55 Thunderbird Gears in 39 Trans

[Fairlane500]

Hey there guys,

Have any of you ever fitted 55 Thunderbird, Customline, Fairlane gears to a 39 - 48 ford Transmission? I have heard it can be done with some modification to the cluster gear shaft housing bores by enlarging bores to 7/8 from 3/4 and spline mods to the input shaft otherwise things apparently fit? Can anyone verify they have done or have seen the mods done?

Regards,

[ford38v8]

So... If it can be done, what would be the advantage?

[Fairlane500]

It gives a very similar gear ratio if not better to Lincoln Zephyr gears.

Transmission Gears and Ratios
26H Lincoln 25-tooth Low Second High 2.12 1.44 1.00
06H-56H Lincoln 26-Tooth Low Second High 2.33 1.58 1.00
Ford-Merc Lincoln 28-tooth Low Second High 2.82 1.60 1.00
Ford-Merc Lincoln 29-Tooth Low Second High 3.11 1.77 1.00
Ford Thunderbird 24-tooth Low Second High 2.32 1.48 1.00

[Lawson Cox]

What Alan said.

[Charlie ny]

500,
You'll need to find the very rare output shaft that has the involute shape
and correct helix to accept the first and reverse sliding gear of the later transmission.
Mac VanPelt assures me that they were made at one time. This shaft allows the use
of the later gear set in an early case...ala '39. The further benefit, and it is substantial,
is the improved gear tooth form and the far superior roller bearing design at the
junction between the input and output shaft. The later design utilizes loose rollers
the fit of which is near zero flex.
Charlie ny

[okiedokie]

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Jim Perkins here in Tulsa made those very mods to 39 transmissions. I am unsure if he sold any or not but I do know he did some. Unfortunately Jim's health is failing and I understand his family is moving him to an Alzimers [spl] care facility. One of the most knowledgeable Ford guys around here. A great loss to our area. I have no idea what happened to the trannys he did.

[Pete]

Originally Posted by ford38v8

So... If it can be done, what would be the advantage?

It can be done.

1- Better steel alloys.
2- Might (big might) be cheaper than a $1000 set of zephyr gears.

[ford38v8]

Pete, those are two excellent reasons. I like reason #2 and I saved the whole $1000 going in!

All kidding aside, I do respect that it's a big deal for some, just not for me.

[B-O-B]

I think I would spend the bucks on a later O'drive tranny like Ol Ron suggests.

[ford38v8]

B-O-B, I don't think an overdrive would satisfy that itch.

[Fairlane500]

Really Keen on any further info on this, would like to give it a go. I have heard of one being completed here but lost in history is what gears from what trans were used.

[Barn Junk]

Originally Posted by Charlie ny

500,
You'll need to find the very rare output shaft that has the involute shape
and correct helix to accept the first and reverse sliding gear of the later transmission.
Mac VanPelt assures me that they were made at one time. This shaft allows the use
of the later gear set in an early case...ala '39. The further benefit, and it is substantial,
is the improved gear tooth form and the far superior roller bearing design at the
junction between the input and output shaft. The later design utilizes loose rollers
the fit of which is near zero flex.
Charlie ny

Yes Charlie they do exist. I found two of them in a salvage yard with lots of old stuff from a nearby SAC Air Force base in eastern WA. They were in Ford side shift trans and had been converted to open drive but had no provision for speedo drive. The 32-48 closed drive u-joint fits the main shaft exactly with a 1951 and later low/rev spline. I think they may have been used in an industrial application like a jitney or towing device for ground support of the new jet bombers in the early/mid 1950s that were stationed at this base. Just a guess but have never seen them documented in an auto application. It was actually quite common to adapt auto components to aircraft ground support.

[scooder]

Gota say, the stronger gears won't stop the gearbox case blowing open and leaving the lay shaft on the asphalt under the car. It's a cool thing, having the better ratios in there, especially with the appropriate rear end gears. And using Tbird stuff to do it, is cool. But I feel the trans case is not strong enough to make use of all this stuff. The yards arnt still full of early Ford parts, so this has to be thunk about.
A nice 4 speed top loader with good close ratio set and converted to fit to the torque tube, would be many times better. Maybe even a T5 done the same (seen a pick of this somewhere) but get those pointless S10 gears out, and put a close ratio set in.
Martin.

[Turdytoo]

Are the parts available? What does a scrounger need to be looking for?

[Charlie ny]

TT,
I guess a big swap meet is where I'd look. When we go to Canfield or
Hershey I always carry a late 1st/rev sliding gear and if I see an output shaft I try
the gear on it. A late slider will bind on an early shaft. At a glance, even side by side
it would be tough see the difference.
I'll bet Bob Drake could make that shaft..........
Charlie ny

[Tim Ayers]

Originally Posted by scooder

Gota say, the stronger gears won't stop the gearbox case blowing open and leaving the lay shaft on the asphalt under the car. It's a cool thing, having the better ratios in there, especially with the appropriate rear end gears. And using Tbird stuff to do it, is cool. But I feel the trans case is not strong enough to make use of all this stuff. The yards arnt still full of early Ford parts, so this has to be thunk about.
A nice 4 speed top loader with good close ratio set and converted to fit to the torque tube, would be many times better. Maybe even a T5 done the same (seen a pick of this somewhere) but get those pointless S10 gears out, and put a close ratio set in.
Martin.

Useless S-10 gears? Not sure what you mean. There were a bunch of different versions of this trans and they had different ratios. Some are better than others, but that 5th OD is a blessing for a flathead.

[scooder]

S10 t5's often come with a 4.03:1 first gear. Pretty useless behind a flathead. Then yawning gap to second. Good for a rubbish engined pickup. Flathead trans commonly use a 2.8 or 3.1:1 first gear. And most can pull away from stop in second which is about 1.6:1. Compare this with the 4.03:1. Their are as you say lots of different applications for the t5, with lots of different ratio sets in them. Often the s10 with a good gear shifter location has the useless gears I speak off. If you were to use a gear set out of say a V8 engined mustang or such with a 2.95:1 first gear, we're talking a completely different driving experience. That 2.95.:1 will pull like a stocker from a stop in first pretty much the same as the three speed, and have closer ratios through the trans and the fifth gear everybody seem to think they need.
This Is what I mean when I say useless gears. If your gonna go through all the stuff necessary to get this t5 in your Ford, why not put one in with appropriate ratios?
Martin.

[Tim Ayers]

http://www.flatheadv8.org/ernie/ernie-t5.htm

Here is some great info on the T-5 trans.

[Fairlane500]

Thanks for the T5 info, but not what I am interested in, I like the idea of retaining the 3 speed.

[rotorwrench]

In 1951 FoMoCo went to the new design sometimes refered to a diamond shaped gear sets. All of these transmissions had the long main output shaft. If a fellow had the wherewithall it might be possible to cut the shaft down & add splines for the U-joint. FoMoCo or Borg Warner might have made a shaft for this so that replacement gears could be limited to the new design so they could discontinue the old style. Mac VanPelt would sure be the one who knows this stuff.