Searched myself to a stop. 4X4 engagement

[Duckpoor]

Thanks to some really smart folks here and a search function, we Have determined what is Not wrong with our 02' Trailblazer.

Terrific Problem determination Aids moved us to the Fact that the Axle Actuator and every thing "upstream from it is working as designed. Waa Hooo!

I can hear the Axle Actuator working and actually if engaged while spinning the right front, I have a ratching (light) sound from the Half shaft coupling. The sound goes away when 2Hi is selected so I am assuming the coupling is doing it thing internally.
Read somewhere someone had to have the "fork Shimmed " following a Warranty replacement. ??
I have a Haynes Manual which isn't much help , so I hope someone can help put this to bed and suggest what needs to be done or have done as far as replacement or adjustments. :undecided

Thanks again for all the information and sharing ya all do so well.

R Green / Springfield,Illinois
Duckpoor

[MTPockets]

This is a tough one.:undecided The front axle disconnect and T-case encoder motors typically work hand in hand. If one isn't working, the other will be 'locked out' from working. What is your dash switch doing (LED wise)?

Joel

[Duckpoor]

Joel,
It seems like everything is working except the "mechinical " lock un lock at the actuator. All indicators are correct on dash.. multip flashes and the solid correct light after 2-3 second for any positions as they are selected. 2hi - auto-4 hi and 4 low . Normal ... good .

Transfer case is doing its thing and the Actual actuator seems to be trying to engage and does fully disengage.

When in 4 hi it tries to engage ..servo motor sort of noise.. and shuts off .
I think the actual coupling of the half shaft is not getting complete . Rt front spins quiet in 2hi -- ratchets when in Auto , 4 Hi or 4 Low . so it is trying to lock it up.

rg

[PROSPHOTO]

GM:
A low speed knock can be caused by a differential case side gear bore that has worn oversize. Inspect the side gears and the differential case assembly and replace the components as necessary.

Have you jacked up the vehicle and gone through the motions with the wheels freehttp://www.aimoo.com/forum/images/messageicon/question.gif

I would run it in the air and engage auto then 4hi, see what happens

Try turning the wheels while performing this test and identify differences

[MTPockets]

Duck, it sounds like you've got a good diagnosis going on. What ever limit switch the system needs to see from the front axle disconnect is being satisifed, but a solid connection is not being made to the right half-shaft. There was a post some time ago in regards to an owner that had the shift fork (not sure if that's the book name) on the front axle disconnect break. It was snapped in two. I'm no expert on the GMT360 chassis 4x4 system, but IMO, if the dash switch lights indicate properly, the T-case encoder motor and that part of the system is good.

Joel

[BluavalancheZ71]

I had this same EXACT some problem, The problem lies inside the front diff. I took mine into the dealer and they found the forks messed up, the housing messed up and a few other things. I will get the work order out and put what they did on here for you to get an idea whats going on. So if get this right the light says 4x4 is on but no power at front wheels? Dealer wanted about $1200 to fix it. So this is also a common problem how many miles are on it? If you have other 4x4 problems more than 3 you may be able to call GM and complain and get it fixed at a reduced cost, thats what I did still ended up being about $680 or so almost half of what it would have been.

[MTPockets]

I had this same EXACT some problem, The problem lies inside the front diff. I took mine into the dealer and they found the forks messed up, the housing messed up and a few other things..

The axle disconnect (fork, housing, bearing, etc..) is seperate from the front differential. It's bolted to the right hand side of the engine oil pan.

Joel