'06 Tremec T-56 into '68 GMC C-15 w/ 600HP BBC 427 questions...

[nikwho]

Hello all,
So, I've got my fresh 433 cubic inch 427 all built and ready to install in my '68. I don't want to eat my th350, which is going to go into my '59 Apache, anyway. My original plan was to find a close ratio Muncie M22, mostly because I like the sound of the gear whine AND because it's period correct! However, I am intrigued by the Tremec T-56 6 speeds, because it's 50% more gears, which equals 50% more fun, by my math. Also figured that I could get away with lower axle gearing and have more fun in lower gears.

I plan to run the 427 that I have built for a while, with serious interest in finding an LS7 427 in the future. I have found a T56 locally that came out of an '06 Corvette. He replaced the transmission with a unit out of an '05, so he had to swap tail shafts. So, this is an '06 T-56 out of a 'vette with an '05 'vette tailshaft. Has 130K miles on it and due for a rebuild. I notice that the Corvette/GTO/CTSV rebuild kits are more expensive than the Viper/Camaro/Firebird/Cobra rebuild kits, which tells me that they are different. I will begin my thorough research, but don't want to miss out on buying this transmission, if it will work well for my application. It shifts through all the gears, but started making noise. Needs syncros and bearings, but I would plan on a full rebuild. It's being sold at a core price, so I feel okay about using it as a core, if for some reason it can't be rebuilt.

I'm just curious if T-56 experts know of any immediate and bvious rea sons why I wouldnt want to use a Corvette t-56? Like, shifter location, strength, etc? I've heard of having to change out tailshafts to deal with shifter locations, which I assume is why the owner had to swap the '05 tailshaft for the '06. Or perhaps that was just for his driveline length?

Anyhow, if this will work well for my application, I would like to buy it and start sourcing parts and getting it rebuilt and ready to install.

Any advice on the matter would be greatly appreciated!

Nik

[geezer#99]

So you’ve got a rompin’ Stompin’ 600 horse 427 that’s not gonna want to run nicely anywhere below 2500 rpm and you want to use a tranny that has likely all the wrong gear ratios plus o/d and you wanna change the rear gear too.
If you don’t mind running around in 3rd most of the time and carry those other 3 gears for a top end run, then it might work okay.
What gear ratios does this new tranny have?
Have you looked into a wide ratio m22?

[crazy longhorn]

Originally Posted by geezer#99

So you’ve got a rompin’ Stompin’ 600 horse 427 that’s not gonna want to run nicely anywhere below 2500 rpm and you want to use a tranny that has likely all the wrong gear ratios plus o/d and you wanna change the rear gear too.
If you don’t mind running around in 3rd most of the time and carry those other 3 gears for a top end run, then it might work okay.
What gear ratios does this new tranny have?
Have you looked into a wide ratio m22?

Agree (one geezer to another)! I like a mid 3 gear on the street, & I feel that the wide ratio Muncie will work with that. If you plan to run a 4.10, or 4.56 gear + OD on the trans, understand about drive shaft speed.....Have a good shaft built/balanced, to deal with it! The speed on that shaft is engine rpms, on a 1 to 1 high gear....add the OD, & the D shaft is spinning faster than the engine Longhorn

[nikwho]

I understand. At first I read your response and didn't follow. I read it again with my coffee and understand what you were saying.

[Tom]

Originally Posted by geezer#99

So you’ve got a rompin’ Stompin’ 600 horse 427 that’s not gonna want to run nicely anywhere below 2500 rpm and you want to use a tranny that has likely all the wrong gear ratios plus o/d and you wanna change the rear gear too.
If you don’t mind running around in 3rd most of the time and carry those other 3 gears for a top end run, then it might work okay.

Originally Posted by nikwho

Also figured that I could get away with lower axle gearing and have more fun in lower gears.

So yeah, he's got that figured out already.

My only thing to consider is how you'll have enough traction on a street truck to enjoy 600hp big block and super low gearing. I'd imagine you'll just burn the tires off all the time. Otherwise its a great idea! You can always go with a M series munice plus gear vendors as well.

