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Old 08-20-2019, 08:12 AM   #1
kljfamily
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2003 transfer case parts

Hello,

Just picked up a 2003 8.1 2500 with about 170k. Everything was fine until I drove it on the freeway and the t-case (gm 246) started grinding and blew. Found it the pump had rubbed through the case (know I know common problem).

Not a novice, so I tore into the t-case. Turns out the planetary gear exploded in there so I have a lot of shrapnel.

A friend has a 2002 t-case I can have for parts on the cheap. Since i just bought this thing I don't have a lot of extra cash.

I see on researching that there was a change in the np246 in 2003. So question is will the 2002 np246 work on my 03? (I think the change had to do with the push button 4x4 but I could be wrong) or at least are they similar enough I can rob parts from it especially that planetary gear which is a costly part. Then I could buy a general rebuild kit and bottom half since it has a hole in it.

My only other option is to go to u-pull it this weekend and see if I can manage to pull out a t-case in the middle of the desert here in Albuquerque.

thanks

Kris
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Old 08-21-2019, 07:54 PM   #2
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Re: 2003 transfer case parts

I can't really help you directly but this link may be of help:

https://www.merchant-automotive.com/t-gastruck.aspx

I think you can get the parts schematics and compare..


Also, I wanted to thank you for posting this. I just bought a 2003 8.1/Allison 1000/NP263XHD with 185k miles. I didn't know about the pump rub issue and researched it. I went out to my truck and found a pinhole and wet transfer case...
looks like another weekend day soon to be occupied! But, that's better than a grenaded case and being left on the side of the road.

Best of luck!

Wil
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Old 08-23-2019, 12:52 AM   #3
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Re: 2003 transfer case parts

Quote:
Originally Posted by kljfamily View Post
Hello,

Just picked up a 2003 8.1 2500 with about 170k. Everything was fine until I drove it on the freeway and the t-case (gm 246) started grinding and blew. Found it the pump had rubbed through the case (know I know common problem).

Not a novice, so I tore into the t-case. Turns out the planetary gear exploded in there so I have a lot of shrapnel.

A friend has a 2002 t-case I can have for parts on the cheap. Since i just bought this thing I don't have a lot of extra cash.

I see on researching that there was a change in the np246 in 2003. So question is will the 2002 np246 work on my 03? (I think the change had to do with the push button 4x4 but I could be wrong) or at least are they similar enough I can rob parts from it especially that planetary gear which is a costly part. Then I could buy a general rebuild kit and bottom half since it has a hole in it.

My only other option is to go to u-pull it this weekend and see if I can manage to pull out a t-case in the middle of the desert here in Albuquerque.

thanks

Kris
I don't see why not. It should bolt up mechanically as long as the spline count is correct.
If the shift motor is different you can probably swap the shift motor from your burnt xfer case. Any switches the same way.


Quote:
Originally Posted by OldCreek View Post
I can't really help you directly but this link may be of help:

https://www.merchant-automotive.com/t-gastruck.aspx

I think you can get the parts schematics and compare..


Also, I wanted to thank you for posting this. I just bought a 2003 8.1/Allison 1000/NP263XHD with 185k miles. I didn't know about the pump rub issue and researched it. I went out to my truck and found a pinhole and wet transfer case...
looks like another weekend day soon to be occupied! But, that's better than a grenaded case and being left on the side of the road.

Best of luck!

Wil
If you already have a leak you'll need to replace the rear case half. It's common enough that there are aftermarket replacements.
Worst case you have to swap a bnch of bearings along with the pump repair.
Make sure to get the o-ring for the pump pickup tube. It doesn't come in the kit.
I always clean off and put the magnet back in the pickup screen area even tho some folks say not to.

Look at the South Main Auto re-assembly video for the GM NV261. Eric does a pretty good job of explaining how to put one back together. The 261 & 263 are pretty similar.
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Last edited by hatzie; 09-06-2019 at 02:28 PM.
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Old 08-24-2019, 12:39 PM   #4
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Re: 2003 transfer case parts

Thanks for the replies.

