Clunking noise coming from 5-speed transmission

Jhabke

New Member
Joined
Sep 16, 2021
Messages
4
Location
Calgary, Alberta
I have a very good operating clutch and transmission. It shifts very well, very smooth operation BUT when you hit 25mph or higher you get a very consistent rhythmic clunk that you can feel in the floor pan in the transmission area.
It starts at about 25mph and then it clunks at always the same beat, does not clunk slower or faster as you speed up or slow down.
Only happens while excelerating or holding a consistent speed, if you let off the throttle no clunk.
I have zero driveline vibration and fairly new front driveshaft and all new u joints with no play in drive shaft.
You can get movement of the TCase/Tranny assembly side to side when pushing on the driveshaft under the Jeep to diagnose it.
Could this be a worn out transmission mount with bad bushing, or a broken transmission mount??
It literally feels like something is smacking the bottom of the floor pan with a slow consistent clunk when accelerating but not on deceleration or at low speeds.
There is no whining from the transmission, it shifts very smooth and has no idle rattle or anything like that so I am wondering if the tranny mount may be loose…
What do you all think before I try to take of the skid plate assembly and such to investigate???
I am brand new to TJ’s as I usually restore old pickups but I want to try a Jeep. It is a 1998 Jeep TJ Sahara with 4.0 engine and 5 spd tranny.
I would appreciate any expertise greatly!!!
 
From your description of when and how the noise occurs along with the movement; I suspect the rubber section of the transmission mount is separated and needs to be replaced OR the bolts holding the mount to the transmission are loose.
You need to lower the transfer case skid plate and inspect the transmission mount to confirm what the problem is or is not.