2003 f150 5.4 fx4 with an H9 designation for the rear axle which I think is supposed to be an 8.8 limited slip.
if I'm wrong someone please correct me. After I purchased all to oil, friction modifier and gasket then climb under the truck, this is what i find. Can someone please tell me what differential i have?

Door tag

Rear differential

 

9.75 3:55 l/s .

 

So somewhere along the someone changed the diff.?
does it look like a limited slip or open?

 

H9 means 3:55 limited slip it can be either a 9.75 or an 8.8, yours is a 9.75. It's probably the original diff.

 

That is an open differential you have there
No room for spring or clutch packs in that carrier
The big 10.25 ones have a 2 piece bolt together carrier
The smaller 8.8 and 9.75 axles have an exposed spring surrounding the pin
Yours is open

 

So how will having an open differential effect my 4 wheel drive?

 

I believe the ABS will be trying to brake the slipping wheel. Therefore giving more traction to non moving wheel on the other side. My truck is a XL model with rear 8.8 limited slip. The front is open. I would have rather had front with limited slip as well.
My daughter has a 2015 Expedition 2 wheel drive with open rear diff? Not sure why that is?

 

An open diff will not affect the 4x4
That is what most 4x4s have anyway (an open diff)
Posi just spins both rear wheels at the same time / speed
Most 4 wheel drives these days, you jack up one wheel on a hill and the vehicle will roll away
Unless you have a posi, you cannot drive off a bottle jack

 

I just jacked up the rear end and both wheels turn the same direction, can't hold either one from turning or try to go the other direction

 

If both wheels are turning in the same direction it's a posi. Do they lock when you put it in park?