I have a 07 F150 Lariat Supercrew 4X4 with the 5.4l Flex motor. I was in a accident which bend the rear axle. Since its easier to drop the whole rear end out and throw a new complete one in that is what the shop is doing. I got a call telling me they located a FX4 rear end with 1,000 miles on it.

He said everything was the same but didnt know about limited slip. What happens if my old one had it and the new one does or vice versa? Will it hurt anything? I believe he said the FX4 rear does but he didnt know about the Lariat.

Any help would be appreciated

 

If your original had it and the new one doesn't, it will not hurt anything, but you will not like it. Especially in rain and snow. Also, it better be the same ration as your front.
If it is the reverse, where you did not have it before and this one does, you will definitely be getting a better rear.

 

It wont hurt anything but If it doesn't have the L/S diff the truck will only pull with one wheel.
As long as they both are the same size rear-end the Differential is interchangeable.
So if the 07 has Limited slip and the replacement does not ,you can have the L/S diff from the 07 put in the replacement rear-end.

Phil

 

I know for sure the new FX4 one does but Im not sure about the original(Im sure it did also)

Are there any other things to watch for when swapping rears? I know he got same size/gear ratios/etc so that should all be fine.

 

What year did he get? 07 or a different year? Not sure if there were any differences between 04 and 08, but if the same year, it should not be a problem. Just make sure he changes out the fluid and puts in 75w140 and adds friction modifier.