np136 vs np236

[Captn. Crunch]

I know I said I was gonna take the winter off from doing any mods but I have just found myself blessed with the Patron Saint of Mods who is willing to lend me a hand so here we go! One of my must have's is a two speed t/c and AWD. I collected both a 136 and a 236. Both had issues and I wanted to see where they differed. To my delight there was only one difference besides the obvious one speed - two speed thing. There is a ring pressed into the front half of the two speed case that is lacking in its one speed little brother. My two speed front half was cracked so we were able to cut out this ring and press it into the one speed case. Midwest transmission says there is no GM part number for this. They call it NV ring gear and will sell you one if you ever need one. So bottom line is I have installed low range in an Np136 case and will be swapping it into my van here shortly. I will run the single speed encoder motor for now as I work out the plan for accessing low range.
Next up is pulling the carrier from my recently acquired cast iron front diff and sending it off to Engineered Performance for the limited slip/posi upgrade

[doyoulikeithere]

You lucky dog !

[Captn. Crunch]

You lucky dog !

[Stroverlander]

Nice, glad we don't have to wait to read about these mods too! =D>

[Captn. Crunch]

Just to add a sidebar for conversation from my forum brothers here is what I plan to do right away and why. I will swap out my perfectly fine 136 for my recently modified 136 with low range. I will swap out the encoder motor from my exsisting to the modded unit because I know it works. I will perform a truetrak II fluid change after a 50 mile shakedown and look for anything unusual ( metal?) if all is well with the tc I will finish up the cast iron front diff with the Engineered Performance LSD. New seals minimum and will leave the two piece axle for now. There has been some debate at the zr2 site that running this front end with two solid axles may cause binding due to the clutch pack pre-load. I will eliminate all vacumm controls and be cable operated so as to easily differentiate any binding.
I have talked at length with pmc programmers who state my computer being AWD should recognize four wheel drive and a tccm swap a four button switch and a few wires should get me my low range and maintain my AWD feature.
Feel free to add anything to this list up to and including questioning my sanity!

[El_Fuego]

Captn. Crunch, have you done the swap? Does it really work? Can you show some more photos?

[Captn. Crunch]

Well the modified t/c has been installed. I had to do a tranny and as the whole mess was on the ground I thought it a good time to put in the new case. Well that's not entirely true. I like to swap one thing at a time so it's easier to figure out if something's wrong. I didn't do that. I put in the used trans and the modded tc together. I don't have the wiring set up for the two speed case so I pulled the fuse till I can get it wired up. I should have listened to that little voice in my head. Something is dragging. I'm not sure what it is. The front end is binding at low speed in a sharp turn. I'm gonna throw the one speed back in on Saturday thanks for following my adventure And stay tuned...

[El_Fuego]

I found pictures with disassembled view of NP136 and NP236 in the Internet. They have equal mechanical details. I would say they are the same. Maybe those pictures are mistaken, but if no it means that NP136 can use low range. It is not used by TCCM. For this reason, it is not necessarily to swap transfer case, it's only enough to swap (or reprogram) TCCM.

Please correct me if I am wrong and give a link on a correct view of disassembled NP136.

[photo_van]

Well I've never had a 136 apart, but I'm pretty sure it's a one speed transfer case. If not, you're really on to something!!!!

[Stroverlander]

I found pictures with disassembled view of NP136 and NP236 in the Internet. They have equal mechanical details. I would say they are the same. Maybe those pictures are mistaken, but if no it means that NP136 can use low range. It is not used by TCCM. For this reason, it is not necessarily to swap transfer case, it's only enough to swap (or reprogram) TCCM.

Please correct me if I am wrong and give a link on a correct view of disassembled NP136.

No, they are not.

NV136



NP236 (Notice the hub #18, gear #34 and planetary gear #37)



http://www.gmpartseast.com/Page_Product ... =53M&Year=

http://www.gmpartseast.com/Page_Product ... =54S&Year=

[Captn. Crunch]

Oh you are correct the 136 is a one speed and the 236 is a two speed. The 236 I picked up had a cracked case so we took the guts out, pressed the "nv ring" into the front half of a 136 case and put it all back together. The nv ring is the only difference between the two EMPTY CASES. And because they are the same except for that ring, if you install the ring then you can install low range also. Sure I could have bought a good 236 and put that in but where's the fun in that? All I'm saying so far is all the parts fit in the 136 case and its bolted up under my van. It's not hooked up so I can't say it works but I'm working on it. I have a line on a harness and PCM from a 4x4 S-10. Im hoping to weave that into my harness and power up that two speed case. And on a different note my previous post stated I was experiencing some dragging and I thought it was the transfer case. Which was odd because its not powered up and should be no way that there would be any more than the standard clutch pack pre-load being transferred to the front wheels. I thought I would pull it back out. Tonight I was driving in slow circles in a dirt parking lot while my son watched and the hopping is coming from the rear end! Three years or so ago I put a used torsen diff in and it's been smooth as silk. Why it started this just now is a puzzle. I have done two fluid changes since install. I'm thinking of adding a friction modifier or a Lucas additive to see if it makes a difference. I'm not in the mood to set up another rear end. Wish me luck and thanks for playing along!

[El_Fuego]

Thanks guys) Now I definitely see the difference)

Captn. Crunch, believe in yourself and you will do it! Probably you will be the first person who has done this kind of modernization.
It will be great if you post a report (with pictures) of the modernization, when you finish it. Maybe someone will follow your example)

[Captn. Crunch]

Well I was wrong. I thought running the 236 unpowered wouldn't cause any hate and discontent. I had to work on the ground in the driveway so I dropped the front and rear driveshafts, pulled off the tc skid plate and removed the 236 encoder motor. I swapped it out for the 136 em and buttoned everything back up. The test drive proved there was something being transfered to the front end. The van turned and accelerated as it did before the swap. I did some slow turns with the wheel hard over and smooth as silk. I put the nose of the van up against a 15' tall pile of dirt, dropped it in low and stomped on the gas. From a dead stop we almost made it to the top.

We might have if I kept my foot in it so yes the awd works just like it should. Now to access low range

[Astrophysics]

Hi Captain,

Good work on the investigation of the NP236 internals and nP136.
This will be great to have another option to get low range.
The np236 was used in Chevy Avalanche etc. Is it AWD is is it the 4 button type GM with 2HI, 4HI, 4LO and 4 Auto?

thank you,

AP

[Captn. Crunch]

Yup it's true. The four auto is exactly the same as our awd with the 136 which is why I want this swap so badly. I could have gone the way others have gone but living in New England I just love the awd and will go the extra mile to keep it as an option on my dashboard