gear ratio choice and questions

pugsly · Post by **pugsly** » April 11, 2011, 9:25 pm

I have the stock rear end in my 65 lwb f100. I have an AOD installed and belive my ratio to be 3.20:1 i want more low end. thinking of 3.89:1 just dont know what bearing size, splines, etc. it is. Is there a way to tell before I tear it down?

Post by **Greg D** » April 11, 2011, 9:44 pm

Jim,
I believe our trucks were generally built with 28 spline rears.
3.73:1 would be the stock performance gearset for a 5.0 Mustang with an AOD - that should give you a little food for thought.

pugsly · Post by **pugsly** » April 11, 2011, 9:50 pm

thanks greg. i am trying to figure out what the pinion bearing diameter is. I see all these different sets. some have a bearing on the rear of the pinion gear. some don't. i am pretty confused on this

Post by **Greg D** » April 11, 2011, 9:54 pm

I'd just look for a good 9" center section and swap it out. Should be pretty easy to come up with a 3.73 or 3.89 set from a yard.

cdherman · Post by **cdherman** » April 11, 2011, 10:38 pm

Greg D wrote:I'd just look for a good 9" center section and swap it out. Should be pretty easy to come up with a 3.73 or 3.89 set from a yard.

That's right. Unless you want limited slip, you should be able to just find an old center section and swap it in.

Of course, an awful lot of old iron is just getting melted down these days....

frdnut · Post by **frdnut** » April 13, 2011, 10:14 pm

Greg D wrote:I'd just look for a good 9" center section and swap it out. Should be pretty easy to come up with a 3.73 or 3.89 set from a yard.

Agreed..That way if you don't like it you can always swap it back again..

dotcentral · Post by **dotcentral** » April 13, 2011, 10:27 pm

frdnut wrote:
Greg D wrote:I'd just look for a good 9" center section and swap it out. Should be pretty easy to come up with a 3.73 or 3.89 set from a yard.
Agreed..That way if you don't like it you can always swap it back again..

Easiest way to go. Hit the pull-a-part type places and see if you can find a 6 cylinder truck, those usually had the steeper gear sets. You can get the door tag info here: http://home.earthlink.net/~threynolds2/ ... s6166.html

Assuming the pumpkin hasn't been swapped out and tag is on the door, easiest way too see what the potential donor truck has.