I was under my 1980 f150 today cleaning it up and getting it ready to put my 351C in. The truck originally had a 351M in it. After I was done pressure washing the twenty plus years of grease and dirt out from under it i happend to look at the rear diff tag and it said the gears were 2.75. thought that could'nt be then proceeded to find that tag was right, it was 2.75. I'm thinking that this may not be thr original rear end in the truck now. I always thought that all the 80 - 96 f150 4x4's came stock with 3.50's. There was no tag on the dana 44 IFS in the front for me to compare it too. I'm hoping the on ly thing I gotta do is swap ther rear diff. I would appreciate the info fellas.
IF YA AIN'T EVER BEEN STUCK, YA AIN'T BEEN 4WHEELING

 

so jack up the rear end mark a tire and count how many revolutions you have to turn the driveshaft (by hand) to get 1 tire revolution.

 

>so jack up the rear end
>mark a tire and count
>how many revolutions you have
>to turn the driveshaft (by
>hand) to get 1 tire
>revolution.



already done that....... they are 2.75 s

 

she must fly on the hiway

 

i have a 1980 ranger f-150 explorer with a 400 cui engine
it has a stock 3.51 in the rear
i don't know if the explorer package would beef up the rear up but that's what i have.

 

>she must fly on the hiway
>

I bought the truck in pieces, an now she's bout together..she might fly on the highway....... but she's gonna sink like a C!@#y in a mud hole with them kinda gears....

 

Yeah its the right number. In 80 FORD used higer gears for better hiway driving. My 82 came stock with 3.00 gears. FORD made up for the high rear gears with low geared trans. and transfer case. Swap those out for some 3.55's you can tell the differance.

 

Do you still have the build tag on the driver side door jamb? Under rear axle you should have a two digit alpah-numeric code. The lowest ratio I can find is the 3.00 with a code of H7 for 1980. I do believe that Ford only sold 2WD units and the three speed with the 2.75's. That was their economy model. The 3.50's were the deal in the 4WD, but not a gaurantee.

Looks like you have a custom swap because I can't find anywhere that Dana built a 2.75 and the lowest I can find is a 3.08 for the 44. Have you tried this thing in 4WD and how the heck does it work?

-Kerry

 

2.75 was the standard axle ratio for F150's back then. The basic reason for the low numerical ratio is emissions. By having the motor turn slower, the oxides of nitrogen are reduced and thus the federal government allowed Ford to sell the truck to the public. Lots of counterproductive engine/drivetrain developments came along to try to reduce engine emissions before a decent EFI system was available and this was one of them. The low first gear in the manual trannies made the effect less noticeable out of the hole, sorta like a higher numerical ratio with overdrive.

 

[updated:LAST EDITED ON 14-Mar-02 AT 10:43 AM (EST)]Not discounting what you say slimersoup, but this is a 1980 4x4. Like I said in my previous post I can't locate anywhere that DANA built their DANA 44 fronts with a 2.75 gear ratio.

I know that emissions were a key reason to have lower gear ratios, as was the gas mileage issue. My parents and I owned a '76 Granada with the 2.75 9" and a 250-6. We could get 22 mpg (if I didn't gun it) in Colorado. Just take for ever to get to 70mph.

-Kerry