I picked up the 02 and as far as I can see externally it is all the same. You were right on the actuator it is different on the 03 but the bolt pattern is the same so I'll swap it. The splines match up perfect.

Hopefully this gets me back on the road.

The planetary gear in the 03 was what fell apart throwing shrapnel everywhere. the clutch pack also was in pieces throughout the casing as well as several bearings blew out. It was as bad as it could be upon internal inspection.

I got the 02 t-case for $75. So if this swap works then I got off way cheap and will rebuild the 03 slowly over time as a project.
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Old 08-24-2019, 10:06 PM   #5
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Re: 2003 transfer case parts

If you have a case full of shrapnel you are probably better off to start with a different case.

This is the Autotrac II xfer case that uses the blue Smurf blood for oil is it not?
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Old 08-25-2019, 08:59 AM   #6
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Re: 2003 transfer case parts

Turns out the actuators in fact different. The 02 has more of a square rounded head head and the 03 has more of a star bit gear looking piece. Also it looks like the bolt pattern is slightly different on the actuator to the back case.

Soooooo...I'm going to rip apart the 02 and see if I can scavenge the internals. Not sure exactly how i'm going to proceed until I get in there and see what is what. I may be able to use the rear half off the 02. I have the 03 case soaking right now.

Once i get the 02 apart and I can my attack from there.

So new plan is 1. take apart 02 2.compare internals 3. Frankenstien a case together.
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Old 08-25-2019, 01:43 PM   #7
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Re: 2003 transfer case parts

I'd bet most of the guts from the new case will fit in the damaged one as long as the 2003 case shell doesn't have too much battle damage from the fragged planetary.
It'll give you a chance to refresh all the seals and any bearings that look or feel questionable along with updating the pump if that needs to be done on the 246. A nice clean case doesn't hurt a thing either.

I'm surprised they used the 246 behind the 8.1 Vortec.
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Old 08-25-2019, 02:09 PM   #8
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Re: 2003 transfer case parts

Thats a rare t-case you have there. Expect to pay $200-$300 for a used unit. I would expect it to be different because I believe they went to the 3-button only units 2003+.
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Old 08-25-2019, 03:00 PM   #9
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Re: 2003 transfer case parts

Are you darn sure this is a NV246 behind the 8.1 and the Allison? I thought they used the 263 and 261 with the 8.1 Vortec.

NP8 on the SPID is the NV246
This is the NV246 shift switch.
Name:  Autotrac dash switch.jpg
Views: 299
Size:  12.7 KB

NP1 on the SPID is the NV263
This is the NV263 shift switch.
Name:  NV263 dash switch.jpg
Views: 268
Size:  7.7 KB


NP2 on the SPID is the manual shift NV261...
Hard to miss the big old fashioned shift lever on the floor.
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Old 08-25-2019, 03:30 PM   #10
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Re: 2003 transfer case parts

It is def a 246. the red tag says gm 246.

I took apart the 02 this morning. Guts are almost 100% identical.

The only thing I see again is the actuator area.

On the 02 there is a blue plug that has a spring under it coming in from the side that rests against the metal actuator plate inside.

also the actuator plate itself has a shorter travel on the 02. But I think like others suggested here it has to do with the buttons being different.

The 02 internals look beautiful. There is not a spec of anything in it and I would assume from the looks of the bearings and other parts it had been recently rebuilt.

So I am going to try and just mount the 03 actuator plate and actuator to the 02 case. Since all the gears and bearing look the same I'm not sure why not. Other than that blue headed spring on the 02 everything else is exact.
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Old 08-25-2019, 03:36 PM   #11
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Re: 2003 transfer case parts

Quote:
Originally Posted by hatzie View Post
Are you darn sure this is a NV246 behind the 8.1 and the Allison? I thought they used the 263 and 261 with the 8.1 Vortec.