[kerber63]

I’m sure you’ve already researched the differences between a corvette T56 and all other T56s (different input design - not mounting directly to the engine; and different output housing design - mounting directly to the differential instead of to a driveshaft), so I’ll just give testament to my 6 speed for the sake of it being a 6 speed.

I put a T56 from a 96 LT1 Camaro behind my tubo’d 454 and couldn’t be happier. The low end torque from the motor allows me to run in 5th as low as about 30 mph, and in 6th at about 55 mph. The tires will blow off if I get into it in those gears at those speeds, but that’s what downshifting is for. 1st-4th gears are pretty similar to a Muncie spread, 5th and 6th give the truck legs to run and run and run. My sweet spot for cruising on the highway is 6th gear, 75mph, ~1700 rpm. 4.11 rear end, 275/55/20 street tires.


It’s an awesome feeling when somebody comes up on me at highway speed and I drop 3 gears and run next to them. I usually get a shocked look, then row the boat and leave them behind.

[nikwho]

Okay, in an attempt to respond to all of you guys in one post; my first thought was to run a M22. I figured that the expense of a M21 or Muncie M22 and a gear vendors over drive would quickly start climbing into the realm of the expense of a T56. I am building my axle after I have determined what transmission and rear tire I am going to run.

As for F/R weight ratios, how far down and back my engine can go will be determined my shifter placement options/configurations of the transmission that I choose. Lots of options out there.

In my reading I have realized that the Corvette T56 isn't the way to go. Sounds like an LT1 T56 is the best choice. I'll just start my search for the right transmission. I do appreciate you guys taking the time to help out!

Nik

[scottofksu]

Originally Posted by nikwho

Okay, in an attempt to respond to all of you guys in one post; my first thought was to run a M22. I figured that the expense of a M21 or Muncie M22 and a gear vendors over drive would quickly start climbing into the realm of the expense of a T56. I am building my axle after I have determined what transmission and rear tire I am going to run.

As for F/R weight ratios, how far down and back my engine can go will be determined my shifter placement options/configurations of the transmission that I choose. Lots of options out there.

In my reading I have realized that the Corvette T56 isn't the way to go. Sounds like an LT1 T56 is the best choice. I'll just start my search for the right transmission. I do appreciate you guys taking the time to help out!

Nik

Something to consider... I recently purchased a T56 out of a ‘94 Camaro. The cost was just $350; so I went with it! My engine is a 400-550 HP SBC (haven’t had it dynoed yet, hence the range), and I have interest in even more wild options in the future. As such, to make the trans live a long life, and to put the shifter where I needed it (i.e., mounted to the access port just behind the bellhousing) I sent the trans off to be rebuilt and modified. That cost $2700. Then there’s the flywheel ($600), and bellhousing ($600 for AFI), and clutch ($550)... You can see how things add up! Now I’m not certain I wouldn’t have just been better with a TKO600...
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[nikwho]

Good to hear the cost involved to make your swap happen. From what I've read, the cost of a new T56, or buying used and having rebuilt, seems to be about half of the actual cost of the full swap. I have every single part (sans the actual transmission) to install a Muncie, down to the clutch, flywheel, clutch cable, throw out bearing, bellhousing, etc. I am in no particular hurry to find a 6 speed to install. I will likely install a M21 or M22 in the mean time. Then, once that's finished, it may actually be wise from that point to install a gear vendor overdrive into it! I really like the nostalgia of a M22, with the loud gear whine! Perhaps that is the way to go.

Even if I do go with the M21/M22 for now, it's not wasted money, as I have a '59 Apache and soon to have a '65 Chevelle that will each eventually need a standard transmission. I currently have a freshly built 700r4 in the '59 that I can manually shift & for my preferences, it's just not the same as a standard transmission. I do appreciate all of your guys' opinions and input!

