WonkoTheSane
WonkoTheSane Reader
2/2/15 7:08 p.m.

So I was plowing with 2000 Chevy 2500 w/ 6.5l diesel automatic, and I got a bit stuck trying to clear a spot to put the chains on. I tried reversing, no deal, I tried forward, no deal. I shoveled out a bit and then when I tried to reverse, nothing spun except the engine. That's Odd, thought I, putting it into forward only to have the rear wheels were spinning. Huh. So I put it in 2wd drive, and the rear spun just the same.

In 4wd forward, the fronts will very, very slightly turn when the backs are spinning like crazy. In Reverse, nothing turns at all.

Any ideas? I'm thinking have it towed somewhere that knows WTF they're doing, 'cause I sure don't when it comes to these things...

Spinout007
Spinout007 UltraDork
2/2/15 7:36 p.m.

Likely, check your linkage to make sure it's fully engaging, but it sounds like you probably broke something in the t case.

Streetwiseguy
Streetwiseguy PowerDork
2/2/15 7:37 p.m.

Which transfer case? If its the one with the AWD or full time option, you may have toasted the clutches inside. They don't actually have a mechanical actuation, its all clutch application to drive the front wheels. Check the oil in the Tcase. If its black, get out your money gun. The right front axle also has a electrically controlled disconnect in it, which can fail. If the front driveshaft is turning but the wheels are not, either the front diff actuator has failed, or its died internally.

WonkoTheSane
WonkoTheSane Reader
2/2/15 7:38 p.m.

Looks like people are saying the 4L80e's had a problem with broken pistons in the direct clutch drum. And that (like mine) it can happen suddenly and without any sound/notice.

Does that sound likely? If so, it's rebuild city: Population me, or is a reman/junkyard one a better choice?

Thanks!

Knurled
Knurled UltimaDork
2/2/15 7:41 p.m.

What would that have anything to do with the front axle not getting power?

You may have exploded the transfer case, especially if you've been training it to run low on fluid. There's also an axle disconnect that likes to fail, GM used a wierd electrically heated plunger to engage the axle. There are kits to replace it with an underdash cable.

WonkoTheSane
WonkoTheSane Reader
2/2/15 7:41 p.m.
Streetwiseguy wrote: Which transfer case? If its the one with the AWD or full time option, you may have toasted the clutches inside. They don't actually have a mechanical actuation, its all clutch application to drive the front wheels. Check the oil in the Tcase. If its black, get out your money gun. The right front axle also has a electrically controlled disconnect in it, which can fail. If the front driveshaft is turning but the wheels are not, either the front diff actuator has failed, or its died internally.

This truck has push-button 4 hi/lo, so it's pre-AWD/Full Time, if that makes my bending over any less painful..

WonkoTheSane
WonkoTheSane Reader
2/2/15 7:42 p.m.
Knurled wrote: What would that have anything to do with the front axle not getting power? You may have exploded the transfer case, especially if you've been training it to run low on fluid. There's also an axle disconnect that likes to fail, GM used a wierd electrically heated plunger to engage the axle. There are kits to replace it with an underdash cable.

No idea, I'm a RWD kinda guy... I've never been inside/around 4x4s before...

Edit: The fluid was good a few months ago, I bought the truck back in july, gave it a solid once-over then (fluids checked/changed, the norm), but I haven't been back to inspect it since then. It doesn't seem to noticeably leak, though.

mazdeuce
mazdeuce UberDork
2/2/15 7:51 p.m.

Do you have a code reader to ask the computer what it knows?

WonkoTheSane
WonkoTheSane Reader
2/2/15 7:52 p.m.

I do, I'll go plug it in. Nothing lit up, though.. I would expect it to warn me if it knew of a problem. Unless the CEL is dead :)

Spinout007
Spinout007 UltraDork
2/2/15 8:29 p.m.

Push button 4wd at least on the S truck/suv line is vacuum activated. supposedly there is a vacuum 'noid on the front axle that can go bad with no warning. Hence the bazillion and 1 kits to convert to cable actuation.

Woody
Woody MegaDork
2/2/15 8:33 p.m.

I've had good luck with these guys. Transfer cases are not hard to swap.

http://www.transfercase.com/

Leafy
Leafy HalfDork
2/2/15 8:33 p.m.

Or the vac line could crack. That was a common thing on dad's old push button ranger. Like every 2 years it needed a new vac line for the 4wd.

evildky
evildky Dork
2/2/15 8:43 p.m.

If it's like the 1500 it's not actually a transfer case but a low range box. The front axle is engaged with an encoder motor located on the front axle. Could have damaged or dislodged the encoder motor on the front axle.

WonkoTheSane
WonkoTheSane Reader
2/2/15 9:08 p.m.

So I'm going with the assumption that there are two separate problems, both caused or related to being half-embedded in the snow, then..

It seems like a transfer case failure wouldn't cause the reverse issue at all, so I'm assuming the tranny is boned, it'll take a tear-into to determine how bad and what route to take.

