anyone know what would be needed to use a GM T56?

I am running a T56 but I am sorry I can't answer your question about the input shaft. I purchased the T56 designed for the windsor block.

I have contemplated this too. I have a Viper T56 in my 66 and would love to swap one in the Falcon. The GM T56s go for under $1000 sometimes and I think they are weaker than the Ford and Viper T56 but for a street car would be bullet proof.
The GM guys have an adapter plate that allows the T56 to bolt up to a GM 350 bellhousing. Summit sells it. I do know that to mount a Ford T5 behind a GM 350 the spacer adapter needs to be about 3/4" thick(I know this from a previous project). And, to mount a Ford T5 behind a toploader bellhousing should be spaced back about 1". So, if the GM T56 also gets spaced back about that much then it would be close enough to fit well behind a toploader bell.
You will need a Ford flywheel, and pressure plate. Use a GM 10.5" clutch disc. The adapter plate for GM t56 behind a GM 350 bell uses a bearing adapter bolted to it to center the tranny behind the bell. I say, replace that with a Ford bearing retainer. Use a Ford throw out bearing, and to simplify things use a hydraulic TO bearing. Not sure on the specs but somehow get a pilot bearing machined with an outer diameter to fit ford crank and iner diameter to fit the GM t56 input shaft.
For my Viper T56 swap, i used a Ford bronze bushing, punched out the center hole and pressed in a Mopar pilot bearing.
I found my Ford T5 input shaft was the same length as the Viper T56 one. If this goes the same for a GM t56 then you could use a Ford T5 bell and go with a cable clutch like I had. I'm going hydraulic TO bearing soon.
Then...you will need a shortened driveshaft using the GM slip yoke and ford U-joint on the back end.
There are a few ways to do this mod. Quicktime sells a bellhousing for Ford T56 behind a ford. If the input shaft is the same length fr the ford and GM t56s then you should be able to use that bell and it would be a bolt on.
That's a lot to digest. I hope it helps.

I had no idea if the Viper T56 was going to fit when I bought it. I brought it home, sat it on the kitchen floor and started measuring and comparing it to a spare Ford T5 I have. I spend a good week measuring and remeasuring and dialing in exactly what/how I was going to do it. For GM T56, I am told to use the later model Camaro Tremec T56, I think after 1992. Pontiac Trans Am WS6 T56 will work too. Don't use the Corvette 6 speed (pre t56) nor the Corvette T56. Although, if you use the Vette T56 you should use the Vette rear end as well. Research research research.
Oh, an idea I've been tossing around...The shifter I used for my T5 was a short throw and I always had to sit forward and reach for 1st, 3rd and 5th. The T56 shifter sits in the same place so this time around I made a long shifter so I could sit back and bang through the gears. I found that the Pontiac GTO T56 and the Cadillac CTS T56 have a "moved back for better comfort" style bolt in shifter. I don't know how hard it would be to use one of these shifters on a different Make T56 but I suspect just drilling new mounting holes could do it. The GTO and CVS T56 go for double price of a Cobra T56.
I ended up moving my engine back a little so don't use this as standard but my driveshaft was custom ordered 45".
80 mph at 2000 rpm.

I don't know if this helps but it is a picture of my old T5 next to my new T56. The biggest difference I noticed about the two is the bellhousing is much shorter with my T56. That compensated for the difference in shifter location. Mine came out in the same position. If that is the same for a GM I have no idea. Have you tried going to tremecs website for measurements of the different versions?

wicked93gs said:

according to the picture I saw, the T56 shifter sat back about 2-3 inches from the location on the t-5, I think it was a GM T56 just because of the shifter location



take a look, this is why I think the toploader bell will work

p.s. this is a ford T5...not sure if the t56 is GM but I think so

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The shifter location would be a benefit there. That is probably a GM T56, the shifter handle box is rectangle, Ford and GM were like this. Ford input shaft is 10 spline. The input shaft looks like Chevy T56. If you go with a Chevy T56 try to find out if the input shaft is the same length or close to same length as the Cobra. If so, you won't need an adapter plate. FYI, the Viper, Ford and GM T56 will bolt up to the same bellhousings meaning the bolt patterns are the same.
Quick Time Performance Products has both sbf to Cobra T56 bell, and Viper T56 bell.
The angle in you pic doesn't show the length difference well. Here's what I did.

