Rear Diff Fluid Change
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Fleet Mechanic
Joined: Jan 2006
Posts: 1,510
Likes: 7
From: Anchorage, AK
Rear Diff Fluid Change
Thinking about changing my rear diff fluid since she seems to "thunk" louder than usual when I turn left and right sharply.
I know that I will need friction modifier but how much and what fluid should I be using? If I change the front axle, I don't need modifier up there right?
Thanks guys.
I woke up this morning and found out I have a day off!
I know that I will need friction modifier but how much and what fluid should I be using? If I change the front axle, I don't need modifier up there right?
Thanks guys.
I woke up this morning and found out I have a day off!
Postmaster
Joined: Dec 2008
Posts: 3,340
Likes: 2
Guzzle has write-ups on the front and the rear oil changes: Welcome to guzzle's Rear Differential Maintenance Web Page. It pretty much explains it all.
Post Fiend
Joined: Feb 2007
Posts: 14,541
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From: Dallas-Ft. Worth
Yes and yes.... 75w-140 in the rear (most have FM in it already), and supposedly the same up front. When I asked the dealer, they said 75w-140 up front, but when I asked why, they said because Motorcraft quit making 75w-90. I would think whichever would work. Up there in the frozen north, I'd be tempted to run the lighter fluid...
Post Fiend
Joined: Feb 2008
Posts: 10,977
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From: Lancaster, Pa.
They sell the friction modifier at the dealer for about 5.00 for 4oz I believe, even if the new fluid has it in it already, mine needed a little bit more, Royal Purple 75-140 syn(F-M added) user here.
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Fleet Mechanic
Joined: Jan 2006
Posts: 1,510
Likes: 7
From: Anchorage, AK
Thanks for all the information guys. Next time I get down to the "big" town of Wasilla I will try to pick up all the right stuff.
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Posting Guru
Joined: Jan 2008
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From: Bridgewater, VA
If it's an 01, its Dana 50 correct? My understanding is 02 and up had 60's.
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Posting Guru
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From: Tiverton,RI
I went with the Mobil 1 syn. 75-140 in the rear and 75-90 in the front. It has the FM in it also and it worked out great, zero chatter now matter how tight I turn and instant posi every time.
Posting Guru
Joined: Mar 2009
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From: Tiverton,RI
This is something I've been trying to figure out too. My 01 came with a D50 according to the build sheet but, doesn't the D50 have 30 spline axle's? When I changed my hubs, the guy got me hubs for the 35 spline D60. I didn't realize it til I had the old ones off and when I counted, I found that I do indeed have 35 spline axles........? Any thoughts?
Logistics Pro
Joined: Jul 2009
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From: Lansdale, PA
This is something I've been trying to figure out too. My 01 came with a D50 according to the build sheet but, doesn't the D50 have 30 spline axle's? When I changed my hubs, the guy got me hubs for the 35 spline D60. I didn't realize it til I had the old ones off and when I counted, I found that I do indeed have 35 spline axles........? Any thoughts?
I had thought the F250s had the Dana 50 front until 02-03 and all the F350s had the Dana 60 front.
I was also curious if the front had hypoid grease instead of either 75-90 or 75-140. My diff tag is gone so I'm curious also. Ill probly use whatever synthetic is on the shelf anyway. Maine is not cold enough to need a debate on the lighter or heavier fluid.
While you have the diff cover off though, remember to check seals and bearings as well as make sure your vent tube is not plugged and long enough to be above the top of the tire.
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Rob.D
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Aug 4, 2008 09:21 AM
