I filled up my transmission today (with ATF+4 and some Lubegard) and tried driving the Jeep (1994 ZJ 5.2 4x4 46rh). It will shift into drive or reverse no problem, and seems to move fine (I didn't drive it far at all), but the transmission made a fairly loud noise. Sounded exactly like the power steering pump on an old Ford, and was not present in neutral. The sound varied with engine RPM. What could cause this?

 

..Fluid starvation. Did you change the filter?

 

Nah, just topped up the fluid that was already in it and added Lubegard. Previous owner said he had replaced the filter right before I bought it (showed me receipt and empty filter box), so I figured it had already been done. I thought a clogged filter makes a noise in neutral too...

 

Ah ok. And the previous owner..that would be the one that SOLD it to you, right? Let me tell you about my 'previous owner'.
When I bought my zj for 900, it wasnt shifting right. He had just had it to Aamco for service and a checkup. He said it needed solenoids, which was reasonable to me. On the way home it wouldn't shift at all automatically.

First thing I did was to pull the pan when I got home. The screws for the filter were in the bottom of the pan. The fluid was filthy. The pan was filthy. No filter. The pressure sensor's screen was plugged solid.

 

The addition of Lubegard is not something I would ever do to my vehicle.

The ATF+4 is the only fluid I put into my transmission.

The FSM is required for owning / maintaining this vehicle.

There are four possible causes for Buzzing Noise listed in the FSM.