Thread: Burned crank rear bearing after TC change

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I changed the cam in my 383 to a roller and at the same time decided to go with a higher stall TC from Hughes. I measured .150" space between the TC and flex plate before bolting the two together. After about 1000 miles the thrust bearing is toast and the rear crank thrust surface has a groove about .045" deep, so the crank is toast too. There is still .150" clearance when I pry the crank all the way to the rear.

Could there be some reason that the TC is shoved forward hard enough to cause this damage when driving? Has anybody dealt with a similar issue. Fixing the damage is time consuming and not cheap but straight forward. I don't want to put it back on the road without figuring this out.

Thanks in advance

What is on the front for driven equipment? I'd be curious if they are all in alignment? If they are pulling the crankshaft forward it could be an issue. Do you know how much fore and aft movement of the crank you started with? The only other thought I would have is the "stack"of clearances in the transmission is allowing to much forward movement. It's possible that the bearings in the trans have to much play and when the clutch packs are pressurized it's pushing the Convertor forward. The crank being pulled forward I have actually seen. The transmission pushing the TC forward is plausible.. I haven't witnessed it. It may be possible to test the theory though.

Each auto trans TC I've installed:

I spin the TC until it drops in three times, and when bolting it up to the flywheel the TC has to be moved slightly towards the engine to align to flywheel face. That's how I know the TC has fully dropped in.

It sounds as if your 0.1 clearance was just fine.

Your TC rides on the splined input shaft and drives the pump. The only thing that causes any forward movement is the differential internal area of the front & rear halves of the TC body, which is the area of the hole for the drive snout that rides the splined shaft. Your thrust bearing is designed to take only about 200psi of pressure, but with the small differential area your line pressure would have to be up pretty high (over 100psig) to make the converter move. I think I'd be wondering if the converter you got was the right one, and then if it may have been bad assuming you got it fully seated in the pump.

In hindsight, it's always good to measure from the bellhousing mating flange to the center of the old TC (straight edge across the bellhousing) and then to the TC mounting flange to ensure that the new TC is fully seated in the pump, and measures the same.

Changed to roller cam? Flat tappet cam lobes are ground at a slight angle so they can make the tappets rotate-roller cams are not-- if you don't have a thrust plate or a nose button on your camshaft the cam can be sliding forward and the timing chain can cause the crank to push forward which could cause the thrust area wear---