i bought a 78 300 straight 6 f-150 long bed from my parents and i think it has a car third member in it i won't put the truck in 4th gear until i get to at least 75 mph i am using a 4 speed overdrive rug transmission i was wondering what the stock ratio is i am sure it's not the trans because i had the old one blowup on me and i put a new one in it and it's the same THANK'S TO ALL chad

 

Some of these had a 2.75 ratio ON TOP of the OD trans. Not very practical. I have 3.50s with the OD trans and it's ok, not great with 31" tires.

There should be a tag on one of the studs holding your carrier in the axle housing, possibly about 5 o'clock. Get the numbers off that and it can be decoded.

There may also be an axle code on the sticker on the doorjamb.

 

Welcome to FTE

The AXLE code is on the second line of the Warranty Plate, which is located on the left door face below the latch.

Post what the code is.

Some of these trucks have Dana 44's with ratios of either 2.75-1 or 3.00-1.

Most of these trucks have a 9" rear end, the ratio can vary from 2.75-1 thru 4.11-1.

The Dana rear end has an inspection cover, the 9" does not.

There was a Ford ID tag on the rear end itself. Nowadays, it's usually missing.

On the Dana 44, the tag is under one of the bolts that holds the inspection cover on.

With the 9 inch, the tag is at 5 o'clock under one of the bolts that attaches the carrier to the axle housing.

Winding out the truck in 3rd gear to 75 MPH does not help the engine.

Regardless of the rear axle ratio, by 45 MPH, you should be in 4th.

 

yes the tag say's wdm bc2 8EE 00 9 386E and me and by bro jacked up the tire and we spun the tire one time all the way around and i get almost 1 1/2 turns on the drive line

 

WDM BC2 = Bronco '78, F100, F150 '75-'79. 9", 31 spline, non-limited slip, 3.00 : 1 ratio.

8EE doesn't seem right. If it's a 3.00, that should read "3 00".

Not to argue with "The Maestro", but with a 3.00, your 1:1 THIRD gear, and 225-75 x 15 tires, which are 28 inches in diameter, you should be turning 1620 rpm at 45 mph. Shift to .78 (or.79) OD and drop to 1263 (1280) rpm. If you are on the flat & have no load, you can shift at 45 no problem.

If you shift at 75 with your set up, you should be at 2700 rpm. You wouldn't want to drone across Texas at those revs, but it's hardly enough to cause the pistons to swap holes in a 300. Your shift to 4th at 75 should drop you to a more relaxed 2106 (2233)

Calculator here if you have a different tire or want to see the effect of gear changes etc.

Novak Conversions - Gearing & Gearing Math for Jeeps

There are also some calculators at the top of this forum, but the variables and OD entry aren't there.

 

8EE refers to this: Assembly date code: 8EE: 8 = 1978 / E = May / E = 5th week.

btw: WDM-BC2 = D6TZ4234A .. Axle Shaft-31 Spline

 

what year trucks with a good gearing have posi that i can use

 

Almost any year 31 spline 9 inch will work. Most trucks had several ratios optional, so you just have to check the ratio of the unit you are looking at.

As for the 'posi', Fords limited slips have had several names like Equalok and just plain limited slip. "Posi" is short for the GM Positraction, a similar limited slip unit.

Limited slip diffs many times use clutch packs to either hold or slip, depending on conditions. Since they have to slip sometime, they tend to wear. Once they were, they lose their "limited' factor and act much like an open diff.

So, given that the 9" went out of production so long ago, the odds of finding a fully functional limited slip at the scrappy become a bit long.

You can buy limited slip or locker units as well as gears and change it over that way, or you can search for another carrier, but I would strongly suggest you have it gone through before you install it. Bearings at least.

Good luck.