1964SS

iTrader: (1)

I've seen many people deal with the tiny transmission tunnels when installing a T56 in their A body cars.

One of the solutions is to cut the tunnel off and weld in a couple inch tall strap of metal to raise the tunnel up higher for clearance.

Another solution is to cut the tunnel down the middle and T it up top near the firewall and open the entire thing up a few inches and weld a new piece of metal down the middle. This is the method I used on my chevelle a few years ago and I was happy with the results, but I knew I could do better next time.

Both of these methods work well, but aren't always as pretty to look at. Out of sight out of mind right? Not always.

I started to look around at different tunnel patches being sold and found that the cleanest way to modify these tunnels is to simply replace it. My buddies 66 chevelle was ready for his LS1/T56 install so this was my chance to practice some more.

We made a simple cardboard template for a rough idea of what was needed and I picked up a piece of 36" x 36" 20 gauge steel and cut it to match.



I then marked the center and marked out some lines to give me an idea of how I could roll it. I ended up rolling this tunnel over the rounded edge of my desk at work with my hands. 20 gauge is fairly easy to work with and still very strong.



We set the tunnel into the car to see what we where dealing with.




After trimming up and removing what we didn't need I welded it into place and sealed it all up.





This tunnel cost just under $40 to install and required nothing but a welder and a cutoff tool. I'm happy with the way it turned out and it provides ample room for the much larger T56 trans.

mOtOrHeAd MiKe

iTrader: (8)

Nice!

Motown 454

iTrader: (15)

I agree with Mike, Nice !

showdog75

iTrader: (8)

I'm in the middle of this exact project on my first gen chevy II. I cut what was necessary to get the trans in the car but quickly realized that cutting it completely out would be best. I'm trying to make a cardboard template right now. Biggest issue I have is clearing the reverse lock out solenoid.

1964SS

iTrader: (1)

I have certainly been there showdog. And yes now that I've done it a couple different ways replacing the entire tunnel is easier, looks nicer, and only requires half the welding of lifting the tunnel up with a strip of metal around the base.

CattleAc

iTrader: (7)

I'm getting ready to do this to my 72 A-body wagon...I've done a lot of research on it, and this is the best tunnel mod I have ever seen...(and I have looked A LOT!)

Thanks!

showdog75

iTrader: (8)

I broke mine up this afternoon. This thread helped me out. I knew I wanted to cut out and replace verse patch here and there. It is gonna fit awesome. The front is spot on and the rear I purposely made larger to clear the reverse lock out solenoid and I plan on doing the rear basically like you did here. Here is mine.

1964SS

iTrader: (1)

Awesome guys! I was hoping it would help people out. Also when the tunnel is cut out the floor feels pretty damn flimsy down by the pedals. Don't worry about it. If you use a 20 gauge tunnel welded in the floor will have all it's strength back again when you're done. The radius-ed tunnel adds lots of strength.

lawrenq

iTrader: (2)

Here's mine, I used a patch tunnel from a 1st gen Camaro and 18 gauge for the rest.

1989GTA

Nice work there guys.

Krom

Here's mine for a 4l80:

krwyellowZ28

iTrader: (10)

What are you guys doing for carpet? do the OE carpets have enough give to still look ok?

1964SS

iTrader: (1)

Most of the OE carpets will not fit right with the tunnels enlarged. I cut my carpet down the top of the tunnel so it fit right and then built a console that covers it all up.

Update: With a brand new carpet kit there was plenty of carpet to cover the tunnel we put into the 66 chevelle.

chuckd71

iTrader: (23)

Do you still have that cardboard template? Was curious what the rest of the measurements were. I finally broke down and bought a welder and this looks about as good as any of the premade patches I've seen. All things considered I'd rather burn through a cheap sheet of replaceable steel than a $140 premade part.

Brian Hoss

Yup. Theres a few different ways to skin this cat. I cut the top off and added material. Not sure on the cost as I had plenty of sheets laying around but I'm going to guess is was close to $10. But a huge pain in the a$$ for T56 swaps for sure.

Picture on one in my 67 El Camino.

chuckd71

iTrader: (23)

Where do you buy the sheet metal? And what do you use to grind it down? I mean any wheel in particular? I have an angle grinder but I've only ever used it in ****-cutting mode.

1964SS

iTrader: (1)

Hey Chuck, I do still have the cardboard template, but it was just a rough template. We cut the metal down more to fit it better. I wish I would have made a template of the final sizes. I got the metal from our local metal supply. I use an air cutoff wheel to cut the metal or your angle grinder with a cutoff wheel installed on it.

The cardboard measured 18" acrossed the top and 12" at the bottom, 27" at the widest part and 36" long. This was for a 66 chevelle and we ended up cutting it down some more for final fitment.

I would get yourself a cardboard box and open it up so you can make your template. Once you get it fitting the way you like then transfer it to the metal.

showdog75

iTrader: (8)

When I did mine I found it difficult to put cardboard in to form a template. I took some solid copper wire and bent a piece to fit the front and cut it to length and did the same for the rear. Then I measured each piece of wire to get my front and rear width dimensions then measured the sides. I then transferred my dimensions to cardboard and added a inch to the front and sides the made the rear 8" longer. Worked like a charm.

DW SD

These are great ideas. I don't have an A-body, but cleared a similar hurdle. I just cut a portion of the tunnel hump and opened it up and then filled in the gaps, first making templates from cardboard.

This process of course can be applied to many other tunnels.

chuckd71

iTrader: (23)

Thanks, good info. Today I found a place that will basically give me a decent chunk of the tunnel out of a 2011 Camaro. I'm not sure if I should try that (and then easily mount a Camaro console and ebrake) or just do the roll your own.