Nik

[Tiger Joe]

Any reason you aren’t looking at the TKO-600? Seems like the perfect fit for you, gets you the 4 speed muncie style with an added OD. Won’t require as much modification as a t56 I swapped from a muncie to tko and was able to reuse a lot

[nikwho]

Originally Posted by Tiger Joe

Any reason you aren’t looking at the TKO-600? Seems like the perfect fit for you, gets you the 4 speed muncie style with an added OD. Won’t require as much modification as a t56 I swapped from a muncie to tko and was able to reuse a lot

Yes, there is a reason. It's just not a good reason! LOL. dumb enough that I hate to say it. A 5 speed swap just doesn't excite me like a 6 speed swap. I like the thought of driving a classic with a 6 speed! Now, this is where my rationalization gets weird, because I'm also considering a 4 speed swap! I've always liked the loud gear whine of a M22 "Rock Crusher"! I've just always thought that they were cool. So, I could see adding an overdrive to a M22 & can definitely see swapping in a 6 speed. I know that a TKO-600 would be a sound choice! I just need to get on board! ;-)

[jjzepplin]

What all is reusable from the Muncie setup to TKO?

[Clyde65]

Put in a gear vendors with your rock crusher??

[Trackman101]

Don't waste your time with a TKO. They are not even in the same league as a T56.
They don't like high hp or high rpm.

[nikwho]

Originally Posted by Clyde65

Put in a gear vendors with your rock crusher??

I don't understand your question. Or is that a statement? That was a thought that I had. I've just always liked the gear whine of a M22. Thought that going that route, along with adding an overdrive could be fun.

Originally Posted by Trackman101

Don't waste your time with a TKO. They are not even in the same league as a T56.
They don't like high hp or high rpm.

That, I didn't know. I don't want to dump a bunch of money into something that is not going to last.

[Tiger Joe]

Originally Posted by Trackman101

Don't waste your time with a TKO. They are not even in the same league as a T56.
They don't like high hp or high rpm.

I would disagree with this since I’ve been running one behind my 496 for 2 years. Zero issues.

[jjzepplin]

TKO's get good reviews on here... Rated up to 600ft lbs of torque. People say they really like them. $2500 roughly. M22 is about $2200? Gear Vendors $3000? That MUNCIE would be a really nice setup but DARN! Explain that to my wife. Would make a nice Sleeper! But I might be sleeping in it for a while- Bwahaha.

[Tiger Joe]

Sorry I said muncie before but I actually had a super T10. I reused my Lakewood bellhousing and could have reused my clutch if it was good.

Also, there is a lot more expense than just the trans prices. Like I said I pulled my 4 speed wound up needing a new clutch, then everything from the install- crossmember, Trans mount, speedo cable, cut and rebalance driveshaft. All told I was into my swap probably $3500. But i only had to do minor tunnel mods. I think to fit a t56 in i would have needed to do a lot to rework my tunnel

[StorminNorman]

The vette T56 can have a 2.66 or 2.97 first.....VS the 2.2 for an M22.
Vette T56's use triple cone syncros, that's why the rebuild kits (if include new blockers) are a fair bit more expensive.
It costs a fair chunk of change to convert a Vette T56 to a "Normal" (front mount) config. You basically need to get the trans for free to make it worth it as opposed to getting a new T56 Magnum for ~$3100.

[nikwho]

Thank you! I'm going to start looking for a transmission, but I'm in no hurry. I have feelers out for an LT1 T56, but may end up buying a brand new transmission. The nice part about if I stumble upon a M22, but still want to run a t56, is that that the Muncie could be repurposed to my '59, or a '64/'65 Cheverly that I am looking that he hath pick up after my two trucks are finished.

[Mike C]

Do some more research. The LS trans appears to be a better swap for an older vehicle. It's common to convert the LT style to an LS.

I have a 427 I built for my 64 Corvette. And I decided to buy the McLeod street 5 speed. Fitment wise, it is by far the easiest. Rated to 500 lb/ft. Hope I made the right choice...

FWIW, I own and will someday use 1 of 2 different LT style T56, but converting them to the LS style was the conclusion I came to for swapping. It's just too big to swap easily into a mid-year vette, so back to using something different for me. And the McLeod was easier than a TKO 500.