22s check your rear diff!
Hotshot
Joined: Jun 2003
Posts: 12,341
Likes: 4,366
From: SW VA
I think mine called for 75w-85, but 75w-90 is much more common to find and cheaper, so that’s what I went with. Won’t hurt a thing.
Mountain Pass
Joined: Mar 2022
Posts: 109
Likes: 53
From: NE Kansas
Fleet Mechanic
Joined: Apr 2015
Posts: 1,641
Likes: 507
From: Phelan CA
You have to look for someone selling a take off cover. As far as I know, Ford won't sell these covers to anyone by themselves.
You also will need new bolts. The thread is an M10x1.5 30-35mm long.
I went with OEM part# N803942-S439 from Ford.
You also will need new bolts. The thread is an M10x1.5 30-35mm long.
I went with OEM part# N803942-S439 from Ford.
Mountain Pass
Joined: Feb 2011
Posts: 192
Likes: 30
From: Upstate NY
I would check your owners manual. I thought the 3.55 was the 10.5 rear, which (according to my manual) uses 75w-85
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More Turbo
Joined: Mar 2022
Posts: 537
Likes: 224
75w140 won't hurt it a bit. You may loose .0001mpg. I pulled my I from from diesel truck resource. I would use Redline or Amsoil. If you have Limited Slip yes, buy the LS additive. If you have an electronic locker, don't add anything. I run 75w140 in both front and rear of both trucks. I tow heavy....never an issue. I even fo UOAs on the differential s.
Hotshot
Joined: Jun 2003
Posts: 12,341
Likes: 4,366
From: SW VA
Correct. I used 75w-90 as it’s easier to find/more common and cheaper.
More Turbo
Joined: Nov 2019
Posts: 550
Likes: 262
From: Northwest CT
Out of curiosity, does it matter which LS additive? Like do we have to use the Motorcraft stuff or will Amsoil Slip Lok work fine?
Anyone who wants OEM stuff, Rockauto has it.
EDIT: Oddly enough, if I take out the $20 renewal for my Amsoil account, Amsoil is cheaper than Rockauto by a few dollars.
Anyone who wants OEM stuff, Rockauto has it.
EDIT: Oddly enough, if I take out the $20 renewal for my Amsoil account, Amsoil is cheaper than Rockauto by a few dollars.
4wd Low
Joined: Feb 2022
Posts: 12
Likes: 5
I have a 22, F-250 Lariat with less than 1K miles. I have been hearing the clunk sound from the rear diff from the first day also. It is more so when you are cruising at low speeds, take foot of gas pedal and then depress it again. Feels like a play in the rear diff.
Laughing Gas
Joined: Mar 2007
Posts: 1,063
Likes: 329
From: Ontario
Chances are it's the slip yoke you're hearing, and that's normal.
Posting Guru
Joined: Feb 2018
Posts: 1,555
Likes: 516
There is play in the differential. That is a consequence of the ring gear backlash. When backlash is checked, you set up a dial indicator on the ring gear and rock the gear back and forth on the pinion gear without moving the pinion. That play allows the gears to work correctly as they heat up. Of all the differential setup specs, backlash is generally easiest to set as all you have to do is adjust the side bearings to move the ring gear closer or further away from the pinion. It just about is impossible to screw up. There is a spec range and if it's on the loose side, you would probably feel that slightly. But very slightly.
Lead Driver
Joined: May 2021
Posts: 5,843
Likes: 3,465
From: Uh oh, CA
I've seen this thread enough that I have finally ordered 4 quarts of 75 140 and will do a drain and refill once it gets here... lol! By the time I have it, I will have about 5500 miles on my truck. I guess I'll plan to do it again around 30k.