotate the other by hand, nor should the tires rotate in opposite directions as with an open diff.

While it’s open, make sure the vent fitting and hose are clear.

evsnova74

The rear axle was on my list last time I went through this, namely the bearings. I replaced bearings and spider gears on our 97 work van long ago and I don't remember it being too hard, but it's a simple and quick thing to check either way. Thanks for the suggestion.

Going back to the yoke play, maybe I'll put a dial indicator on it to see just how much play there is. You can actually hear it clunking back and forth so I don't know how normal it is. Will report back next time I get a chance to work on this.

Gumby22

If you’re concerned about excess play in the slip yoke, just pull the driveshaft to inspect the yoke and output shaft. Even if you take a measurement, it doesn’t mean anything unless you know what it’s supposed to have, and if you decide it’s got excess play, you’ll be pulling the driveshaft anyway.