Hi All:
I"m New to the forum so bear with me please. I just finished a 4.3 swap from a 2000 S-10 Blazer LT 4x4 into a 1999 S-10 Blazer LT 4x4. I was swapping Motor, Transmission and Transfer Case. T-Case ended up being different so i put the original one back in the 1999. The T-case from the 2000 has 3 vacuum lines and one main connector going to it, the 1999 has 5 electrical plugs going to it. The main connector where they plug in just behind the ABS Pump are totally different. I pulled the motors with their wiring harness intact unplugging them from the PCM, Transmission, T-Case and Fuse Box, Then swapped PCM's. After I finished it up I attempted to start the 1999, it would start then die. I presumed it was a security system issue so I put the original PCM back in the 1999. The truck started right up and runs great. Problem is the Tach isn't working and the service 4x4 light is on. The 2000 Does not have a vacuum switch on the firewall and the 1999 does. So my question is could mixing the wiring harnesses (2000 Engine Harness is in the 1999 with the 1999"s PCM) have anything to do with it. Like maybe the Tach wire is pinned different to the PCM from the harness. I think the 1999 T-Case is supposed to have a vacuum line on it but I can't find it, must have gotten pulled off. and there is no fluid in the T-Case yet which may explain the service 4x4 light, but I did top off the Transmission. The Transmission does shift from drive to reverse and moves but I haven't taken it on the road yet till I get fluid in the Transfer Case.

I hope this doesn't sound to confusing but I seriously need help.

Thanks in advance for any and all replies.

 

Here is some background that might help:

This vintage of Blazers came with two types of transfer cases/4wd systems; the "3-button" and the "4-button". The former is the basic 2-speed 4wd type (2Hi, 4Hi, 4Lo). The later is the Auto 4wd system where the transfer case can go in and out of engagement depending on tire slippage; 2Hi, 4Hi, 4Lo, and Auto 4wd.

These use different transfer case control modules (TCCMs), 4wd instrument panel switches and different types of actuation. There are likely other differences in the electronics but I don't know. The 3-button systems have vacuum lines that control the transfer case engagement whereas the 4-button ones are controlled electronically. The 4-button 4wd systems had the vacuum switch mounted to the top of the center of the firewall that controlled the vacuum supply to the front axle engagement mechanism. The 3-button systems did not.

I would suggest doing some research on these systems to see what would have to be swapped to make either one work in the other truck. If the transfer cases are good, then the simplest approach might be to keep the 4wd system the same. I wouldn't know about the PCM but I hope this helps.

 

You have found out the hard way why you need to use the original PCM and transfer case and wiring and all stuff hanging on the engine from your original Blazer. You will have to switch over anything that is different on the replacement engine. That would include intake and exhaust manifolds (you need to replace those LIM gaskets anyway). Someone else will really have to answer if the trans is compatible, but I suspect that it is.

 

Thank you so very much for your quick reply:

The Truck runs perfect. I got tach to work, there were 2 blown fuses in the engine fuse box. Matched up 4 main plugs that go to PCM and they are exactly the same. Can't vouch for T-Case in the 1999, Transmission was bad in that one anyway and someone had spliced some wires on the harness that goes from PCM to Tranny. Transmission from the 2000 Shifts fine.So as far as the 4 wheel drive goes, just ignore the light or unplug it at the T-Case. They are not going to use it anyway. Personally I thought it was a waste of time anyway. Pulled motor which they did have a lot of money tied up in, and Tranny from 2000 because it got T-Boned. Bought the 1999 for 600 bucks, suspension and steering totally shot, but that's what they wanted.