I was wondering, how different are 2003 Harley differentials from regular F-150 Screw differentials?

Ever since I slapped on some 22's on my Screw, it has greatly reduced take off power, and also down shifts quite a bit on steep hills.

Are both differentials 8.8? What gears come stock onHarleys? Are Harley posi units as strong as aftermarket units? Do Harley diffs have more splines than F-150's?

I want to upgrade my differential, before I add more performance parts to my Screw, so any help will be greatly appreciated.

4point6

 

9.75 rear just like the lightning and HD F150s that are non 7700 lb GVW models. Good luck finding a locker that isn't 600 bucks for it. Limited slips are a plenty.

 

Since you added bigger wheels and tires, to keep your stock "pick up" off the line you will need to swap gears. I don't know what the harleys come with stock but I'm guessing it can't be over 3.73's. I would go with at least 4.10's maybe lower depending on how much more you want to spend on gas!

 

Thanks Monte Carlo, and Fordninja for your input. Monte, so you're saying lightnings, harleys, and f-150's come with the 9.75? I though they came with the 8.8......

My local high performance shop quoted me around $750 for an Eaton posi unit and 4.10 gears installed....is that a good price?? I would guess I could get a Harley differential from a junk yard for around that price too; but if I have to also install gears in it, I'm better off rebuilding the one I got on it now.
What do you guys think?

Thanks,
4point6

 

That's not bad for parts and installation. I paid about about $240 for a Ford LSD alone, and that was a good deal. Figure another $250 for gears and $250 for labor.

 

Thanks for the reply Jordan. I see you're packing a Procharger; how do you like it? Is it worth it?
My ultimate goal is to slap one on my Screw. The same shop quoted me $4,200 for an intercooled Procharger, turn key..... is that a good price?

Thanks,
4point6

 

I wish I had bought the blower to begin with. The truck is so much more enjoyable to drive, I can't get enough of it.

If that price is for a new Procharger plus install, then it seems like a great deal. I think retail is like $3800, and most shops charge at least $1000 to install it.

If you have the coin you should upgrade your fuel system (injectors, fuel pump, MAF and chip/tune) as well, for the most power. Or you can go the used kit route that I took, the money saved went to the fuel system mods.

Check out the superchager forum. Lots of good info for you in there!

 

Jordan, I currently have a power programmer, K&N intake, and Magnaflow which helped quite a bit. Yes it's a brand new kit installed. It's kind of hard to dish out $4,200 with a wife, kids,house and car note, but hopfully in the near future.