T56 magnum in 2nd Gen with DSE subframe

[Alponcho]

How much, if any, of the floor/tunnel will I need to modify? It's an original 4-speed car. I'd like to be able to have the bottom of the car painted and it would be convenient if I didn't have to worry about mocking it up first.

[Craig@Bowler]

You will have to cut. You'll need about 2" more height in the front and at least another 1" in the rear. Several that I've seen, the guys have just made a 2" taller patch from front to back. So yes, you will want to do a mock up and modify the tunnel first unless you want to repaint that area later.

[Alponcho]

I'm curious to know whether a 4L80e would fit with less work to the tunnel?

[KEV 190164]

sorry for hijacking the thread . I have a t56 magnum for my 79 trans am but I am keeping the original front clip. will I have to cut my tunnel out if so by how much. cheers kev

[TheJDMan]

You did not say if you are using full height or half height sub frame mounts. Half height mounts will require more tunnel clearance.

[Alponcho]

I'm going with full height mounts. I checked out the 2nd gen project photos on DSE's website. Most showed extensive tunnel mods and a brace running across the floor over the shifter area. Not sure what this is for. But it looks like a lot of work. I've really been on the fence with regards to t56 or 4L80e...if the latter fits with significantly less work, it might be the deciding factor.

[Craig@Bowler]

sorry for hijacking the thread . I have a t56 magnum for my 79 trans am but I am keeping the original front clip. will I have to cut my tunnel out if so by how much. cheers kev

Kev,
It will be the same for yours as well. Regardless of the front clip, you will have to create more room for the T-56. How much exactly is determined once you get it in there. Not every car is built exactly the same, but you can figure on opening up the top of the tunnel from side to side. If you're going T56 don't compromise the drive line angles by hesitating on how much to cut your tunnel. Go for it and make it right.

[Craig@Bowler]

I'm going with full height mounts. I checked out the 2nd gen project photos on DSE's website. Most showed extensive tunnel mods and a brace running across the floor over the shifter area. Not sure what this is for. But it looks like a lot of work. I've really been on the fence with regards to t56 or 4L80e...if the latter fits with significantly less work, it might be the deciding factor.

I'm not going to say that you won't have to cut to fit a 4L80 in there, we've done installs that we didn't have to cut to get them to fit. It will most likely be touching the tunnel though and we do recommend that you do cut them just so that there's plenty of room for drive line angle adjustment. You will have to make room for the cooler lines and fittings on the case. This can be done by "massaging" the side of the tunnel with a hammer or cut to fit. Not knowing what the torque output of your engine is, but if you can get by with using a 4L60 instead, it will fit no problem without cutting. Just a thought.

[Alponcho]

535ci IAII, should make about 700 ft/lb…not sure a 4L60 will hold up.

[Craig@Bowler]

535ci IAII, should make about 700 ft/lb…not sure a 4L60 will hold up.

I would say your best bet would be to stay with the 4L80 then. We can build a 4L60 to hold up to 550ft lbs after that we would put you into a 4L80.

[KEV 190164]

thanks for the reply craig. my trans am is fitted with a buick 455/464 the magnum is not fitted yet . does the drive line angle have to be spot on I made my own motor mounts so not sure what the angle is at the moment . cheers kev

[F-Body International]

thanks for the reply craig. my trans am is fitted with a buick 455/464 the magnum is not fitted yet . does the drive line angle have to be spot on I made my own motor mounts so not sure what the angle is at the moment . cheers kev

Driveline angle (trans to rear end) is crucial for your driveshaft to survive. There are various sources where you can find proper driveline angle online or speak with a professional. Modifying the transmission or rear end angle is possible.

For the T56, I can't remember but I believe some have swapped in a Viper or Cobra tailhousing on the trans so that the stock 4 speed console could be used. I know I have atleast seen one done like in person.

[badazz81z28]

I have Marks crossmember and DSE frame and all I cut was the hole for the shifter plus a few inches forward. Up near the front I just massaged the floor pan.

[Craig@Bowler]

Driveline angle (trans to rear end) is crucial for your driveshaft to survive. There are various sources where you can find proper driveline angle online or speak with a professional. Modifying the transmission or rear end angle is possible.

For the T56, I can't remember but I believe some have swapped in a Viper or Cobra tailhousing on the trans so that the stock 4 speed console could be used. I know I have atleast seen one done like in person.

yes, you definitely want it to be correct. I would just be willing to do what it takes to make it right. Last thing you want is to pour that much time and money into a project and something silly like a bad driveline angle ruins your experience. Plan everything out and once you have all the components in place to do the final set up don't compromise by not doing what it takes to make it work out.

[Craig@Bowler]

I have Marks crossmember and DSE frame and all I cut was the hole for the shifter plus a few inches forward. Up near the front I just massaged the floor pan.

Thank you for the pictures. That is a great representation. Also another way to show that not every car will be the same.

[rreichert82]

I purchased the American Powertrain crossmember and shifter. They say this does not require and chassis, tunnel, or console modification and the shifter will come up in the factory 4 speed opening. I was originally going to do a 4L80E until I realized the 78 Formula I had to much rust for me to fix and I bought a 79 4 speed TA shell to work with. I figured that was the sign from above I needed to do the T56 swap I was already trying to talk myself out of lol. If you are going to do the 4L80E route I am trying to sell the crossmember I bought from G-Force.

[badazz81z28]

I purchased the American Powertrain crossmember and shifter. They say this does not require and chassis, tunnel, or console modification and the shifter will come up in the factory 4 speed opening. I was originally going to do a 4L80E until I realized the 78 Formula I had to much rust for me to fix and I bought a 79 4 speed TA shell to work with. I figured that was the sign from above I needed to do the T56 swap I was already trying to talk myself out of lol. If you are going to do the 4L80E route I am trying to sell the crossmember I bought from G-Force.

With a T56 Magnum? I highly doubt that, but interested to see the results. The transmission would be hanging low if you didn't cut the tunnel.

[Alponcho]

I've decided to stick to my original plan and go with the T56…was considering options to save time and to delay having to spend $$$ and there are merits to an automatic, but I may as well do it right…the car is a shell so the tunnel mod isn't really a big deal.

I guess I'll need to get some prices on a close ratio unit, bell housing, hydraulic clutch set up, flywheel, cross member, etc., so that I can get everything mocked up…nice that the IAII block has dual bolt pattern (pontiac and chevy/corporate). Wondering if there's a tested/proven combo of parts that will work?

[KEV 190164]

I've decided to stick to my original plan and go with the T56…was considering options to save time and to delay having to spend $$$ and there are merits to an automatic, but I may as well do it right…the car is a shell so the tunnel mod isn't really a big deal.

I guess I'll need to get some prices on a close ratio unit, bell housing, hydraulic clutch set up, flywheel, cross member, etc., so that I can get everything mocked up…nice that the IAII block has dual bolt pattern (pontiac and chevy/corporate). Wondering if there's a tested/proven combo of parts that will work?

bought my close ratio t56 kit from Schwartz performance emailed a couple of companies Schwartz were the only one to reply so went with them good price too

[Alponcho]

Thanks for posting the pics. Is that the 67-69 crossmember, and did you have to modify it in any way?

Wondering if there are benefits to the DSE weld-in crossmember? It's a much more expensive route, but maybe itadds stiffness to the floor and benefits exhaust clearance?