The Ford Barn

scooder · 07-12-2015, 01:00 PM

Alan, he's talking overdrive type trans, the F150 four speed is direct drive in third and overdrive in fourth, like fourth and fifth gears in a T5.
So I guess his question is about the ratio of the overdrive gear in different trans.
Will have to say this, you will not kill a flathead at 70 mph with a 4.11:1 rear gear. Sure it'll be buzzing some, but it'll live on fine. An overdrive will drop the rpm to what most would be more comfortable with. A Flathead V8 and a Model A engine are almost from different universes. A stock V8's valve springs will govern the high rpm (too about 5000-5500) at this rpm the engine won't eat its self, most folks won't go near that rpm. A stock model A engine can easily get to a rpm level that will shorten the life considerably. And that rpm is a lot lower.
Martin.

07-12-2015, 01:00 PM	#4
scooder Senior Member Join Date: Jul 2010 Posts: 2,595	Re: 1936 Coupe Tranny options ?? Alan, he's talking overdrive type trans, the F150 four speed is direct drive in third and overdrive in fourth, like fourth and fifth gears in a T5. So I guess his question is about the ratio of the overdrive gear in different trans. Will have to say this, you will not kill a flathead at 70 mph with a 4.11:1 rear gear. Sure it'll be buzzing some, but it'll live on fine. An overdrive will drop the rpm to what most would be more comfortable with. A Flathead V8 and a Model A engine are almost from different universes. A stock V8's valve springs will govern the high rpm (too about 5000-5500) at this rpm the engine won't eat its self, most folks won't go near that rpm. A stock model A engine can easily get to a rpm level that will shorten the life considerably. And that rpm is a lot lower. Martin.