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BALTANAKT
September 15th, 2017, 07:51
Hey guys,

A year ago I picked up a '91 Cherokee with a 4.0 and an automatic transmission.

It ran great for six months, but then I realized the crank was walking back and forth about 3/8"-1/4", sending the pulleys out of alignment and making a huge racket.

I've heard you can get crank walk by riding the clutch, but this is an automatic.

I'm pretty much at a loss for being able to explain what happened, and I am worried about it occurring again once I put in a new motor. Could the tranny/t-converter/flex-plate be responsible in some way? Or was it something else?

Thanks for your help

RCP Phx
September 15th, 2017, 07:59
The only way you can have excessive end play is if the thrust bearing is toast and that is caused by wear or possibly something not installed correctly!

Anak
September 15th, 2017, 08:15
3/8"-1/4" sounds like more play than a worn thrust bearing. I think you would have to completely eliminate that bearing and then some in order to get that much play.

Have you checked the balancer itself? Could it be loose on the crank? Or perhaps the outer rim loose on the center?

BALTANAKT
September 15th, 2017, 08:24
3/8"-1/4" sounds like more play than a worn thrust bearing. I think you would have to completely eliminate that bearing and then some in order to get that much play.

Have you checked the balancer itself? Could it be loose on the crank? Or perhaps the outer rim loose on the center?

Actually I put in a new balancer thinking that was the problem. That's when I realized the whole crank is shifting back and forth. :eeks1:

techno1154
September 15th, 2017, 17:13
Crank shaft thrust bearing? Isn't that part of the rear most crank main bearing? If that is so then both front and rear lips (sides) are only about 1/8" thick, iirc. Assuming that is true, it mean both front and rear lips are gone to allow 1/4" of movement,....or is it possible to put a bearing in that do not have the lips on both sides? :dunno:

Anak
September 15th, 2017, 17:16
Sounds like time to pull the pan and figure out what is going on.

I can't imagine any way around it.

trippled
September 15th, 2017, 18:04
It should be the middle bearing that's the thrust bearing, and it is pretty thick. there is the possibility of a torque converter ballooning under pressure, and basically forcing the crank into the thrust bearing the same as a clutch would. I agree before anything is done a pan drop is in order.

RCP Phx
September 15th, 2017, 20:49
Yes the thrust bearing is the middle bearing!

Hypoid
September 15th, 2017, 21:41
Or was it something else?
Is it possible that the engine is not original to your XJ?

BALTANAKT
September 16th, 2017, 09:59
Is it possible that the engine is not original to your XJ?

I just went out and looked.

My Jeep was built 5/91.

Engine reads: I09MX27

Not sure what an "I" indicates. Trying to find some info on that. I'm assuming it means "1". If so, that I think it would mean the engine was built after the XJ.

Hypoid
September 16th, 2017, 11:03
There is a cast date on the driver side, toward the back, just above the ribs that run the length of the block.

When I pulled the engine out of my '90, the block had a cast date in 1991. ;)

techno1154
September 16th, 2017, 15:24
Yes the thrust bearing is the middle bearing!

Thanks for the info. :cheers:

I have been in there once and that was in 2001 to change a rear main seal.

BALTANAKT
September 16th, 2017, 16:56
There is a cast date on the driver side, toward the back, just above the ribs that run the length of the block.

When I pulled the engine out of my '90, the block had a cast date in 1991. ;)

Thanks!

Block reads: 83091
Vehicle built 05/91

Guess that's feasible.

Here's a video of the crank walk. :doh:

https://youtu.be/L4XN_mSOk_o

Green XJ Jeep
September 18th, 2017, 07:37
Your thrust bearing is shot.
Down and dirty quick fix is drop the pan and put new bearings in it. Keep in mind this is not the correct way to fix this.
The bottom end should be gone through since all the bearing surfaces are probably full of metal from the thrust bearing