Chevy & GMC Vans

Hey there. A long time ago, I've researched the replacement of a 136 with a 236. I've found that the cases are almost exactly identical and can bolt up without modifying. Just like how the 233, I believe the 236 can bolt right in without any modification of drive shafts or cross members.

However I found the hardest part is the electronics. I found the TCCM from the 236 requires a 2-way input to/from the PCM. The TCCM come pre-programmed for every possible configuration of vehicle and require a check via the class 2 serial bus to the PCM every time the van is started for the VIN# to configure itself. From the VIN, things like wheel size, axle gearing, etc are set and the appropriate settings are used. I haven't looked to see if an override was possible...and don't know if the TCCMs will recognize astro VIN#s or of our PCM broadcasts that data if asked. That pretty much made me throw the towel because of the complexity.

If there's a way to provision the communication from the PCM/TCCM I think we have a winner here. I'm looking forward to seeing your project as it comes along.

chuck.z wrote:Hey there. A long time ago, I've researched the replacement of a 136 with a 236. I've found that the cases are almost exactly identical and can bolt up without modifying. Just like how the 233, I believe the 236 can bolt right in without any modification of drive shafts or cross members.

However I found the hardest part is the electronics. I found the TCCM from the 236 requires a 2-way input to/from the PCM. The TCCM come pre-programmed for every possible configuration of vehicle and require a check via the class 2 serial bus to the PCM every time the van is started for the VIN# to configure itself. From the VIN, things like wheel size, axle gearing, etc are set and the appropriate settings are used. I haven't looked to see if an override was possible...and don't know if the TCCMs will recognize astro VIN#s or of our PCM broadcasts that data if asked. That pretty much made me throw the towel because of the complexity.

If there's a way to provision the communication from the PCM/TCCM I think we have a winner here. I'm looking forward to seeing your project as it comes along.

While researching an LS swap, I've learned there are guys out there that can easily reprogram the PCM to have it do whatever is needed... meaning if it needs to pretend to be a specific 4x4, no problem! (You can purchase the software/hardware to do it yourself too, but it isn't cost-effective unless you are going to be doing a lot of programming.)

Great info on what to expect on the electronics end of things. I was going to order parts for the t/c rebuild this weekend and my fuel pump quit on me. $100 tow and $300 pump wiped out my parts stash. Ever forward...

My apologies to anyone keeping an eye on this thread looking for cool new happenings. As is my life, my van has decided to get needy on me these last couple of months. Fuel pump, a.c compressor and now front hubs have thwarted my every attempt at making any headway on my two speed tc and cast iron front diff. I think it wise to just get ready for winter at this stage of the game and take my time getting all the pieces and parts ready for spring. I really hate being poor!!!

Well it's official! All of the parts I think I'm gonna need to bring the np236 to life are here. I built the transfer case from two damaged units. An np136 and an np236. They are same same except for to low range in the 236. I'm running the 236 now with the 136 encoder motor. Awd works like its supposed to. Next step is to swap tccm's from stock to donor 4x4 blazer. Swap encoder motors and plug in the dash switch. We will see what will talk to what and if I have been just chasing my tail on this one [-o<

Looking forward to this. If you find the need for any miscellaneous wiring diagrams, I'm happy to contribute from my GM eSI manual.

Thank you Stro'. I would not be at all surprised if I find myself in such a predicament. I will certainly let you know.

Captn. Crunch wrote: I think it wise to just get ready for winter at this stage of the game and take my time getting all the pieces and parts ready for spring. I really hate being poor!!!

Spring has sprung, you have the parts and I'm warming one of the cheap seats in the bleachers.
I can relate to the poor part but I think it has more to do with where we live Cap, it's a relative thing. Being on or near the shore there is lot's of money but the little those of us earn in the service industry pales in comparison to those we work for.
I'm a wealthy man compared to many of those I work for, no money mind you but a good wife, 2 kids grown to young men making their way and two safaris in the drive. I could ask for more but I don't need it.

At a job a while back the son was throwing a fit yelling at his dad, disrespectful, whining, little punk. My youngest was working with me and those were his comments about the kid, mine were not fit for print,,,
The kid was mad his car was not back from service and he had to drive the spare on a date. His new porshe was in the shop and he had to drive the year old BMW!

Woodbutcher wrote: I'm a wealthy man compared to many of those I work for, no money mind you but a good wife, 2 kids grown to young men making their way and two safaris in the drive. I could ask for more but I don't need it.

Wise words my friend. I live close enough to hear the waves crash on the beach so you know some of my neighbors have DEEP pockets. As sons of a Maint. Painter for a local submarine builder my two high schoolers show no signs of entitlement and are a joy to be around.
I must admit to a bit of perverse pleasure as I ride my open headered antique Harley to work at 5:30 am. Knowing that in lovely bedrooms high above the breakers, rich people are punching their pillows and muttering curses in my general direction!
I have the box of parts and its fair to say that it's not gonna be just a few wires and I'm done. There's gonna be a bit of wire schematic studying and rewiring plugs where they couldn't pull the harness so they cut the wires. But all the pieces are here. Time to make it work.
First order of business is to swap tccm's. right now I'm running the 236 with the 136 encoder motor. I'm curious to see if i can plug in exsisting to the 4x4 tccm and have it function.
Most of this job has been about what stock gm parts will plug and play. Torches and sawzalls have their place but once you break those out your on a whole nuther road. I love plug and play.