Hello all. My 61 f100 has undergone some major transformations over the past year. I swapped in a 302 from a 93 mustang, along with the 5 speed that came with it. The problem is that the stock rear end has such tall gears that I can't take advantage of the power of the new motor -- not to mention I have yet to see 5th gear. My slick came with a 3 speed on the column.

Anyway, anyone know what the gear ratio of my truck is now? and what would be the ideal gears for my truck? (I'm interested in power and performance - I won't be towing anything).

Off hand I'm thinking somewhere between 3.50 - 3.83'... Would you guys agree? I don't know what the stock mustang ratio is.

Also, stupid question for some, but will my rear axle take new gears? I would rather not swap in a new axle if i don't have to.

Thank you so much!

 

Rich stop thinking & start digging. 1st, get under the truck to see if the small metal tag is still attached to one of the bolts that holds the center section to the axle case. It will have the ratio on the tag as it left the factory.

2nd On a garage floor if you can or very level ground with a friend at hand, hand roll the truck one complete tire revolution while counting the revolutions of the driveshaft. This will give you the actual ratio with all present.

Some may say jack up this or that wheel, just roll the truck on level ground.

The friend is there for just in case you try on not so level ground and can help keep the truck under control.





John

 

I'll look for the tag. The gears are super tall -- the truck bogs down when I take off from a dead stop.

Also do you know if any rear end can or cannot take a new gear set?

 

It is more about finding the gears, but there should be swaps out there for just about any domestic rear end. That being said, just make sure that you go to someone who has a LOT of experience building them or it will be a loud unpleasant experience.

 

Many 1961 F100's with a 9" rear axle & a M/T have either 3.70's or 3.89's, but other ratios were available.

Post the AXLE code stamped on the Warranty Plate, located inside the glovebox door.

While not an absolute after 40 + years, when decoded, the original ratio will be known.

The Ford ID tag is under one of the bolts that retains the carrier to the housing, usually at 5 o'clock.

But, today...many are missing.

The 9" Ring & Pinion gears (there's over 10 ratios) were used in: 1957/79 Passenger Cars / 1957/83 F100's / 1966/86 Bronco's / 1969/86 E100/150's / 1975/86 F150's.

 

Rich, What engine did you pull out of the truck?

I think you have timing/tuning issues. Even with a 3.25 ratio that may have been behind a 292, it should not bog in 1st gear as described.

Yes gears can easily be swapped if you have a 9in rear.

Bill mentioned 3.70 & 3.89 ratio, either should be great behind your engine if it is setup properly.



John

 

Yes I had a 292 with a 3 speed on the tree. It doesn't bog per se, but you really have to feather the clutch. And it ain't ever chirping the tires in the way it is right now.

I will look for the tag -- it just feels so tall right now. And please correct me if I'm wrong, but 3.70 gears are taller than 3.08's, right? Meaning that the higher the number, the quicker the truck will be out of the hole?

 

I guess what I am trying to say is that with the 3 speed and the 292, I could cruise the highway in 3rd gear at 65 mph. With the 302 with a 5 speed, i can still cruise in 3rd gear at 65 mph. 4th is like 80 and 5th -- only god knows. I would like to get this back down to how the mustang was, where I use 5th for highway cruising. I am assuming shorter gears would do the trick?

 

Rich, Let's get your ratio before we shoot anymore holes in the dark, OK?




John

 

The lower the number the taller the gear. 3.70's and 3.89's are not tall gears.

 

No tag. Gonna have to do it the old fashioned way.

 

It's pretty easy to hand roll the rear tire on a garage floor while watching the DS rotate. I have done it several times to different trucks.





John