Overdrive install possible on a '63 727?

[Ron H]

Question about 727 overdrive installation possibility on a ’63 PB trans. Poly 318 with some performance modifications. I’m not any expert on tranny’s. My trans was upgraded to a modern TQ and spline some 5-years ago. My first mistake was taking out the 3:23’s installing 3:55’s. Thinking of going back to 3:23's; but the swap seems marginal for freeway speeds. Cruising for extended durations is a PIA approaching 65 mph. Any possibilities with an OD setup on this trans?
Thanks

 

[Darter6]

I believe it can be done.Many convert the tail to slip joint and remove the rear pump to the later 727 parts.
With that understanding something like Gear Vendors may have the answer.

 

[#41]

If it was me, a 318 poly isn't making any power so I would drop in 2.76 or 2.94 gear and spend the Gear Vendors $ on something else.

 

[dvw]

I believe it can be done.Many convert the tail to slip joint and remove the rear pump to the later 727 parts.
With that understanding something like Gear Vendors may have the answer.

You can not remove the rear pump. It will not shift. Governor pressure is supplied by the rear pump. The later 727 parts do not bolt up, different bolt pattern, the park cable installs in the tail housing.
Doug

 

[PurpleBeeper]

Yep…2.76 or 2.94 gears

 

[66 Sat]

Ron, what rear tires do you have on there? I'd swap the 3.23 gears back in, put a slightly bigger diameter rear tire and use the money you'll save on the overdrive in getting your car running right. Swap that exhaust to a 2.5" system and fix your vacuum advance.
My 318 poly with virtually the same build as yours (3.23 rear, stock converter) was running 15.2 @ 93 mph which should be fast enough for a geezer.
With a 24.5" diameter rear tire (245/60/14) I cruise at about 2,900 rpm which is a sweet spot for the engine and is 65 mph.

With a taller tire you could drop those rpms to probably 2,750 which will be just on the cam. Any lower you'll probably have worse gas mileage as the engine won't be in it's efficient operating band.

 

[dvw]

Here's my take. A 318 poly will have limited power. If off the line acceleration is not a huge concern the two easiest and least expensive options are larger diameter rear tires. Or a 2.94 or 2.76 rear gear. Once its rolling at 25 mph the aceleration with any of the gear ratios will be similar. Unless you drive daily on the freeway, the cost of an overdrive will never be recouped. An even then it'll take many miles. Will the higher rpm bother the engine on the freeway with a 3.23 or 3.55? No.
Doug

 

[Ron H]

Ron, what rear tires do you have on there? I'd swap the 3.23 gears back in, put a slightly bigger diameter rear tire and use the money you'll save on the overdrive in getting your car running right. Swap that exhaust to a 2.5" system and fix your vacuum advance.
My 318 poly with virtually the same build as yours (3.23 rear, stock converter) was running 15.2 @ 93 mph which should be fast enough for a geezer.
With a 24.5" diameter rear tire (245/60/14) I cruise at about 2,900 rpm which is a sweet spot for the engine and is 65 mph.

With a taller tire you could drop those rpms to probably 2,750 which will be just on the cam. Any lower you'll probably have worse gas mileage as the engine won't be in it's efficient operating band.

I have 15” wheels with the 60 height. Suppose I could have stayed with 70’s or even a 65. Been thinking of another set of wheels and tires anyway; but then other things on deck for the Ply. Good memory! I’ve yet to tackle the distrib. Hope to this spring yet.
Just irritating driving at 3-grand for extended periods, took off the Flowmasters replacing them with the Hemi's and some improvement.
Thanks!