1992 jimmy 4 wheel drive stangeness

20

Asked by Dec 02, 2015 at 12:48 PM about the 1992 GMC Jimmy 4 Dr SLE 4WD SUV

Question type: Maintenance & Repair

Purchased this old beast, most likely completely stock..There are problems
going in and out of 4 wheel...mostly 4hi more than 4 low. Sometimes going
between the 4's does not work.
When it is on it is a great thing...
Have replaced the vacuum actuator, the small vacuum switch on transfer
case. and new CV axels.
this leads me to believe it is the encoder since this vehicle is completely
stock it seems.
It is a manual engage, how would I test if the front motor is bad.
or what else would i test for.
thank you

14 Answers

17,905

If it has a lever on the floor for the 4x4 then you don't have an encoder motor. What does it do between 4hi and 4lo when it doesn't work? Does it grind? Not engage the front? Or not go in low range? Is it staying engaged when in 2wd?

1 out of 1 people think this is helpful.
20

ok, just discovered that I knocked of the small thin vacuum line coming off the engine that seems to connect to the ball and everything else...After further testing notice we can now get air through the vent and the floor where at one time we did not. Took it out for a spin in mud 4L seems to work but of course the front tires mover so slow even when the backs are spinning, is 4H on this model a kind of on-demand because it seems to work. The main problem was stopping in one 4 and shifting to another. Tomorrow taking the battery oout after it starts and seeing of actuator is getting 100% sucked. The problem has been sometimes it will not engange and sometimes it does work perfect.

20

some people said you have to roll this model back to engage. 4L never seems to be a problem. Question: if the vacuum actuator was working half-ass would it slip in and out while in use?

1 out of 1 people think this is helpful.
20

what about the thing that the vacuum pull that locks the wheel that looks like it screws into the front case

56,315

If your front tires are moving slower than the rears then you have a gearing problem or miss-matched tires.

20

really not sure if they were moving a separate speeds or not..kinda asssumed that from 19 year old son...if i understand correctly the front and rear shafts move at same speed. if you had it on a lift everything would move the same.

20

unless there is some kinda LSD going on, again not sure with this model

56,315

Well they are supposed to move at the same speed unless some fool replaced a differential and installed one with the wrong gear ratio. Are you sure the front hubs are locking in? Have you put it up on a rack and tried it out?

56,315

If there were a center differential that would explain things but I doubt this truck has one. This ruck should be old school.

20

is there something similar to a front axle shift actuator in this car

20

and if the shift fork is not moving is it possible that the left side(axel driven) is moving but the right side that needs to be engaged is not?

17,905

Ok, first to shift between hi and 4lo you must be in neutral and stopped. There isn't any lsd going on it is just a traditional transfer case. The parts of the 4x4 system that are responsible for shifting are the lever, the vacuum switch on the transfer case, when in 4wd it sends vacuum to the

17,905

Front axle actuator under the battery tray. This moves a cable attached to a lock collar on the front axle to engage the front axle to make it 4x4. If someone changed gear ratios it would be barely noticeable by looking at it stuck in mud unless the rear was 4.55 gears and the front had 3.08's. Even then idk. Sometimes the shift collar/fork on the front axle gets stuck. There are no hubs to lock on these. Sorry for 2 seperate responses, I hit submit on accident...

17,905

Also it is technically always attached to the left shaft, but due to the nature of a differential there is in way for it to spin. The only way it would without the actuator engaged would be if the diff was welded up or the spiders were sized. These front diffs are hard to get at so I doubt anyone welded it up. And it's highly unlikely the Spider gears are damaged, these diff unusable die from the bearings going weak and/or leaking all its fluid out.

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