Need advice on "SERVICE 4WD" warning

[Hummie2]

Steve R is right. Its no biggie.

What happens is when you are in 4lock (either high or low) the front axle and rear axle don't travel the same distance when you turn corners and go over uneven terrain and this results in a tortional load on the gears in the drivetrain if you are on a hard surface. Thats why there is a differential in the transfercase that operates in "4 high open". This differential in the transfercase is locked solid in "4 lock". I have seen manual shifted transfercases that you could not shift out of 4WD no matter how hard you pulled on the shift lever. The solution was to backup a few feet while keeping pressure on the shifter and when things unwound alittle it would shift out usually with a loud clunk.

The H2's electric shifter on transfercase didn't have enough power to overcome the torque load on the gears. When you requested the shift into "4 high open" the computer starts a timer and if the shift doesn't happen within the alloted time the shift aborts and triggers the warning message. This is a sign that you have been in 4lock on too hard of a surface and there was no slippage in the tires to relieve the tortional twist in the geartrain. If it won't shift out try backing up a ways to unwind the twist and try the shift again.

Tortional load or twist places alot of unnecessary wear on tires and gears. Only use 4lock when on a slippery or poor traction surface otherwise stay in "4 High Open".

Hope this explanation was clear.

Don