t56 6 speed

by McCauley5983 Thu Sep 08, 2011 1:00 am

does anyone know how much modification is involved to install a t56 six speed

by The Dude Thu Sep 08, 2011 10:03 am

Well not with a G3, but a G2 should be similar. Swapping from a Muncie 4 speed to a T56:

It uses the same bell-housing, flywheel, pilot bearing, throw-out bearing and pressure plate as a Muncie. You need a new crossmember. Probably have to make your own. It will be about 4" back & 1/2" lower. Have to make sure that your driveshaft is a 32 spline yoke. Speedo will hook up alright. Shifter will be moved back a few inches, so your console will need to be modified or run without one. I believe you will have to modify your trans tunnel. Also be aware that there are several different styles of T56's out there. Won't be able to use mechanical linkage unless you build an adapter plate. Most people switch to hydraulic.

This is just what I have collected from helping a buddy with his older Chevelle & hearing what others have said. Coolest 6 speed swap I've ever seen was a 440 & a Viper T56 in a mid 60's Belvedere.

by jerry46765 Thu Sep 08, 2011 7:27 pm

Rago wrote:Well not with a G3, but a G2 should be similar. Swapping from a Muncie 4 speed to a T56:

It uses the same bell-housing, flywheel, pilot bearing, throw-out bearing and pressure plate as a Muncie. You need a new crossmember. Probably have to make your own. It will be about 4" back & 1/2" lower. Have to make sure that your driveshaft is a 32 spline yoke. Speedo will hook up alright. Shifter will be moved back a few inches, so your console will need to be modified or run without one. I believe you will have to modify your trans tunnel. Also be aware that there are several different styles of T56's out there. Won't be able to use mechanical linkage unless you build an adapter plate. Most people switch to hydraulic.

This is just what I have collected from helping a buddy with his older Chevelle & hearing what others have said. Coolest 6 speed swap I've ever seen was a 440 & a Viper T56 in a mid 60's Belvedere.

Today must be twilight zone day....

NO NO and NO.

First of all there are different flavors of T56; it depends what the T56 is from as to what you will need.
The T56 will NOT use the same bell-housing, flywheel, pilot bearing, throw-out bearing and pressure plate as a Muncie.
The speedometer is electric pulse drive on a T56 so there is no cable connection.
The clutch is hydraulic and I am sure with enough work, you could fabricate mechanical linkage.
The T56 is alot bulkier than a munice and will require massaging the trans tunnel to fit.
The T56 has backup light switch built in it, reverse lockout switch, pulse vehicle speed, and skip shift control which all need additional wiring and/or interface with the old car wiring.
The 5th and 6th gears will be useless unless your rear axle ratio is at least 3.73 or numerically higher.

Any specific questions, let me know.
I have done a few T56 swaps in old cars.

Thanks -

by McCauley5983 Fri Sep 09, 2011 12:06 am

thats all i needed to know but why are 5th and 6th useless say if i was running the factory 273 rear end

by JB2wheeler Fri Sep 09, 2011 6:53 am

billy-ray wrote:thats all i needed to know but why are 5th and 6th useless say if i was running the factory 273 rear end

Because by the time you are in 6th gear with the 2.73 rear you are geared so high that at 60 MPH your engine will be lugging at about 1200 or 1500 RPM and your gas milage and engine detonation will skyrocket. Now if you lived somewhere where you could cruise alone at 120 MPH without slowing down, you would be in hog heaven. JB

by The Dude Fri Sep 09, 2011 10:14 am

Rago wrote:It uses the same bell-housing, flywheel, pilot bearing, throw-out bearing and pressure plate as a Muncie.

Jerry46765 wrote:The T56 will NOT use the same bell-housing, flywheel, pilot bearing, throw-out bearing and pressure plate as a Muncie.

Sorry, I just went off of what my buddy told me what he used when helping him install his. I stand corrected.

Rago wrote:Speedo will hook up alright.

Jerry46765 wrote:The speedometer is electric pulse drive on a T56 so there is no cable connection.

I need a smack in the head for this one. I will admit that I misinformed here. There are conversions out there that will allow you to run a mechanical speedo, but they do run a VSS stock & again I completely spaced out here. Still yet there should be a cable, just electronically operated.

Rago wrote:I believe you will have to modify your trans tunnel.
Also be aware that there are several different styles of T56's out there.
Won't be able to use mechanical linkage unless you build an adapter plate. Most people switch to hydraulic.

This is just what I have collected from helping a buddy with his older Chevelle & hearing what others have said.

jerry46765 wrote:
First of all there are different flavors of T56; it depends what the T56 is from as to what you will need.

