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Unusual Main bearing thrust wear

RCP Phx

NAXJA Forum User
Location
Phoenix,Az
I've got the oil pan off right now for my "oiling project", in the mean time I was looking for a low rpm knock that had developed a while back. Well the crankshaft end-play measured .020" which is un-acceptable but I do not see any reasons why? I will install a new set of bearings tomorrow but I'm looking for input on why this might have happened. The wear is totally smooth so "gouging" is out.
 
This is getting stranger, I pulled a rod bearing and it looks good. I need to pull the timing cover as it looks like the chain is hitting the "front" of the cover. Got the new mains and will install just the thrust bearing as all the others look good.
 
Did anything change on the back of the engine? Flywheel,Flex plate,TC ,anything that would force the crank forward.
 
The only thing that changed during my stroker build was the crankshaft itself.
 
Was the end play in spec when it was put together ? And who did the work?
 
The original build end play was .002" and I assembled the motor myself.
 
Was this your first 4.0 ?

The reason I ask is,I was looking in the FSM and the procedure for doing the #3 main cap(thrust) was different than any other motor that I have assembled.I thought it strange that all the other mains were torqued to spec before the #3 cap was torqued down.

FSM also said that if endplay was out of spec a new crank was needed.
 
Did you change the harmonic balancer? I had one go bad. This caused a similar problem.

Yes and that's definitely something that's going to get looked. It's a good one so separation/movement is not likely but I'm very concerned with the pulley alignment.

Was this your first 4.0 ?

The reason I ask is,I was looking in the FSM and the procedure for doing the #3 main cap(thrust) was different than any other motor that I have assembled.I thought it strange that all the other mains were torqued to spec before the #3 cap was torqued down.

FSM also said that if endplay was out of spec a new crank was needed.

It's my first build with a 4.0 but probably my 10 thousandth build over all. You always need to torque the thrust bearing last after being finger tight you need to set it full lateral movement of the crank. The crank was a brand new Scat crank and I have already verified the cranks dimensions and the loss was on the bearing itself.
 
Ok.Good that you knew that. Is there wear on only one side of the thrust bearing, or on both sides? Trying to tell if the crank was pushed or pulled in one direction.
 
I just got off the phone with Russ explaining all this. There was .005" more wear on the front of the bearing vs the rear, but that may not be indicative on anything now that crank begins to move at all. I won't know anything more until I pull the timing chain cover and then the chain, lots of investigation to do still. The weird thing is that there are not that many causes for this type of wear but I'm lucky to catch it now, remember there is only about +5k miles on this motor.
 
Automatic or manual trans?

One thing I was pleasantly surprised about when I first got my XJ is that Chrysler didn't put a switch on the clutch pedal to keep you from accidentally starting the engine while in gear. This means I can just put the shifter in neutral and start the engine without depressing the clutch. That is what I do for whatever benefit it may afford the thrust bearing.
 
It a AW4 so that's why I find it hard to think about "torque converter ballooning" as a cause.
 
This is getting weird, I got the timing set removed and compared it to the new set. The Rollmaster (what I was using) bottom gear is about .006" longer than the new Cloyes set. It's hard to say which is correct, I'm going to go with the new set and go back to the Jeep spring/pin for the cam. I will just install the new thrust bearing and then check for flex-plate run-out. If that seems to check out I will buttom it back up and "prey"!
 
Keep us posted. I do have a stroker, I'm building from Russ. I think the 'spring pin' for the camshaft was 2000 and up on the 4.0L. Russ had some upgraded part, or I went with a 2000 up cam from him. Something like that.
 
I am using a '98 cam but I installed a solid cam button instead of the spring/pin combo. Here is the rubbing on the front cover.......
P1080756_zpswfqdboyt.jpg
 
You wouldn't have pics of the piston dish orientation? Russ describes it as shadow of the combustion chamber.
 
You didn't show the rubber snubber normally mounted to the cover. Was there one? Can I see the wear?

I didn't look hard, but was this a manual or auto?
 
You wouldn't have pics of the piston dish orientation? Russ describes it as shadow of the combustion chamber.

These are Russ's Racetec pistons with a 9.4CR ......

P1080510_zpszrlfib5k.jpg

You didn't show the rubber snubber normally mounted to the cover. Was there one? Can I see the wear?

I didn't look hard, but was this a manual or auto?

The rubber was removed before the pic but didn't show any wear and this is in a AW4.
 
I am using a '98 cam but I installed a solid cam button instead of the spring/pin combo. Here is the rubbing on the front cover.......]


None of this is making me feel good, my stroker's bottom end has the same combination of parts as yours, they came from the same supplier.
Sure hope you get this figured out.
 
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