Transmission swap 4wd question?...

[Tech_guru21]

So I swapped the motor in my 97 2door Tahoe to a 4bolt main 350. Removed all wiring and made it carbureted. I decided to change the transmission because had trouble getting the 4l60e to work with out the throttle body and without buying expensive parts. So I rebuilt a th-350 and put that in. So now my 4-wheel drive wasn't working. It wasn't kicking in. I checked the actuator at the front axle and after bench testing it was good. I was getting no power or ground to the actuator at all. I found a 4 pin plug that I think went to the transmission and two of the wires went to the actuator. So I put ignition to the brown wire going to the transfer case and grounded the black wire going to the actuator. So now I got 4wd low working but I don't think the 4wd high is working. I can make it with 4low but I'd like to know what the deal is. Am I missing something? There are two more wires on the 4 pin plug and I don't know what they go to. Please help and thank you in advance...

 

[Ice98]

4hi you must be moving to engage, ideally very slowly

4lo you engage in neutral

 

[Tech_guru21]

Hmm.... I know that! But the point is it's not factory anymore. I need to trick the transfer case to working. Any other help?

 

[lesterl]

There is a control module under the dash that controls the transfer case if it is a pushbutton and I suspect if that is the case you are lucky 4wd low works.....

 

[Tech_guru21]

Well I took it to the beach thinking 4lo works but it DOESN'T! So when I wired the actuator all it did was make the actuator open when I put it in 4lo or 4high. But it's only the actuator that's opening I dont think the transfer case is working. Also it is a floor shift not with electronic buttons. Does the floor shift still have a module? How can I trick it to working? Thanks for the replies though.

 

[lesterl]

I dont know on the floor shift, but I suspect that is a good thing, if nothing else you could swap out a early 90's or late 80's Tcase, but let me check a few things in an hour or so...

 

[Tech_guru21]

Ok thanks.

 

[lesterl]

PM me your Email addy.... Schematics to follow....

 

[Tech_guru21]

I have a schematic but there is a gray/black goes to ecm and I don't know if that has something to do with it.

 

[lesterl]

Does the 4wd indicator come on?

Looks like the Grey/ Black gets grounded when you shift the Tcase.

Does the front driveshaft spin freely when the tcase is in gear?

 

[Tech_guru21]

I haven't checked that yet... I will be home in about 3 hours and will check then. I wonder if it will if the acuator is opening. I know for sure the acuator is opening. I will check the driveshaft and get back to you... On the diagram I have it looks like the gray/black gets ground and goes to the ecm...

 

[lesterl]

Blk/GRY instructs ECM that you are getting ready to get dirty,,,,

 

[Tech_guru21]

So what does that mean? The ecm is basically worthless now cause I bypassed it and went carbureted. Ran all my own sensors to factory gauges and got all working except speedometer. Maybe the gray/black isn't the issue? What do you think? I know the switch works on top of the tranny cause there is power to brown wire. Then when I go to four on the floor shift the switch sends power to the actuator and opens it. But what else needs to get sent? I have the gray/black on that same switch, and other wires from a switch on The back of the transfer case. There's also another switch on the front axle but what I understand is that it's just for the 4wd light. I'll have to get back to the truck to tell exactly what wires I have. What am I missing? Guess I could try to ground the gray and black when I put it in 4wd.

 

[Tech_guru21]

This is the diagram I found.

 

[Tech_guru21]

If I can figure how to post it

 

[Tech_guru21]

Here is the diagram

 

[Tech_guru21]

Can't post it from iPhone...guess I'll have to do it on laptop

 

[Tech_guru21]

Unless you want to email me what you have and I'll tell you if I have the same. Or give me your email and I'll email it to you. Thanks

 

[lesterl]

Sounds like you got the same one, sent my copy to you tho..

If I read the schematic right the Tcase switch grounds out the Gry/Blk wire so the PCM knows that 4wd has been shifted, then it sends 12v feed out to Blk/Wht wire to power the front axle actuator and if the mechanical linkage is right and the Tcase is locked into 4x4 then the front actuator should now lock the front axle in and the wheels (if front is lifted off ground should be locked in.)

 

[Tech_guru21]

So today put it in 4hi and noticed the driveshaft doesn't move anymore. But I have a question... Is the front axle actuator supposed to extend all the way. It seems like it's not opening enough or something. It opens about an inch or an inch and a half. Can't find a picture of it opened all the way on the Internet.