Convert from powerglide to 700r4 or t56

[Rob68c10]

Hey guys as of right now I have a 307/powerglide in my 68. It's getting close to that time where I start thinking about drivetrain. My goal for this truck is a nice cruiser. Doesn't have to be a power house. I want something I can drive on longer trips and not break the bank. I have been thinking about doing a very mild build on a 327 I have, or just hopping the 307 up a little bit. However the power glide has to go. I just can't decide between a 700r4 or a t56. Is there a huge cost difference in one swap or the other? This is one part of the build of this truck where I honestly have no major preference of which selection to make and the cheapest reliable option will probably beat out the other. So convince me.

[SS Tim]

Since your truck is already an automatic I would go with a 700R4 or 200R4. Should be a nice easy swap. Just need to get a quality reliable trans. not a CL or junkyard refugee. If it does not have a warranty it is a core! Might need a ratio change if you have tall tires and a 3.73 though.

[Rob68c10]

Not sure what ratio is in the rear I have going in the truck but I plan on running 295/40/20's in the rear and a 255/40/20 in front.

[GMCJOE]

T56 would be nice if you are going for a performance application. There is a lot more involved in the swap. I doubt with the 307 that you would be pushing enough power to get the full potential of the T56.

I agree with Tim, you probably got something like 3:08's or so in the rear end, and 3.73 would be a great change with either.

If you are going to drop a nice built motor into the truck, you have the option of the T56. It would go great behind a LS swap, or an engine running about 300hp. Ultimately, the 700r4 or 200r4 is going to be the easier swap and fit your application the way it's with a gear ratio change in the rear end possibly.

[Rob68c10]

Originally Posted by GMCJOE

T56 would be nice if you are going for a performance application. There is a lot more involved in the swap. I doubt with the 307 that you would be pushing enough power to get the full potential of the T56.

I agree with Tim, you probably got something like 3:08's or so in the rear end, and 3.73 would be a great change with either.

If you are going to drop a nice built motor into the truck, you have the option of the T56. It would go great behind a LS swap, or an engine running about 300hp. Ultimately, the 700r4 or 200r4 is going to be the easier swap and fit your application the way it's with a gear ratio change in the rear end possibly.

Thanks for the info. I do not plan on running an lsx at this point in time. I want to kind of keep this thing simple (yeah right). 300~ horsepower is about the limit of what I want. Enough to kick the tires and set me back in the seat. What ratio would you recommend running?

[GMCJOE]

3.73 is a great ratio to be running, and that is my suggestion. I have a 4:11's in my rear axle, it came to me that way and I believe they are factory. I will be running a 700r4 with my setup. Can't afford that T56 transmission, they don't sell cheap!

[GMCJOE]

There is a thread on here that breaks down the axle codes if you want to check it to see what ratio you have currently. But that may not be what is in the axle, so it better to pull the cover and see what you got or do one of the other methods of checking. I believe SSTim is well versed in the axle codes.

[Critter]

In my opinion if you are not going to be making gobs of power (350hp+) then don't waste the money on a t56. A nice world class t5 can handle the amount of power you are talking about for a daily driver/cruiser no problem. Some people give them a bad wrap because they can't handle a lot of power especially when they are abused, taken to the track a bunch, etc. If you decide against a manual trans then a 700r4 will be the most readily available.

[lowrollin70gmc]

I've done both a 700R4 (67 Chevelle) and currently have a T56 in my 63 Chevy II.

I had 3.08s with my 700R4 and a stockish 350 and that car was a great daily driver as the deeper first gear of the 700 helped with the shallow rear. I currently run 4.56s with the .50 6th gear t56 in my 63 and enjoy that as well, regularly cruising at 75-85 with my hopped up 250. It all comes down to if you want a third pedal or not.

Cheapest way for a t56 is 93-97 FBodies but you would need a conversion flywheel to go to a pre 85 motor (about $400) as well as a way to hook up a hydraulic clutch (pretty simple with a welder).