When i shift my jeep from park to reverse and then to drive it clunks with each shift, the u joints were bad so ended up just replacing the whole rear driveshaft, there isnt any play in the rear dif and it sound like its coming from the transfer case, also the car shakes when im going 30 mph and stops then starts again when im going 65 70
My car has 170440 miles.
My car has an automatic transmission.
The "clunk" indicates there is a loose coupling somewhere is the driveline. As you diagnosed, u-joints and the differential are the most likely fault points, but this could also be harsh engagement of the transmission due to worn clutches, clutch servo pistons, or high internal pressure within the transmission.
If the entire driveshaft was replaced, it is possible that the new driveshaft is not properly balanced. The fact that it vibrates at about 30, then again at twice that speed (that kind of vibration is called a harmonic vibration, which repeats at multiples of the first occurring speed), indicates an imbalance problem. It is also possible that the output shaft bushing on the transmission is worn severely, allowing the driveshaft to wobble from even the slightest imbalance.
To avoid any unnecessary repairs, I would recommend having you car's shifting issue inspected by a mobile, professional mechanic, such as one from YourMechanic, to diagnose this problem, get an accurate assessment of damage and cost estimate for repairs.
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