95 Grand Cherokee front drivetrain
First off, thanks for the detailed description of your problem. I wish they were all as well written as yours.
It's tough not being able to hear the noise it's making. Luckily I can draw parallels to my own experiences with GC's. Mine has 'Select-Trac', which like your 'Command-Trac', enables us to shift on the fly to 4WD. Meaning, we don't have to stop, get out, lock the hubs, get back in then shift to 4WD. Also like yours, my front end was making some noise.
What was up with mine: The 'Select-Trac' on my G.C. is a lever type switch on the center console. When I switch from 2WD to 4WD it routes a vacuum line to an actuator which engages the transfer case. The moving parts are all near the T-Case. While in 4WD, going any faster than a crawl I'd hear a mild grinding/whirring sound. It increased with speed, all but disappeared as I decelerated and made me crazy.
What it turned out to be was a Vacuum leak. The 'bellows' (for lack of a better description) type actuator was only partially engaging the the 4WD. Enough to lock the drive train, not enough to fully mesh the gears resulting in all sorts of worrisome noises. I found and fixed the leak, adjusted the range on the mode rod and that was it.
You're thinking, 'That's special'.
Well here's the parallel.
Command-Trac is also vacuum actuated. The difference is it engages your hubs from the the front axle by means of a 'shift fork'. The technical name is the 'Command-Trac Axle Shift Motor'.
When applied, the vacuum actuator moves the fork one way or the other, engaging or disengaging the hubs.
From your excellent diagnosis, it sounds like 4WD isn't fully disengaging.
You were correct about the front drive shaft. It should not be spinning while in 2WD.
Qualifiers: Is the grinding sound different at low speeds? While making sharp turns?
Have another look with these new facts in mind. Check vacuum lines, lubricant in the axle.
If you get me your engine size, tranny type, etc. I can probably scare up some vacuum diagrams (on the off chance you need them).
I hope this opens new doors for you.
Comment me back with what you come up with.
Good luck buddy.
Oct 14, 2008 |
1995 Jeep Grand Cherokee