Thrust Bearing- Abnormal Wear

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Franko

Franko

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I noticed a lot of crankshaft end play on my 71 340. It supposedly doesn't have many miles on it since a rebuild. The spec is .002 - .007. Mine came in at .033. Attached are pictures of the thrust bearing showing that the crank was thrusting forward and chewing up the side of the thrust bearing.

Does anybody know what could cause this? Could it be that the main bearings were torqued with the crank too far forward and the end play was never checked?

Or is something else seriously wrong?
 

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Without knowing long- term history, impossible to say. Maybe the crank was damaged, and never properly refinished. Did / does the car have a heavy clutch? What is the history of that?

I've seen some of these engines with considerable wear (end play) that ran just fine. This also seems to be true of rod side clearance.
 
The most common causes of thrust bearing failure is 1) torque converter failure and 2) riding the clutch in a manual transmission.
 
There were several reports of ballooning torque converters casing this a couple years ago. Do you know what brand converter you have ?
 
With respects,

A pic of the back side of the bearing... focused in on the #'s,

Thx!
 
Also check the thrust surfaces of your crankshaft to make sure that they are not worn too wide.
 
To answer a few questions:

The 69 Dart is a 4 speed. I've only had the car for a year so I can't say what happened before that. It had a broken transmission mount (maybe caused by a big block fork instead of the small block fork) and really bad clutch chatter.

The 340 does not have screw in ARP studs.

I will have the thrust surfaces of the crank checked by a machine shop.

Thanks for all the advice.
 
The bad fork also caused the thrust bearing to be burnt out. By looking at your pic of the bearing I'd say the crank's thrust surface may be a problem.
 
moper said:
The bad fork also caused the thrust bearing to be burnt out. By looking at your pic of the bearing I'd say the crank's thrust surface may be a problem.
Click to expand...

Yes, check the crank thrust surfaces for dimension and surface finish (smoothness).
 
I had a thrust bearing looking like that,, only it was a little blue in color from heat..

It was a marine engine that had an OMC outdrive on it, Apparently they have two diff length imput shafts for the outdrive,, this one was too long.. Boy did that motor stink, literally..

Perhaps check the 4-speed to see if it's one of those you're supposed to trim the tip off the trans imput shaft, if the crank wasnt drilled for a 4-spd,, Perhaps the shaft wasn't trimmed quite short enuff,, and is shoving the crank forward... just a thought..

hope it helps
 
Looks like all the excess bearing wear is on one side....is that correct? Pretty interesting.
 
No, that's normal if something is constantly pushing the crank forward (or pulling it backwards). it's not meant for that kind of force.
 
Yeah, I finally re-read the first post to see that the OP said that! I'll catch up eventually....
 
Looks normal to me for the 4 speed Guy's, if it has a heavy Duty Clutch ***. And or someone is holding the clutch in to long.....
 
I re-read whole thread,, this is a pieced together car,, and I think you need to make sure that crankshaft has been drilled for a manual trans,,.

Could we please see pix of the end of the trans imput shaft,, and the crankshaft flywheel flange with pilot bearing ... ??? thnx

Does your trans go into the crank, like this ?? , here's a similar dicussion

attachment.php


http://www.forabodiesonly.com/mopar/showthread.php?t=274784
 
I just got back from vacation. Here are some belated responses to some excellent questions.

The transmission input shaft measures 8 9/16" to the surface that bolts to the bell housing (picture attached).

I don't know if the crankshaft (No. 2532457- P4R10) flywheel flange is correct for a 4 speed (picture attached). The far end of the inside of the flange doesn't look rusty, but the end of the input shaft doesn't look worn. It's hard for me to tell if the input shaft is hitting. I can't put the input shaft into the crank flange yet because the short block is on an engine stand, until I take it off to deliver it whole to a machine shop.

I should also mention that I discovered this issue when I pulled the trans to replace the LUK clutch and pressure plate that I installed last summer. The clutch pushed in hard at the top and easy after that, which made it difficult to drive on the street. I put about 1,300 miles on this setup.
 

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That Shiny circle at the end of the crank hole,, appears to be where the imput shaft is touching/polishing,, the less shiny area in the center matches the hollow on the shaft .. the way I see it..

I'd start looking there..

Did you experience any shifting problems ?? noisy trans ??

hope it helps
 
I didn't experience any shifting problems, although I bought the car in winter 2013 and had the A833 rebuilt in spring before I drove it.
 
Are both upper and lower bearings worn the same? Maybe the middle #3 cap was not installed correctly, Last and prying the crank forward? Bad thrust surface on the crank? Too light of an oil? I've run a heavy clutch without thrust bearing problems. Like mentioned previously, something most likely was applying constant forward pressure to the crank. You should grease the pilot bushing also, it looks pretty dry.
 
The smooth part of that input shaft seems mighty long to me.
 
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