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.

 

[DaveO9]

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.

Thanks for the info and vid link. seems like a plausible explanation. Do these problems continue to the MP t-cases of late 2000s? I think your 2002 would have been an NP261? Just trying to figure out if this is a systemic problem with the MP3023. I purchased a used one from LKQ today - 120K miles for $265. 6 mo/6000 mile warranty. I pick it up tomorrow and hopefully will install same day. Fingers crossed I don't have same problem with the new one in 6 months + a day.

At least the MP t-cases don't have the pump rub problems that the older ones had.

 

[Geotrash]

Thanks for the info and vid link. seems like a plausible explanation. Do these problems continue to the MP t-cases of late 2000s? I think your 2002 would have been an NP261? Just trying to figure out if this is a systemic problem with the MP3023. I purchased a used one from LKQ today - 120K miles for $265. 6 mo/6000 mile warranty. I pick it up tomorrow and hopefully will install same day. Fingers crossed I don't have same problem with the new one in 6 months + a day.

At least the MP t-cases don't have the pump rub problems that the older ones had.

Yep, my 2002 had a different TC, but I was having problems with it in 2016 so I just remembered coming across that video in my research.

 

[DaveO9]

"New" T-case from LKQ is in and rig is running and driving - no noise! $275, from a silverado with 119K. Install went pretty well except for the fact that exactly .5 seconds after I got it seated on the adapter I remembered I needed to install the gasket. Back down to the ground on the trans jack so I could add that in. I'm still not sure I understand the need for a gasket there. There's a v-groove in the adapter's mating flange so it's definitely not going to hold any fluid that leaks out of the trans. Oh well, it's in.

It took less fluid than I thought. I originally bought two quarts, but I used part of one to do a minor flush, and then a bit leaked out through the output at one point when I got it too catywampus. (I added fluid before install in the hope of avoiding use of a transfer pump) So I was expecting to have to go get at least another quart, but after everything was installed, I pulled fill plug and fluid dribbled out for several minutes so it seems like I had too much in there when I was expecting there to be not enough.

 

[Geotrash]

"New" T-case from LKQ is in and rig is running and driving - no noise! $275, from a silverado with 119K. Install went pretty well except for the fact that exactly .5 seconds after I got it seated on the adapter I remembered I needed to install the gasket. Back down to the ground on the trans jack so I could add that in. I'm still not sure I understand the need for a gasket there. There's a v-groove in the adapter's mating flange so it's definitely not going to hold any fluid that leaks out of the trans. Oh well, it's in.

It took less fluid than I thought. I originally bought two quarts, but I used part of one to do a minor flush, and then a bit leaked out through the output at one point when I got it too catywampus. (I added fluid before install in the hope of avoiding use of a transfer pump) So I was expecting to have to go get at least another quart, but after everything was installed, I pulled fill plug and fluid dribbled out for several minutes so it seems like I had too much in there when I was expecting there to be not enough.

Way to go! Glad you got it all buttoned up. My guess is that the gasket is there to prevent fretting between the two metal parts.

 

[DaveO9]

Just to close the loop on this, I finally got around to disassembling my old t-case to see what happened. Looks like the planetary gear set failed. Also the input bearing seems to be toasted, but maybe that was collateral damage. (or vice versa?) The pics show a slight crack in the carrier at one of the pin locations, and two of the planet pins failed. One is so loose that it feels like there are no bearings at all in there. I still can't believe we made it home (500 miles away) with it like this.

Everything else in there seems to be fine, including the viscous coupling. Throw it up on CL for $75 for parts and see if I get any takers?