I have a 2006 Lexus LS430 with about 230,000 miles on it currently. A used transmission was installed recently with about 60,000 miles on it after the previous transmission experienced the horrendous "stuck in 3rd gear" issue.

So far everything has been very smooth going after the install, but I've noticed recently some of the upshifts, specifically 1-2 and 5-6 can be particularly noticeable, with the 5-6 pushing the car forward in a sort of jerk.

I just had the rear differential serviced, all bushings and mounts were inspected and all of them looked great, had my ECU sent off and repaired before the transmission swap. Does anyone have any ides on what may be causing this?