MP3023 Transfer Case Grinding/Chattering

[DaveO9]

2800 mile family road trip over Thanksgiving week in the Tahoe. Ran great, really no major issues until about mile 2300 on the way home. Felt a hard shift from the trans (at least that's what it felt like) and from then on had a significant, impossible to ignore, metal-on-metal sound from the t-case. It took some diagnosis both on the road and now, since I've been home, to determine the t-case is the culprit. Engine off and coasting with trans in neutral - noise occurs. Same scenario, but with t-case in neutral as well - no noise. So by my logic, test 1 tells me it can't be anything forward of the trans output, and test 2 tells me it can't be anything behind T-case output. We were driving through the night and of course, this pops up at 10 pm in the middle of nowhere. No options other than to keep driving and hope for the best. Made it the final 500 miles home without further incident - more things to add to the list of things to be thankful for . The noise didn't ever get any worse, and actually went away or became not noticeable with long stretches of highway driving. We got home at 6 am this morning. After a long nap, I did some more testing this afternoon and of course it's still there.

Front of truck is up on jack stands now. No obvious external damage or signs of significant leakage. Took the fill plug out expecting nothing, and was surprised when fluid came shooting out. (transmission fluid level is good - I don't think I'm getting fluid transfer from trans to t-case). Fluid is black and smells a little burnt, though. Obviously something is really bad in there, but not sure what that would be so it still drives fine, but have the bad noise. (There was one point when I was getting a lot jerking and bucking at slow speeds, but that has gone away). Typical failure modes for a 3023? Truck has 193k miles, but everything in undercarriage is really clean. I have no idea on originality, but one clue: the shift motor looks like it's been replaced since it's a Dorman unit. I never did find an ID tag on the case. Should there be one somewhere? My RPO code in glovebox is NHQ.

With 500 miles of grinding I'm not sure a rebuild is worth it. I think my two options are either a reman ($900-$1000 shipped) or used with a 1-year warranty ($300-$400 shipped). I'm leaning towards the latter. Thoughts?

 

[wjburken]

Were you driving in 2WD or Auto 4WD? Can you get all 4 wheels off the ground safely? If so, might be worth doing so and seeing what happens with the transfer case when in it’s various modes just to confirm the source of the noise.

 

[Geotrash]

2800 mile family road trip over Thanksgiving week in the Tahoe. Ran great, really no major issues until about mile 2300 on the way home. Felt a hard shift from the trans (at least that's what it felt like) and from then on had a significant, impossible to ignore, metal-on-metal sound from the t-case. It took some diagnosis both on the road and now, since I've been home, to determine the t-case is the culprit. Engine off and coasting with trans in neutral - noise occurs. Same scenario, but with t-case in neutral as well - no noise. So by my logic, test 1 tells me it can't be anything forward of the trans output, and test 2 tells me it can't be anything behind T-case output. We were driving through the night and of course, this pops up at 10 pm in the middle of nowhere. No options other than to keep driving and hope for the best. Made it the final 500 miles home without further incident - more things to add to the list of things to be thankful for . The noise didn't ever get any worse, and actually went away or became not noticeable with long stretches of highway driving. We got home at 6 am this morning. After a long nap, I did some more testing this afternoon and of course it's still there.

Front of truck is up on jack stands now. No obvious external damage or signs of significant leakage. Took the fill plug out expecting nothing, and was surprised when fluid came shooting out. (transmission fluid level is good - I don't think I'm getting fluid transfer from trans to t-case). Fluid is black and smells a little burnt, though. Obviously something is really bad in there, but not sure what that would be so it still drives fine, but have the bad noise. (There was one point when I was getting a lot jerking and bucking at slow speeds, but that has gone away). Typical failure modes for a 3023? Truck has 193k miles, but everything in undercarriage is really clean. I have no idea on originality, but one clue: the shift motor looks like it's been replaced since it's a Dorman unit. I never did find an ID tag on the case. Should there be one somewhere? My RPO code in glovebox is NHQ.

