Pulling off the Perfect NP246 Transfer Case Rebuild

[Matthew Jeschke]

The next item on my to do list is rebuilding a NP 246 Transfer case. I bought a spare on just to do this. I need to disassemble it and get a better idea of what's involved. Bit nervous as well as I have original pumpkins in my differential housings and old Transfer Case in my truck. Those are the ONLY three parts of my truck that haven't been rebuilt. I checked gear lash on front and rear diffs though and it's well within spec so pointless to rebuild them. I currently have some driveline play and assuming it's in the transfer case as such. Hope I can swap that out and have a nice tight running drivetrain.

Listed below are the parts I know I need to get, with some questions pending. I'll update this original post as I learn more and questions are answered.

Parts List

New Chain I'm looking at USA Standard Gear replacement chain ZTCHHV072 prefer to use OEM stuff. However, the OEM chain is three times as much. Please comment below if you know where these chains are made and if there's private label just as good as OEM. I'm looking at .

Rebuild Kit I prefer Timken parts but not sure if they make a kit? Looking at USA Standard Gear ZTBK351. Note my kit came with the plastic shift fork tabs.

Transfer Case extension Housing bushing my rebuild kit did not include this but the one in my case was well warn. It's the last bushing in the case before the slip yoke on the driveshaft. Here's the part number AC Delco #15665313

Transfer case vent Simple enough, I've bought these before. Dumb things break off, there's a metal one, curious if that will fit? It's listed for a different transfer case.

Transfer case bearing snap ring You can reuse these but they are so cheap I'd prefer to just throw one in my order to make sure I have a new one. Doesn't appear rebuild kit includes one. FYI ~ I used ALL new snap rings in my 4L60E when I built it. My buddy even tack welds them in place (wouldn't work for NP246 just saying is good idea on 4L60E).

Case Saver Pump upgrade by Merchant Automotive HERE or with extra stuff HERE. Verified with merchant automotive that it fits.

Six pinion gearset Good chance you already have a six pinion planet. Tear down before you order one. Otherwise the NP 263 transfer case has them and they are compatible. DO NO BUY AFTERMARKET. Only use OEM planets / gear assemblies.


Clutch Pack mine had 10 clutches Part # 89059648 and 9 steels Part # 12547608. The OEM clutches and steels are SUPER expensive. Curious if there's just as good as OEM. Otherwise my clutches look PERFECT. Steels are a bit warn but not heat damaged or anything. Precision Transmission video claims same clutch pack as Dodge 47RE overdrive clutch & Steels HERE. I'm going to test Raybestos GPZ clutches & steels HERE, clutch part number is GPZ115-518

Encoder Motor Make SURE to replace the encoder motor gasket, cannot seem to find one for sale. It appears the encoder motor itself is not rebuildable. Haven't found anything on that yet.

Removal and Installation The NP 246 is LIGHT. You can remove it by hand with some effort. I think it's 80lbs dry something like that. I tried to use a jack when I installed my new transmission put mine back in but wasn't feasible more of a PITA to situate the jack for the transfer case so I just put it on by hand being VERY careful to not drop it on my face.

That said, anybody know of a good jack for this specific job? It's always better to have the extra, mechanical hands...

Questions:

what RTV or sealant do I use to reconnect the case halves?

I know doesn't use regular RTV. Thankfully Merchant automotive pump upgrade (case saver) came with appropriate RTV for case halves.

What solvents if any can be used to clean the case?

I ended up cleaning with Zip Degreaser a pressure washer, and lastly grease and wax remover. Then I painted with DupliColor Ceramic Engine Enamel paint. Same way I cleaned my transmission case and seemed to work.

What are specs on the clutch pack?

Same as 47RE or 48RE Chrysler Overdrive Clutch

Clutches Measured 0.086" x OD6.080" 54 teeth.
Steels Measured 0.070"

Pump screen and pickup?

Nobody seems to replace this on tutorials. Where can you buy it if need be? I don't see it on RockAuto.

Rebuild manual for NP 246?

Zumbrota Drivetrain Parts Booklet

 

[Matthew Jeschke]

Helpful video explains some of the differences between NP 246 and it's HD equivalent

Here's another helpful video:

 

[Matthew Jeschke]

 

[Matthew Jeschke]

Clutches used

 

[Matthew Jeschke]

Side issue my 4x4 indicator on the instrument panel does not work. Says I can command all lamps on from a scan tool.

 

[Matthew Jeschke]

Finally found the clutch assembly procedure

 

[Matthew Jeschke]

FINALLY found the rebuild instructions for the NP 246 in All Data DIY. It's listed under...

