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Old January 7th, 2018, 17:57
NAXJA Forum User
Join Date: Jul 2015
Location: Boulder, Colorado
Posts: 163
Documenting My Crank Walk - Jeep 4.0

Greetings all. Thought I'd create this thread to help others in the future.

The Basics
  • Purchase Jeep in Fall
  • 1991 XJ 4.0HO
  • 130K
  • Engine running great, good power, great mileage
  • Winter - Belt started squealing
  • After checking everything I was mystified
  • It turned out crank was walking 3/8", throwing the harmonic balancer pulley out of alignment

See video of crank walk here:

What to do?
  • I debated pulling the oil pan to try to replace the thrust bearing.
  • Found video on youtube with exact same symptoms
  • Turned out the guys crank was destroyed at the thrust bearing
  • Decided there was a good chance mine was also destroyed

Pulled my engine
  • Found shards of copper thrust bearing in bottom of oil pan even though oil came out clean
  • Discovered my crank had a massive groove worn in it from the thrust bearing
  • Thrust bearing is also destroyed

See images here:

So what caused the carnage?
  • I am not sure
  • The coolant bottle is very dirty
  • Could have been a head gasket leak at some point ruining the lubricity factor
  • Could be the oiling grooves on thrust bearing were not milled enough
  • Could be a ballooning torque converter
  • Could be high pressure in the transmission lines (so I've read, and my pressure was high)

As it's been difficult to find the culprit, I am doing what I can and crossing my fingers. Replacing engine and torque converter. Also had transmission line pressured adjusted back down to where it is supposed to be.

I wonder if these bearings or crank were original? There was a number paint markered into the back of the crank where it meets the flex plate. And two marks on the thrust bearing cap.

Hope this next engine survives and that this will be helpful for someone down the line.

Last edited by BALTANAKT; January 7th, 2018 at 18:02.
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