My 1999 2Dr Tahoe is stuck in 4wd. If I push the 2wd button I can hear what sounds like the front end disengaging the 4wd light goes off or flashes, then I hear the front engage again and the 4wd light comes on. I've tried in park, neutral, drive, reverse, and coasting forwards and backwards.
Help '99 Tahoe 4wd won't disengage
- Thread starter TurboBu
- Start date
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ch4d
Full Access Member
i dont know if this will help but here is something
Problem solved, Here's the solution I purchased the truck from someone that never used the 4wd. The transfer case shift sector was very tight from no use. I installed a new transfercase Teflon(R)-coated shift detent plunger (poppet) GM Part #12474072 and fresh auto trac II fluid. Then put a cresent wrench on the shift sector coming out of the transfer case and worked it at least a 100 times until it felt like shifting my motorcycle trans nice easy clicks. It was so tight before it was causing the encoder motors to fail right away. I had the transfer case scanned at the dealer twice and it said bad encoder motor open circuit both times 2 new motors turned into junk. The parts store was good about taking the motors back. Now I think every fall I will remove the encoder motor work the shift sector with fresh auto trac fluid in the transfer case before winter.
Problem solved, Here's the solution I purchased the truck from someone that never used the 4wd. The transfer case shift sector was very tight from no use. I installed a new transfercase Teflon(R)-coated shift detent plunger (poppet) GM Part #12474072 and fresh auto trac II fluid. Then put a cresent wrench on the shift sector coming out of the transfer case and worked it at least a 100 times until it felt like shifting my motorcycle trans nice easy clicks. It was so tight before it was causing the encoder motors to fail right away. I had the transfer case scanned at the dealer twice and it said bad encoder motor open circuit both times 2 new motors turned into junk. The parts store was good about taking the motors back. Now I think every fall I will remove the encoder motor work the shift sector with fresh auto trac fluid in the transfer case before winter.
TTZ06
Full Access Member
pull the fuse
SunlitComet
OBS Jedi-Do Good
shift motor encoder
pulled the motor off and pushed buttons with it off and the motor seems to be working smoothly. but will not stay in any position but 4Hi. Someone mentioned a detent switch on top of the front output that tells the switch that the tccm that the shift has actually been made. could that be the problem or is the motor too weak to make the shift? It seems to be moving fine and the shaft coming out of the transfer case is moving free and smoothly.
SunlitComet
OBS Jedi-Do Good
i will say it again, shift motor encoder. its part of the shift motor.
My last post wasn't directed at anyone, I'm extremely frustrated with this Tahoe. I've even had it at a shop with no success. Scanned with modis scanner and showed no current codes. History codes were C0310 A/B circuit open and C0323 T-case lock cirtuit low voltage, we were driving with encoder, and front driveshaft removed.
yesterday I removed the axle actuator and with the key off it's out, push 2wd button and the actuator pulls in then out and does this twice. The encoder motor also cycles twice in and out of neutral and high range everytime the 2wd button is pushed. when I first screwed the actuator back in the front axle the 2wd light was on. but as soon as I rotated the front tire with it off the ground the front diff locked and the light went back off.
Then I managed to get it the encoder motor to shift into low range and tired about 6 different ways 20 + times to get it to shift back to high range with no success. The encoder motor I have on there now is a new aftermarket unit from O'rielly's no sure of brand. I called and talked to Rockland std gear and the tech there seemed to think the aftermarket unit was bad.
I'm at wits end on this thing. I think I understand how most of this works. The mechanical part anyway.
yesterday I removed the axle actuator and with the key off it's out, push 2wd button and the actuator pulls in then out and does this twice. The encoder motor also cycles twice in and out of neutral and high range everytime the 2wd button is pushed. when I first screwed the actuator back in the front axle the 2wd light was on. but as soon as I rotated the front tire with it off the ground the front diff locked and the light went back off.
Then I managed to get it the encoder motor to shift into low range and tired about 6 different ways 20 + times to get it to shift back to high range with no success. The encoder motor I have on there now is a new aftermarket unit from O'rielly's no sure of brand. I called and talked to Rockland std gear and the tech there seemed to think the aftermarket unit was bad.
I'm at wits end on this thing. I think I understand how most of this works. The mechanical part anyway.