NP8 on the SPID is the NV246
This is the NV246 shift switch.
Attachment 1931953

NP1 on the SPID is the NV263
This is the NV263 shift switch.
Attachment 1931952


NP2 on the SPID is the manual shift NV261...
Hard to miss the big old fashioned shift lever on the floor.
The avalanche 2500 is on the same frame as a suburban 2500. They are 8600 gvw. There is no Alison on those. Just a 4L80E. Every 4wd GMT800 suburban/avalanche 2500 I’ve worked on had the nv246.
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Old 08-26-2019, 10:17 PM   #12
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Re: 2003 transfer case parts

So the 02 rear case is just different enough that it wonít allow the actuator to fit correctly. It is really close but not close enough to make it work. So Iím back to full dissembly of the 02 to rob the parts and just need to clean the 03 rear case really well and put everything back together from there.
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Old 09-05-2019, 01:57 PM   #13
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Re: 2003 transfer case parts

After messing around with it my 03 case was just too damaged to salvage any of it. The planetary gear from the 02 would not spin in the 03 as the 03 had minor damage to that area as well. Not enough to visually see but enough to stop the gears from turning. The 02 case halves were very similar with just where the actuator area being different.

On the 02 there is a spring and plunger that rests on the control actuator lever inside. You remove it from the outside. On the 03 there is no hole and that piece doesn't exist. So I just didn't use it when I installed the 03 actuator in the 02 case and just but back the bolt without the spring and blue rubber piece. I then had to modify the bolt hole for the shifter control on how it mounts as one of the bolts is slightly different. The rest went together smoothly. It is sealed up and I am waiting 24 hours to try to install.

So what I wound up with is a slightly modified 02 case with an 03 actuator parts in it. From what I can tell this should work.

The only piece I just could not get back on was that darn rear output shaft c clamp. that is the one you have to take off from the outside where there is a long oval rubber plug before you can remove the two halves.

SO I am running without it. It look like a minor piece that helps hold things together but there are so many c clips in this thing I and hoping missing this one is going to be ok.
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Old 09-05-2019, 02:17 PM   #14
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Re: 2003 transfer case parts

I assume you mean the circlip that's accessed through the slot in the tail. It holds the output shaft in the proper position. I wouldn't run without it.

You need flat and wide bill circlip/lock-ring pliers and long thin screwdrivers to open and position this kind of snap ring. Open the ring and lift the shaft into position. Using regular pin hole circlip pliers is an exercise in frustration. It can be done but it'll drive you to drink.

Knipex 4510170 are a pricy but excellent tool. If the $40 pricetag doesn't put you off... buy them. You can find similar lock-ring pliers from Proto and others in the $20-$30 range. all of em are cheaper than $$nap-On or MAC or Cornwall or ... They're handy for outer CV joint locking rings and various transmission and transfer case locking rings.

This is Eric at South Main Auto doing an NV261. Same operation to hook the clip in. He starts fighting with it just after 54:15
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Last edited by hatzie; 09-06-2019 at 02:30 PM.
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Old 09-05-2019, 04:51 PM   #15
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Re: 2003 transfer case parts

To tell the truth I was waiting for someone to tell me to stop and do it right. It was half the reason I posted an update.

arghhhh. so Ill split the case again and put that darn piece back in until I get it right. All it will cost me is a little more time and an other small tube of sealant.
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Old 09-06-2019, 08:25 AM   #16
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Quote:
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To tell the truth I was waiting for someone to tell me to stop and do it right. It was half the reason I posted an update.

arghhhh. so Ill split the case again and put that darn piece back in until I get it right. All it will cost me is a little more time and an other small tube of sealant.
So late last night after work I split the case again and went at it. I realized my alignment was off and the bearing wasnít high enough to clip in right. So after a few adjustments and some light love taps I got it aligned and then with some fiddling got that last c clip in place.

