Overdrive Vibration

I have a 1998 GMC Jimmy with 115,000 miles on it. The transmission seems to work fine through the lower gears but has a small vibration in overdrive. When driving over 50+ mph the truck seems to shift as it is supposed to do into overdrive. But when the truck is in relatively low RPM's and you put a little pressure on the throttle (say for a hill) the truck starts making a small vibration or shudder until the rpm's reach a higher level or cathces up to speed. It still accelerates like it should while it vibrates. Wondering if anyone would have any idea what would cause this shaking/small vibration.

When was the last time you had the tranny serviced?

I'd start there.

If it's been serviced recently, it may be time to rebuild it, new torque conv. and all.

Hope this helps.

U-Joints