The clutch is hydraulic and I am sure with enough work, you could fabricate mechanical linkage.
The T56 is alot bulkier than a munice and will require massaging the trans tunnel to fit.

by jerry46765 Fri Sep 09, 2011 4:39 pm

JB2wheeler wrote:
billy-ray wrote:thats all i needed to know but why are 5th and 6th useless say if i was running the factory 273 rear end
Because by the time you are in 6th gear with the 2.73 rear you are geared so high that at 60 MPH your engine will be lugging at about 1200 or 1500 RPM and your gas milage and engine detonation will skyrocket. Now if you lived somewhere where you could cruise alone at 120 MPH without slowing down, you would be in hog heaven. JB

Bingo. 2.73s with a .5 overdrive 6th gear would be about 1000rpm at 60mph.

If you have a high lift cam with a power range of 2000-6500 rpm, the engine would be lopping at less than idle speed and out of the powerband.

Plus another nasty side effect with massive overdrive and numerically low axle that I ran across running dual exhaust with 2 chamber Flowmasters; it would hit a nasty resonant frequency in this rpm and engine load range where all the interior panels would rattle and vibrate inside the car.
It’s even better when the cruise control is engaged…. You think the car is going to rattle apart…

by BlackChevelleSS Fri Sep 09, 2011 11:51 pm

Doing this swap soon
Im going to be running a LT1 t56, 153T flywheel, 69Z28 camaro clutch and PP, Mcleod hydraulic Throwout bearing, firewall adapter and modified master cylinder.

Thats as far as ive gotten, havent figured out what to do about the speedo,wiring, shifter, trans tunnel, driveshaft yet. Im running 3.31 gear and 28" tire. But I plan for 3.73s or dropping my tire size a bit smaller.
Another problem im having is finding a 454 153T flywheel which are around but not common.

The reason im staying with the LT1 T56 is because with the shorter bellhousing the trans is pulled forward more thus its in a larger part of the trans tunnel, im hoping that its enough that I wont have to annihlate the trans tunnel to get it to fit like with the ls1 t56 with the adapters.

by jerry46765 Sat Sep 10, 2011 5:00 pm

All the swaps I have done were with LT1 boxes but one, which was all LS1.
And these gearboxes aren't cheap, and I have always tried to use as much OEM stuff as possible. So, I can't really help with aftermarket bellhousings.

If you are using the OEM LT1 bellhousing, you will have to use an LT1 style flywheel, clutch and pressure plate. The packaging is different with the LT1 stuff. It doesn't interchange with the 1st gen stuff because the flywheel/clutch surface is about an inch closer to the gearbox.

Here is a LT-style Centerforce flywheel for an externally balanced 400 and would be similar for a big block:
t56 6 speed 400_flywheel

If you are planning on using the stock cable driven speedometer, the Cablex drive will accept pulse from the gearbox and drive the cable. The new Cablex 30 slot encoder drive will work lots better than the old 8 slot at low speeds which was the complaint in the past.

Wiring, yeah a pain, I got a loom from TPI Specialties and ended up pulling it all apart and redoing it. You could reuse the trans loom from the gearbox donor car and modify it for your car. I am sort of particular about wiring, and have done each one using connectors from the donor car.

Actually, wiring, trans tunnel, shifter, and driveshaft are all items you have to sort out on an individual basis. It seems like everyone is a little different.

I have a spreadsheet for sorting out rear ratios and tire sizes with the T56 or I guess any gearbox. It will calculate speeds and engine rpms in order to decide what combination will work best. If you want to try it, send me a PM with your email, and I'll send it to you.

Thanks -

by BlackChevelleSS Sun Sep 11, 2011 2:43 am

Im using the OEM LT1 bellhousing but not any of the clutch. The LT1 uses the pull style clutch, I will be using a standard old push style clutch pressure plate (69 Z28 is the one im using for mock up) a plain 153T nodular flywheel from a boat and a mcleod hydraulic "push" throwout bearing. It will work in theory as long as the clearances are right.
I have seen the cableX boxes they are pricey but its cheaper than the conversion tail shaft.

by jerry46765 Mon Sep 12, 2011 10:59 pm

Let me know how it goes?

I have looked at using a Ram hydraulic throwout bearing that you shim to get proper clearance. No reason why it shouldn't work.

But, I have been getting all the parts as a package from donor cars, and the only aftermarket custom part is the flywheel. No thought is required if they need replacement parts in the future since it's all LT1 Camaro stuff.

What are you using for a clutch and pressure plate?
I have been using Spec, and am amazed by the abuse it could take and still be very street durable.

by jerry46765 Mon Sep 12, 2011 11:11 pm

Oh, forgot about the Cablex. I took all the measurements and researched machining the tailshaft housing for my own car.

After looking at it, you have to do wiring for the gearbox.
There is no way around it unless you don't care about backup lights, and retaining reverse lockout.
So why not include the pulse speed in the wiring?
The Cablex box mounts under the dash with the ECU, lambda controller, and the circuit panel for the added electronics.
It sort of cleaned up the whole package.

What would be even tidier is to convert the vintage cable speedometer to electronic pulse.
But then what to do with the odometer?
I haven't worked through that yet, and would really rather just go drive the car.

Thanks -

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