Can somebody please tell me how to find out what size diffs I have (not the gear ratio) I would liketo get some 4:56's but I need to know what size the diff is to order. I called the dealership they said they could not tell me without me bringing the truck in.

Any help would be great!

 

Look at the toe tag on one of the differential cover bolts. They'll say something like "88" or "975." The front differential on a 4x4 is an 8.8" axle, the rear is 9.75".

 

unless you have a 4.6 engine, then the rear diff is 8.8". All cases, Front differential is reverse cut.

 

Thanks for the inof I'll check it out after work.

 

not correct, if you have a 4.6 than you have the 8.8 but if you have the 5.4 than you have the 9.75, in most cases

 

umm, isn't that exactly what I said?

 

actually I am going to have to agree with bigtruck. The way you made it sound that 5.4's have the 8.8 which they dont. You said "unless you have a 4.6 you have a 8.8. so that means if you have a 4.6 you have 9.75 and 5.4 you have 8.8. It sounds like you know what you are talking about but just said it wrong is all. Thats all im pointing out. No problem.

 

I guess nobody saw the quote I was responding to which said:

that's why I quoted it in that post. Go re-read it again, but don't forget to read the quote first. There was a reason I put it in there...

Read slowly, try to get every word. Don't forget the comma and 'then'

 

To give you a perfectly clear and correct answer to your question, read this!

ALL FRONT diffs on the F-150 is a reverse rotation 8.8. DO NOT buy a regular 8.8 gear, it has to be reverse rotation.

The 4.6 trucks have the 8.8 rear, the 5.4 trucks have the 9.75. Only the 7700 lb GVW package F-150s get a 10.25 rear, but that option isn't available on an FX4, so don't worry about having that diff or option if you're unsure.