My 99 Jimmy 4X4 has a front end noise typically when making a hard left turn. My neighbor works for a GMC dealer and we diagnosted it at home as having to do with the 4X4 trying to engage, even when in 2Hi. We disconnected a vacuum hose and an electrical connection at the firewall and the noise went away. Of couse I can't use my 4X4 unless I reconnect these two items. With winter and rainy weather I would like to keep these connected all the time. Any thoughts as to what is going on? I haven't taken it into the shop yet, just at home trial and error hoping to save $$!
BTW I have replaced the 4X4 Control module last year due to quick shifting...it thought it was in 4lo all the time and was shifting to high gear before I even got out of the driveway!

Thanks,

FirstJimmy

Push button or shift from the floor to go to 4x4?

Push button on the dash. In addition to the 2hi, 2lo and 4lo, it also has the automatic 4wheel option.

Electronic encoder motor or vacuum actuator is shot.

Are these things a Saturday Mechanic can replace or does it need to go into the shop? If I can replace them, would a Chilton or Hayes book help?

Yes, pretty straight forward.

Grab a Haynes or Chilton's repair manual to help you out.

Thanks...as soon as I find some time, I will give it a try!

good luck bro