Quote Originally Posted by Bellicose Right Winger
There's a service bulletin in the TIS on the early 4hp22's regarding vibration as the TC goes into lockup. I know it covers 535's, not sure if it covers 525's also. I'm out of town and can't give you the bulletin no, maybe another board member can post it, or better yet post the bulletin. Seems on some vehicles the TC went into and out of lockup very rapidly causing the vibration. I think it was a solenoid problem. If this isn't the problem, I'd get out the ETM and figure out how to disconnect the wire that engages lockup, before I replaced the TC. Fuel mile will take a hit though. Does the vibration go away if you shift into 3rd just before trans goes into lockup?

Paul Shovestul
The gearbox kicks down instantly, holds all gears as it should, and basically has no other problems!