While gathering the parts and supplies for a rear end gear oil change I began to run into a little problem. Every parts store in town carried a 10 bolt diff gasket for a 2005 F150 4x4 but not a 12 bolt. I went to several other auto part stores to find the same puzzled look and no 12 bolt diff gasket. A Napa rep helped me find a 12 bolt gasket for a older Ford but looks are deceiving and this part was close but no cigar. I went ahead and did the diff fluid change and used some blue rtv as my new 12 bolt gasket.

Can anyone help to understand why I have a 12 bolt rear end in a F150. I have a 10 bolt in the front end. My door sticker states that I have a 3.55 Ls rear end but this too is incorrect. Nothing like pulling the diff cover on my 12 bolt rear end and seeing nothing but gears when I pull the cover off. No Ls no way no how is anything like that going on in that axle(LOL). I am going to assume that the ratio is the same as the front (3.55)but this is not a limited slip diff.

I started this project because my truck was shuddering in slow corners and most of the posts here pointed to either the LS gear oil and additive or the parking brake adjustment.

Oh, my truck only has 31000 miles on her. 4 speed auto, towing package and 17 inch wheels if this helps.


Thanks

E

 

A little more info on your truck would be helpful. Ford put 3 different rear axle assemblies in the 04-up 150's.

If you have a V6 or the 4.6 V8 then you got the 8.8" axle
If you have the 5.4 V8 then you got the 9.75" axle
If you have the 5.4 with the heavy duty payload package then you got the 10.25" axle with 7 lug wheels

All 4x4 get the 8.8 axle in the front regardless of the engine you have.

Since you have 3.55's, I'm guessing you don't have the heavy duty package, because they only come with 4.10's. And since you have the 10 bolt as you called it in the front, that is an 8.8" and the 12 bolt in the rear, I'm guessing you have the 9.75 in the back and a 5.4 under the hood.

Just looked at your gallery and I see that you have the 5.4 so you definitly have the 9.75" axle. And get rid of that stupid ricart badge on the tailgate.

 

RTV is the only gasket available.

 

I did get rid of that stupid Ricart badge this weekend and thanks for the update on the axles.