OD transmission opinions

[Bill Dedman]

I am looking for information relative to the good and bad points involved in the use of 4-speed OD Mopar transmission swaps into A Bodies.

I have a '72 Valiant with a supercharged 360 Magnum in it, BUT, it is a very mild engine combination, and doesn't make a whole lot of power. Maybe around 450 at the flywheel on a cool day... with 8 pounds of boost.

It makes 12 inches of vacuum idling at 475 rpm with a Hughes hydraulic roller (214/218 @ .050", with .525" lift at the valve.) VERY m9ld specs... but, drives like a 318 2bbl...

I have run a 904 with a shift kit with no hint of a problem, and was curious about a comment I saw on another forum.

I have seen several "how-to's" about installing the A518 tranny into an A Body chassis, and every one talked at length about how BIG the OD unit is and how it was a lot of work to butcher the floorpan and rear crossmember for tailshaft clearance. I understand that.

Somebody on another forum in passing, mentioned, I THOUGHT, that the OD unit's external dimensions were somewhat smaller on the A500 than the A518.

Is this actually true, and how much smaller? Is it enough smaller to make a significant difference in floorpan alterations compared with installing an A518?

I am totally in the dark, but if that is true, since a 904 stands up op the kind of abuse I put it through, wouldn't an A500 work as well?

I don't want to cut this unibody floorpan any more than I have to...

Can someone enlighten me please? I've never even seen an A500 out of the vehicle, so, I have no clue...

Thanks for any information.

Bill

 

[dgc333]

I am pretty sure that the OD section on an A500 and A518 have the same external dimensions. In either case you will still need to cut the floor open the crossmember to make it fit.

A friend of mine has an A518 in his 67 Barracuda. Though not a trivial task it was not hard to make the clearance. He split the floor and cut the torsion bar cross member. Opened the floor at the cross member about 2.5". He welded in another section of cross member he took from a doner and then cut a piece of sheet metal to fill the floor gap.

His floor console still fits just fine and from inside the car you would never know he had done the surgery.

 

[Bill Dedman]

Thanks for all that good info, Dave. I suspected that, but wanted to hear it from somebody who actually knew... Couldn't imagine that Ma would tool up different size overdrive modules for such similar transmissions.

That tranny swap (A500 into an A-Body) might get done, yet.. I have a 2.73 third member, but as I get older, installing it for a trip now and then is rapidly losing its appeal, and what makes those pigs gain weight? Every time I go to swap center sections, it seems they have gotten heavier!!!

How do they do that?????

Bill, scratching his head, in Conway, Arkansas