The front axle thing could be transfer case, mechanical or electrical, I'll have to dig in. Thanks for the clarifications, guys!

Further news, though, I think that the front axle is locked up somehow. I just got in from my neighbor helping me, we tried to pull it out backwards, no dice. We tried to push it forward, nada. It's crazy that even in neutral we couldn't move the pig, and the front was sliding sideways, leading me to think something is seriously wrong up there..

Now I gotta figure out how to get it up to the garage..

Fueled by Caffeine
Fueled by Caffeine MegaDork
2/2/15 9:17 p.m.

Does the front end have one of those thermo couplers?

http://www.chevytalk.org/fusionbb/showtopic.php?tid/234612

Check that actuator.

WonkoTheSane
WonkoTheSane Reader
2/2/15 9:25 p.m.

From what I was reading, it doesn't since it's a 2000.. It also has instant feedback when you hit the button to 4 hi or lo, so I'm guessing it's all electric.

WonkoTheSane
WonkoTheSane Reader
2/3/15 9:19 a.m.

Dumb question: How hard is it to rebuild a 4L80e?

Gearheadotaku
Gearheadotaku PowerDork
2/3/15 9:35 a.m.

You stated the rear wheels would spin, so I'm guessing front axle engagement issue. The trans/t-case are pretty tough on these trucks.

Ranger50
Ranger50 PowerDork
2/3/15 9:44 a.m.

If it isn't the front axle actuator and related wiring, stupid design where and how it's placed, it could be an encoder motor and its related wiring on the t case.

Edit: beyond the t case having issues with a steel on aluminum wear internally, there is a fix for that, the t case and front axle, besides the aforementioned actuator and seals, are pretty damn bulletproof for a GM.

Moving_Target
Moving_Target Reader
2/3/15 10:12 a.m.
WonkoTheSane wrote: So I'm going with the assumption that there are two separate problems, both caused or related to being half-embedded in the snow, then.. It seems like a transfer case failure wouldn't cause the reverse issue at all, so I'm assuming the tranny is boned, it'll take a tear-into to determine how bad and what route to take. The front axle thing could be transfer case, mechanical or electrical, I'll have to dig in. Thanks for the clarifications, guys! Further news, though, I think that the front axle is locked up somehow. I just got in from my neighbor helping me, we tried to pull it out backwards, no dice. We tried to push it forward, nada. It's crazy that even in neutral we couldn't move the pig, and the front was sliding sideways, leading me to think something is seriously wrong up there.. Now I gotta figure out how to get it up to the garage..

Crawl underneath the truck and unbolt the front drive shaft...(assuming the front axle is still fine.) I had to replace the transfer case on my dad's 2001 Silverado a couple of years ago due to no lubrication destruction of the transfer case. It was an $800 touch from SGI for a used t-case. Thankfully dad's truck was a low option model and didn't have electric engage/disengage junk on it for the 2wd/4wd just a floor shift.

Ranger50 wrote:

If it isn't the front axle actuator and related wiring, stupid design where and how it's placed, it could be an encoder motor and its related wiring on the t case.

Edit: beyond the t case having issues with a steel on aluminum wear internally, there is a fix for that, the t case and front axle, besides the aforementioned actuator and seals, are pretty damn bulletproof for a GM.

I was under the impression the cases were magnesium?

WonkoTheSane
WonkoTheSane Reader
2/3/15 1:10 p.m.
Moving_Target wrote: Crawl underneath the truck and unbolt the front drive shaft...(assuming the front axle is still fine.) I had to replace the transfer case on my dad's 2001 Silverado a couple of years ago due to no lubrication destruction of the transfer case. It was an $800 touch from SGI for a used t-case. Thankfully dad's truck was a low option model and didn't have electric engage/disengage junk on it for the 2wd/4wd just a floor shift.

Yeah, I figure that'll be tonight's fun. Any idea how bad they are to get off (in a snowbank)?

patgizz
patgizz PowerDork
2/3/15 1:52 p.m.

not horrible especially if you can get an air hose to the snow bank and get impact on it.

when the trans in my avalanche puked though, i got under the truck, looked up, and had it towed to the shop. too much crap to deal with for the $400 extra labor to R&R versus a bench build.

jstand
jstand Reader
2/3/15 2:28 p.m.

Check and see if its easier to get to the actuator for the front axle than the driveshaft.

If you can pull the actuator to disengage the passenger side axle the front axles should spin without the driveshaft moving.

Once you pull the actuator, you may need to rock the truck a bit to get the shaft collar to release from the axle.

WonkoTheSane
WonkoTheSane Reader
2/3/15 7:44 p.m.

Any idea if this is documented in the harness manual? We ended up gOing out to dinner with a good friend, which was way more enjoyable than climbing around under a truck in 2° weather, so that's now tomorrow's project.

And yes, I am going to check the manual :) I just haven't gotten home yet and the manual is for the gasser engined ones.

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