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2wd/4wd transmission tunnel question

RockinChevy

RockinChevy

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I bought an 2wd 84 crew cab body with minor surface rust, will be swapping out cabs sometime down the road. My 82 k30 has deep rust under the paint in the rockers and on the upper door jambs. It wasn't bad until my kids poked around with it and I just want a solid clean truck.

I want to take out the '84 "non-removable" 2wd tranny tunnel and bolt on my '82 "removable" 4wd tunnel.... but before I do this, can anyone tell me if the tunnels are the same size? I know the 4wd tunnel is a couple inches taller than the 2wd one. Not sure if it matters any, but I have the 454/th400/205 combo, I guess that's the standard driveline. I figure ask first before pulling up the carpet.


Taking out the non-removable tunnel is easy, drill out spot welds.


Also found out the 84 cab is a Camper Special, it's got the teepee emblems and the thicker lip in the rear glass rubber seal for the camper seal. Not sure if this is limited edition or what. I don't see any other differences other than the tranny tunnels.

EDIT: I think I type as funny as I talk, had a major brain fart... Changed "pan" to "tunnel". Thanks 4x4high...
 
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You mean tranny tunnel not tranny pan. I have no idea if the removable versus non removable are the same size but when i get around to it i'll have figured it out. In my case i'm going to use an early bolt on tranny tunnel in my 89 in place of the welded in one.
 
Anybody else?

I don't have to swap cabs until after I install the AIR system and get it to pass Phoenix emissions and register it in my name sometime after Blazer Bash. I'd like to get some insight on if my tunnel cover will fit the 2wd cab and prepare myself for anything that needs to make it fit.
 
bronc3buster842001 said:
They can be swaped. Just pay close attention to when ya cut the floor out not to cut to much. The back part is where things get tricky.
Click to expand...


Oh boy... I was hoping I wouldn't have to cut the floor. Was wishing for a direct swap for reasons if I end up selling the truck (yeah, over my dead body), I want it to pass visual inspections if they ever get up and close to matching the VIN to everything on the truck. I didn't get the title for the 84 cab because the seller needs it to convert the frame and bed to a trailer.

I'm gonna remove every trace of evidence to make this cab appear original to '82 4wd, hence swapping tunnel covers and other stuff.
 
I don't remember exactly, but the 2wd cabs have an indentation in the metal (where a machine simply pressed that portion out for 4wd), you will have to cut that out, but the outline should be there exactly where you need to cut. Take off your 4wd tunnel (that is bolted) and lay it over the 2wd to ensure. Then make your cuts.
 
Any progress on this? Not to hijack, along the same lines here...

I need to do similar. I've got a transmission tunnel from an unknown 4wd. Believed to be from a K5. It's an auto/205, I've got a manual/205, so that should work.

I always thought the non-removable tunnels were spot welded in place, but from what I understand now, they are actually just stamped as part of the floor pan? If that's the case, if you cut the tunnel out, is the earlier tunnel bolt flange wide enough so that you just need to drill holes for the bolts once the new-style tunnel has been cut out? I hope that's clear.

I wish I had that picture. It looked to me at a glance like the bolt flange was actually still stamped into the floorpan on the non-removable tunnel trucks, so if you cut the metal on the "inside" of the stamped flange (against the tunnel itself), the bolt on tunnel flange would mate up with the metal that would be leftover on the floor side.

Lastly, if this turns out to be a truck tunnel, is that a factor, or are all 4WD tunnels the same? It would be nice to list these things something like:

1973-80 2wd bolt in, interchange with 1981+ 2wd
1973-91 *truck* 4wd tunnels interchange, save for bolt in vs. weld in and trans/t-case cutout differences.
1973-91 4WD Blazer tunnels interchange, save for bolt in vs. weld in and trans/t-case cutout differences.

Again, those are made up examples, but it would be nice to collect this info in one post. It comes up every once in awhile, and it seems like one person knows X,Y,Z interchange, but not if T and V interchange, which someone else knows. :)

I thought there was just another thread on this, with pictures, but I can't find it for the life of me.
 
On my 89 blazer the trans tunnel is a separate piece from the floor itself and is glued down (possibly welded as well). I have an unknown early bolt on trans tunnel that i plan to use when i install my doubler.
 
Yeah after I posted that I remembered a bit of glue or some sort of foam tape hanging down on mine that I saw years ago, so they must not be stamped as one piece, at least for either of ours. Not sure about my '87 though, haven't been under that.

