Switching to 4Hi

kmanz1

Original poster
Member
Dec 31, 2012
12
Hello folks,
First post here since being directed here from another site. Hope you can help.
Was not able to engage 4Hi, but no problems with A4WD or 4Lo. I can hear both motors working. I have since been able to now engage 4WD by going slow and turning at the same time. However, it seems somewhat noisy, clunky. Not so bad with 4Lo and I do not have to turn the wheel, just put it in neutral. Is this clunking sound normal? Is it normal to have to turn the vehicle while switching to 4WD?
Thanks in advance for your help.
Ken
2004 GMC Envoy SLT, 4.2L, 79,400 mi.
 

Sparky

Member
Dec 4, 2011
12,927
Welcome!

Sounds like maybe a potential problem with your disconnect on the passenger side. Does the clunk come from under the truck or from the front end? Could you pull the passenger wheel and check for any slop where the CV axle goes into the housing? Slight wiggle is normal, but it shouldn't move much or flop around.
 

kmanz1

Original poster
Member
Dec 31, 2012
12
Sparky,
Thanks for a quick response. I need to get under the truck to determine exactly where the clunk is coming from. When it gets a little warmer, I will check the slop in the CV. Is the play left to right or in/out?
Thanks,
Ken
 

Sparky

Member
Dec 4, 2011
12,927
Usually when there is wear on that outer bearing the play is up/down/left right, like it wiggles around but doesn't really move in/out much because the retainer ring is still holding on. If it moves in/out then it is really beat.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
In my experience, I'd guess the transfer case before the front axle disconnect. But definitely look for play at the oil pan side of the passenger's CV shaft.

The disconnect ONLY actuates in the 2HI->A4WD mode change. And it disengages ONLY in an A4WD->2HI transition. The noise you hear in all other mode changes is the transfer case encoder motor.

Did you change the transfer case fluid at 50K?
 

kmanz1

Original poster
Member
Dec 31, 2012
12
Hey guys,
Thanks for all your help.
Sparky, Do I need to disconnect anything to check for play in the CV? Roadie, How do you check for a bad encoder or to make sure the transfer case is engaging? I did not change the transfer case oil since owning the vehicle. I purchased it with 65k mi. No sure if this info is available in Carfax.
Thanks,
Ken
 

Sparky

Member
Dec 4, 2011
12,927
Nope, just get under there and try to wiggle the tripot base around.

At 65k miles it should have and may have been done once already, but there isn't a good way of finding out. If it were me I'd go buy 2 bottles of Autotrak II from the dealer (use nothing else but that or you'll kill the case), drain the case, and refill with new just to be sure. Make sure you pull the fill plug first before pulling the drain plug. The plugs use a 10mm allen wrench, but you'll need something to get leverage. That fill plug is usually pretty darn tight.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
kmanz1 said:
... Roadie, How do you check for a bad encoder or to make sure the transfer case is engaging? ...
Locate a trustworthy independent mechanic with a GM Tech II tool or equivalent that can talk to the TCCM and command the encoder motor to go through its paces.
 

kmanz1

Original poster
Member
Dec 31, 2012
12
Sparky, Roadie,
Once again, thanks for all the help. I will also go through the check process of raising the front of the vehicle and turning the wheels, etc.
Great site!
Ken
 

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