After letting it dry a bit I attempted to move it under the burb to install and dropped the heavy thing on my pinky finger, not broken but bruised to heck. So called it a night. Will try to get it again Saturday.
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Old 09-06-2019, 02:33 PM   #17
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Re: 2003 transfer case parts

Sounds like you're in the home stretch.
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Old 09-19-2019, 05:52 PM   #18
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Re: 2003 transfer case parts

Update..

t case is winning like 10-1

So I did get everything back together. using the 02 case and 03 internals.
When I got the 02 I checked the drive shafts to make sure they fit but neglected to check the input spline........arghhh its 27 and mine is 32... so off to the junk yard again as my 32 had broken teeth.

Found the 32 after an hour got it out of a np241 which is the same. lucky grab on the cheap..split the case (3rd time) and replaced that.

Finally got it installed. But had 4L flashing and service 4wd light on. Took off the actuator and the warnings went off. Looking at some u-tube i guess I have to have the tcase and acutator set to neutral when installing.

Running out of steam I'll mess with that tonight.

2 questions...

1. there is a long hose coming down the passenger side over the t-case that is not hooked up. its not the one that goes to the t-case. I cannot figure out what it attaches to.

2. I put the car in D (with all 4 wheels up and no acutator attached) and I test ran it. Believing I was in 2H. The tires Spin! Which is great but I was getting a little noise from the t-case. Is some noise normal? It sounds a little like a bicycle that is between gears. If it should be whisper quiet then I have some issue but can't imagine what could be loose.
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Old 09-19-2019, 08:18 PM   #19
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Re: 2003 transfer case parts

The 241 is worth assembling and re-selling. The 27 spline will fit the 4L60E/4L60/TH700R4.
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Old 09-20-2019, 08:12 AM   #20
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Re: 2003 transfer case parts

The t- case is still winning.

Last night we went to but the t-case and 4wd selecter/actuator into neutral.

On the t-case the half moon goes in the lowest 6 o clock position. I plugged in the actuator to the harness but did not have it installed on the t-case. Turned the car on and everything was fine..no 4wd service lights and 2wd selected. So I pressed the 4H to test and the actuator moved...cool. pushed 4l and it moved again. I then went to hit neutral holding the 4l and 2H buttons and the lights went out and the service 4wd came back on. Tried turning it off and on, removing the battery cable, pulling fuses ect with no avail.

Any ideas? Could be the actual switch went out on the dash? They all light up when I start but then go out. Tried my code reader and got a c0327 which is the encoder. There has to be some way of resetting this thing as it was working fine just before going out.
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Old 09-20-2019, 02:44 PM   #21
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Re: 2003 transfer case parts

You shouldn't connect the encoder/servo without having it bolted to the TC. It may be damaged.

There are probably updates for the TCCM 4wd controller. If you have an MDI or Tech 2 or a J2534 pass-through device that's recognized by AC Delco TDS you can do it your darnself. If you were nearby in New England I'd offer a hand. Albequerque is a wee bit too far.

http://www.youtube.com/watch?time_co...&v=kldd1fu_csY
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Old 09-21-2019, 01:28 PM   #22
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Re: 2003 transfer case parts

Does anyone know spline positions for 2h 4l 4h and neutral?

It's my understanding that N is with the half moon on the spline at the 6 o clock position. You can move the spline with a pair of channel locks but i want to get it into 2H.
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Old 09-21-2019, 03:15 PM   #23
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Re: 2003 transfer case parts

IIRC on the NP208. 2WD is all the way counter-clockwise looking straight at the shaft and 4LO is all the way clockwise.
Pattern turning from 2WD is 4HI, Neutral, and 4LO.

GM calls the shift motor shaft encoder a "Transfer Case Range Select Position Sensor". They're around $30 from AC Delco.
The electric motor and the attached gears positions don't matter. The motor and the gears don't have any stops.
For some reason the shift computer doesn't protect the shaft encoder from traveling beyond its' stops when you have it plugged in while it's not connected to the transfer case. This breaks the encoder. My guess is that's what happened. It's probably similar to the motors on the HVAC doors. The controller does some kind of calibration as soon as you give it power.

