92 sub. transfer case shifting on its own

[corpse]

Got a 92 or 93 suburban (actually my g/f's), and she has a strange problem with the 4wd... If she is in 2H, and puts the truck in reverse and give it some gas (like backing out of a driveway), it will pop out of 2h and go into neutral. If it's in 4H, it will pop into 2H. There are other symptoms, but those are "noises and feelings" which are harder to figure out in a forum.

I checked the linkage adjustment, and the lever is in 4H when the transfer case is engaged in 4H.. Although, when under the truck, I noticed where the shift lever goes into the transfer case, there's some oil on the case like there's a blown seal.

I know nothing about 4WD - but I looked in the haynes book and didn't notice anything in the transfer case section about being able to change oil - are you able too? I know on an auto trans, running low on trans fluid will cause shifting problems - I'm hoping that is more of the case here, and not her transfer case about to blow..

thanks!

[TrailLeadr]

Got a 92 or 93 suburban (actually my g/f's), and she has a strange problem with the 4wd... If she is in 2H, and puts the truck in reverse and give it some gas (like backing out of a driveway), it will pop out of 2h and go into neutral. If it's in 4H, it will pop into 2H. There are other symptoms, but those are "noises and feelings" which are harder to figure out in a forum.

I checked the linkage adjustment, and the lever is in 4H when the transfer case is engaged in 4H.. Although, when under the truck, I noticed where the shift lever goes into the transfer case, there's some oil on the case like there's a blown seal.

I know nothing about 4WD - but I looked in the haynes book and didn't notice anything in the transfer case section about being able to change oil - are you able too? I know on an auto trans, running low on trans fluid will cause shifting problems - I'm hoping that is more of the case here, and not her transfer case about to blow..

thanks!

If I had to guess, I'd say it sounds like it could be a broken motor, or trans mount. When you put it in reverse, and torque it a little things are shifting, and it's popping out of gear.

the x-fer case doesn't operate the same as the auto transmission. So it's unlikely that low fluid would be doing this, but it would be contributing to wear on the x-fer case components. An oil change would certainly be a good thing either way. There should be a couple bolts on the case. One for filling, and one for draining.
Maybe someone else can fill you in on more of the details of where they are. I haven't looked at mine in some time, and it depends on what case she has.
If it's a 93, then it's likely to have a NP-241C case. Not sure what the '92 year had.

[84fiero123]

If I had to guess, I'd say it sounds like it could be a broken motor, or trans mount. When you put it in reverse, and torque it a little things are shifting, and it's popping out of gear.
.

Yup

Open the hood, have your G/F put her foot on the brake.

Put the truck in revese and rev the motor, if a mount is gone the motor will rise, more so than if the mount is good.

[GaryL]

Check out this thread that I started a while back, it may be the same situation.

http://www.gmtruckclub.com/forum/showthread.php?t=2509


Keep us posted.

[corpse]

It seems the motor mount is ok - does not seem to have "excessive" play. I had my g/f drive the truck hard, flat footing it off the line - and nothing weird happens.. but if she backs up and use the gas pedal, like even 10% throttle, it will pop out of 2H.. when it does pop out, you can hear the transfer case spinning in neutral... If it's in 4H, it will pop out of that into 2H.. so, if it's not the motor mount, anything else easy I can check?

update: seems that the snap ring is broken - problem solved! ok, not solved - just identified - not onto getting it fixed.. thanks for the feedback guys!