With 500 miles of grinding I'm not sure a rebuild is worth it. I think my two options are either a reman ($900-$1000 shipped) or used with a 1-year warranty ($300-$400 shipped). I'm leaning towards the latter. Thoughts?

The fluid shooting out seems a telltale sign that you have transmission fluid entering the T-case.

 

[DaveO9]

I was in 2wd. I did try auto and 4-hi while diagnosing on the road. - no change to the noise. But it went into all modes without issue.

I can get all four wheels off the ground safely. I think I’ll do what you suggest. I’m beginning to suspect I don’t have 4wd. Front suspension needs to be loaded a little when doing this test I believe? It shouldn’t just be hanging? (Jackstands currently on frame)

 

[DaveO9]

The fluid shooting out seems a telltale sign that you have transmission fluid entering the T-case.

Only the front wheels off the ground (by about six inches). And “shooting out” was a poor choice of words - put the plug back in right away when I saw there was fluid at the fill plug level.

It would be an easy fix if that were the problem, but I don’t think that’s it.

 

[swathdiver]

Get the used one and then you can perform a post-mortem on this and decide whether or not you want to rebuild it yourself or not. They are not complicated. It seems like the pump got clogged and quit sending fluid around to the bearings from my chair.

 

[Geotrash]

Get the used one and then you can perform a post-mortem on this and decide whether or not you want to rebuild it yourself or not. They are not complicated. It seems like the pump got clogged and quit sending fluid around to the bearings from my chair.

+1. Used low mileage is the way to go. You can also check car-part.com to see if there's one nearby.

 

[DaveO9]

Thanks, guys. I think that’s what I’ll do. I like rebuilding stuff when I don’t have to worry about trying to get it back together because I need to use it in two days. I’ve done engines, steering gear, alternators, starters, etc - time to try my hand at a T-case.

 

[DaveO9]

Got the T-case out tonight and split it apart. I'm pretty sure the problem is with the planetary set itself. Everything looks good on the output half and spins nicely. But spinning the planetary by itself I hear the same grinding I heard when it was running. And there are ribs on the inside of the case next to where the gear set spins that are shiny and ground down. And the pins that the pins ride on look like they got very hot based on the visible discoloration. And when I took the drain plug it looked like a work of art with all the metal on it!

Any thoughts as to what happened? Is there a thrust bearing on the input side that could have failed? It seems like the gear set has fore/aft play that it shouldn't have, if it's riding on the ribs of the case. I'm not sure how to remove the gear set from the case, but I didn't spend much time on it. I do kind of want to figure out what happened, if nothing else to see if I have anything to worry about with a used case that I'll be putting in.

Not sure a rebuild is worth it if the planetary is shot?

 

[Geotrash]

Got the T-case out tonight and split it apart. I'm pretty sure the problem is with the planetary set itself. Everything looks good on the output half and spins nicely. But spinning the planetary by itself I hear the same grinding I heard when it was running. And there are ribs on the inside of the case next to where the gear set spins that are shiny and ground down. And the pins that the pins ride on look like they got very hot based on the visible discoloration. And when I took the drain plug it looked like a work of art with all the metal on it!

Any thoughts as to what happened? Is there a thrust bearing on the input side that could have failed? It seems like the gear set has fore/aft play that it shouldn't have, if it's riding on the ribs of the case. I'm not sure how to remove the gear set from the case, but I didn't spend much time on it. I do kind of want to figure out what happened, if nothing else to see if I have anything to worry about with a used case that I'll be putting in.

Not sure a rebuild is worth it if the planetary is shot?

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That's a pocket bearing and they're known for cracking on these, which I would wager is what's happened to yours. The root cause is a broken snap ring groove on the rear main shaft that forces the shaft into the planet, breaking the bearing. I only know this because I had a transfer case problem on my 2002 and remembered this detail from my troubleshooting on it. This video shows it well, starting at 5:00.