Carrier bearing (center support bearing) causing this?

[aeidian]

89 2.9 4x4 5spd FM146

I swapped out my 70/30 bench for a 2 buckets and a center console. I used some bolts from lowes to attach that bracket for the console to the floorboard, but they were a bit too long, specifically right above the transfer case. The rear of the transfer case where it bolts to the drive shaft (I wanna say the yoke, but I don't know if that's the right term), the big ring that the bolts go into from the u-joint, seems to hit the end of one of the bolts when taking off in first. I trimmed the bolt down with a dremel, but it's still a bit too long, because it still hits. Seems like the drive shaft is tweaking when taking off in first and hitting that bolt, making a popping sound. It didn't do that before I put the bolts in, and I know it's hitting so I don't think it's the u-joint popping. Anyway tonight the truck started shuddering on take off. Revving the engine in neutral it didn't have an issue, it wasn't until it was put under load by being in gear did it start to vibrate and shudder. It does it in each gear, but lessens as I get to cruising speed. It doesn't stop completely, just lessens. Lifting the rear end and putting it in gear I can see the transfer case wobble a bit, and a bit of up and down play on the driveshaft. The bushing part of what I believe is the carrier bearing (center support bearing) seems a bit worn. Could a worn out carrier bearing be causing this shudder and vibration?

Also when I had the rear jacked up off the ground and in gear, one wheel spun, the other didn't. I didn't think that there was limited slip differential or whatever that far back. I can hold one side and the other moves, but then I can hold the other side and the one side will move. I thought they were both supposed to move all the time, is this normal for one side to move and not the other when it's in the air? I've seen front wheel drive cars do this, but on newer ones.

 

[Earl43P]

Yes, the worn DS carrier can make it shuddder and vibrate. You may also have worn transmission crossmember mount rubber, letting it flex so much that it hits that bolt (have you considered putting that bolt in head facing down instead?)

The rear wheel behavior is correct for an open differential. A limited slip would spin both tires, an open won't.

 

[aeidian]

Thanks for the explanation on the rear end, everything I do is a learning experience. I knew the rubber was good on the transmission mount because I just R&R'd the transmission a couple of months ago, but I took a look at it anyway after you suggested. Turns out that the nuts that bolt the mount to crossmember, one was missing and the other had a couple threads from falling off. Guess that explains why the transmission felt like it was bucking, and why it had gotten worse. Failure on my part to tighten them good enough. Off to Lowes to get some replacement nuts and lock washers, then on to advance to get a new carrier bearing. I'd like to replace the u joints too, but that will have to wait for another time. I'll post back when I'm done, hopefully with good news.

 

[aeidian]

Got it all put back together, no shudder during take off, but a pretty strong vibration during cruising at about 45+. Sounds like someone blowing over an open glass bottle too. Jacked up the rear and shift through the gears to 4th, held it at 45 and looked at the rear wheels while it vibrated. Drivers rear has a bit of a wobble. Took the tire off and drum, there's in and out movement on the hub, and a slight up and down. So I take it the wheel bearing is toast. The manual I have says there was a Dana 30 and a 7.5 differential, the book says the Dana 30 was on Aerostars and the illustrations for the bearing removal do not look like mine. There's no window whole on the stud part of the hub, so I'm guessing I have the 7.5 one? Looking over the instructions it seems like a bitch to get the bearing out, having to disconnect shit inside the rear end, special tools. Ugh.