Small Block Mopar Thrust Bearing issue

[Mopar Mike]

I haven’t ever seen this before, but the crank looks to be pushed forward from the torque converter and is wearing down the thrust bearing. This is a cast crank 340; there is about a 1/8 to 3/16 gap unbolted between flex plate and converter. Spins freely, and moves back and forth easily. The forged crank 340 has no problem with same Trans and converter. Any ideas?? Thanks,
Mike

[X-TECH MAN]

Originally Posted by Mopar Mike

I haven’t ever seen this before, but the crank looks to be pushed forward from the torque converter and is wearing down the thrust bearing. This is a cast crank 340; there is about a 1/8 to 3/16 gap unbolted between flex plate and converter. Spins freely, and moves back and forth easily. The forged crank 340 has no problem with same Trans and converter. Any ideas?? Thanks,
Mike

Did you check the end play with a dial indicator on the crank with the main thrust torqued to spec. ? Some I have checked have been zero or .001. I have almost ALWAYS had to sand the main on a piece of glass with fine grit paper to get the correct end play on 340's and 360's. Sometimes 426/440 engines also. Hold them together by hand and use a little WD-40 or ATF and sand a little of each thrust surface (front and back) in a circular motion using the glass plate or a granet surface plate with the fine grit paper and lube to keep the bearing halfs together and flat then wash them check again. If you take to much then its new bearing time.
Of course you might have another problem but I found this to be a good fix in my case as the same problem came about on a 340 several years ago. I used to do it on 428 S/S Ford CJ's also.

[mike natoli]

what part of the thrust bearing is showing wear?

[donc]

if the thrust is worn on the back side another words look like crank is moving forward. its most likely the converter is putting pressure on the crank ,or something in the tranny is at fault. also check timing chain alignment.

[BlueOval Ralph]

Converter Balloning or Input saft to long on a 4 speed

[magnumv8]

What I have seen that has caused excessive thrust clearance is misaligned pulleys on the front of the engine....this creates pressure forward or rearward on the crank causing either the bearing or crank flange to wear....it takes very little misalignment to create this internal drag especially with a V-belt set up.....


D L Rambo.....

[mopar]

check the back of the crank where the pilot bearing would be. have found that to be the problem even with convertor spinning free. do not have any measurements.


Ron Waters s/st 1346

[Mopar Mike]

Originally Posted by magnumv8

What I have seen that has caused excessive thrust clearance is misaligned pulleys on the front of the engine....this creates pressure forward or rearward on the crank causing either the bearing or crank flange to wear....it takes very little misalignment to create this internal drag especially with a V-belt set up.....


D L Rambo.....

D L Rambo, Will check that out also. Thanks for the response.
Mike

[Mopar Mike]

Originally Posted by Mopar Mike

I haven’t ever seen this before, but the crank looks to be pushed forward from the torque converter and is wearing down the thrust bearing. This is a cast crank 340; there is about a 1/8 to 3/16 gap unbolted between flex plate and converter. Spins freely, and moves back and forth easily. The forged crank 340 has no problem with same Trans and converter. Any ideas?? Thanks,
Mike

Thanks to all that have replied, I was thinking converter and will look closer at other possibilities.
Mike

[Henry S]

There is a lot of info on the net. Do a search for thrust bearing problems. and look for the AERA paper on diagnosis and symptoms. most likely restricted coolers or cooler lines cause the torque converter to be pushed forward causing thrust problems. check your cooler line pressure.