1992 GMC Jimmy 4 wheel drive engage

Tiny
GARYGNU23
  • MEMBER
  • 1992 GMC JIMMY
  • 4.3L
  • V6
  • 4WD
  • AUTOMATIC
  • 267,000 MILES
First. This car was probably bought completely stock.
replaced vacuum actuator under battery and vacuum switch on transfer case.
also realized that the thin vaccum line coming off engine (that seems to run everything)was apparently knocked off at one point that has been fixed.

before all the new parts and putting the hose back on, 4 wheel had a problem engaging. When it did it was spot on but to stop in one and shift to another sometimes did not work.

Question(s):
-Does this car need to be rolled backwards a hair to engage 4 wheel? That sounds weird.
-if the 4 wheel STILL does not engage properly 100% what else could be the problem(the thing that the vacuum actuator actually pulls to lock the front diffs? That is screwed into front case)
-you feel the car in 4 low. Barely moves feel the power. On this vehicle is there a power transfer to the wheels on the front as to give the illusion of the front and back tires spinning at different speeds? Depending on traction.
do I assume that if I lifted this car and put it into 4 wheel all the tires would move at the exact same speed.

ty

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Wednesday, December 2nd, 2015 AT 11:52 AM

4 Replies

Tiny
HMAC300
  • EXPERT
You should be able to shift in and out no problem. However if gear ratio in front is different from back a problem ensues. This should be scanned for codes as it's electronically controlled with amotor on the tcase. There are 3 different tcases for this vehicle one has the electronically controlled motor the other two have the vacuum motor. Either of these can fail causing your problem. Or a part going to motor if they work. There is a ID tag at back of case which tells you what you have. If you have the electric motor it's a 233 otherwise it's a 207 and 231. If both are operated on dry pavement in 4wd then you have to back up to unwind torque load. If you have a shift lever for it make sure it's adjusted correctly. If you are shifting from 4L to neutral you have to stop. Also make sure it has proper lube to correct level. You might check the vacuum switch see pic
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Wednesday, December 2nd, 2015 AT 12:27 PM
Tiny
GARYGNU23
  • MEMBER
It is a manual shift on the floor, I replaced the three pronged vacuum switch on the transfer case.
Because it is vacuum I assume there is not motor.
What does the vacuum under the battery pull in the front diff and could that item be the problem?
It seems to engage but I wonder that there is torque.
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Wednesday, December 2nd, 2015 AT 12:36 PM
Tiny
GARYGNU23
  • MEMBER
Reading up. If the shift fork is not working properly does only the left side/front work because the right side does not engage.
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Wednesday, December 2nd, 2015 AT 12:48 PM
Tiny
HMAC300
  • EXPERT
Your last reply talks about the axle not tcase the actuator under battery supplies vacuum to switch on tcase. That is why I sent previous pic to see if you are getting vacuum and if the switch is working or not it tells how to test i.
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Wednesday, December 2nd, 2015 AT 1:03 PM

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