I am currently putting in a 6-speed tranmission (t-56). I'm building the car from ground up and I was wondering if anyone has done this switch. It looks to me that the rear of the transmission is to high from the differential. I'm thinking I might have the wrong crossmember for the 66 GTO. I have a pontiac book that describes the crossmember haveing two rubber mounts on the sides and one in the middle. I bought the car as a basket case and I'm not sure if I have the right crossmember. The crossmember that I have is just bolted to the frame. Thanks for reading.

I am currently putting in a 6-speed tranmission (t-56). I'm building the car from ground up and I was wondering if anyone has done this switch. It looks to me that the rear of the transmission is to high from the differential. I'm thinking I might have the wrong crossmember for the 66 GTO. I have a pontiac book that describes the crossmember haveing two rubber mounts on the sides and one in the middle. I bought the car as a basket case and I'm not sure if I have the right crossmember. The crossmember that I have is just bolted to the frame. Thanks for reading.

I am assuming that you do not have a 66 GTO
convertible. The crossmember should have the rubber insulators on the ends if it is a GTO, LeMans, or Tempest piece. The Chevelle piece is bolted to the frame. Either will work ok as you still have the rubber insulator going from the cross-member to the trans.

I believe Jack Blum has done the T-56 swap but on a Firebird. I have installed a Doug Nash 5 speed in my GTO and had to lower the crossmember to keep the drive shaft from hitting the tunnel.

Another thing to look for is the trans mount.
Repops from India have the trans mount height
about 1/4" higher than the older Pontiac OEM
mounts.

Maybe someone can post a dimension from the center of the tail shaft (where the front yoke
slides on) to the floorboard on a 66 GTO and you can then duplicate that dimension.

Tom V.

66Tiger,

I just finished a T-56 swap on my 67 GTO, and there was a LOT of work envolved. The first thing I did was cut out the entire transmission tunnel to give me plenty of clearance for installation. Then I bolted the T-56 up to the motor and set up the pinion angles so I could fit the crossmember to the proper transmission location. To have the pinion angles correct, I found that you would have to extremely modify a stock crossmember so I ended up ordering a tubular crossmember kit from Art Morrison. The crossmember has double humps bent in it for exhaust clearance, and brackets for a standard GM rubber or urethane transmission mount and brackets for mounting the crossmember to the car. With this crossmember I had to tweak some of the bends for a proper fit, and I also had to box the frame of the car on each side to provide a mounting point for the crossmember. The next things that needed to be done is either shorten or have a new driveshaft made and also fabricate a new larger transmission tunnel. Fabricating the transmission tunnel took quite a while for me, but the time was worth it as it looks almost factory. If you have the T-56 with mechanical speedo your cable will be too short also, I used a cut to fit speedo cable kit from Lokar that was very easy to make.

While it was a big project that required a lot of cutting, grinding, and welding. I can honestly say that swapping to a T-56 was the best upgrade I have done so far. Even though I still don't have any carpet in the car (since I need to have one made for the larger tunnel), I have already driven my car more this year than I did all last summer. It is really nice to be able to do 75 mph at around 2000 RPM.

I have a t56 in a '64 LeMans. Cutting out the entire tunnel would have been easier, but I ended up splitting it down the middle and spreading it apart and adding a piece in the middle. For a crossmember I ended up using a tubular one out of a chevelle (which had a lower trans mount pad) and still lowered the pad another inch. I had problems with (almost)hitting reverse when shifting into 5th, so I installed the lockout solenoid (activated by a dash-mounted pushbutton) and covered it with the stock shifter porch.

Thanks for the help guys.

dh_gto, Where did you find the correct pinion angles? I bought my t-56 from D&D performance the transmission is a retro fit. At there web site the mention some of the same things you had to do but they only mentioned getting a custom cross member for early Camaros. If I knew what the height is suppose to be I probably would find out if I'd have to custom build a cross member also. Like I said I bought the car as a basket case (in pieces)so I'm not sure if I have the correct stuff or not, and I'm sure it doesn't help that I don't have the car on the frame. Thanks for your help again.

Actually Tom it's a 68 GTO. We used the stock cross-member but cut out the center where the TH400 sat and flipped it over and welded it back in. This lowered the rear of the T56 just enough to sit level. Here is a link to How We Did IT. Good luck to you and feel free to email with any questions. [email protected].

Quote:

"Actually Tom it's a 68 GTO. We used the stock cross-member but cut out the center where the TH400 sat and flipped it over and welded it back in. This lowered the rear of the T56 just enough to sit level. Here is a link to How We Did IT. Good luck to you and feel free to email with any questions."

I am SO EMBARRASSED!!!
Sorry Jack!

I knew you had done the swap but did not pay
that much attention to the car it was under.

I will read you "How we did it" again! http://forums.performanceyears.com/g...icon_smile.gif

Tom V.