 

[AngryFish]

Best of luck with the build. I plan to be doing something very soon to mine... I think there may be some seepage through the casting in the normal pump rub locations.

Can you give a bit more info on the 4wd switch issue? If I recall, I took mine apart to check for and resolder all the connections, but that did not fix any issues I had with intermittent service 4wd issues. I did replace the backlight bulbs with LEDs while I was there, though, so that was a bonus.

When the truck starts up, all 4 lights should illuminate, as well as the neutral, as a form of function check. Does yours do that, but then the system warning appears?

You may want to replace the encoder inside the encoder motor. I had the dreaded intermittent shift issue, and that was due to the encoder sensor itself failing. Part is 88962315 or similar, and I recommend the internal transfer case motor gasket at the same time. (I had purchased a reman replacement motor assembly that didn't fix the issue. Apparently that encoder ring had failed as well.)

The new gasket is due to the swelling of the original. You can re-use it by putting it back in place with some patience, but it expands quite a bit so a new gasket or some RTV to waterproof the motor is recommended.

A scan tool can make quick work of the diagnostics there. IMO, completely worth the $35 - $50 to have a new encoder. I've had no 4wd switch issues since. With the scan tool you can see the transfer case position and current gear, as well as the raw voltage from the sensor. Mine was so far out of range it thought it was in neutral and a bump sent it to 4lo. When I wasn't lucky, the TCM actually decided to switch gears on me, and that could be really fun when it wouldn't change back in traffic.

Best part is it's like a new motor assembly without the $400 cost.

 

[Matthew Jeschke]

What year is your truck? I have a 2001. My transfer case control buttons don't do a LED self check.

I actually have no issues with my transfer case right now. Just bought a spare one to rebuild so I have a fresh transfer case. Well I have ONE issue, when I put it in 4wd, the LED doesn't illuminate in the instrument cluster. I cannot figure out why. The instrument panel is good, I took it out and probed the LED.

Thanks for tip on encoder! I will add that to original post / parts list. Very helpful.

Also the gasket, I forgot to put it on the parts list. I'll add that too.

 

[rockola1971]

My man getting all NP246E OCD.

When you make it more difficult than it really is.....It will be more difficult. Its a transfer case, not a Turbofan Jet engine.

You will be pleasantly surprised once you open the Tcase up at just how basic and very little parts that are inside. It aint a transmission.

 

[AngryFish]

What year is your truck? I have a 2001. My transfer case control buttons don't do a LED self check.

I actually have no issues with my transfer case right now. Just bought a spare one to rebuild so I have a fresh transfer case. Well I have ONE issue, when I put it in 4wd, the LED doesn't illuminate in the instrument cluster. I cannot figure out why. The instrument panel is good, I took it out and probed the LED.

Thanks for tip on encoder! I will add that to original post / parts list. Very helpful.

Also the gasket, I forgot to put it on the parts list. I'll add that too.

My truck is a 2003. Showing some age but still moving along.

The switch module should start up right away and do a self-check just like the dash. All the LED's should light just like all the lights on the dash cluster so you can see if they are burnt out.

Each LED is on its own wire, with a transistor on the common/ground side. Could be a wire thing, could be a transistor failure. Easiest way is to find someone with a scanner or beg, borrow, or steal (or purchase) your own bi-di scanner. They can turn on the LED's individually. It is also possible for the LED itself to fail, so you can check to see if the resistance to ground through the transistor changes when the light is on (positive lead of the meter on the wire and common on the ground or it may not work). This is a very low current circuit, so don't use a standard test light or you will likely have to replace a transistor.

More commonly is a broken solder joint on either a pin for the switch module or on the board for the LED or resistor. I had a similar issue with most of the modules in the dash. Once I reflowed the solder joints, I was able to get it working again. The lead-free solder is very bad about fractures due to the brittle nature of the lead-free solder failing due to the vibration of the car. I've fixed several similar issues on other vehicles, too, with just re-soldering the pins.

 

[rockola1971]

Interesting what GM did there. Each switch mode has a resistor in series with each switch.(built into switch module) Each one of the resistors would have to be a different value atleast 25% lower or higher than the next one. The 5volt reference(supplied from Tcase module) comes in across the switch that is pressed and voltage is dropped from the reference 5volts. Dropped voltage of course depends on the value of respective resistor. The final value is sensed within the Tcase control module at the A6C1 terminal which is marked "Switch signal". The module works its magic inside and closes what is likely an electronic switch (transistor) and that closing gives the respective switch position led a ground to show that you are now in that 4wd/2wd mode.
The switch assembly has an internal connection for the 5 volt reference and the outgoing signal form the respective resistors also. Each one of those legs is common to ALL switch positions. If either one of those becomes electrically open then the switch module is useless until repaired or replaced.

