f100 9" 2800lb vs 3750lb

[nthe10s]

Hello,
Been on the lookout for a 9" from a 1981-83ish f-100 for my 69 Ranger. Want it for the wider stance and 5 on 4.5 bolt pattern.

Found a 1982 f-100 in a local yard. Door tag says "01" Comes out to a 2800lb rating 9" So my question is what is the difference between the 3750lb and 2800lb rated axles? 28 or 31 spline? Housing thickness? Strength issues?

Want a tough one!

Thanks everyone!

[ultraranger]

Hello,
Been on the lookout for a 9" from a 1981-83ish f-100 for my 69 Ranger. Want it for the wider stance and 5 on 4.5 bolt pattern.

Found a 1982 f-100 in a local yard. Door tag says "01" Comes out to a 2800lb rating 9" So my question is what is the difference between the 3750lb and 2800lb rated axles? 28 or 31 spline? Housing thickness? Strength issues?

Want a tough one!

Thanks everyone!

'80-'83 Bullnose F100 9-inch rear ends were available in the trucks with a 5 x 4.5" lug pattern but not all '80-'83 F100 9-inch rears had the 5 x 4.5" lug pattern. Some '80-'83 F100 9-inch rears also had the 5 x 5.5" lug pattern so, verify the lug pattern is the smaller bolt circle.

All '67-'72 Bumpside F100s with a 9-inch rear end had 3300# 28-spline axles. Only the '68-'72 F100s with the Ford 9-3/8" rear ends came with 31-spline axles (either 3300# or 3600# rated axles --depending on open or Traction-Lok differential, respectively). MOST Dentside 9-inch rears had 31-spline axles but there were also some with 28. All Bullnose 9-inch rears from 1980 through 1986 had 31-spline axles.

The higher the axle pound rating, the heavier the load it can handle. The Bullnose 9-inch rear end housing is a robust design.

An "01" axle code for an '82 F100 9-inch rear end will be for a 31-spline open (single track) differential with 2.75:1 gears.

[nthe10s]

I have verified the bolt pattern. Should be good on everything. I was just confused on the different weight ratings. Not super excited about the 2.75 open diff, but that's only temporary.
So for about $100 should I pull the trigger??

Thanks for the reply ultra!

[ultraranger]

I have verified the bolt pattern. Should be good on everything. I was just confused on the different weight ratings. Not super excited about the 2.75 open diff, but that's only temporary.
So for about $100 should I pull the trigger??

Thanks for the reply ultra!

For $100.00, that's cheap.

I'm going a little different route on my '69 F100 Ranger. I have an '81 F100/F150 9-inch rear end that has the 'Torino' style large axle bearing housing ends. --3/8" diameter backing plate bolts on a 3.56" x 2.00" 4 bolt flange pattern, as opposed to the current 1/2" backing plate bolts on a 3.50" x 2.375" 4 bolt flange pattern. I also gave $100.00 for this Bullnose rear end. Wrecking yard owner was asking $150.00 for it.

This '81 Bullnose 9-inch rear end currently has 31-spline axles with a 5 x 5.5" lug pattern, single track differential and a really wimpy set of 2.47:1 gears. I'm going to install a custom set of 31-spline axles with a 5 x 4.5" lug pattern. The 'Torino' style flange is directly compatible with bolting on '95-'01 Explorer rear disc brake assemblies. I'll replace the 2.47 geared 9-inch single track 3rd member with the Daytona 9-inch N-case Traction-Lok 3.50 geared 3rd member I have. On the front, I'll have the '77 F100 front rotors redrilled from a 5 x 5.5" lug pattern to a 5 x 4.5" pattern to match the rear. --this will give me a LOT more and better looking wheel choices to choose from, compared to 5 x 5.5" pattern wheels.

In your case, if you wanted to run rear discs and if you have an '80-'83 F100 9-inch rear end with the 5 x 4.5" lug pattern, you can install '94-'04 Cobra Mustang 11-5/8" ventilated rear discs and calipers with a set of adapter brackets that are available from Currie Enterprises.

[nthe10s]

I ended up grabbing it on Saturday. Total around $115. It's ugly but it should work.
I have a CV parts car that will be donating it's front suspension. I'd be interested in the explorer brake setup. Explorers are all over still. I want to be able to run 15" drag wheels so I don't want too big of rear brakes.
I will be going to aftermarket axles and center section before it's over. But this should be a near bolt in and easy to get rolling and fitting wheels.

[ultraranger]

The CV front rotors are 12" in diameter. As a general rule, you need at least 4" greater wheel diameter than the rotor diameter. This means you would need at least a 16" diameter wheel to clear the CV front calipers --17" would most likely be better.

The '82 9-inch rear end you have has the old style large bearing 1/2" backing plate bolt flange pattern --3.50" horizontal flange pattern by 2.375" vertical pattern (Explorer rear discs requires a 3.56" x 2.00" 4-bolt flange pattern with 3/8" backing plate bolts). The 9-inch rear end you have isn't compatible with the Explorer rear disc brake assemblies but, it is compatible with the '94-'04 SN95 Cobra rear disc brakes when using the adapter brackets I had previously mentioned.

http://www.ford-trucks.com/forums/14272 ... st16149710

[nthe10s]

Just did a quick measurement on the backing plate. 2" x just over 3.5" So looks like I may be in luck on the explorer swap!?!

[ultraranger]

Just did a quick measurement on the backing plate. 2" x just over 3.5" So looks like I may be in luck on the explorer swap!?!

What is the diameter of the (4) backing plate bolts per side on that rear end --3/8" or 1/2"?

[nthe10s]

Haven't pulled it apart. Pretty sure they are 3/8" though.

[Bronco_77]

I'm not real sure what I've got any help would be greatly appreciated. I got a rear end from my cousin who runs a junkyard he said was out of a 80-83 f-100. I tore it down today and it has 31 spline 5x4.5 axles but after checking the backing plate flange bolt pattern it shows to be what yall are calling the Tornio style. They are 3/8 volts and the pattern seams to measure out to it. If this is so will the explore swap work and what is this thing out of.