Transfer wiring question

[4Robinsons]

Have a 99 suburban with 4l60e and np8 in it... both quit at same time so replaced with a 4l60e and np1 from a 97 suburban...hooked all up and chased wiring n did some splicing n replacing off connectors...trans shifts and drives fine...speedo works can push 4wd button n it goes in but won't go back to 2wd by button and when parked it n started it back up the transfer was in neutral so had to remove shift motor and manually put it in 2wd for now...want to know if anyone has done this swap and can tell me how to wire the encoder motor and transfer switch the right way to work or has transfer wiring diagram of both year transfers so I can figure out myself...any help or ideas appreciated...thanks

[4Robinsons]

No takers yet on this challenge? guess can't blame you

[hatzie]

You're mixing GMT800 & GMT400 parts...
Sounds like you have the wiring at the transfer case sorted out... however the controllers on the GMT800 are a bit more tightly integrated than the old T400 chassis.
The GMT800 NP8 (NV246) and the GMT800 NP1 (NV263) use a different 4x4 controller or at least a different program in the controller. You may get away with using the NV263 electronics for the 1997 NP1 (NV243C)... It may be as simple as getting the 3 button switch and 4x4 control box from another 99 but probably not. It's probably easier to get an NP2 (NV261) from a 2500HD or a NV241C from a T400 and put a stick on the floor.

[95 S_Trucker]

His 99 suburban is a GMT400

This post should be in the 88-98 section.

OP, It was only 15 hours between posts. These sections get a lot less traffic than the 67-87 sections.

So let me get this straight, you put a 243 where a 246 used to be? The switch, wiring, and control module is all different between the two.

If you want to keep the np243, I would go to a salvage yard and get all of the wiring you can for the transfer case. That includes some underdash wiring. I would also get the switch and control module.

It would be easier to get another 246(or have your old one rebuilt) and repair all of the wiring and install it.

You could get a 241, but that would still mean wiring changes(to get the front diff actuator worked and the get the signal to pcm to change shift points) and you’d have to cut a hole in the floor and run wiring under your carpet.

I would not get a 261. It would have a 32 spline input(instead of 27) and they never came in GMT400 trucks, so you may need driveshaft modifications.

[hatzie]

Originally Posted by 95 S_Trucker

His 99 suburban is a GMT400

I hadn't even thought about the fact that the SUV was a T400 for a couple more years. My 2000 C2500 is a holdover as well. Sorry to add to the confusion.
That's what makes these year vehicles exciting...

[95 S_Trucker]

Theres no need to be sorry. I think this forum should use the GMT platform for subforums after 1988. It would be less confusing.

At least its easy for the half ton stuff. 99 for the trucks. 2000 for the SUVs.

The 3/4 ton and bigger got dicey for a couple of years

[hatzie]

It would help in a lot of places. T400, T800, T900, K2 etc leave zero room for interpretation.

[4Robinsons]

Could I use the 3 button switch n controller from the 97 in the 99? Or would that completely mess it up

[4Robinsons]

Would like to keep this set up cause it's lower milage and was free...what all would I need for wiring to make it work...could I use the 3button and controller from the 97 or would that mess it all up

[hatzie]

You'll need a good bit of the associated wiring. If you still have the 1997 donor it's probably just your time to pull it out and move it over to the 99.

The 1998 service manuals have the wiring spread around a bit but you can download them and dig using PDF search.

[4Robinsons]

Ok thanks..I'll check it out some more and dig in and will post what I find and figure out