Viper T56 VS Ford T5. The mounting surfaces are lined up, and the input shafts are about the same length. I know you're wanting to use GM T56, I'm just trying to give you some reference and ideas.

This is the Viper T56 mated to the Ford T5 bell using a Ford T5 bearing retainer to center it.



Here's the GM T56 to GM bell adapter.
View attachment 274229
you would have to center a Ford bearing retainer where the GM one is seen. Also, need to drill the holes to bolt up behind a toploader bell. I believe one of the 4 holes, top right when facing the back side of the bell, overlaps between the Ford and GM patterns.

wicked93gs said:

out of curiosity, would I be able to use a T5 behind the cobra engine?(I know...its only good for 300tq, but thats good enough for a stock DOHC 4.6L) maybe by using a t56 bellhousing?

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There's an interesting thought. I suppose if you used the adapter plate in reverse, meaning bolt it to the T56 bell and have the T5 bolt to the adapter plate. You would need to punch a 3" hole in the center of the plate to allow the bearing retainer to center behind it. That wouldn't be so difficult if the hole was traced out where the bearing retainer is bolted to the plate. Then you'd need to account for the clutch fork pivot, a T5 pivot is part of the T5 bellhousing. The Cobra T56 pivot bolts to the face of the tranny. I think it would work. Another idea, the T45 bolts up to the 4.6. You have some fun ideas. I just don't have enough cars to try all my ideas. Keep us updated on what you decide to go with.

wicked93gs said:

out of curiosity, would I be able to use a T5 behind the cobra engine?(I know...its only good for 300tq, but thats good enough for a stock DOHC 4.6L) maybe by using a t56 bellhousing?

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Can't help you with the actual question, but my motor makes 300 rwtq (exactly... should be way higher but it isn't running right) and the T5's held up fine with everything I've thrown at it. Even though it leaks tranny fluid and was down almost 1.5 QTs last I checked (and yes, the only hold 2.3-2.5 quarts total)

The T5 would be fine with a stock DOHC 4.6. Best years are the 90-93 GT ones (other than Cobra T5zs etc)

wicked93gs said:

well, I would love a 6 speed, but I dont want to pay $1000+ for one, and I dont want to hack up my tranny tunnel to fit it. I already have a WC T5 with something like 30k miles on it from a 2001 V6 mustang, which if I remember correctly has an input shaft 3/4"? longer than the v8 version, which might mean I would just need a 3/4" adapter plate? I've made one of those before, they arent too difficult, do you have a picture of the t56 pivot?

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If you're bolting your 2001 T5 behind a 289/302 you could use the toploader to T5 spacer. Just use it as an earlier T5 bell to your T5 tranny spacer.
I don't know what the T56 pivot looks like, I imagine just like the T5 one. I know the Cobra T56 uses one because the 03-04 Cobras use a cable clutch mechanism. The Viper doesn't use a cable clutch and the tranny isn't tapped for the pivot boss, but since I used a T5 scatter shield, the pivot was already in the bellhousing. Your adapter plate, you could easily drill and tap a hole and mount the fork pivot.
I assume you've seen the T56 bellhousings? They are more of an integral type bell, they don't have a mounting surface in the rear except for the outer lip. That's why you'd need an adapter plate. If you are using a Cobra T56 belhousing you will need more than a 3/4 plate. Remember, its the Viper T56 that has the same length input shaft as the V8 T5 (non-94-95) not the Cobra T56.
I own a Cobra T56 bellhousing and it is about 2 inches shallower that the T5. I'm out of town right now but I can take a measurement this weekend. I think the V8 T5 bell is somewhere between 5" and 6". I can measure the T56 bell, if my memory serves me right the box is only about 4" thick. A V8 T5, or better yet a 94/95 T5 with the short input shaft would be ideal for the shorter Cobra T56 bell, if you are going to try to mate a T5 to a Cobra 4.6 engine using the Cobra T56 bell. Heck, the 94/95 T5 will bolt up to a 4.6 using a 94/95 bell.

i have been considering using a camaro 6 speed myself. i found this thread over at corral VERY helpful. it discusses a lot of the interchangeability issues between the different boxes even though it focuses mostly on the newer tr-6060.
Swapping in TR-6060 for a T-56? - Corral Forums