Rear diff fluid
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New User
Joined: Aug 2011
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Rear diff fluid
I have a 2002 psd and looking to change the diff fluid in the rear, does anyone know the capacity or how often your suppose to change fluid? How to tell if I have limited slip rear? thanks
Molon Labe
Joined: Dec 2006
Posts: 5,272
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From: Alaska
Jack up the rear end and spin a tire, If they both move in the same direction you have a LS, if they move in opposite directions you have an open rear.
Not sure about the change interval. I would also like the answer.
Lead Driver
Joined: Jan 2007
Posts: 6,708
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From: Kiowa CO
Here's a great write-up. Welcome to guzzle's Rear Differential Maintenance Web Page
The Sterling 10.5 diffs (SRW) take 3.5 quarts of 75w-140 synth gear oil.
The Sterling 10.5 diffs (SRW) take 3.5 quarts of 75w-140 synth gear oil.
More Turbo
Joined: Jul 2011
Posts: 594
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From: Full-time RV
And the DRW Dana diffs take 4 quarts of 75W-90 synth gear oil. Just in case you have a dually. I followed guzzle's instructions and ended up back at the auto parts store swapping 75W-140 for 75W-90, after I noticed my diff cover looked different than the one on guzzle's page.
Also, for the DRW, the filler is the plug in the middle of the diff cover, not on the front part of the diff like the Stirling units.
Also, for the DRW, the filler is the plug in the middle of the diff cover, not on the front part of the diff like the Stirling units.
Senior User
Joined: Mar 2009
Posts: 354
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From: Patterson, Ca.
Here's a great write-up. Welcome to guzzle's Rear Differential Maintenance Web Page
The Sterling 10.5 diffs (SRW) take 3.5 quarts of 75w-140 synth gear oil.
The Sterling 10.5 diffs (SRW) take 3.5 quarts of 75w-140 synth gear oil.
9 ECHO 1
Joined: Aug 2009
Posts: 12,467
Likes: 58
From: Missouri
As far as change interval... Ford says not to touch the things. They are "lifetime"...
However, I, along with most people, thing that all fluids should be changed. I did mine at 150k miles and it looked good. It really doesnt need to be done often, but shouldn't be forgotten.
However, I, along with most people, thing that all fluids should be changed. I did mine at 150k miles and it looked good. It really doesnt need to be done often, but shouldn't be forgotten.
More Turbo
Joined: Jul 2011
Posts: 594
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From: Full-time RV
I agree with Trey. I did mine at 147k miles and it looked good, as well. Not even much on the magnet. I'll probably do mine again in 150k miles just because.
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Senior User
Joined: May 2011
Posts: 223
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From: West ID
I think the interval really depends on a lot of factors, like type of driving, towing heavy, deep water crossings, and maybe even climate (wet, dry, dusty, etc). I just change my diffs every 40k or so, I use the Mobil 1 75w-140 synthetic in the rear that comes with friction modifier and I've never had to add any more, and M1 75w-90 synthetic up front. It always comes out looking good, but it's cheap insurance IMO.
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9 ECHO 1
Joined: Aug 2009
Posts: 12,467
Likes: 58
From: Missouri
While youre under there, do the front too (if you are 4x4). Also, since you are draining the fluid anyway.. might as well do something about the diff cover. You can replace it with many aftermarket options, or the 08 Diff cover will fit (you will need new bolts) and offers superior heat dispersion.
Or, if you arent worried about heat and just want it to last longer, you can do what I did and that is just paint the covers with some good rust preventing paint.
My little after the fact, post. Has some cool before/after photos.
https://www.ford-trucks.com/forums/1...-bit-diff.html
Or, if you arent worried about heat and just want it to last longer, you can do what I did and that is just paint the covers with some good rust preventing paint.
My little after the fact, post. Has some cool before/after photos.
https://www.ford-trucks.com/forums/1...-bit-diff.html
Lead Driver
Joined: Jun 2003
Posts: 8,298
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From: Damon (South East Texas)
6.9 pts (approx 3.5 qts, as mentioned) The recommended interval is every 60k miles. That's how often I do mine. The number on the differential ID tag will have an "L" instead of a "dot" on the ratio when it is equipped with a LSD. If adding the friction modifier to a LSD, start out with a small amount first and test drive. Gradually add more until chatter is eliminated while turning. Too much is not a good thing and will reduce the grip of the clutches.
Cargo Master
Joined: Jul 2011
Posts: 2,675
Likes: 975
From: Walpole, MA
6.9 pts (approx 3.5 qts, as mentioned) The recommended interval is every 60k miles. That's how often I do mine. The number on the differential ID tag will have an "L" instead of a "dot" on the ratio when it is equipped with a LSD. If adding the friction modifier to a LSD, start out with a small amount first and test drive. Gradually add more until chatter is eliminated while turning. Too much is not a good thing and will reduce the grip of the clutches.
Also an 08 diff cover, like 60-65 bucks at most dealers, and some 5/16-18x1.25 bolts and your good. Great addition, I recommend it to anyone!
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Thanks for the input guys. My thought is if your towing especially heavy loads its a good idea to change the fluid. I understand when they say lifetime fluids but you have no idea what kind of life that truck is going to have, you can't simulate real world situations. My buddy has the same truck i do 02 psd ext cab sb, when the truck is unloaded and no trailer, he gets a howl from like the driveline it sounds like around 60 mph. On the gas you can hear it when you let off its quiet, do you think he might need a diff fluid change?
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May 31, 2009 08:40 AM
