Clunk from rear - U-joints suspected

[packmule1911]

If I'm cruising along and either slightly decellerate or accelerate, I hear and feel a short clunk from the back end. I haven't gotten under to take a look, or jack it up to unload the check for u-joint play, but the sound is what I'd imagine with a u-joint that is worn.

Also, the sound is new since the 2.5" lift, so I'm expecting that they were already worn and changing the angle pushed them over the edge.

Does this theory sound likely?

If so, what's the difference between rear u-joints that are specified "at transmission" and "at axle"?

Thanks.

[4.3LXJ]

here is quite a bit if difference between rhe two. Inner vs outer snap rings and physical size.

[packmule1911]

Understood. Got both, but hadn't looked at them yet.

Does it sound like my diagnosis is correct?

[XJ Wheeler]

I'd say it's a good possibility. The change in angle does funny stuff to parts that are suppose to adapt to angles...

Sent via messenger pigeon. I talk, he types.

[packmule1911]

U-joints look good, haven't leaked, and don't wiggle. The TC at the rear driveshaft however, doesn't seem good at all.

XJ 231 TC - YouTube

[4.3LXJ]

Lots of slop in that diff. How are the pinion bearings, tight I hope. Also see if you can get any side to side wiggle at the tcase output

[packmule1911]

There's slop and noise in the rear differential, but nowhere near what's at the transfer case output. I know the rear differential needs work. The front was much worse and it was rebuilt a couple years ago.

I can get slight wiggle at the TC output, but I think it might be just a little from the u-joint. If I secure the shaft from the TC and tug the driveshaft, it feels more u-joint, but again very little.

Do TC's usually sound that crappy?

Symptom update: when coasting, if I ever so slightly apply the gas I can get a constant growl, like the clunking at a much faster rate. Sounds like those highway shoulder cuts that wake you up when you drift.

All of this is new since my baby light, except for knowing the rear needed a rebuild before too long.

[4.3LXJ]

They can when the chain is worn out

[packmule1911]

Been looking at TC rebuild kits, SYE kits, etc.. Seems inevitable.

[Pinkyman]

Your noise sounds similar to the noise i had when i originally put my 2.5 Add-a-Leaf in....

Did you install a transfer case drop? Thats what it eventually took to fix mine.



I also noticed that since the lift, I get a humming/rumblestrip noise from the rear when I let off the gas. A quick Google search seems to lead me in the direction of me needing to install my t-case drop in order to remedy that.

[packmule1911]

Your noise sounds similar to the noise i had when i originally put my 2.5 Add-a-Leaf in....

Did you install a transfer case drop? Thats what it eventually took to fix mine.

Nope.

Talked about doing so in my lift thread, but didn't do it because it seemed I was within a reasonable range of lift to not half to. I admit, I'm not visualizing how you drop (lower) the transfer case. Inexperienced in this area. Haven't dug around enough. It bolts to the transmission, so it all has to lower. I'll keep reading and stop embarassing myself in public.

How much did you drop?

[Pinkyman]

Nope.

Talked about doing so in my lift thread, but didn't do it because it seemed I was within a reasonable range of lift to not half to. I admit, I'm not visualizing how you drop (lower) the transfer case. Inexperienced in this area. Haven't dug around enough. It bolts to the transmission, so it all has to lower. I'll keep reading and stop embarassing myself in public.

How much did you drop?

I did the 1" drop, and it seems good now (no more noise). It was relatively simple compared to the lift. The crossmember bolts for the transfer case came out with hand tools, but i needed heat to get the studs out.

It really only took me about an hour to drop it and get it all back together.

[packmule1911]

I did the 1" drop, and it seems good now (no more noise). It was relatively simple compared to the lift. The crossmember bolts for the transfer case came out with hand tools, but i needed heat to get the studs out.

It really only took me about an hour to drop it and get it all back together.

OK, so you're just lowering the tranny cross member, and because the transfer case is sitting on (an bolted to) the cross member, it's allowed to ride lower because what's supporting it's weight is lower? The drop is determined by the spacers you use at the ends of the cross member?

Thanks.

[Pinkyman]

OK, so you're just lowering the tranny cross member, and because the transfer case is sitting on (an bolted to) the cross member, it's allowed to ride lower because what's supporting it's weight is lower? The drop is determined by the spacers you use at the ends of the cross member?

Thanks.

This is absolutely correct :thumbsup:

I dont think ive ever heard of anyone doing anything bigger than a 1". But from the sounds of it, that should take care of your issue.

[packmule1911]

That's a relief. Plucked from the fires of stupid at the last second.

What is recommended for bolt dimensions and hardness?

[Pinkyman]

What is recommended for bolt dimensions and hardness?

That part i cant help you with :-(

I know that the kits are usually like $40, and that they come with the bolts most of the time.

[blazer2]

When i dropped mine i went to a hardware store. I took a bolt with me and match them up.
And at the same time i picked up some 1" spacers for my drop. Out the door.
It was under $25.00.
The bolts i picked up where grade 5. And the same for the spacers.
I have seen some where they stacked up washers.

[packmule1911]

I got bolts, lock washers, and four stout steel couplers. The couplers inside diameter just allowed the bolt to pass through. It was a pain to line everything up while laying under there, but it's done. Sounds and sensations gone, and the drop is 1.25".

Funny though now is that it runs a little different since doing this.

Always something, but I am thankful the other problems seem alleviated.

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