I recently had my '69 Z/28 transmission (M20) rebuilt by a very reputable Camaro expert. He recommended I use a needle type pilot bearing (GM Part # 14061685) instead of a solid bearing.
In doing some research on the web, I came across the following statement:
"GM has changed their part numbers several times and are currently referring to the bearing (part #14061685) to be used. We strongly suggest NOT using this bearing as it is a needle type bearing designed for 6.2L diesel trucks which have a limit of only 4,000-4,500 rpms. You can imagine how fast those little needles will turn at over 7,000 rpms. We have seen some failures which were quite interesting. The ideal bushing replacement is a bronze type with three grooves (or flutes) spiraled inside and is available under the GM part number 10125896."
(From http://www.zr1netregistry.com/ZR1_troubleshooting.htm.)
So, I have conflicting recommendations. Can anyone shed some light?
Confused... ???
I've used the GM needle roller bearing in several project cars (after dialing-in the bellhousings) with no problems at all. Gotta love the comment above about the needles at 7,000 rpm - there's no relative motion between the needles and the input shaft unless the clutch pedal is depressed; how often does anyone free-rev the engine to 7000 rpm with the clutch pedal on the floor?
The correct oilite bronze bushings work fine too, but take a magnet with you when you buy one, and don't take it if it's attracted to the magnet; there are lots of Chinese counterfeit bushings out there that are mostly iron, and they'll score the input shaft.
Thanks for sharing your good experience with the needle bearings. As you point out, there is very little relative difference in rotation. I don't think my Z will spend that much time at 7,000 RPMs anyway. Off to install!