2007 Buick LaCrosse transmission jolt

Intermittent, unpredictable, can’t make it happen, no pattern to transmission jolt from dead stop or up to 2 mph. Mechanic had pulled codes and then installed a 4T65E Shift Kit from Transgo. This was suppose to relieve the line pressure problem noted by the code. However, the jolt is still there but not as severe but still totally unpredictable. No codes show on the analyzer. 131,259 miles. All other functions work fine; passing gear acceleration and normal shifting. I’d pull my hair out if I had any. I’m due to take a 3,000 trip in the not too distant future and I want to make sure this thing won’t go ka-fluee. Mechanics I know and talked to have no suggestions. A transmission guy said “drive it till it breaks.” Your best thoughts would be appreciated.

Plano, Tx…not a fancy place just plain o tx

It could be the computer and the computer may not be storing the codes.
As far as your trip, you might consider a rental. You don’t want it to ka-fluee a thousand miles from home!