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....I have an '81 Bullnose 9-inch rear end assembly that has a stock set of 2.47:1 gears in it. If you had about 5 miles of straight road, could probably get the truck up to about 140.
It would probably be even more of an epic adventure if you had sloppy steering, suspension and brakes.
This is the '81 9-inch rear end I have with 2.47:1 gears, 31-spline single track differential and with a 5 x 5.5" lug pattern. The plan is to eventually replace the stock 31-spline 5 x 5.5" lug pattern axles with a custom pair of 31-spline axles with a 5 x 4.5" lug pattern.
This rear end housing has the 'Torino' style large axle bearing end flanges (the 4-hole backing plate bolt pattern is 3.562" x 2.00", compared to my current old style large axle bearing backing plate bolt pattern of 3.500" x 2.375"). The 'Torino' end flanges will make it possible for me to bolt a set of Explorer rear disc brakes onto this 9-inch rear end housing.
I would get the front rotors machined from the 5 x 5.5" lug pattern to a 5 x 4.5" pattern. Once everything was swapped over onto the truck, I would have power 4-wheel discs and a LOT more and nicer wheel choices to choose from than the limited number of wheels that are available for the 5 x 5.5" lug pattern --since currently, I'm just running a stock set of (black) '92-'96 Ford F150 wheels.
I had an 81 Supercab with an anemic 351m and those 2.47 gears. It turned like 1300 RPM at 70. Got crappy mileage, and had trouble pulling my boat up a steep boat ramp without spinning the right rear!
2.75 is wrong for FE 3 speed tranny. 1st to 50 mph, 2nd to 70 mph and don't think of hitting 3rd unless you doing 70. I did drive it from Dallas to Tupelo and got 23 mpg with the a/c on at 85 mph. BAD for in town driving.
2.75 is wrong for FE 3 speed tranny. 1st to 50 mph, 2nd to 70 mph and don't think of hitting 3rd unless you doing 70. I did drive it from Dallas to Tupelo and got 23 mpg with the a/c on at 85 mph. BAD for in town driving.
i don't understand, are you saying that 2.75 is good, or that it is awful? i definitely cant get up to 50 in first with my current set up. hell, i can barely get up to 60 all the way though, i don't have a tach so im not sure what RPM's im running at that speed, but i drive her pretty easy. id love to see myself cruising at 65 comfortably at a lower RPM, i don't expect it to be as low as my car, but if i could be in the 2500 +/- range i would be elated. I guess i should order a tach to see exactly how im performing right now.
2.75 is a very good road gear. Acceleration department is lacking some, but with only 3 gears and no overdrive, you can't have both acceleration and low rpm cruising.
2.75 is a very good road gear. Acceleration department is lacking some, but with only 3 gears and no overdrive, you can't have both acceleration and low rpm cruising.
At the rear edge of the door, there should be a warranty plate rivited to it. Assuming the plate is still there and if the door is original to the truck and the gear ratio has never been changed out in the rear end, there's a code under the "Axle" heading on the tag. This code will tell you what ratio the gears are in the rear end.
Also look to see if by chance the tag is still on your rear axle 3rd member. It will tell us what ratio and if it's an open or a locker. Also I'd sray the leaking area with brake clean to get it dry. Then watch to find out if it's the gasket leaking or from under one of the nuts that holds the 3rd member to the housing. There are 3/8" copper sealing washers supposed to be under those nuts.
this is all awesome info, i will be under the truck tonight and ill snap some pics to upload. im pretty sure its all original because its all the same rusty blue color haha.
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