THRUST BEARING FAILURES
This is written for small block Ford thrust bearing issues using automatic transmissions.
Some of the best thrust bearing articles I found are here;
http://www.atra.com/crankshaft/
http://www.4secondsflat.com/Thrust_bearing_failures.html
http://www.gnttype.org/techarea/transmission/trantsb.html
I run a 363 cubic inch all aluminum 8.2 deck height small block Ford with twin 80mm turbos. I was killing thrust bearings (and steel billet crankshafts) every 5-9 quarter mile passes. Spending over $2300 a pop for cranks it got real serious real fast.
The cause of thrust bearing failures in my case was attributed to improper torque converter clearance and a “soft” thrust bearing. What I learned in the process was you need at least .120 thousands between the end of the crankshaft and the snout of the torque converter when the converter is bolted to the flywheel and .140 thousands between the converter and the transmission. These measurements are critical and should net be exceeded by more than .040 or so. You will often times hear about people solving the thrust bearing problem by changing the converter. This is more often due to the differing torque converter physical measurements than manufacturer (unless there is an actual problem with the converter, i. e. ballooning or spline lock). I also found different crankshaft manufacturers leave varying amounts of material on the back of the crankshaft (the metal lip around the pilot hole on the back of the crankshaft) affecting the converter clearance measurements.
If you would like to be fairly sure to solve your thrust bearing issues, these items will help:
1) Reduce the pump volume to the converter from a ¼ inch hole to 1/8 inch hole (have a trans person do this one).
2) Change the main bearing to a harder material bearing that will take more heat.
(No, not Clevite or Federal Mogal)
3) Modify (chamfer) the thrust bearing per one of the articles listed above.
4) Make sure your trans yoke is not bottoming out during launch.
5) Make sure you have the correct clearance when installing the trans/converter.
6) I found approx .006 thrust clearance proved to be optimal for small block fords.
If you follow the above listed items you should solve your thrust bearing issues assuming the converter itself is not bad, the crankshaft is machined properly and the engine is assembled/machined correctly.
Please read the articles that are referenced above, they have great information and are accurate.
These items worked for me when I was pulling my hair out trying to find the thrust bearing issue on a 1700+ hp race motor. Additionally, thrust bearing failures require a “combination” of the listed items. One listed “fix” by itself may have a positive effect however the “combination fixes” have a much higher success/longevity rate and are not detrimental to performance what-so-ever.
Some of the information contained in this short paper was obtained from various race parts manufacturers; converter manufacturers, transmission shops, race bearing manufacturers, engine machine shops, and race only engine shops. The basis and core of the information contained in this short paper was learned by experience and various parts failures and analysis.
Disclaimer: I assume no liability for anything. Race motors, transmissions and converters and automotive parts in general are often abused and may fail due to numerous reasons.
Hope this helps.