T56 clearance in 1968 Mustang

1968-coupe · Mar 28, 2010

I am looking into installing a T56 6-speed in my 68 cupe, however I was reading an article the other day about a 66 fastback that was getting a 5.4 with a T56, they expanded the tunnel 1.5inches to acommodate the extra girth of the T56. IS THIS ABSOLUTELY NECESSARY? Has anyone here fitted a T56 into a classic?

tcrote5516 · Mar 28, 2010

Can I ask why the T56 and not a T5?

The T56 is physically larger and just about twice as heavy. How much motor is in front of it?

68EFIvert · Mar 28, 2010

I did a T56 conversion. Here is a link to a thread I did on another site. I had a T5 before the T56 and love the fact I have 2 OD gears. I feel it is a perfect combo for my 3.70 rear gears.

Started my T56 conversion. - Vintage Mustang Forums

1968-coupe · Mar 28, 2010

If i understand right you installed the T56 without modifying the tunnel. is here a reason others have had to modify theirs?

a LONNGGGG motor, a 300. . . . . . . . Yup a 300 I6!!!! WITH dual webers, hot cam, shorty headers, polished ported head with 194/1.60 valves all good for 325hp and 425ft-lb or torque. I REALLY want to use the T56, but I may default to a TKO 500. I am going to have too see if the finished engine product can stay within the 450ft-lb limits of the T56. The "big block" 6 is a torque monster.

Im going to have to MAKE my engine mounts, I may get a little bit of play there. Not sure. Im replacing the floor pans and I dont want to completely fis the flow only to find the trans wont fit, BUt I dont want to buy a $2500 trans for a car that has rusty floors.

68EFIvert · Mar 28, 2010

The mods I had to make were to use engine lowering motor mounts and a custom tranny crossmember. Since you are going to make the motor mounts I don't see what the big deal would be. I used Ron Morris lowering mounts (drop the engine 1/2"). I am not sure where the end of the 300 would be in relation to the firewall but I don't think it would matter that much. The bellhousing isn't where the fit is tight. It is tight under the floor support brace that is in front of the shifter hole. I have about a pinkie distance there.

I wouldn't be too worried about the torque limits on the T56. Make sure you have a clutch that can handle the power. My new engine should have about 550 rwhp and about the same torque. I am not worried one bit. If I was taking it to the drag strip with slicks I may have a bit more to be worried about.

Shakin66 · Mar 29, 2010

I also have a T-56 but its a 66' I agree that theres nothing like the feeling of having 3:70 gears and then being able to use your o/d gears to calm the engine down at 70MPH. unless the 68 has a MUCH different tunnel you will have to cut it to get the angle right. its not that big of a deal as Darkhorse has the replacement "hump" and the crossmember as do others. I also wouldnt worry about hurting it with whatever you can thrown at it...Its tough.
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1968-coupe · Mar 29, 2010

So it looks to me like the stock tunnel is wide enought just not tall enough??

I just love the though of the guy running you counting your gears and just when you hit 5th and he starts to pass you slam into 6th and leave him in he dust.

68EFIvert · Mar 30, 2010

The tunnel is both wide enough and wide enough for a 67-70 car. The have a larger trans tunnel than 65-66 cars. I am living proof that you can have a 2.5-3 degree drivetrain angle and the original tunnel. It comes down to lowering the motor a little. If you don't drop the engine you will have to cut it like shakin66 did. Check out RonMorris.com and look at the install of a T56 in a 65/66 car with only trimming the floor support brace. They used their drop motor mounts and their tranny crossmember.

Since you are running a 6 it will require custom mounts. Since you are going to have a 300 in there and that likely will require custom mounts anyways I can't see why you wouldn't give it a go.

ron morris performance

Shakin66 · Mar 30, 2010

I found in that lowering the engine wouldn't be possible as my headers already scrape. If you have any floor repairs that need to be done it may warrant looking into. Your use of a 6 cyl. Kinda takes me out of the game. All I can say is mock it up with exh. and see. One things for certain... You'll love it.

1968-coupe · Mar 30, 2010

Im following the advice of Cliffords engineer. Im going with shorty headers with an X piep, which in their tests has produced more torque than the full length header, also a full length header would have to be custom built for the car as a long tube is not offered for the 300 in an early mustang, with the exception of a massive drag header by Clifford.

68EFIvert · Mar 30, 2010

Header clearance is an issue. I have an almost new set of Headman Long tube headers that I am taking off in the next couple weeks and replacing them with JBA shorty's. I had the headers coated locally and they look great. Kind of sad to have to swap them but ground clearance is an issue. I have scraped them twice. Once on a small speed bump in a parking lot going about 1 mph. It wasn't an issue with standard mounts. Add that to the expense of doing my T56 conversion.

1968-coupe · Mar 30, 2010

A lot of people seem to think that the T56 is overkill, i am under a LOT of preassure to go with a TKO 600 or G-force T-5.

I however dont like the big gap between 1.00/1 and the .64/1 4th and 5th gears of the 5 speed. As best i figure I will turn 1400 rmp at 70 in 5th, well many places here have 55mph speed limits with puts me in too low of an rpm for 5th, but a high rpm for 4th in the 5 speed, unless I go with a lower top gear (.82) then I sacrifice my low rpm 70mph cruising. With the 6 speed I have a nice 55mph cruising gear (.82)and a nice 70mph cruising gear (.62), and I likes it

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