Heavy shaking when accelerating into third gear

[ducky]

Hello!
This is my first time posting on this thread but have lurked for many years. If this is the incorrect place to ask this question then please let me know!

As said above, I've scoured the site for over a decade getting information on fixing my Jeep. There is one problem that I have not found a solidified solution for which brings me to ask the question myself.


1999 Wrangler Sport V6 4.0 liter automatic

The issue I'm having is when it shifts into 3rd gear the gas pedal, dash and steering column shake vigorously but still accelerates slowly and the shaking will eventually stop. Only way to stop it immediately is throwing it into neutral.
This happens pretty much every time I try to drive it cold; Letting it warm up for 20-30 minutes negates it from happening but it's not ideal trying to go to work in the morning.
I had the transmission completely rebuilt about 3 years ago, so my first thought was old/burnt transmission fluid but after checking it's still red. Haven't had any slipping gears or delayed shifting since the rebuild so I'm unsure what's causing this to happen.


If anyone can shed some light on possible fixes I would appreciate it very much, please ask questions if you need more info.

 

[Tejasol]

Check the transmission mount and motor mounts.

 

[TheBoogieman]

The V6 is causing it.

 

[ducky]

Check the transmission mount and motor mounts.

Will do, but if it is the mounts causing the shaking I don't understand fully how having it warm stops it. Had it running for 20 minutes this morning and no issues.

Metal expansion on the mount from the heat or a rubber mount seizing from heat overtime makes sense.

 

[MPat]

I'm undergoing pretty much the exact same thing with a 03 4.0 TJ. Did you ever isolate the cause? Any insight would be most helpful.

 

[brackrichard74]

2000 jeep Tj acceleration into 3rd gear violent shaking if I keep accelerating into 4th it’s shakes violent but stops if I go fast enough into 4th then nothing 2nd acceleration into 3rd.
My front track if I shake the front it does wiggle, and was told it should not.
Can anyone give me alit help . 1st gear is good 2nd gear good until I get close to 3rd then it’s violent into 3rd other that that it rides really good if I could just get any opions would be a lot of help