Swapping an 8.8" in place of a 9"?

[460]

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Is an 8.8" rear from a newer F150 the same overall drum-to-drum (WMS) width as the 9" in my '79 F150 2wd?

Is the u-joint the same size?

I'm wanting to swap in an 8.8", I think.

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[Lost]

Why ?? They have same bolt pattern and yes can be swapped . But the 9" is way stronger. Most here have not switched because of electronics (Speedo sensor) Also they r still way common and can fine gear sets way easier used.

But do what u want. If u have 1 laying around use it .There just a jiont swap to make driveshaft work What number I have not a clue. Good luck

 

[460]

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I'm on a budget build and can usually find complete rears in the local yards for $150. Sometimes I can buy complete parts trucks cheap too.

I'm swapping in a 5.0 HO (keeping the fuel injection) with an AOD transmission and I want to run 3.73 gears. I could go with 3.55 or 4.10, but 3.73 would be the best. I'd swap in an 8.8" with 3.73's and a trac-loc if it's cheaper than buying a 9" unit.

I know the AOD and 8.8" aren't the best choices, but this truck is very light duty and won't haul any heavy loads, and the truck weighs less than the car the donor engine and trans came from. I'm just trying to build a dependable "point A to point B" daily driver... on a budget.



Here's the engine I have. It has 79,xxx miles on it:

 

[Skandocious]

It would be a mistake-- the 9" is a lot stronger. But it CAN be done.

 

[TexasNomad]

I"m with them on that one.
The 9 is a superior rear end and easier to work on to.

 

[masterbeavis]

The spring perches might need to get moved, and or the ebrake cables might not be the same. The 9" is also a semi float rear end, the wheel bearings do not ride directly on the axle shaft, the 8.8 has the bearings riding directly on the axle shaft. If you break a shaft in the 8.8 it will spit out. Typically, if a 9" breaks, it will not spit the axle out, unless it breaks in between the bearing and the wheel flange.

 

[460]

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Fine, fine... I'll keep the 9". I may try to swap the gears myself in it. The gears are cheap enough that if it doesn't last long at least I'm not out big $$$.

I currently have 3.50 gears, which will work with my swap, but I lack any type of traction device. This truck gets horrible traction as a one-wheel-wonder.

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[Skandocious]

Well if you're going to swap in 3.73s then you have to take the carrier our anyways... Might as well replace it with a locker while you've got it out

 

[1973 F-100 4x4]

If you're going to put a locker in a daily driver, I would recommend a selectable locker that can be disengaged when you don't need it.
ARB makes a good air locker, but it requires an on board air compressor.
Eaton also makes an electronic selectable locker that is very reliable.
This will prevent tire scuff when turning corners, and excess wear on your rear axle components.
They are a little pricey though.
Usually around $600-$800.

 

[Skandocious]

Either that or just get a trac-loc/limited-slip. Better for a daily driver that gets occasion off-road use.

 

[surewhynot]

It's not hard to do a gear swap in the 9 inch. You do need access to a press and a dial indicator though.

And a beeg azz breaker bar & torque wench.

 

[460]

If you're going to put a locker in a daily driver, I would recommend a selectable locker that can be disengaged when you don't need it.

Either that or just get a trac-loc/limited-slip. Better for a daily driver that gets occasion off-road use.

Yeah, this is just a daily driver 2wd that will be on the street mostly. Occasionaly it will be in the grass or something, so I don't want to get stuck. Most vehichles I've owned have had a posi-type unit or a locker in them, so that may be why this open differential seems so odd to me.

It's not hard to do a gear swap in the 9 inch. You do need access to a press and a dial indicator though.

And a beeg azz breaker bar & torque wench.

Thanks man, I'm going to compare the cost of having one geared locally and then the cost of a DIY job and see what the difference is. I need to search Google for it too, I'm sure there's quite a few tech articles on regearing the 9".

.

 

[TexasNomad]

I know a place where you can get a how to video to rebuild 9s.
I think its like 30 bucks or so.

 

[masterbeavis]

Howabout finding a used third member??

 

[Skandocious]

Howabout finding a used third member??

Don't bother looking in Florida. Tony's third member is un-used.

 

[Blue Goose]

Don't bother looking in Florida. Tony's third member is un-used.