 

[Matthew Jeschke]

I'm trying to figure out where to get a decent deal on the tool to setup the clutch clearance. Kind of hate to buy a one time use tool.

 

[rockola1971]

I'm trying to figure out where to get a decent deal on the tool to setup the clutch clearance. Kind of hate to buy a one time use tool.

You dont need a special tool. All you need is a caliper to measure your clutch stack and compare to specs. Measure your old stack for comparison.

 

[Matthew Jeschke]

see next post...

 

[Matthew Jeschke]

I've got all the parts ordered minus few incidentals; encoder, clutches, vent, etc. Actually not sure where to order factory clutches from... Rock auto didn't have them, ebay does but I never fully trust eBay.

You dont need a special tool. All you need is a caliper to measure your clutch stack and compare to specs. Measure your old stack for comparison.

You have convinced me What you mention is how I did it in my 4L60E build (more or less). I'm really perplexed as to why they do it differently for the drum on the NP246 with that stupid complex tool. For the 4L60E build I put a feeler gauge between the pressure plate an the top clutch and checked the gap met spec in my book.

The only question, and I'm sure you're accounting for this... They don't give me a spec for gap, only for using that stupid tool. So if I spec off the old clutch pack height, won't there be wear to account for? I've 250,000 miles on that transfer case. Do clutches wear much? idk...

Practically fell apart, really easy to work on except for those double seals. Came with 6 pinion planet already.

 

[rockola1971]

@Matthew Jeschke Give me the thickness measurement of your new and your old stack and I will dig around for the numbers you seek. During tranny clutch loaded measurement most shops just hit the drum with a air hose and measure the gap of the pack when air is released. Hit it with air a couple times and take multiple measurements to make sure around the gap.

If you hit that gap in 3 different places around the drum and you get .002", .005" and .010" using new steels and clutches...well you just measured the gap of a warped drum that got too hot and is JUNK! Not likely to happen in a Tcase but very probable in a tranny.

Dont forget to let auto clutches soak in Autotrac fluid before installing them! I let mine soak overnight.

Get your caliper and feeler gauges out and blow off the dust!

 

[Matthew Jeschke]

@Matthew Jeschke Give me the thickness measurement of your new and your old stack and I will dig around for the numbers you seek. During tranny clutch loaded measurement most shops just hit the drum with a air hose and measure the gap of the pack when air is released. Hit it with air a couple times and take multiple measurements to make sure around the gap.

If you hit that gap in 3 different places around the drum and you get .002", .005" and .010" using new steels and clutches...well you just measured the gap of a warped drum that got too hot and is JUNK! Not likely to happen in a Tcase but very probable in a tranny.

Dont forget to let auto clutches soak in Autotrac fluid before installing them! I let mine soak overnight.

Get your caliper and feeler gauges out and blow off the dust!

Awesome! I'll try to get into the drum tonight after work and measure thickness of the original clutch stack-up.

Curious, I have LOTS of dextron VI. The parts store now says to use Dextron VI in the NP246 tcase. However, that seems highly disputed online. I've no clue haha can I use the NP 246? I can no longer find Auto Track II. Some say to use Dextron III but I would prefer to use what I already have... Any tips there?

 

[rockola1971]

Awesome! I'll try to get into the drum tonight after work and measure thickness of the original clutch stack-up.

Curious, I have LOTS of dextron VI. The parts store now says to use Dextron VI in the NP246 tcase. However, that seems highly disputed online. I've no clue haha can I use the NP 246? I can no longer find Auto Track II. Some say to use Dextron III but I would prefer to use what I already have... Any tips there?

If you have the auto4wd then you need auto trak fluid. Its blue.

Amazon.com : acdelco auto trak 2 transfer case fluid

 

[Matthew Jeschke]

Clutch hub and drum was immaculate. Some wobble in the needle bearing though at neck of drum. no abnormal wear on the shaft or anywhere. Maybe is typical.

I measured the clutch pack including the apply plate and spacer. Measured in three places was and pretty uniform. When measuring I held clutch pack with one hand in a fist to squeeze it together, while I measured with dial caliper next to my hand. I measured all the clutches and steels as well. They were pretty uniform. Rough dimensions below:

Ten clutches ~ 0.086" each
Nine steels ~ 0.067" each
One spacer = 0.071"
One pressure Plate = 0.252"

Stack up ~ 1.803"