Transfer case motor issue?

[Wylie_Tahoe]

03 Tahoe Z71

Anyone had an issue with what seems like a transfer case shift motor being weak and moving on its own, resulting in a partial 4wd engagement or neutral? Had a case where I had no reverse ( i know, sounds like trans), then some some weird vibrations/noise another time. Turning into my parking spot this AM, the truck jerked like 4WD was on or the rear diff dried to lock up.

With the rear wheels jacked up, runs normal forward, but lots of clanking and jerking from transfer case in revers. Front prop shaft was turning. I could stop it by hand, but it took some effort.

IIRC, the shift motor is not splined but slotted, so it not likes its off a tooth.

TIA,

 

[Wylie_Tahoe]

Well, something is for sure, bound up now. Guess im going to have to split the transfer case from the transmission to see if its in the transfer case or transmission. Just wont be happening for a couple weeks though.

 

[Fless]

Which TC do you have? There's an RPO code for it in the glovebox, should be something like NPx.

And yes, the TC motors get weak. I had one on my '04 that would appear to switch to 4wd but, in fact, it was in AUTO. Only the Tech 2 would show the correct selection. Bad grounds can also affect how the front diff engages, if you have the AUTO NP8.

 

[Wylie_Tahoe]

Ok, i ended up pulling the TC yesterday afternoon. Figured I would, since the truck was broke down at the shop, I had no ride home till later

After getting the case down, with the trans in neutral, I can rotate the transmission output shaft in the forward direction, but some quite a bit of tension, but cannot rotate it in the reverse direction.

So I think the trans has suffered a major mechanical (hard part) failure.

With the drive shaft plugged back into the output of the TC, it rotates perfectly smooth and quite. Input rotates. Front output turns a little, but I tan hold it, so seems just like a little residual friction. I plan to pull the shift motor off, and manually shift if retest.

I also plan to drop the trans pan and check further, but feel the issue is the trans. But will not rule out an issue with the TC shift motor.

May also crack the TC case apart just for a look. If nothing wrong, its an hour time and a gasket just to see.

@Fless, ill check the RPO's in the AM.

 

[rockola1971]

Tranny fluid burnt? Been drag racing it? Tow alot? In OD? Sounds like reverse clutches are burnt and steels are cupping like a frisbee.

 

[Wylie_Tahoe]

Trans fluid color and smell were normal. Drag racing? Not since I got. Tow alot? Its a mileage rig, and I got it 5 months ago. I do know a single mom with a bunch of kids owned it the past 2 years.

Trans is indeed toast. Pulled the pan.

 

[JonnyTahoe]

Sounds like what mine was doing. Inside of pan had some sludge on the magnet and in the bottom of the pan and one needle bearing but that's all.

 

[Wylie_Tahoe]

Mine was tight, but broke loose. I would suggest using a quality 6 point socket. The head is shallow and seems soft. Mine was somewhat rounded from previous removals.

T/C RPO is NP8. Based on the chunks in the pan, I will likely not crack the transfer case. but I will still suspect the motor as being weak, but not likely the root cause of the trans.

 

[JonnyTahoe]

Well, something is for sure, bound up now. Guess im going to have to split the transfer case from the transmission to see if its in the transfer case or transmission. Just wont be happening for a couple weeks though.

Mine was doing exactly what you have explained. Removed the T-Case seems fine. was not able to even coast down the driveway in neutral without it binding and jerking. Would Jam-up as I tried to move it into the garage. 295,000 mi. More info coming soon.

 

[JonnyTahoe]

Well, something is for sure, bound up now. Guess im going to have to split the transfer case from the transmission to see if its in the transfer case or transmission. Just wont be happening for a couple weeks though.

 

[JonnyTahoe]

Which TC do you have? There's an RPO code for it in the glovebox, should be something like NPx.

And yes, the TC motors get weak. I had one on my '04 that would appear to switch to 4wd but, in fact, it was in AUTO. Only the Tech 2 would show the correct selection. Bad grounds can also affect how the front diff engages, if you have the AUTO NP8.

Mine is a NP-246

 

[dougo]

sounds like a failing transfer case encoder , The encoder tells the body computer what position the transfer case is in 2 HI 4 Hi or 4 Low if it sends the computer the wrong info, the computer will try to move it typically while you driving , I though my drive shaft fell out , it should have displayed a fault, search encoder ring its inside the transfer case motor , I get about 50-60 k that reminds me its time to order another

 

[Wylie_Tahoe]

Old trans is out and draining. While waiting on the new one to be built and ship, ive got an oil leak to chase down.

Looks like the original trans, but its certainly been out. Converter looked nearly new. Someone been hunting an issue, and I think they missed the mark by quite a bit

 

[Wylie_Tahoe]

New trans has not shipped, yet, but been addressing a few minor issues while the trans is out.

Oil change with the longer AC Delco PF61 filter.

New oil pressure sender and connector with pigtails. Easy with the trans out.

Rear main seal and rear main housing gasket in attempt to stop was seems to be mostly a passive oil leak. also replaced the oil cooler adapter gasket. Crankcase is filled back up, so ill watch it the next couple days and see if it still drips. if it does, it will likely need an oil pan gasket.

New trans mount ready to go back in with the new trans.

 

[Wylie_Tahoe]

Trans delivered last Thursday, but busy schedules have prevented its installation.

Good news is, no static oil leaks!

 

[JonnyTahoe]

That's a lot of work. I pulled the Transfer case thinking that was my issue it was not. put it back together so I can move the truck around. Will not pull the trans myself retiring the truck from service at 295.000

 

[HiHoeSilver]

That's a lot of work. I pulled the Transfer case thinking that was my issue it was not. put it back together so I can move the truck around. Will not pull the trans myself retiring the truck from service at 295.000

Boooo! How's the rest of the truck? Why not replace the trans?

 

[rockola1971]

Trans delivered last Thursday, but busy schedules have prevented its installation.

Good news is, no static oil leaks!

Your drain pan grenade looks like the sprag locked up and come apart and while doing that it took some of the inner side of the case with it. Thats what all those aluminum pieces are. There is no other aluminum parts inside the tranny. The hard parts are all steel. That case is destroyed and unusable as a core. But dont let anyone lie to you, some of your hard parts still have some value. Dont be suprised if your builder doesnt credit you back your core fee if you had one.

 

[Wylie_Tahoe]

Your drain pan grenade looks like the sprag locked up and come apart and while doing that it took some of the inner side of the case with it. Thats what all those aluminum pieces are. There is no other aluminum parts inside the tranny. The hard parts are all steel. That case is destroyed and unusable as a core. But dont let anyone lie to you, some of your hard parts still have some value. Dont be suprised if your builder doesnt credit you back your core fee if you had one.

For that reason, I actually sourced a reman that did not need a core return. So this old unit will get hauled to the scrap yard for its weight.

 

[JonnyTahoe]

Boooo! How's the rest of the truck? Why not replace the trans?

It was a tough call. Rear Diff needs a rebuild as well as other things didn't want to pour cash into a high mile truck with 295k. Bought a yukon same year and color RWD from Texas with half the miles on it.