swanson

Hey guys,

I have a bone stock '98, 4.0L, 5 speed manual. No lifts, anything like that, it's been my daily for 12 years.

Bout a month or so ago the rear diff let go (the pinion bearing went and the shaft crashed into the carrier). Found an axle from a wrecker and swapped it, confirmed same gear ratio and type, just older - 3.07 gearing, Chrysler 8.25, but the axle came off a 95 instead of a 98 - I think the only difference is the actual axle sizes (older ones had the 25 spline, newer ones had the 27). The transfer case is a NP231 I believe but I'll have to check.

Ever since, I've had driveline vibrations when you get it up to highway speeds, almost exactly like a ujoint is shot. I replaced the rear driveshaft ujoints (the axle ujoint was worn). Still there. Took it off and put in 4WD, got it back up to highway speeds, smooth as silk, so it's not in the front end. Got my tires balanced as well and it's still there. I've rotated the yoke on the front ujoint 180 degrees, vibrations still there.

The wrecker axle looked in good shape, nothing wrong with the gears, the bearings seemed good, and I'd think if it was something with the diff I put in, I'd feel it even if the rear driveshaft was out.

So my question - are the driveshafts tuned to the axle they're with? I shouldn't have changed any angles at all, the axle we swapped was nearly the exact same (unless there was some slight differences between those years or something). The transmission mounts seemed... alright but they could be going, the things got a lot of miles on it.

It didn't appear that any weights were missing on the driveshaft, but I'm gonna take it off and get it rebalanced when I have the time.

It's honestly driving me crazy.

00t444e

Driveshafts are balanced by themselves doesn't matter what axle it gets used with.

swanson

That's what I thought but I figured maybe there was something weird with these. I'm gonna park it and take the shaft off and do some more fiddling.

boxburn

Jack the rear up and spin the wheels, does either side have a wobble to it? One of my old D35 shafts is very slightly bent and you could see the edge of the tyre moving in/out about 1/2" when spinning.

Seabee

May be a long shot, but check the pinion angles between the two. You may have to shim the new axle housing perches to match the old housing angle.

yorkee

Na

BwanaBob

You might try another rear driveshaft. Maybe one of the yoke ears was
damaged and it just isn't true anymore.

swanson

So I finally got the driveshaft to a driveline shop. One of the yoke bores was worn out and was letting the ujoint cap move around. I had noticed one cap was pretty easy to get in but didn't pay attention to it, when it was together it seemed tight so I didn't worry about it. Either way.... they put welded a new yoke on and balanced the driveshaft for me.

And it's still vibrating at high speeds. I put it on jackstands again, took the tires off, took the drums off, had a friend speed it up, it still vibrates. The hubs seem to my eye be running true. The vibration can be felt in the axle and the transfer case.

I greased the slip yoke, just because it needed it - no change. Checked diff fluid, it wasn't low but I added a little bit anyways. No change. When you drop the driveshaft and put it in gear, it doesn't vibrate.

The hubs have very little play in them. Not anymore than the ones one the axle I took off. I measure driveshaft angles and the axle and transfer case are parallel, at least within a degree.

I'm almost at a loss here. I don't know if I'm just crazy and it always had this bit of a vibration, and I'm just noticing it now, or if there was something ****y with the diff I put in.

97grand4.0

Hows the brakes? A sticky shoe can do that, frozen park cable,..check temps

swanson

Soooooo after thinking, I remembered when I was first trying to fix the vibration, I had swapped the yoke 180 degrees, which did nothing. I phoned the shop I took the driveshaft to and they said they had balanced the shaft without the yoke on it. So I swapped the yoke back 180 and vibrations are gone, or at least it's now down to the normal shakes and rumbles that it always has had.

So the driveshaft was a bit buggered after all.