[_stucky]

I fully understand what cases will and can bolt up. My question is what needs done on the electronics side of things to make the bravada think it’s supposed be there. I have half a dozen cases here, and even a full donor for wiring. When we were messing with it, I saw a 2 wire plug for the shift motor and a Vss. For this truck, slightly cobbled is ok, but he wants to actually be able to put it in 4wd. It (the awd 136gm) is very unpredictable now. Once I find him a usable front axle, he wants to axle swap it, but the tcase issue makes me wonder if bravadas are a bad candidate for axle swaps. I really didn’t find anything useful googling this

 

[DRLExpress]

…..I bought a plug at napa to fill the hole for the vacuum switch, and traced all those hoses to their source and eliminated them.....

Just to make sure I understand it correctly. The vacuum switch in the Tcase just controls the front diff. Doing a SFA I can eliminate the switch and 3 lines?

Thanks
Doug

'94 Blazer

 

[_stucky]

Just to make sure I understand it correctly. The vacuum switch in the Tcase just controls the front diff. Doing a SFA I can eliminate the switch and 3 lines?

Thanks
Doug

'94 Blazer

Correct. The only thing running to my 233 is the wires for the shift motor. Nothing else. Make sure you plug everything. I’m not sure where it’s at on a 94, but my 04 has a vacuum canister “ball” inside the driver side fender that needed plugged.

 

[Rhotpursuit]

Correct. The only thing running to my 233 is the wires for the shift motor. Nothing else. Make sure you plug everything. I’m not sure where it’s at on a 94, but my 04 has a vacuum canister “ball” inside the driver side fender that needed plugged.

I would'n plug the vacuum can. It works with the HVAC also. Plug the used lines instead.

 

[_stucky]

No. Plug the canister. What good does it do to plug the line if the other end goes to nothing? Hvac works fine.

 

[DRLExpress]

Thanks for the reply guys. On my '94 Blazer the vac "ball" mounted on the inner fender, kind of between the battery and the coolant tank. Also in the vac system, if I can figure out how to attach a photo, this is right next to the "ball". It has a vacuum line and a wire, not the same line as the "ball". What is it? I'm guessing switch for the 4x4 indicator light?


https://www.s10forum.com/forum/attachment.php?attachmentid=313487&thumb=1


Thanks

Doug

P.S. Sorry the pic is rotated. Is right in my computer. What did I do wrong?

 

[Rhotpursuit]

No. Plug the canister. What good does it do to plug the line if the other end goes to nothing? Hvac works fine.

Well...I disagree. If that's the case, why do the 2wd have a vacuum ball at all? Parts of the HVAC are vacuum controlled and if the vacuum drops, the system changes where the air goes. It may be temporary, but why not have it work as designed?...just my .02

 

[_stucky]

I’m not sure without looking at it personally what the doodad in the pic does.

As far as plugging the vac ball, the way I see it is... so in stock form, the tcase vac switch lets vac through when you push the buttons, then that goes to the front diff to move the plunger to connect the 2 piece shaft and engage the front axle. Now take the plunger out the equation and you can plug the port on the vac switch. But it still has vacuum going to the now pointless switch. So take the switch out, and you have a hose going to the ball. But what good does it do to leave the hose, so trace it back to the source and put a rubber cap on it. Easy peasy. It doesn’t effect the hvac controls at all since it is leaving it completely alone. There is no longer a need for vacuum there with an axle swap.

If I remember correctly, there was, maybe not a recall, but a known issue for sure, with vacuum switches, since they are in fact tying the hvac to the Tcase. The switch would let atf from the case get sucked into the hvac system. My truck had the updated switch, and I’d think most trucks by now have had it swapped since it was a fairly common and known issue.

As for why does a 2wd have a vac canister, well I’d guess it’s for the hvac haha. Does a 2wd canister even have the little t it to put a hose on that would run to the switch on the case? If not, well that tells me it isn’t necessary. Essentially pre plugged from the factory. I might have to find a 2wd and pop the hood to check, I’m now curious haha

 

[_stucky]

Just to make sure I understand it correctly. The vacuum switch in the Tcase just controls the front diff. Doing a SFA I can eliminate the switch and 3 lines?

Thanks
Doug

'94 Blazer

Off the top of my head, I can’t think of where the 3 lines went. 1 for the canister in the fender, 1 for the plunger on the diff, what/where is the other one? I’m thinking it goes back to the switch, but it’s been a few years since I did this. In any case, I eliminated them all and it works fine, as long as it is plugged and no leaks.

 

[DRLExpress]

Thanks guys,
I think I figured it out. The 3 lines on the switch are, 1-vac supply(tee's off right below the check valve at the manifold next to the tee to the ball), 2-plunger at diff, 3-vent


The "doodad" I pictured must be for indicator, I tested continuity on the 2 wires and they closed when I sucked on the line. It was tee'ed into the vac line to the diff actuator.


Doug

 

[noclinkers]

I am looking for the writeup on the pcm when doing the 233 to 231 swap. Thought I had it bookmarked, but can't seem to find it. Thanks

 

[eshaw]

Make a post for the exact information you're looking for. The PCM doesn't control the transfer case as far as I'm aware. That's a function of the BCM I believe.