Wonder how that tunnel comes out if it's glued in place? I can imagine it may be a bit difficult to separate the two pieces without damaging that flange on the body side.
 
bronc3buster842001 said:
They can be swaped. Just pay close attention to when ya cut the floor out not to cut to much. The back part is where things get tricky.
Click to expand...

Yep. The front part matches the firewall contour. The back end you are going to have cut out of your old cab. Otherwise, you are going to have 3'' gap in the back.

I never got around to doing it and the truck is gone now but here is a picture of a 82 4WD trans tunnel in 77 2WD crew cab.
8142Trans_Tunnel_2.JPG



Lastly, if this turns out to be a truck tunnel, is that a factor, or are all 4WD tunnels the same? It would be nice to list these things something like:

1973-80 2wd bolt in, interchange with 1981+ 2wd
1973-91 *truck* 4wd tunnels interchange, save for bolt in vs. weld in and trans/t-case cutout differences.
1973-91 4WD Blazer tunnels interchange, save for bolt in vs. weld in and trans/t-case cutout differences.
Click to expand...

Actually, The 77 crew cab had a solid trans tunnel. The truck came with an automatic. There was no bolt-on tunnel. A 2wd truck with a manual may come with a bolt-on tunnel that is taller in the front, but it dips down in the back.
The 73-80? 4wd tunnels should interchange.
The 81-91 4wd tunnels are either solid or bolt-on, and the bolt-on tunnels are longer than the 73-80. The transfer case shifter hole has a different shape and reinforced for the floor mounted shifter.

82 bolt-on trans tunnel on the left, 73 tunnel on the right. Both are 4wd.

8142Trans_Tunnel_1.JPG
 
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Great post, thanks. Now I need to get that tunnel in my hands so I can compare it to the photo. I'm hoping its not the one on the right.
 
I still haven't pulled back the carpet to check, been too busy working to pull in more money. Thank you fellas for bringing this back up with detailed posts, they were helpful in a big way.

I'm sort of pondering on going with a body lift if this becomes a pain. Or I'll have someone fab up a center console similar to Kert's (cybrfire). Or I'll just get the NWF cable shifter and toss out the 205 linkage. I just won't know until I get around to swapping the cabs and see how the 400/205 clear the 2wd tunnel cover. I was more concerned about getting the tunnel cover to match the VIN so I don't get popped in years to come. I'm learning now that DMV guys don't really give a sh!t on the older trucks, hence so many parts are swapped around.
 
JDNobodi said:
Yep. The front part matches the firewall contour. The back end you are going to have cut out of your old cab. Otherwise, you are going to have 3'' gap in the back.

I never got around to doing it and the truck is gone now but here is a picture of a 82 4WD trans tunnel in 77 2WD crew cab.
8142Trans_Tunnel_2.JPG





Actually, The 77 crew cab had a solid trans tunnel. The truck came with an automatic. There was no bolt-on tunnel. A 2wd truck with a manual may come with a bolt-on tunnel that is taller in the front, but it dips down in the back.
The 73-80? 4wd tunnels should interchange.
The 81-91 4wd tunnels are either solid or bolt-on, and the bolt-on tunnels are longer than the 73-80. The transfer case shifter hole has a different shape and reinforced for the floor mounted shifter.

82 bolt-on trans tunnel on the left, 73 tunnel on the right. Both are 4wd.

8142Trans_Tunnel_1.JPG
Click to expand...



Very good info :bow:

I too learned this in my Blazer . The 83 tunnel bolted to the firewall on my 75 truggy , and the extra length just tucks under my seat tubes .

The 75 tunnel sat on the 83 floor and gave a nice open hole at the rear :laugh:
 
Still haven't done anything yet but a solution has been found. Sorry guys, no hacking or grinding...

Since Jason4x4 recently acquired a K30 c&c dually, and it is already painted white, he will let me have this cab in exchange for the 2wd cab that I have sitting in my garage. Originally the white cab was supposed to go to Travis (mtnman) but eventually agreed to a trade. So.... it works out very well for me, 4wd hump, interior has clean white paint, and it is a diesel cab which works real well since my VIN registers my current K30 as a 6.2.

Thank you Jason and Travis for making this all work out, as you know this just saved me a bunch of money, no painting, no hacking, and no buying more parts. Done deal!
 
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