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Transfer Case Motor - how to replace


SM 2007
Full Member
Apr 15, 2007
Sheboygan, WI
I just purchased an '02 Avalanche Z71.? I was told in advance it would need a new transfer case motor by the previous owner.? I'm wondering if it is pretty straight forward to change, or if there is something I should be ready for?? Are there directions around from someone that did it already? (I tried searching)

Not sure.  But  :welcome: to the site.

I had the dealer do my 05 on a TSB.  Took them two days with it on the lift the whole time. I'd be affraid to do it myself.  But yet again, It took me about 40 posts and 9 hours to change out my 02 sensor!  :laugh:
Encoder motor?

Might want to look in this section for issues with the 4x4 light on...

if memory serves me it was not new encoder required but a reprogramming of puter?
The dealership gave the previous owner the part number 12474401, so I am fairly confident that is the problem.? He was going to order it from the dealer for nearly $500, but I said hold up because I found it rebuilt for a lot less.

Thanks for the welcome.    :D
I would get a second opinion before shelling out that kind of money.

Read this thread:

very long but you can read the history of the problem and see where dealerships thought it was encoder motor at first but this did not fix problem.. and re program tended to be correct repair..
I know NAPA has them rebuilt now for alot less than the dealer. Its a fairly straight forward replacement. Just remove the shield and the front driveshaft and then you will have full access to the motor.
Here's a graphic for some reference...

ygmn said:
Encoder motor?

Might want to look in this section for issues with the 4x4 light on...

if memory serves me it was not new encoder required but a reprogramming of puter?

  i think you are right.  seems like i remember the dealer telling about a re-programming that was done to my Trailblazer.
Thanks guys.  That graphic helps a lot.  I'll get a second opinion first from the dealer as was suggested.

I actually have a 2000 Suburban but I've been told the Encoder Motor is bad (noise and ratcheting sounds when turning in snowy weather), so I tried to replace the motor the other day only to find out that the one I received was the wrong part-oops. (Got all the way through the exercise before my wife delivered the part to me).

Only problem was I could not figure out how to disconnect the motor connector as shown in Reply #6.

Does anyone know the secret?

Ok, so i finally did this today.  It wasn't all that bad, except trying to get the encoder lined up with the TC, or vise versa.  I had to move the TC about 1/4".

BUT!  Now I am having issues.  Once I put everything back together I rolled the truck off the ramps and put it in drive.  NOTHING.  Put it in park, grinding noise, then NOTHING.  WTH just happened? 

Also, the lights on the 4WD selector still do not show which drive it is in.  It didn't before and it doesn't now.  The switch is new.

My only thoughts is that something needs to be done with the computer.
Well you could try the old standard, disconnect the battery for 15 minutes to reset the PCM 
I disconnected it for about 30 mins.  Still same thing.  I don't know if it worked because my seat memory was still active.  Do i have to disconnect both cables, i would think not.
Me either, let me do some  searching I'll be right back.

Double check the electrical connections on the tranny to be sure that nothing pulled out
Were the connections OK, also did you disconnect the battery before you started the fix ???

Check the tranny fluid level

I'll check the fluid level and connections after work tomorrow, and report back.  No i didn't disconnect the battery.
ItsStopher said:
Just added to CAFCNA's Sperry Tech Center

Transfer Case Motor/Encoder Replacement

Nice how this part wasn't in the directions I rec'd with the new one...


o If the motor/encoder assembly is being replaced because it is defective, make sure that the transfer case is in the neutral position. Manually shift the unit at the shift shaft. Use a crescent wrench if necessary.
o When installing the motor/encoder unit to the transfer case, make sure that the transfer case is indexed properly and it is flat against the transfer case before tightening the mounting bolts.

So the only thing I think I can do is leave the truck in Park where it was when I did it.? Take it all a part, put the TC where it was when I found it.? Then put the truck in Neutral and then turn the TC like it says above.  Thoughts?
Figured this out guys.? I took it all back apart and re-did it with the truck in Neutral.? Still didn't work.? Indicator light still didn't show on the button selection switch.? Had me thinking, WTH is going on.? I grabbed the manual to see if there was any kind of Relay or something electrical, because it was like it wasn't being sent a signal to change drives.? The fuse in the cab was good, but the ATC or Automatic Transfer Case fuse under the hood was bad.? It probably happened when the motor went bad, but I am not going to go back under there and put the old motor in to see if it was even bad.? Now everything works.? Thanks for the help with this guys.

Glad you get it fixed.
Looks like I need another TC motor.  Near the end of February I was leaving the daycare parking lot.  The back wheels were on snow, the front on dry pavement.  I had to hurry out of the lot because of traffic and it was in Auto4wd.  As soon as the front engaged the dry pavement I heard a clunk and then the Service 4wd light came on.  I had the dealer reset that, but the TC will not shift into 4WD HI or LOW; only in 2WD and Auto4wd.

Also the front drive shaft spins even though it is in 2WD, or at least according to the indicator light.

Any thoughts?
Is the TC making any noises like something is broke, it almost sounds like a broken chain inside the TC which I hope is not the case.
MichiganSilver03 said:
Is the TC making any noises like something is broke, it almost sounds like a broken chain inside the TC which I hope is not the case.

Should the front driveshaft be turning, with the selector switch in 2WD?

You mean like this noise that just started last week.  It only happens on acceleration...

Following up on this.  It turned out my transfer case was locked into 4wd.  Bought a used one at a nearby junkyard.  Had that installed along with two new front hubs.  Everything is driving much more smoothly as you can imagine.  Might be because my pockets are $1200 lighter.  lol