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09 2500HD - HELP Can't get 4wd Engaged Grind Neutral


frased

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It all started with the old SERVICE FOUR WHEEL DRIVE message.  I have the NQF case

 

Ok so I've done the relearn trick for the TCCM.  Neutral, past 4LO, wait click etc.  No luck.

 

Replaced the transfer case actuator.  Did the relearn again.  No luck.  

 

Replaced the front axle actuator.  Did the relearn again.  I now no longer have service four wheel drive, but still isn't engaging.  

 

Replaced front axle fluid with fresh new oil.  No luck.  

 

Checked transfer case oil level.  It's fine.  

 

when I go to 4 HI all the lights on the dial work etc. but it stays 2wd.  Then I go to 4 LO and my truck DOESN"T MOVE.  Like the entire truck is in neutral.  just revs.  

 

So am I looking at a transfer case rebuilt?  

 

One time I put in 4 HI...  drove a mile and then I heard grinding like it all of a sudden started to want to go in.  And I had done the neutral etc. to engage prior.  It just doesn't want to go in.  

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I would first take off the encoder motor on the transfer case and see if I can manually rotate the shaft and how it feels to rotate.  But it sounds like something is wrong in the transfer case, might just be the shift fork, but could be the gears as well.

 

If you have basic tools and the truck is a '07 classic or earlier, it's a pretty straightforward job to fix it (I'm assuming it's an NP263HD), probably the hardest part is removing/reinstalling the transfer case just because it's heavy and awkward to get in/out (you pretty much want a second person to help, and a transmission jack makes it go better as well).

 

If you do fix it or get it fixed, and your truck is an '07 classic or earlier, also make sure/install a pump rub fix kit, prevents a catastrophic failure of the case which happens over time, regardless of whether you use 4wd or not.

 

 

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Sorry forgot to list my year. It’s a 2009. Has the MP NQF transfer case. 

 

I’ll do that next. Try to rotate the encoder gear manually. Looks like I could put a fine tooth socket on it. 

 

I was reading about the possibility of the shift fork too. Thanks for bringing that up. Maybe now I’m getting closer to root cause. 

 

Going to drop the case myself if it comes to it. Drained so it’s lighter. And crack er open for diagnostics. Doing the transmission shop thing is not an option. 

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I would suggest first figuring out which specific transfer case you have (NQF is just a RPO code, which could be one of two different transfer cases).  Then google for an exploded parts diagram and/or videos of dissassembling/reassembling it, so you know in advance what tools you need and how it all works.  Maybe even spring for a couple of days of alldata.com or helminc.com, which might/should have repair info on the transfer case (maybe contact them to make sure before paying for it).

 

And if you are removing it yourself, if it's at all similar to do as mine was (ie, the torsion bar crossmember is in the way of dropping it), it has to be twisted/rotated as it is being dropped from the transmission, as the transfer case weighs 80-100 lbs.  You will definitely be wanting a transmission jack to help, as well as a separate jack to support the transmission.

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I found this write up to be super helpful in possibly diagnosing my issue when I pull the case.  

 

http://www.atra.com/Gears/2011/2011-07/2011_7_28.pdf

 

@davester looks like one of the common issues in my first gen MP NQF case may be the fork you mentioned.  Looks like something you were describing?  On page 31 there is a section "Grinding, Pops out of Gear"

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Might also be the snap ring problem they mention just after that.

 

If you want to minimize downtime for your truck, you might want to verify the exact model you have, then phone around to local transmission parts shops (should be some if you are in a city) and see if they have parts for your model.  They'll be cheaper and will be more likely to actually stock the parts, vs your local GM dealer who will likely say "we have to order it in".

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Any of you get the transfer case out without jacking up the truck?  I have the proper trans jack and other jacks.  But the truck rides so high was wondering if stands were even needed.  Or just a quick tilt with another jack to slide it out.  

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I did mine using ~10inch high drive-on ramps, wasn't quite enough to get the transmission (4l80e) in/out of the truck on the transmission jack, but the transfer case was no problem.  If your truck is lifted more than a couple inches, it shouldn't be a problem.  The TC weights about 80-100 lbs or so, so it's not that bad to get it on a transmission jack after pushing it under the truck.  The hard part is twisting & rotating the TC to get it over the torsion bar cross member (at least, it was for my truck, it may be different for gmt-900s).

 

The other thing that sucks was removing/installing the nuts holding the transmission adapter to the transmission (I believe that's what the FSM says to unbolt to remove the TC, not the bolts from the adapter to the TC), as there isn't a lot of space to do it and depending on how high the truck is, you have to raise & support your upper torso to be able to do it.

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All,

 

Any tips on opening up the case?  It will be my first transfer case split.  Just wanted to know if there are any tips/clips/etc on getting it opened up without issue?  Remove speed sensors etc. ?  

 

I believe I have an MP 1625 according to a writeup I found.  http://www.evopower.ca/mrws/filedriver/MP_Transfer_Cases.pdf

 

Do you all use an original gasket or black RTV when putting the 2 x case halves back together?  

 

Before I pull it though I'm going to try and move the shaft manually.  After the encoder is removed again.  

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I don't know your model, but you should be able to find exploded parts diagrams for it.  If it has a gasket of some kind between the case halves, they will show it.  My NP261HD didn't, I believe GM specced using an anaerobic sealant for it, which I used.

 

Don't know anything about rebuilding your model.  The GM full-service manuals probably won't have any info on it (my don't have anything about the insides of the transfer case, just how to fix stuff accessible from the outside of the case).  It's possible the online services include this info (helminc.com, alldata.com)...  You could contact them and ask, and it's really cheap for just a couple days.

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On ‎11‎/‎25‎/‎2017 at 8:24 PM, davester said:

I would first take off the encoder motor on the transfer case and see if I can manually rotate the shaft and how it feels to rotate.  But it sounds like something is wrong in the transfer case, might just be the shift fork, but could be the gears as well.

 

If you have basic tools and the truck is a '07 classic or earlier, it's a pretty straightforward job to fix it (I'm assuming it's an NP263HD), probably the hardest part is removing/reinstalling the transfer case just because it's heavy and awkward to get in/out (you pretty much want a second person to help, and a transmission jack makes it go better as well).

 

If you do fix it or get it fixed, and your truck is an '07 classic or earlier, also make sure/install a pump rub fix kit, prevents a catastrophic failure of the case which happens over time, regardless of whether you use 4wd or not.

 

 

So I have a 2001 2500HD w the Allison tranny. Is the "pump rub fix kit" something a local mechanic can get and install for me? Is it a GM thing? I have heard of the transfer case failures but assumed it was from overwork. TIA for any info you can shoot my way.  Mike

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google "gm pump rub fix", there's lots of info about solutions and how to do it.

 

From least to most expensive, common solutions to the problem:

-pressed metal plate, goes against existing oil pump housing

-billet oil pump housing, replaces pump housing

-replace tail housing of transfer case with new version made of another material besides magnesium

 

A regular mechanic can do any of them, if you go to a dealer, they probably will pressure you into doing the most expensive thing.

 

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Update: I can hear the gears in the case almost engaging when I go 2HI to 4HI.  Going to check the manual shift trick tonight after pulling encoder motor.  

 

I joined the alldata for 1 year...  excellent diagrams and steps.  If I pull the case this week.  :-(  

 

Do you guys know is that clamp on the front shaft is salvageable when removed?  On the boot right at the transfer case.  I can already see I'll need clamp tool and new clamp potentially.   #4 below.  

frontshaft.gif

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