99 Jimmy T-fer case

[droptop73]

For any mechanics that understand the 4wd stuff.

My son has a 99 Jimmy and he called from K-zoo Friday night telling me the car is making a grinding noise from underneath. We picked it up yesterday and hauled it home. Here's what I know, it will not move in reverse (I have not yet checked the fluid). The trans was rebuilt last winter, we bought it without realizing it had a cooked trans... oops!! It will move forward without issue except for what sounds like a real loose chain rubbing on the inside of the case. I drove it on the trailer and into my storage unit. When in reverse or drive the rubbing noise can be heard without the car moving.

I need some advice, I can't find much online about these other than the shift motor. Some of what I've seen says don't try to repair. I plan to let the thing sit until we are in the new house and I have my garage set-up. What am I in for guys? I have never worked on 4 wheel drive stuff.

Thanks tons!

 

[caspianwendell]

I am no expert on trannies but as the transfer case is behind the trans, it would not be engaged unless the car is in a drive gear so it should not be making noise in park, or neutral. Have you tried shifting the transfer through its gears (hi, lo, neutral) to see if there is a difference? Also, have you looked under it to check for obstructions, loose parts, etc.? reason I ask this is because my daughter bought a damnrango that had an engine swap and they did not tighten all the bellhousing bolts and the trannie came loose and broke the input shaft. It does sound like a transmission problem to me but I would check the obvious first, such as put transfer case in neutral, and check for noise in transmission through it's gears.

 

[Mister 4x4]

Do you have the [New Process] NP 236GM transfer case (push button control), or the manual shift NP 231C or NP 241? I'm assuming it's a 4.3 with auto (4l60e), since there weren't as many of Jimmys with manual transmissions.

Regardless, it "sounds" like the chain could've stretched or let go (Capt. Obvious, here). But, if it's an electronic-shift unit, the control module, shifter motor, or even a fuse and/or relay in the system could be bad. I'm more concerned about the reverse issue - it could be a combination of the transmission and transfer case, since reverse is rarely affected by the T-case alone. The 'case having been rebuilt could also be the issue (the more modern 'cases don't seem to like being messed with internally as well as the 'old iron,' like the Dana 300 in my Jeep).

Crackin' the 'case is not as horrible as it sounds... unless you can't get replacement parts for it. A quick look this morning says that it will be a challenge to get replacement 'hard parts' very easily, but they can be had. Control modules and motors seems to be the biggest issues for the 236GM case, since that's what's most plentiful.

IF it's an NP 236GM case: http://www.makcotransmissionparts.com/NP236.html

I wish I was closer - I'd love to help out with the rebuild.

Also: Pirate 4x4 has a link on how to swap to more 'common' 'cases (if you're comfortable modifying a vehicle's main components, that is ).

http://www.pirate4x4.com/forum/chevy/907854-1999-gmc-236gm-transfercase-swap-out.html

Other common problems:

http://www.automotiveforums.com/t493484-discuss1999_jimmy_4wd_control_problems.html

http://gmcowners.com/gmc-forum/showthread.php?t=18602

http://www.justanswer.com/chevy/8h950-chevrolet-s10-4x4-1995-s-10-4x4-v6-4-3-automatic.html

 

[droptop73]

Thank you very much guys! I'll need to let this one sit until we're somewhat settled in our new digs. He'll need to drive my ranger and I'll be FORCED to drive the 'vert.