T800 rear end vibration

Carrier bearing was changed couple years ago, no change. No caps spinning on u-joints. All are new, all get grease to all four corners.


As for the driveline angles, I bought an electronic level a couple years ago. Head mechanic at kw told me to check angle the engine is sitting at by setting the level on top of the valve cover, and compare that with the angle of the first drive shaft between trans and carrier bearing. He said the angles have to be identical, but after the carrier bearing the angles of the shafts can be different. I did, and need to check it again but I'm pretty sure I'm within a tenth of a degree.

All air bags have been replaced with last 3 years. Everything with them is tight, and nothing broke I can see.

Tires wear very nice, both front and rear. Had a 3 axle alignment done few months back, no change.

All the suspension bushings have been a concern of mine. They are still the OEM black rubber, and appear to be ok. But I would like to do some more investigation there, to see if I have slop somewhere.

I will have to look up what the pinion bearing is to be honest. That's one thing over my expertise.

 

I have considered opening up my front rear, but have never been into a rear end before. Is there timing or anything else I have to know about, or do I just take bolts out, take things apart, inspect, and put things back together?

I tried looking up a video or parts breakdown of a rear to familiarize myself with it all before tearing into it, but am not finding much.

 

I had a local shade tree (but very very knowledgeable) mechanic do my axle bearings, as it was soon after I bought the truck and I wasn't comfortable doing it. He drained rear ends, of course, and didn't not find anything to alarm him.

Since then, on all my10k mile PM, I drain a little out of each one and haven't found anything. Oil looks great.

 

I'm sure when I replaced my carrier bearing I put it back just like I found it. That's not saying a whole lot tho, and by that I mean this. I am very picky about the mechanics of my machines, vehicles, trucks, etc, but the previous owners of this truck....not so much. So, it may not be correct. I have found several things repaired by previous owners that I wouldn't consider done right.

Will do some more checking on the driveline angles. I hate to take it to a shop and say, here fix it, but am about ready to. So far, 95% of the repairs I have done myself. Or should I say, throwing parts at it. Regardless, I don't have much labor money in it. But I kinda wonder if I had taken it to a pro driveline shop right after buying it if they wouldn't have possibly found it and saved me a lot of grief.

Is it possible to break the pinion shaft and still drive the truck normally? Reason I ask is, around the time I had my shade tree guy replace axle bearings, we found excessive play at the pinion shaft. (Looked it up, know what you're talking about now) He took it apart, and I distinctly remember him saying something was completely broken, and I thot ahah, that's my problem!

(It was a shaft of some sort I think, but kinda forget)

But no, didn't fix vibration. But did eliminate the excessive play. I need to check that again, but last I greased it all up I pushed on it and could just barely detect movement. Which I assume is about right, just a few thousands of play....

 

Update- I have done more work/investigating. The movement of the transmission I feel in the shifter does not happen if I drop the drive line after the carrier bearing, and bring drivetrain up to speed. Smooth as silk.

I did remove my front diff assembly, and took it to Inland Truck Parts in KC. They disassembled and inspected, and said it looked like brand new. Replaced thru shaft bearings, and yoke on front diff input shaft at that time.

No change.

Took main drive line to them, and they went over it with a fine tooth comb. Replaced slip joint and yoke, replaced another weld yoke or two they thought didn't look the best, all new u joints, and balanced it.

This drive line work has actually magnified the problem. It is more noticable now, and is prob as bad as I have ever felt it.

ITP mentioned the ujoints being not so great on the drive line, and I told them they weren't really that old. 2-3 years maybe, 50-75k miles or so. They kinda acted like that wasn't a good sign. I do pull oversize and heavy a lot tho.

But I feel like whatever this problem is is causing drive line wear. A couple months ago I replaced the main frame crossmember under the 5th wheel, as I found it was cracked pretty significantly on both sides. No change in hop. Upon more inspection, I have a crossmember bracket under the cab that has 3 bolt holes, and the one clear on the end is broken away from the others. Need to get that changed someday.

Guess in conclusion, whatever the problem is is clearly causing a lot of strain and stress on the drive line and frame components. I hope to take the whole truck up to ITP soon, and let them look it over. I am at my wits end with this thing, looking for a big creek to drive it into!