After pulling a somewhat heavy load for 15-20 miles my tranny started to shutter and shake when I stepped on the pedal to far. I had it locked out of overdrive running around 50 to 60 mph. I have 184,000 on it. No issues other than solenoids and filter / fluid changes. After getting home I unhooked and took it down the road. From a dead stop it felt good, but when going from 3rd to 4th I could make it shake and chatter. Any ideas on possible causes? I've been expecting it to go sometime but not today. Thanks!

 

Sounds like the torque converter is slipping. Once you slip it a couple of times it usually needs to be replaced. You could try to add a shift kit which will increase line pressure for the lock up. I would also check the condition of the fluid to see if it got burnt. With the mileage you have on that tranny, it might not be a bad idea to pull the transmission and do a rebuild.

 

Throw a good shift kit in it and BE CAREFUL with it and it will be OK for a while. Are you sure the lockup solonoid isn't causing the problem?