Chances are there's an adapter for your car's transmission...
We had made some decisions long before finding a restorable '55 T-Bird. A new, 80s Mustang-derived front suspension with disc brakes and rack-and-pinion steering will be substituted for the old Ford's hardware. The rear end will be stabilized by a Panhard rod and the car's frame, aft of the center x-brace, will be strengthened. Air conditioning will be added, as will an electronic ignition system.
The problem was the transmission, which carried over to the engine. To move along at today's highway speeds (let's face it: 75-80 is the norm) the engine would have to rev rather high. The old T-Birds were equipped with 2-speed automatics or 3-speed manuals and overdrive was available only in manuals, but even then the old Y-Block V8 engines had to wheeze pretty heavily at higher speeds. If the project car's engine was in good condition, we reasoned, how might we retrofit a more modern transmission to it? If this was not possible, we'd have to go through the effort of mounting a newer engine, with all the attendant problems.
Well, the project (automatic) car was obtained and the engine was found to be in very good condition, so we started asking around to see if anyone had ever successfully adapted a new automatic overdrive transmission (AOD) to a Y-Block. Why did we want to do this? Because an AOD would give me three forward gears and a 0.6 to 1 overdrive ratio, which means the car would accelerate briskly and smoothly and then settle down to less than 2000 rpm at 65 mph. Newer V8-powered cars are equipped this way, so they cruise at high speeds effortlessly.
That's when we found Bob Bendtsen. Bob is the owner/designer of Bendtsen's Transmission Center (www.transmissionadapters.com) in Ham Lake, Minnesota. His company has done all the engineering to adapt automatic overdrive, electronic automatic overdrive and 5-speed manual transmissions to a large number of older, classic, if you will, cars (these are listed below). He offers complete adapter kits to restorers and hot-rodders for a very reasonable price. In the case of the Ford Y-Block V8 to AOD transmission adapter kit, the cost is $695.
It doesn't get much simpler than this...
The adapter kit isn't just a piece of metal plate with a bunch of holes drilled in it. The kit contains a machined aluminum adapter to lengthen the end of the crankshaft by about 1 1/4 inches; a large, thick (close to 2 inches) half-moon-shaped aluminum adapter that mates the AOD bellhousing to the engine's rear face; a new AOD flex plate and a modern, gear-drive 12-volt starter that mates to the flex plate. All hardware is included and the instructions are straightforward and clear.
The first step is to bolt the spacer onto the crankshaft.
To adapt the AOD to our Y-Block all that was necessary was to clean off the back end of the crankshaft and fit the machined spacer to it. Class 8 bolts were provided in the kit and these were torqued to the flywheel. The instructions warn you that the bolts may need to be shortened (ground off) a bit to clear the block and this was the case. Next, the large aluminum adapter plate was bolted to the back of the block. Finally, the flex plate was fitted to the crank spacer and this too was fastened with the hardware supplied in the kit.
Everything fit perfectly and the entire process took less than one hour.
Next, the adapter is bolted on to the block.
Finally the flex plate is fitted to the crankshaft spacer.
The AOD transmission mated precisely with the new adapter plate and the input shaft lined up with the crankshaft with no alterations. In short, the kit proved to be machined very well and worked as advertised. Was it worth the price? Well, a conservative estimate of how much work and time would have been involved to engineer this conversion ourselves would be at least 40 hours, not counting trips to salvage yards. The answer is a resounding "yes."
More Good News
Bendtsen's has adapter kits to fit a host of other engines, whether you want to mount an automatic or more modern 5-speed manual. Here's a list of some presently offered:
Buick (53-56, 57-63, 64-66) to Chevy auto or manual
Buick straight-eight to Chevy
Buick 215 aluminum engine to Chevy
Ford Y-Block to AOD or T-5
Ford FE (352, 390, 406, 410, 427, 428) to AOD or T-5
Ford FE to Chevy transmission
Ford flathead to Chevy auto
Lincoln 337 flathead to Chevy transmission
Lincoln/Mercury 317, 341, 368 to Chevy transmission
Lincoln/Edsel/Mercury 383, 410, 430 to Chevy or Ford transmissions
Studebaker to Chevy transmission
Cadillac to Chevy auto or manual
Cadillac 346 flathead to Chevy transmission
Cadillac 365, 390, Northstar to Chevy
Pontiac 287, 316, 347, 370, 389 to Chevy transmission
Pontiac straight 8 to Chevy transmission
Chevy late model B.P.O.C. - all models
Chevy V8 to Ford transmission
Ford manual transmission to Chevy bellhousing - 49-64
Hemi-Chrysler 51-53 manual transmission
Prices for these kits range from $135 to $695. Bendtsen's can probably make a kit for your purpose no matter what that might be, so there's no reason to discard the idea.