see if someone with a scan tool can view tcc lock up % when the vibration occurs.
when the vib occurs...any change if you wot or let off the gpedal?

 

I talked to a knowledgeable mechanic today who's 99% certain that the problem is with the programming. In his humble opinion, the transmission shudder can be cured with a programming of the tranny via my local Chevy dealer. It's fairly inexpensive so I've made an appt. today to have that done. We'll go from there. And yes, when the shuddering occurs, it immediately goes away when I let up on the gas. And it occurs almost precisely at 45-47mph, which is what I'm finding out, points to a torque converter lock up issue.

I also did a further inspection of both upper and lower ball joints and I don't see any looseness, movement or wear. I've been overly **** about greasing those (luckily, they came with zirk fittings), and the truck doesn't have any weird clunks, noises or loosenes from the front end, so I feel pretty certain that the problem is in the tranny.

We'll see how it goes and I'll report back.

Thanks,

RPG

 

makes sense. gm probably has a tsb on it.

 

I wanted to report that I took my truck to another Jasper (transmissions) dealer and he test drove it and he's confident that the problem is in the clutch pack section. He's arranging to have a warranty replacement.

RPGR90s

 

Update: My new mechanic talked to Jasper. They recommended that we use LubeGuard Shudder Fix. Within 20 miles, if the shudder abates, he assumes that the wrong fluid was installed with the tranny and he'll do a full service (fluid and filter) and monitor.

If the shudder guard doesn't resolve the issue, he believes there's further issues and will order a new trans and replace under warranty.

RPGR90s