SunlitComet
OBS Jedi-Do Good
those codes are to be expected with the shift motor assembly disconnected. Have you tried to see the action of shift motor while removed from the case and trying the functions? also did I read you right in that when in 4hi the control panel briefly indicates nuetral then reverts back to 4hi after depressing 2wd?
from the top:
Wife engaged 4wd in snow to go to work. Snow melted she tried shifting to 2wd, wouldn't happen, she eventually got it into 4low and had a hell of a time getting back into high.
I tested it and push 2wd and I could here the front actuator and transfer case cycle through 2 shifts. 2wd light flashes on then 4wd light twice stopping on 4wd.
Pulled encoder motor, pushed 2wd button and watched encoder motor rotate, cycling twice.
Bought new encoder motor from O'reilly's not sure of brand probably Dorman. Installed it, didn't run it not bolte up to trans. Fired up tahoe and tried shifting and it acted exactly the same as the old motor. I pulled it loose and watched it rotate exactly the same as the old motor. Tried shift transfer case with wrench and i could get it into neutral but not 4 low, but that was with the wheels on the ground, front drive shft out and rear drive shaft in, even had my kid push it while I tried shifting w/wrench. It shifted cleanly into neutral and seemed fine applying pressure to clutches. (I wouldn't think hard to shift into 4lo would have any effect on 2hi/4hi).
Called Rockland Std Gear and tech said Dorman chinese encoder motors are junk and the Tccm won't always reconize them. I reinstalled the aftermarket encoder motor, start the tahoe with 1 front wheel off the ground, the front diff was locked in, screwed out the diff actuator and pushed 2wd button. The front actuator would pull in, push out, pull in and push out and stop and I could hear the tranfer case shifting in and out of hi and neutral. I shut the engine off, screwed the actuator back in turned the key to run position, 2wd light was on. As soon as I rotated the front wheel the front axle locked and the 2wd light went off.
Then I tried shifting into 4lo and it eventually did after several tries. Then I couldn't get it back out of 4lo for nothing. that was yesterday. I gave up. Didn't tell the wife not to drive it this morning and she backed it up in 4lo and then when she went to pull forward it went into neutral and she didn't push any buttons.
Tonight I got in it, it was in neutral, I pushed 2wd and 4wd and nothing happened. pushed 4lo button and it shifted into 4hi.
I don't think the clutches are being applied, I think the front accuator is not staying retracted as now no lights are on but the front end is locked. I have not tried rotating the front output with a wrench to see if it turns.
Wife engaged 4wd in snow to go to work. Snow melted she tried shifting to 2wd, wouldn't happen, she eventually got it into 4low and had a hell of a time getting back into high.
I tested it and push 2wd and I could here the front actuator and transfer case cycle through 2 shifts. 2wd light flashes on then 4wd light twice stopping on 4wd.
Pulled encoder motor, pushed 2wd button and watched encoder motor rotate, cycling twice.
Bought new encoder motor from O'reilly's not sure of brand probably Dorman. Installed it, didn't run it not bolte up to trans. Fired up tahoe and tried shifting and it acted exactly the same as the old motor. I pulled it loose and watched it rotate exactly the same as the old motor. Tried shift transfer case with wrench and i could get it into neutral but not 4 low, but that was with the wheels on the ground, front drive shft out and rear drive shaft in, even had my kid push it while I tried shifting w/wrench. It shifted cleanly into neutral and seemed fine applying pressure to clutches. (I wouldn't think hard to shift into 4lo would have any effect on 2hi/4hi).
Called Rockland Std Gear and tech said Dorman chinese encoder motors are junk and the Tccm won't always reconize them. I reinstalled the aftermarket encoder motor, start the tahoe with 1 front wheel off the ground, the front diff was locked in, screwed out the diff actuator and pushed 2wd button. The front actuator would pull in, push out, pull in and push out and stop and I could hear the tranfer case shifting in and out of hi and neutral. I shut the engine off, screwed the actuator back in turned the key to run position, 2wd light was on. As soon as I rotated the front wheel the front axle locked and the 2wd light went off.
Then I tried shifting into 4lo and it eventually did after several tries. Then I couldn't get it back out of 4lo for nothing. that was yesterday. I gave up. Didn't tell the wife not to drive it this morning and she backed it up in 4lo and then when she went to pull forward it went into neutral and she didn't push any buttons.
Tonight I got in it, it was in neutral, I pushed 2wd and 4wd and nothing happened. pushed 4lo button and it shifted into 4hi.
I don't think the clutches are being applied, I think the front accuator is not staying retracted as now no lights are on but the front end is locked. I have not tried rotating the front output with a wrench to see if it turns.
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