Can the 42RLE transmission over pressurize and cause excessive pressure on crankshaft?

Andrew Mac

Andrew Mac

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Aloha,

While replacing the rear main seal on the 4.0L I discovered galling on the Main Bearings. As well as evidence of wear on the thrust bearing and crank face at the Thrust Bearing mating surface. Its clear the crank has had excessive forward pressure applied to it during some period of operation.

Over the past few years I have replaced the serpentine belt, idler pulley, Alternator and water pump due to a "chirp" originating from the belt rotation when first starting. It has happened only a handful of times during the first start of the day.

After replacement of the main bearings the crank fore and aft movement is now .0010. slightly out of factory limits, not the .0127 present at inspection of rear seal replacement.

I have heard that the transmission can over pressurize and cause excessive pressure onto the rear of the crank?
Trans oil level has never been over serviced. No cooler lines are pinched.

2004, 170,000 miles. owned since new, driven by an old guy! not trashed!

I have ordered a new radiator, thinking maybe some possible restriction? will also install additional trans oil cooler.

Can any of you Jeep Guru's shed some light on this for me?

The over pressurization makes perfect sense, the belt chirping caused by pulley misalignment when the crank was being pushed forward. The wear on the rear portion of the thrust bearing of the Crank.

Mahalo, Andrew
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The drivetrain has 170K miles, it could be normal wear, oil starvation, torque converter. When you replaced the mains, what did the crank thrust surface look like?
 
Not something I've ever heard of, but I don't want to say it's not possible, as I'm not a guru on the subject.

It sounds like it may just be normal wear and tear possibly?
 
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OP, sounds like you’ve done some research. Here’s some information for you to read. Pictures of the old bearings and the crank journals would help a lot.
 

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Thank you for the article, that's what has prompted me to replace the radiator and add the additional cooler to the system. I will perform a pressure check when i jump into the project next week. The rear half of the thrust bearing is warn about 60% of normal, the mating surface of the crank is also worn. I installed new bearings and as stated the fore and aft crank movement is now about .0010, slightly more then factory new specs.
I do have a replacement crank and bearings sitting here ready to go if necessary!

Additionally the slinger ring on the rear of the crank showed signs of contact with the engine case.
 
Andrew Mac said:
Thank you for the article, that's what has prompted me to replace the radiator and add the additional cooler to the system. I will perform a pressure check when i jump into the project next week. The rear half of the thrust bearing is warn about 60% of normal, the mating surface of the crank is also worn. I installed new bearings and as stated the fore and aft crank movement is now about .0010, slightly more then factory new specs.
I do have a replacement crank and bearings sitting here ready to go if necessary!

Additionally the slinger ring on the rear of the crank showed signs of contact with the engine case.
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You must mean .010, because .001 is way too tight.
 
Andrew Mac said:
The engine was running without issue. I went into it due to a very small rear seal oil leak. I'm glad I discovered this issue when I did. who knows how long it would have lasted?
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No Kidding. I would put a mechanical gauge on the engine to see what the oil pressure is. Make sure it’s not fluctuating. Did you disassemble the oil pump? What did the suction screen and pickup tube look like?
 
Daryl said:
No Kidding. I would put a mechanical gauge on the engine to see what the oil pressure is. Make sure it’s not fluctuating. Did you disassemble the oil pump? What did the suction screen and pickup tube look like?
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Clean, no particles. With the new bearings I notice the oil pressure is a tad higher, about a needle width.
 
I think the system pressure in the 42RLE determines the speed at which it shifts. If it is shifting normally it is running at the correct pressure. If it was abnormally high the shifts would be quick and dirty and I think you'd notice something wasn't right.
 
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Andrew Mac said:
Clean, no particles. With the new bearings I notice the oil pressure is a tad higher, about a needle width.
Click to expand...
pagrey said:
I think the system pressure in the 42RLE determines the speed at which it shifts. If it is shifting normally it is running at the correct pressure. If it was abnormally high the shifts would be quick and dirty and I think you'd notice something wasn't right.
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Like @pagrey stated, your shifts would be extremely firm if it was a transmission high pressure issue. Those bearings appear to be damaged from a lack of lubrication. You’ve addressed the symptom now you need to figure out the why. You already know this because of the existence of this thread. Anyways, I think the engine lubrication system needs further investigation. It may take a mechanical gauge temporarily installed so you can see it while driving under different conditions and see if the needle fluctuates.
 
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