Hello,
This is gonna be a long explaination. I want to put all info out there to get a good response.

I have a 91 Extended Cab P/U. It is 3vze with auto trans. and has the A.D.D. system in it. When I bought the truck ($500) the head gaskets were blown and the trans felt like it was slipping. I found a donor truck that was slid into a tree sideways so I bought it for the engine and trans (paid $500). It was an 89 with 89K on it and it runs strong. The trucks were identical except for the fact that it had a manual hub lock at the wheels. It still had the ECT button in the center console and everything else looked the same. My mechanic friend swapped out the engine and trans for me. I recently went to use my 4 wheel drive and WTF..no 4x4.
I checked to see if linkage was hooked up and it was not. I hooked it up and still nothing. The place that it hooks to looks like neutral safety switch and is real sloppy forward and reverse. I removed the switch off the pin and checked the pin going into the transmission. It clicked twice and then just spun free like a gear broke off inside the trans. Could this be part of my 4x4 problem? I reinstalled all the parts and now the truck is "slipping" like the old trans did. If i hit the gas it struggles to move. Im wondering if Im better off finding another A340H like what I had in there originally. The donor trans says 30-80le on it and I believe it is an A340F. Im at a loss here. This truck has been fighting me for months now. I need help.

 

First, this will help:
http://www.personal.utulsa.edu/~nathan-buchanan/93fsm/

Note that the tcase is considered part of the automatic transmission in this Factory Service Manual.

The way the ADD works is that moving the shifter into the 4WD selection makes a switch, which sends a signal to a vacuum solenoid, which then uses vacuum to slide the yoke over in the diff. The position of the yoke lights the 4WD light on the dash.

SOOOO, if you have the 4WD light on, then your ADD is working, and likely you don't have 4WD because of a REALLY broken CV or an issue inside the diff.

If the 4WD light is NOT coming on, then it's in the ADD system. My guess is that the vacuum lines are not hooked up between the new (non-ADD) engine and the diff.

 

have a friend sit in the drivers seat and put it in 4lo. put it in drive and roll forward while you look from outside the truck and see if the front driveline is moving. if it is moving in 4 lo also try 4hi. if it moves in 4wd then the problem is the ADD here is a link to remove that system (http://www.4x4wire.com/toyota/tech/add/) it is prob a problem with the vacuum lines or a solenoid. if you do what the link says it will fix it.
if the driveline does not move then your tcase might be screwed OR like you mentioned linkage might be out of alignment. good luck

 

The 4wd light does not come on. I will have to find out what vacuum lines are missing/disconnected. If someone sits inside and shifts into 4wd I can still move the driveshaft that runs forward by hand as if it is not engaging.

 

When I did my engine swap I defeated the ADD system as the 4x4wire link shows in post #3. Sounds like the way to go IF you switch to manual hubs.

 

go here it has alot more info http://www.ncttora.com/fsm/1993/susp...26addcontr.pdf it will help out alot more

 

I jumped TE1 to E1 to see if there were any codes. Thought there may be a bad solenoid. The dash lights just keep flashing constant, no breaks, and make me think there is no code being thrown. Am I right on that? Also went to stealership for some info. They dont even have a tech that can work on a 91 pickup. They only fix newer vehicles!! Say What?!?!

 

I see from your myspace link that you're in Maryland ... might try posting on www.shutupandwheel.com to find local peeps to help you out if you need it.

But wait - with all 4 wheels on the ground, the tranny in drive, and the tcase in 4WD, you can spin the front driveshaft easily? More easily than the rear driveshaft?

 

what that doesnt make sense if they can only work on newer vehicles then you would be better off going somewhere else i dont think id take anything to them

 

Yes, I can put it in 4wd and drive and spin the shaft that runs to the front of the truck. My guess is that it is not engauging 4 wheel at all. Now the truck feels like it is locked in low gear and the auto wont shift out of first gear. If its not one thing its another with this truck.

 

I pulled the truck out of the garage this morning and forgot to take the jumper out of the diagnostic box. It is showing either a code 51 or codes 5 and 1. While running, the check engine flashes 5 times-2 second delay-1 flash. I think Im gonna take this to a trans. shop to see whats up. I just want this fixed and driveable again.

 

See for details on code 51
http://personal.utulsa.edu/~nathan-b...85diagnosi.pdf

 

Well, I think I may have found one of the problems Im having. I dropped the rear pan on the transmission. The shifter key that tells the trans 2wd, 4wd-hi, 4wd-lo was broken off. I replaced it from one in the junkyard today. Im gonna test it out later tonight or tomorrow. The only issue Im having now is that the floor shifter feels tight and doesnt want to go into 4lo. That may be a whole different problem though. Anywho...just wanted to post some progress.