4x4 grinding gear noise

[UTEX72]

Problem is when in 2HI, and after fifteen miles of city driving, when I stop and put the trans in park there is a horrible gear grinding noise that comes from behind engine in the middle of the TB. It will not engage reverse either. If I put it in any other gear range it is fine. No leaks, all fluid levels are fine.
2003 TB LTZ 4x4 113K miles, pampered maintenance, all fluids changed 3K ago, driven 15 miles a day at 45 mph or less, never over 50 mph. 4x4 used 3-4 times a year. This is a gently used TB, never abused.
All lights on switch work properly. Actuator makes appropriate noises when switched from 2HI to all other settings. A4wd now runs in 4HI. 4HI and 4LO work fine.
No computer codes.
Diagnosis so far. One trans shop says no codes and transmission is going out. $2500.00 to fix.
Second trans shop says no codes, can't duplicate.
Chevy dealer says front axle disconnect is going out. $1,000.00 minimum to fix.
Dealer did not inspire confidence.
Can't find a local Chevy 4x4 mechanic.

Has anyone else had this problem? I sure could use some help figuring it out.
Don't mind repairing it if can figure out the problem. Or can drive in 4x4 all of the time until something falls off.

 

[Wooluf1952]

Welcome

In case you haven't heard:
http://gmtnation.com/f5/welcome-gmtnation-com-heres-story-226/

Did you buy the truck new and has the transfer case fluid been changed every 50k miles?

 

[The_Roadie]

Problem is when in 2HI, and after fifteen miles of city driving, when I stop and put the trans in park there is a horrible gear grinding noise that comes from behind engine in the middle of the TB. It will not engage reverse either. If I put it in any other gear range it is fine.

Welcome! You're saying that when your 4WD system is in 2HI, you can't go into reverse? But in 4HI, it's OK? What happens when you put it in reverse? Does the engine stall, or does the engine act like it's not connected to the drivetrain and you get high RPMs but no movement?

No leaks, all fluid levels are fine.

It's so clearly a transfer case problem that there should be some evidence of damage in the transfer case fluid. As mentioned, have you been religious about changing it every 50K?

...A4wd now runs in 4HI.

What does this mean precisely? If you put the mode switch in A4WD mode you get the driveline binding when you turn slightly on pavement that you expect to get in 4HI? This more than anything else points directly to sticky/broken/jammed transfer case clutches. Or a bad TCCM, but that would throw a code.

Diagnosis so far. One trans shop says no codes and transmission is going out. $2500.00 to fix.

Has this shop never worked on a transfer case before?

Second trans shop says no codes, can't duplicate.

Has this shop never worked on a 4WD vehicle before? I assume it does it every time for you. Didn't you take it for a drive with their tech?

Chevy dealer says front axle disconnect is going out. $1,000.00 minimum to fix.

If your symptoms are as you posted here, this dealer didn't even take it for a drive, and is severely lacking competence and honesty.

Dealer did not inspire confidence.

Escalate it to GM if you want to educate them and get them to work on it. I wouldn't let a dealer touch mine, but corporate should be notified so they don't victimize others in your situation.

Can't find a local Chevy 4x4 mechanic.

Is it a problem of distance to a larger town? Finding recommendations? They're out there. I hope.

Has anyone else had this problem? I sure could use some help figuring it out.

Check these links from our offroad sister site:
Offroadtb.com Diagnosing the 4WD System
Offroadtb.com Front Axle 4WD Disconnect
Offroadtb.com Transfer Case Operation: NVG 226 (NP8)

Don't mind repairing it if can figure out the problem. Or can drive in 4x4 all of the time until something falls off.

Your transfer case is doing its darndest to depart the vehicle.

 

[jrSS]

Correct me if I am wrong...but when u lift up the front end.....in 4wd spin one wheel in a direction the other should be spinning the opposite..correct?? That should at least tell u if the 4wd is engaging. My opinion on the A4wd sucks balls on these trucks. I did not like mine. It only detects wheels slippge and then it kicks in. But good luck man. At least check the level in the front diff. to see if metal shavings or chunks fall out.

 

[The_Roadie]

Correct me if I am wrong...but when u lift up the front end.....in 4wd spin one wheel in a direction the other should be spinning the opposite..correct?? That should at least tell u if the 4wd is engaging.

If the wheels spin in opposite directions, that only tells you the front axle actuator and disconnect collar are operating. That's supposed to happen in all modes except 2HI.

What happens in the transfer case with the clutch pack is a bit more complex - all explained in the three links from ORTB I posted. Required reading.

 

[jrSS]

Ahh I see.....u the man roadster!!

 

[The_Roadie]

Thx. I gotta know these systems for when I break them while 20 miles from pavement and 6000 foot elevation difference.

 

[UTEX72]

Welcome! You're saying that when your 4WD system is in 2HI, you can't go into reverse? But in 4HI, it's OK? What happens when you put it in reverse? Does the engine stall, or does the engine act like it's not connected to the drivetrain and you get high RPMs but no movement?It's so clearly a transfer case problem that there should be some evidence of damage in the transfer case fluid. As mentioned, have you been religious about changing it every 50K?What does this mean precisely? If you put the mode switch in A4WD mode you get the driveline binding when you turn slightly on pavement that you expect to get in 4HI? This more than anything else points directly to sticky/broken/jammed transfer case clutches. Or a bad TCCM, but that would throw a code. Has this shop never worked on a transfer case before? Has this shop never worked on a 4WD vehicle before? I assume it does it every time for you. Didn't you take it for a drive with their tech?If your symptoms are as you posted here, this dealer didn't even take it for a drive, and is severely lacking competence and honesty. Escalate it to GM if you want to educate them and get them to work on it. I wouldn't let a dealer touch mine, but corporate should be notified so they don't victimize others in your situation. Is it a problem of distance to a larger town? Finding recommendations? They're out there. I hope. Check these links from our offroad sister site:
Offroadtb.com Diagnosing the 4WD System
Offroadtb.com Front Axle 4WD Disconnect
Offroadtb.com Transfer Case Operation: NVG 226 (NP8)
Your transfer case is doing its darndest to depart the vehicle.

Thank you for your kind responses.
All fluids changed more often than necessary. Generally every 25 30K miles.
This problem only occurs when the vehicle and weather is hot. All fluids are fine with no metal in fluids.
When in 2HI and hot, when I stop it will not engage park or reverse. It is free wheeling, as if it were in neutral. Gear crashing as if, if it were a manual, trying to shove into gear without the clutch. Then, if placed in 4awd it works perfectly in 4HI. 4HI and 4 Low work perfectly. All lights work right, actuator noises sound right, no computer codes, no extra noises when driving in 4awd.
As long as I don't try and park in 2HI everything is normal.


My thoughts on the local dealers is rather low. They seem to depend on reading the computer codes more than anything else. They are of the once around the block types.
I am thinking rebuild the transfer case, front axle disconnect, front diff, and axles this winter. I will not deal with a bad transmission as my experience with rebuilt automatic transmissions is rather bad.
Thanks again for your help.

 

[UTEX72]

she told me to take it to a Toyota dealer and trade it in on something dependable that gets more than 15mpg.
Appreciate everyone's help on this, but she is right. This truck has been a maintenance nightmare for years and spending any more time and money on it is foolish.

 

[jrSS]

I don't blame u. But toyota?? Eeehh

 

[The_Roadie]

Our standard offer for unwanted GMT360s is $500. :wootwoot: