Hard knock from drivetrain when accelerating

[Mberry0614]

------ 99 Exp. w/227xxx (4.0, 4x4) -------
Experiencing a harsh knock coming from underneath the vehicle upon acceleration. Most noticeable when going up hill. It doesn't do it at all when coasting or going downhill. I can't tell if it's coming from the front or rear of the vehicle, but it's definitely coming from underneath. Unsure if related, but I've had issues with the "O/D off" light flashing when cruising around town. Also have noticed a lot of slop in the gear shifter, and it slipping in and out of gear a little too easy. I checked the u joints, and there is a lot of play in the driveshaft, but the u joints dont appear to be slopping around. It is a very hard knock and quite loud also. Any ideas?!?!

 

[C420sailor]

You need to get the codes read. If you’re getting knocking and slipping with the OD OFF light flashing, that ain’t good.

 

[Mbrooks420]

Probably time for a rebuild, unfortunately.

The loose shifter is bolts, most likely, but the flashing OD light and slipping is bad news.

 

[Mberry0614]

Probably time for a rebuild, unfortunately.

The loose shifter is bolts, most likely, but the flashing OD light and slipping is bad news.

 

[Mberry0614]

Trans rebuild? Or rear end? Or ?

 

[Miles2022]

Sounds like the rear end to me. Based on the fact that it doesn't act up under no load condition.

 

[1.8TTony]

Transmission mount???

 

[Mberry0614]

Thanks All! Turned out to be the transfer case. Swapped it with one from the junkyard for $250 + fluid. The trans code is separate issue, I believe it is the shift solenoid. Project for another day. Lol