What's involved in swapping the T86 Overdrive transmission in my 1955 Thunderbird for a T5 5 speed?   I know I will need and adapter and new drive shaft. I've been on John Mummert's website and it's looks pretty straight forward.   Anyone done this?    Will the transmission fit the tunnel?  Cost?  Drive ability?   Any other problems?

I swapped my Fordomatic for a T-5 . Pretty straight forward , costs are adapter , transmission  a driveshaft and a conversion u joint for the driveshaft at the rear end yoke..  Some floor mods are necessary around the shifter due to the shape of the T-5. Biggest modification was to the transmission crossmember to get the proper angle and height on the T-5.
I also built a trans tunnel cap to close the hole and make a nice mounting surface for the shifter boot.
There are some pictures here on the forum , try searching 5 Speed Conversion .

I can't help with the specifics of fitting it to a T-Bird.
Cost, depending largely on the transmission, used, rebuilt, or new, $1000 - $2500.  I suggest rebuilt or new which will put it toward the higher end.  Driveability will be fantastic.  First gear will be like going a couple ratios shorter in the rear and you get 1 extra gear to work with for city or low speed use, with closer ratios, 1 - 4.  Overdrive may not be a big change since you already have it.  If you get a new T5, it will be the Z which does have a tall overdrive, something like .62:1.  For a stock engine, that tall overdrive may be ok but for a modified engine where low rpm torque is not so great, a high 3s or low 4s rear ratio will be best.


Lawrenceville, GA

Charlie makes some interesting points about the gear ratios. My T-5 has a 2.95 first, and the .8 fifth. (I’m going from memory here). This makes it a very close ratio trans. I had a different unit in the car with a 3.21 or so first, and that was actually too low with the 4:11 rear gears. I was shifting to second in the Safeway parking lot.

So where I ended up was the 2.95 first, and a 3.7 something rear gear. That makes a nice driving combination, but it can be a little tricky starting on a hill. Made worse by an aluminum flywheel. I probably would have gone to a 3.9 or so, but the limited slip unit has to be changed to go steeper than the 3.7, and I was too cheap.

After years of driving it, I’d probably stay with the 2.95 first, use the .62 fifth, and do a 4:11 or so rear gear. There’s a gearset for the Dana rear that’s 4.27 or 4.30, and that would give a killer launch. Would work nice in 5th with a little more cam than stock, too.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

How do you feel about keeping the original three speed O/D vs. a new 5 speed?   My car is not a show car.  It's a 60's style hot rod driver. 

The only problem with the 3 speed o/d for me was the lack of a synchro first gear. My typical drive was 500 ft of altitude change, and I just got tired of driving in slow traffic and double clutching down to first. It wasn’t that I couldn’t do it, I learned that 50 years ago. But compared to my daily drivers ( all manual trans cars for 20 years) I got tired of fighting it.

Not abused, I dont have a problem with the T-86. I’m not racing and I don’t just side step the clutch for fun

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