Knocking Noise from Tcase/Trans

[3wheelingCJ]

Started to drive my Jeep again after doing a disk conversion on the front and noticed a new knocking noise that seems to come from the tcase/Transmission area. Verified the general source area with the passenger too.
The knocking only happens during take off from full stop and speeds up with the jeep until about 10mph, and then goes away. Sometimes it comes back, milder, after releasing the clutch after a downshift, when exiting a turn for example.
Accelerating or decelerating once moving doesn't bring the knocking back.
I removed the tunnel cover to watch the front drive shaft and didn't see it move in 2Hi. That ruled out the hubs catching.
Checked all of the ubolts on both drive shafts and they are tight.
The knocking is still there in 1st or 2nd gear during take off (have a t18a, so use 2nd on the streets). It's also present, milder, in 4Hi and 4Lo.
Not sure what else to check and looking for advice.

 

[Lumpy Grits]

See if the tranny or engine mounts have gone bad.
Could be the t'case shifter hitting the tranny cover.
Gary

 

[3wheelingCJ]

the tunnel cover was off during some of the testing, so it's not likely to be the issue.
I will check on the mounts and bolts to make sure everything is tight.

I am mostly concerned that the knocking seems to speed up along with the speed of the jeep on take off. making me think it's something internal to tcase or Transmission . Hoping someone will talk me off that ledge.

 

[Lumpy Grits]

When was the last time you ck'd ALL the fluid levels?
Do you have ANY play in the u-joints?
When was the last time you greased the u-joints and slip splines?
Gary

 

[3wheelingCJ]

Yeah, good point. Did tcase fluid just a couple of weeks ago before driving, have a leak so it’s a habit.
All other things you mentioned need attention. We’ll work on that and report back tomorrow. Have to get some grease.

Which ujoints should I check for play? Drive shafts are tight. I was thinking if the yoke is loose on tcase, but seems ok. At least without taking off the drive shaft, for what it’s worth.

 

[Lumpy Grits]

Remove the front DS for next test drive.
If the drive is still showing issues.
Pull the rear DS and reinstall the front one and repeat test drive.
Have you had the rear DS out lately?
Did you remove the slip spline?
Gary

 

[CJ]

I'm with LG, sounds like dive shaft slop. Have you inspected the ujoints?

 

[3wheelingCJ]

Checked all the ujoints and greased driveshafts. Fluids are good.
Last time I had rear ds out was last summer when I dropped tcase to put in new gasket. Did a couple long trips since then and some driving around town before parking it in the fall. Didn’t have that issue then.
While crawling around I noticed that both exhaust pipes a loose and move around where they are connected to the manifolds.
I’m going to try to get someone at my work to reweld driver side hander that’s just aft of the tcase and add one on the passenger side.
There’s still a problem with the manifold bolts. They are are very rusty and might be original. I sprayed a ton of pb bluster yesterday and will again today, then try to tighten them.
I’m afraid to snap them and really make the matters worse.

 

[3wheelingCJ]

Also, after greasing the driveshafts the knocking seems to have gotten less noticeable and, maybe wishful thinking, but more like the exhaust hitting something.
Could there have been ds slop if it didn’t move up/down the splines due to not being lubed?
I have greasable ds ujoints, so those got greased too.

 

[Lumpy Grits]

Slop in the slip splines will cause the vibrations you speak of.
How many miles since you last lubed the u-joints and slip splines?
I still feel you have engine and tranny mount issues.
When was the last time you replaced them?
Gary

 

[3wheelingCJ]

The mounts are fairly new and in good shape. Checked engine mounts bolts earlier and they seem fine.
I had Transmission mount bolts blackout before and will have to check them. There’s a good chance that happened again.
I just lubed ujoints and splines yesterday, but before that it has been a year.

 

[Lumpy Grits]

CK the skidplate to frame bolts too.
FWIW: If your engine and tranny are moving around enough to loosen the exhaust up.
You have mount issues-BTDT.
Gary