5 or six speed in my 1966 Chevelle wagon?

[Thumpin'66]

Hey guys,
I am just starting my 66 Chevelle wagon project. I am building a 468 with dual fours and 425HP/454 solid cam. It will be the ultimate family truckster project. Well, compared to some of the high dollar quality rides here I may have to retract my "ultimate" description..lol..
I was just going to throw a muncie in it but have realized that life without overdive on the freeway would stink. I see many debates on the T-56 vs TKO 600 subject and still don't know what to do. I am trying to get prime rib on a hamburger budget so I need the best option. I prefer using an sfi approved bellhousing for my trips to the track such as a Mcleod. I guess my question is two part: (1) What would be the least expensive overdrive combo that will last behind the 468 on the street? (2) What combination of parts would you reccomend if the budget was not an issue?
Please include specific application info or part numbers if possible. I am running a bench seat and want to use a traditional hurst shifter handle. I have my 454 at the machine shop now and will have to buy a flywheel to get things balanced soon. Thanks in advance for any advice..
Russ

[nitrorocket]

There are diehards that like one or the other trans. The correct T56 is bulletproof. I run one behind my LS1 Chevelle with over 1000 hp. If you run a 3.73 gear or higher the 6th gear will actually be useable under that the motor is barely running.

[TonyL]

There's been numerous threads on the subject here, Have you done a search? There's one thread just a few posts down discussing it.

Here's one (https://www.pro-touring.com/forum/showthread.php?t=32177)

[Damn True]

To keep this thread from spiraling into "one of those" t-56 v tko discussions I'd suggest that we rephrase the question:


I am building a 468 with dual fours and 425HP/454 solid cam to put in my '66 Chevelle Wagon. Given the nature of the engine and the weight of the car, which combination of gear ratio and transmission will allow for the best driveability? Keep in mind that this is to be a street car and I am under a rather strict budget so exotic custom setups are probably not doable.

[Thumpin'66]

Sounds better, thanks. I have read all the TKO vs T56 threads. I still do not have enough specific info on what works with an externally balanced 454 for specific components such as flywheel, clutch, mechanical linkage, etc. Maybe some guys with big block chevy/overdrive manual trans combos in heavy cars can give me their setup details for reference?

[HILROD]

For the price I'd say go 5-speed. That way you can have a scattersheild. If you can get an SFI approved one for a T56, It'll be a lot more. I don't have the part numbers handy, i just gave Classic 5 speeds a call and ordered a kit up. Mcleod is good stuff just a little pricey. You can save a few bucks by ordering a Lakewood bellhousing and getting someone elses clucth parts. The Lakewood will need to be checked for run-out for sure. The clutch linkage would either be from a resto place or from Classis 5 speed.

[Morgan]

I put a Tremec 6 spd in mine and on the Power Tour this year I never needed 6th. Cruising on the highway at 85 in 5th was the way to go, every time I went into sixth my RPMs were too low and I was loading up the motor. I know this is car specific due to the fact that I have a carb and 3.89s in the rear but figured I give my 2 cents. If I could do it again I'd go w/ the 5 spd.

[Mkelcy]

Take a look here http://www.camaros.net/forums/showthread.php?t=98387 for some basic information on how to do the T56 swap. Although it's in a Camaros forum, most of the basic information (needed flywheel, clutch, clutch linkage, adapters, bellhousings, etc.) will also apply to your big block Chevelle.

The cheapest setup is likely to be a used T56 with the Mcleod adapter kit and whatever flywheel and clutch will work with your engine, a mechanical clutch linkage and a standard Chevy bellhousing.

[Thumpin'66]

Thanks for the good info and input!

[MarkM66]

I think you may have to do more floor work when using a T56 vs. TKO.

[Thumpin'66]

Someone already cut a hole in my floor so originality is ot a concern. I will probably min-tub it anyhow. I do plan on keeping the bench seat so that may be a challenge due to T-56 shifter locations.

[MarkM66]

Someone already cut a hole in my floor so originality is ot a concern. I will probably min-tub it anyhow. I do plan on keeping the bench seat so that may be a challenge due to T-56 shifter locations.

It can be done with a bench. Even if the stock location doesn't work, there are other shifters out there that mount it further forward.

[redbaron]

I go by a simple rule of thumb. T-56 for LS series engine. TKO 600 on big and small block Chevys. The T-56 takes up more space in the tunnel. Good Luck!

[Mkelcy]

I go by a simple rule of thumb. T-56 for LS series engine. TKO 600 on big and small block Chevys. The T-56 takes up more space in the tunnel. Good Luck!

A "rule of thumb" that completely ignores rear gearing and the engine's ability to run smoothly at the resulting cruising rpm is not too useful. The TKO-T56 determination is not so difficult that one needs to ignore critical issues simply to make the decision easier.

[BobB66SS]

I swapped a D&D T56 into my '66 Chevelle SS. I wanted the sleeper look, using the stock console, so the console had to be moved rearward 2" to match up to where the shifter is on the trans so keep that 2" in mind with the bench seat. The floor had to be reworked quite a bit too due to the size of the thing. I also had the stock shifter handle grafted on to the T56 for more of the sleeper look.

I'll also agree that the overdrive ratios in this trans, for what I usually do with the car, are too much. 5th is 0.74 and 6th is 0.50:1, so I spend most time in 5th gear on the highway. With the 3.73 rear gear, 6th makes the motor load up unless you move way up into the "ugly speeding ticket" range.

[Thumpin'66]

Thanks guys! I am going TKO 600. Researching pricing and install requirements it sure seems like the best way for me to go. I like the idea of the easy mechanical speedo drive and regular style scattershield using the TKO. I figure a TKO and a 3.50 geared 9" behind my big block should work well.

[redbaron]

Back to my rule of thumb. Gear the rear end according to the desired cruise rpm. TKO 600 5th gear ratio is .64, TKO 600 RR (road race) 5th gear ratio is .82. The T-56 Ratios are 5th at .74 and 6th is .50. Classic Chevy 5 Speed's wed site has a useful RPM/MPH chart on it.
We always install the T-56 with a hydralic clutch set up. TKOs with mechanical. By the way you made the right choice. Good Luck!

[mixon]

Grab another gear...go 6 speed