crankshaft endplay

2000 xj, AW4, 231, 4"lift, sye, tom woods front and rear shaft. 140,000 miles. mobil 1 synthetic since 2003.

I was checking flexplate bolts because i have the same low idle knock everyone speaks about and found that they were tight. Problem is that i also checked to make sure the flexplate wasnt cracked and when i moved the flexplate back and forth it moved the crank noticably for and aft. I checked at the harmonic balancer and sure as **** it moves with the flexplate. So I got out a set of gauges i use to measure spark plug gaps so that I could get feel visually of what the allowable distance was for endplay at the crank.

I dont think I should really be able to see the movement? I would think even at the max allowable endplay I would only be able to feel the movement. I am going to measure with a dial indicator tomorrow to see how much endplay there really is. I just couldn't imagine I should be able to noticably see the crank move.

If the thrust bearing is toast then it would seem that the transmission is to blame? I saw no cracks in the flexplate and unfortunately for me all the flex bolts were tight. Tranny lines arent crimped that I could see.

spec is 0.0015 to 0.0065 in. You should be able to feel a little movement. Some info on thrust bearings and failures: http://www.stealth316.com/misc/clevite-thrust-bearings.pdf

still dont have a dial indicator and am looking to see if i have room to even use one with the engine in the jeep. either way i will need eventually so i'll try later today hopefully. i'm still thinking I should not be able to move the crank visually. need to drop the pan still to check out the internals.

i am leaking out of the front and rear main seals.

Talyn said:

spec is 0.0015 to 0.0065 in. You should be able to feel a little movement. Some info on thrust bearings and failures: http://www.stealth316.com/misc/clevite-thrust-bearings.pdf

Click to expand...

that article is designed to make me have to pull my transmission. lots of info there but pretty straightforward. thanks for that.

I doubt its your transmission.

i dont think its the trans but wont know until i start diagnosing it. i wish i had more time. i only have 140k on this engine and have a cousin and buddy that have 2x that mileage. these motors go forever. i have beat the snot outta this thing though. i've been in places that i should never have gone. matter of fact i looked at it from behind watching a buddy drive it from being mildly stuck to fire shooting out the exhaust. makes me happy thinking about it. at one point my jeep was literally a training bed.

The thrust bearing is in the middle of the crank.

The transmission is not to blame.

Aside from the obvious causes, such as dirt contamination and mis-assembly, there are only three common factors which generally cause thrust bearing failures. They are: poor crankshaft surface finish; misalignment; overloading.

when i say transmission i'm really talking about the torque convertor being bad somehow or the flexplate. i don't have any shifting issues so i would think the trans if fine. i'm not sure about crankshaft finish but what would be the cause of that? is that where the misalignment comes in? and if so does that mean a hone of the crank bores, turning the crank, and new bearings? i still haven't taken off the pan becuase i don't have the rear main or front main seal which i need and in order to get a look at the flex plate and convertor i'm thinking i might as well pull the engine and clean it up anyway. gonna dig into this thing when i have access to some dealer items after the weekend. thanks for the help.

if anyone has experience with just replacing the thrust bearing and solving the issue on endplay long term please let me know.

Well, you have 140,000 miles on it. So it might have taken 140,000 to increase the end play, if that is the case. Replace the thrust and you might be good for another 140,000 miles.

just contacted the dealer. they have the fms, rms, and oil pan gasket in stock. not sure if it was the guy i was talking with but he couldnt find the thrust washer as being available. best source for the thrust washer?

There is no thrust waster per se. Its part of the #3 main bearing. You would do better price wise if you got the needed items from Rockauto, Advance auto, etc. You might also need the timing cover gasket as usually the timing cover comes off to replace the front seal.

i need to get the correct bearing dimensions. plastigauge? the original dimensions are on the upper bearing shell correct? can i/should i only replace the thrust washer bearing? thanks for the replies. it's nice to have someone help out.

You'll have to check with a bearing manufacturer about getting it alone. ACL, Clevite, King, are a few. The bottom one should have the size as well, but not sure on that.

Depending on what is really going on,you may need to buy an oversize(thrust) and have it cut down to establish the proper end-play.

thanks guys. i'm going to have to wait a couple weeks in order to get the cash and dig into this. waiting on a machinist from craigslist to get back with me about a dial indicator he has for sale. i don't even know exactly how much endplay i have. all i know is i can see the balancer move a pretty good distance.

i'm also still debating on whether to pull the motor. this thing needs a rms, fms, oil pan gasket, timing gasket, timing chain while i'm there, oil seals for the filter housing, oil pump...

not to mention i just bought an add a leaf for the ome 3" i've been running for years now, installed new rubber brake lines all the way around, new rotors f+r, pads f+r, misc gear oil and such. then i find the endplay on the crank and rear axle shafts.

glad i have help from you all and a full service manual.

No body makes an over sized thrust bearing for the 4.0L.

Really, the first thing you need to do is determine if it is out of specs.

Second, if it is, you will need to use Plastigauge to determine the bearing requirements for all of the crank and rod bearings--you are in there, might as well do it.

Note: It was normal for the 4.0 assembly to mix and match bearings up to 0.025 mm in difference to achieve the best clearance.

The engine section of the FSMs are quite good covering this.