2HI to A4HI randomness

[Frostee]

Ok, so I don't know very much about the workings of the drivetrain. I know that at this time of year, I have it set to 2HI pretty much all the time unless I hit some dirt roads.

So lately, I'll be cruising along the highway at around 110kph, and I will sit there and feel the TB changing from 2HI to A4HI on its own! And then back to 2HI, and the then back to A4HI... :worried:

No change in road surface, nothing, just randomly changes. Only when I'm on the highway. I'll even see the light on the selector switch flashing back and forth. Afterwards, when done my highway trip, it will continue to change, even if I'm not moving. I was sitting in the Tim Horton's drive-thru and i could listen to it switching between the 2.

I know I'm about due for a transmission oil change, but this isn't related, is it?

Ideas?

[ylab]

Your 4x4 selector switch is going bad, it was a problem with the 2002 model year. Mine was replaced a couple of years ago and hasn't had any problem since. The switch actually creates a specified amount of resistance for each mode, problem is if the switch isn't sealed well or the contacts wear/burn a bit, the resistance levels can vary and result in changes in the selected mode.

If you have an extended warranty, just bring it to the dealer. If not, I seem to recall the tech indicating its not a real expensive part. On an Envoy its a snap to access, not sure about a TB....it sits higher in the dash on the TB.

[Frostee]

I remember having to get around that switch when I added the lights on the interior.

And I bought the TB used 6 months ago, so as far as I know, I'm way outta warranty :(

At least the switch is easy to change, just getting to it is a hassle... Hopefully not too $$$ either... Hopefully thats all it is

Thanks :)

[04TBEXT]

Frostee,
Quite a bit of transfer case-related problems with the earlier T/Bs. The transfer case select switch, as others have stated, is a likely candidate.
If you have access to a scan tool, a code B2725 should be present.
Their are also transfer case module updates/enhancements that can be performed to address electronic command anomolies. These are available at the dealers.
Their are also some cases where the transfer case range selector sensor is at fault. This usually will lock the transfer case in one mode and not respond to switching commands. This does not sound like your concern, but might help others. This lock-up condition would typically store codes C0327 & C0550.

[Frostee]

Frostee,
Quite a bit of transfer case-related problems with the earlier T/Bs. The transfer case select switch, as others have stated, is a likely candidate.
If you have access to a scan tool, a code B2725 should be present.
Their are also transfer case module updates/enhancements that can be performed to address electronic command anomolies. These are available at the dealers.
Their are also some cases where the transfer case range selector sensor is at fault. This usually will lock the transfer case in one mode and not respond to switching commands. This does not sound like your concern, but might help others. This lock-up condition would typically store codes C0327 & C0550.

Thanks, I'm hoping that the garage I park at during the day has a scan tool (they probably have something that can check codes).

I havent had issue with it locking into one particular mode though, I can switch it back and forth freely, just switches on its own when I'm going down the highway in 2HI (and feeling the slight 'thump' at 110 isnt a great feeling :no: ).