2 Thrust Bearing Failures - Trans Pressure to Blame?

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2 Thrust Bearing Failures - Trans Pressure to Blame?

Unread postby Killer95GT302 » Mon May 04, 2020 12:25 pm

I'll try to keep the background short, but I've now killed my 2nd thrust bearing on my new 363 stroker within 30 miles. First one I put blame on the thicker flex plate which left me with very little converter clearance ( < .030"). The 2nd time around I checked virtually every clearance I know of and have read to check. Converter clearance is at 1/8", crank pilot was made deeper everything was assembled and verified outside the car and dropped in that way. Everything bolted up easily without force, thrust was in spec and everything moved freely no binding whatsoever. Enough room for driveshaft to slide back and forth (about 1").

I should mention the transmission and converter were the same that I used behind a stock block 302 that I pushed 500hp behind without issues for years. I am running out of things to check as to the cause, and one of the things to rule out is transmission pressure forcing the converter forward.

The only thing I changed as far as tune goes to run on the 363 was SARCHG - All other components have been tuned for on my old 302 which I was gearing up for this motor - MAF, Injectors, Fuel etc. It starts and runs great.

SARCHG was updated to 200 from 166 lb x10^5. I'm not an expert but if I'm not mistaken this may have some impact on how the EEC calculates the pressure to command? Could this be making it command some insane pressure causing it to force the converter forward to wipe out thrust? My only other thing to check is to see if the cooler in my new radiator is a restriction also causing pressure issues - these are the only known pressure variables between my old and new setup.
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Re: 2 Thrust Bearing Failures - Trans Pressure to Blame?

Unread postby wwhite » Mon May 04, 2020 2:59 pm

I'm no expert, and attached is an old article about thrust bearing failure, maybe will help diagnose the issue.

Thrust Bearing Failure, Engine Builder, Larry Carley, May 2003.pdf
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Re: 2 Thrust Bearing Failures - Trans Pressure to Blame?

Unread postby decipha » Mon May 04, 2020 3:19 pm

if the converter and all is the same then i would look elsewhere unless your making quite a bit more power now

what was the crankshaft end play?
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Re: 2 Thrust Bearing Failures - Trans Pressure to Blame?

Unread postby Killer95GT302 » Mon May 04, 2020 3:36 pm

Thanks wwhite, I actually did see this article and countless threads about failures thinking that I would research guarantee it not happening again. I thought I found the culprit with the flexplate.

1st time the end play was at .005. 2nd time I had the thrust on the crank cleaned and polished. The end play was .008, big end of the accepted specs but still good.

In theory I'd be making more power if I can get past just an initial test drive and oil change without copper in the oil filter.

1st time I drove it 30 miles, end play opened up to .030". 2nd drive after rebuild it opened up to .012" after 8 miles.

Another thing I read that can effect pressure was cooler restrictions. I need to see if the cooler in my new radiator might be the source. I have an external cooler in addition that was also there with the new motor.

I was just curious to see if I may have thrown the pressure out of wack by changing displacement in the tune.
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Re: 2 Thrust Bearing Failures - Trans Pressure to Blame?

Unread postby decipha » Mon May 04, 2020 6:58 pm

no
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Re: 2 Thrust Bearing Failures - Trans Pressure to Blame?

Unread postby svt4cobra6 » Mon May 04, 2020 10:34 pm

ran into a bad thrust bearing, also took out the crank but took about 20k miles, this was also a manual car. Heard if your converter is ballooning it can cause the problem but probably a few different possible causes to look into.
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Re: 2 Thrust Bearing Failures - Trans Pressure to Blame?

Unread postby Killer95GT302 » Sat May 16, 2020 10:30 am

Thanks all, Im pretty certain all clearance was in spec. I can't be too certain about the cleaning of the thrust surface being straight, but it was a mirror finish on it and looked straight by eye fwiw. I dont have the tools to check runout on it so had to trust the machine shop.

I want to rule out all transmission related items, it seems to only be an issue when under load, though ive never spun it past 3k on my test drives. Ive let it sit and idle and verified that thrust clearance remains the same after. I don't think id be seeing converter balooning under these conditions, this is a precision industries converter.

Can anyone tell me what the EPC transfer for an expedition EPC would be? (FN620 not sure it maps to the same function in their EEC), I want to check some tune related items and make sure im not forcing
too much pressure under load.

I have line pressure guage and cooler line guage ready to run once i look these things over.
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Re: 2 Thrust Bearing Failures - Trans Pressure to Blame?

Unread postby red5.0fogger » Sat May 23, 2020 6:40 am

the mirror finish on the bearing could be part of the problem. The correct finish leaves minute peaks and valleys to retain oil film for cooling and lubrication. If too smooth it just wipes off. Also when i've heard of this before, internal convertor charge pressure is typically blamed.
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