When you re-assemble the shift motor you set the output gear in Neutral by lining up the matchmark indent dot on the rim of the output gear with the groove on the case next to the wire entry for the encoder.
At 5:16 - 5:18 in the video I linked you can see the Neutral matchmark dot at around the ten or eleven o'clock position on the gear. Look next to the oddly double drilled hole in the gear. The matching groove is not very visible in the video.

The groove is in the housing casting right next to the encoder wires that run under the output gear.
Since the Encoder is driven off this gear it'll be set in Neutral when you line up the matchmarks.
The electric motor drives 360į. The only thing you need to worry about is lining up the output gear matchmarks. I'm not sure why the guys in the video thought it was neccesary to matchmark the gears and the housing with paint probably because they weren't setting everything in Neutral.

Chock front and back of the front wheels.
Lift the rear wheels off the ground. If the propshaft yoke is still out of the transfer case don't bother lifting the rear.
Shift the transmission out of park so you can turn the transfer case with the rear propshaft...
Set the TC in Neutral by turning the shift shaft all the way counterclockwise and then back two positions. It's rumored you can turn it with a 12point socket or box wrench. The wide spline should be near the 6:00 position. Seat and bolt the shift motor/encoder on without plugging it in.
Once it's assembled plug in the shift motor and try it out. If it's still complaining clear the error codes with your Tech 2 or bi-directional scan tool and try again. You should make sure the TCCM is flashed to the latest update... there's an update dealing with C0237 errors and updated calibrations for the AWD.
__________________
1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8


RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.

Last edited by hatzie; 09-21-2019 at 03:38 PM.
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Old 09-21-2019, 07:51 PM   #24
kljfamily
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Join Date: Sep 2014
Location: Albuquerque NM
Posts: 42
I did it!

Back on the road! No service 4wd warnings!

Ok so I took apart the encoder motor all the way down removing gear ect. Cleaned it all up with contact cleaner and reassembled placing the cogs at the neutral position. Reassembled and then plugged back into harness. When I turned on the car low and behold the motor works again and reads in the push buttons at neutral.
So with the shift motor off I hit 2 we and the motor moved to position. I put the transfer case in the matching position and reassembled. It was making some noice off the ground which concerned me...rattling a bit. But when I put it back on the road I couldnít hear the rattle at all.

So to recap:

1 my 03 np246 pumped rubbed out and basically exploded inside. Tons of shrapnel. The planetary gear and clutch back metal was everywhere.
2 broke as hell (my son just turned 16 and we just finished his 01 Cherokee between that and adding an16 year old to insurance Iím flat busted) I search for a used tease but only could find an 02 np246 for 75 bucks off craigslist.
3 come to learn there is some major difference between the 02-03. Feel defeated.
4 decided to mess around with the 02 and really look at the difference. In all they were not that different with the exception of the encoder on the 03 is splines and the selector cog is different.
5 swapped the encoder/spline/cog from the 03 to the 02.
6 noticed the top part of my clutch pack on the 02 was bad and two bearings were as well sourced replacements out of an np241 that I found at u pull it
7 reinstalled everything but found that my encoder motor now had the dreaded service 4 wd code and was frozen
8 took about that motor and cleaned reassembled and aligned both the case and the encoder to 2wd and put back together.


Man that was a long run. In all I rebuilt, sealed, took apart resealed 4-5 times in doing this.

Not sure it will last but should until I can pool some money for a solid rebuild t case. Thanks for all that gave their opinions and advice.
.
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Old 09-21-2019, 09:42 PM   #25
hatzie
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Join Date: Oct 2008
Location: Wentworth, NH
Posts: 3,719
Re: 2003 transfer case parts

As long as you filled it with Smurf blood and the clutches, bearings, hard parts, and seals are in good trim it'll work just fine.

Save up but I bet you get more than a little life out of it. I would run it til it gives up on you. You may be surprised.

Now to get your money back out of the 241 with the 27spline input from the 246.
__________________
1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8


RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.

Last edited by hatzie; 09-21-2019 at 10:51 PM.
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