Technical T4 or T5?

I'm looking to swap out the stock 4 speed in my 49 F1 and thought I would pose my situation for some opinions.
I have a T4 (4 speed out of an 82 S10) and possibly a rear end out of a 66 F100 with 3.25 gears.
Should bring my rpm
's down to around 2100 @ 55 mph with current tires.
If I keep the original rear end and find a T5 instead I will end up with a similar rpm @55.
I will probably end up spending the same amount either way so that is less of a concern than whether there are advantages to going one way or the other. For example, does the 66 rear end have auto adjusting brakes etc.
I've been a lurker for a few months gathering ideas and this my first real post so please let me know if Im posting in the wrong place. Thanks

 

I should add that this is going behind the original 8ba and is about the only "modern" concession that I plan to make.

 

A torque motor goes well with fewer gears.
One factor though, is vehicle weight. Then you divide up accel. into smaller parts w/a 5 spd. Many lightweight drag cars used a mod. Powerglide 2 spd, you can imagine the effects of broad range, and time per gear.

 

FWIW... I have a T4 (maybe out of a Camaro) in my 30 coupe. it has a mild built flathead and it also has a stock 1951 F1 rearend.
1st gear is all but worthless...it gets you rolling but its time to shift before you can finish making a turn at a cross street from a stop.
Cruising in 4th at about 2000 gives me around 50-55 mph (16" rims 6" side wall)
65 gets me up in the 3000 range... and with the exhaust on my car it sounds like its screaming....
This is my first flathead so I am still learning how hard I can push it...
having said all that I thought I should get a T5 the first time I had it above 60mph.
Chappy

 

T5's are still plentiful, and American Powertrain just started selling S10 T5 rear shafts that bolt directly to the Mustang etc. T5s. T4 is kind of an oddball, but should still require the same adapters & parts that a T5 does.

I lived with that same stock 4 speed for years, and I don't blame you for wanting to ditch it.

You're going to have to get your driveshaft shortened with the T5, so you might as well do the 9" at the same time. The shock mounts will be in the wrong place, you can either cut and reweld them, or get a set of F2 shock mounts.

I think '66 is the first year for the brake self adjusters, but you may want to double check on that.

 

Thanks for the thoughts. Another option is use the F100 rear and a T5. I think the ones typically used have the.72 ratio 5th gear. That would bring my rpm down to 1500 or so at 55 mph. Too low? I know, just drive faster!

 

I have a 5 speed OD in my coupe. With 3:55 rear gears, and 225x 75x 15 tires, 1st gear is pretty useless as well, but I sure like that OD. I am running a 6 cylinder motor (more modern) and the 1st gear with the 3:55s can get the thing moving pretty easily when I have the desire to play a bit, and the 5th gear to shift into doesn't kill the gas mileage as bad when I play.
I'm pretty sure you will find the 5 speed is more fun to drive, and you can probably drive the speed limit. Gene

 

T5, all the way.

A T4 and T5 fit in the same space, are the same length, and have the same mount position, so you can start building with the T5, while you shop for a T5.

 

The five speed may bolt directly or can easily be modified by drilling and tapping your 4 speed hogs head.
Personally unless your truck has a 4.11 or lower, I would not worry about the rear. Self adjusting brakes? I'll put it this way, I would not change out a rear axle to gain self adjusting brakes as they still require periodic adjustment, so whats the point?
65 was the first year for self adjusters.

I would be more concerned with how tight the steering gear is, the status of the tie rods, pitman arm and the king pins and bushings. Don't forget shocks and shackles all around. If they are still serviceable that's fine but do check all of that.

My old girl has a slight hood chase at Highway speed. I got used to it. It's very controllable.
Now at Ludicrous Speed that slight hood chase is a whole different matter. It's all you can do to hold it. Was I Scared, no I was too busy doing...nothing. By that I mean, no over controlling.

A wore out F1 will pull straight as a Saturn 5 Rocket until....it reaches the top. Then the ride begins.

Make sure she's tight in the front. With overdrive and good road you could accidentally find yourself way up top. far beyond whats controllable if it has steering and suspension wear.

 

Thanks. F-one, I completely get what your saying. The steering is tight and I have not replaced anything yet but given that the last time it was on the road was 50ish years ago I intend to evaluate and replace anything suspicious this winter. I have gone through the brakes, new lines, hoses, shoes. This is a father son project which I am sure he will ultimately own so I have no intentions of not making it safe for him or others on the road.

 

Good advice. I was leaning toward the T5 to begin with, just had the T4 avalable. It will make a good mockup.