I Have 1996 standard 5 speed f150 with code 18 rear end . It's open differential. My parts truck is a 1990 automatic f150 with a code H9 rear end , witch is limited slip . I'd like to put the h9 in the 1996 f150. Would everything work ? Is gearing different?

 

Yes gearing is different. It would work if your truck is a 2wd but it looks like yours is a 4wd. Therefore it would not work unless you change your front gears to 3.55. H9 is 3.55ls, 18 is 3.08 non ls.

 

So I'd have to change the gears in the front deferential ?

 

yes, they have to match if you want to use 4wd

 

Would that be big job to change gears in front diff ?

 

Not too terribly hard, but You have to put the new gears in just right or they will wear weird and you will need to replace them earlier.

 

Gearing has to match or you risk destroying the gears, transfer case and transmission. Might be easier if you found a carrier and housing and bolt it in place of your old one.