2003 Grand Cherokee 4.0, automatic with Select Trac.

Checked the transmission fluid because of a bearing type noise coming from around the gear selector area. The fluid looked dark and had lots of bubbles, but did not smell burnt and the transmission shifts fine. It honestly looked like motor oil or gear oil mixed in with the ATF.

Is there any seals that separate the transmission oil from the transfer case that could have failed and allowed the oil to mix? Any other explanation to the dark ATF fluid? We've only had the vehicle a few months, but I don't remember the fluid being dark.

Also, any idea what that noise could be? The noise stops whenever you let off the throttle, but starts again when cruising or when gas is applied. No noticeable vibration, and while it's difficult to tell where the noise it coming from, it seems to be loudest around the shift tower/select trac tower.

 

Welcome to CF!

Okay, I think the bubbles are the key to this. I think the pump is sucking air. Two reasons for this, IF that's the problem, are low fluid level or the filter is loose. With these transmissions, the fluid level has to be checked hot, idling in NEUTRAL, not park. It make a difference of about a quart. If the fluid was changed just before you bought it, it's possible the filter wasn't tightened enough and it has loosened up. The proper fluid for both the transmission and transfer case is ATF+4. If the seals between them were leaking, fluid would be dripping out of the mounting flange area. There is a drain slot on the mounting flange.

IDK if this is the problem, but it gives you something to check before seeking professional help.

 

JEEP TSB:
Mopar ATF+4(R) has exceptional durability. However, the red dye used in
ATF+4(R) is not permanent; as the fluid ages it may become darker or appear
brown in color. ATF+4(R) also has a unique odor that may change with age.
With ATF+4(R) fluid, color and odor are no longer indicators of fluid
condition and do not necessarily support a fluid change.

 

Thanks for posting that TSB on the ATF+4 Don I had not saw it before.

 

Thanks everyone for the great responses, never knew that ATF+4 became darker with use. Checked the transmission the proper way (as described above) and it was a quart low.

Thanks again!