Limited Slipped
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Joined: Jan 2009
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From: Yukon, Canada
Limited Slipped
I did a quick search and couldn't the exact answer to a what will probably be a silly question on a limited slip rear end... Here's the short version. Had a leaking rear wheel seal and knew my rear diff fluid was ready to be changed. About to head out on a trip with camper and boat, so, I had both rear wheel seals replaced, and diff fluid changed. I have a limited slip setup (from factory), but, was told that it must not be working because with the truck on the hoist and turning one rear wheel, the other rear wheel turns the opposite direction. As a result, I don't need friction modifier... Maybe I'm getting old, I thought the other side always turned the opoosite direction when in the air? I'm also wondering why we add friction modifier if you can test to see if it's working when the truck is in the air without the friction modifier? sorry, turned out to be long version.
It's a 2006 F350 CC LWB Dually, 100% stock... Thanks for any insight!
It's a 2006 F350 CC LWB Dually, 100% stock... Thanks for any insight!
Posting Guru
Joined: Jul 2005
Posts: 1,617
Likes: 4
From: Denver, Co
Per pages 287 & 289 of the 2006 Owners Manual: (Forgive me, I don't remember which axle comes on the duallies.)
Now, having said that, the general consensus is that 8 oz. is probably too much friction modifier. One of the more popular strategies is to add 4 oz. and take a test drive with the windows down & stereo off. If you hear the clutch packs chattering as you make corners, you need a little more modifier. Add in 2 oz. of additional modifier, and take another test drive. Lather, rinse, repeat.
Have a great weekend!!
F-250/350 (10.5 inch axle) - 6.9 pints Motorcraft SAE 75W-140 Synthetic Rear Axle Lubricant
F-350 (Dana 80) - 8.5 pints Motorcraft SAE 75W-90 Synthetic Rear Axle Lubricant
Both entries have a #1 footnote on them which tell you:F-350 (Dana 80) - 8.5 pints Motorcraft SAE 75W-90 Synthetic Rear Axle Lubricant
"1 Add 8 oz. (236 ml) of Additive Friction Modifier XL-3 or equivalent
meeting Ford Specification EST-M2C118–A for complete refill of limited
slip axles. Ford design rear axles contain a synthetic lubricant that does
not require changing unless the axle has been submerged in water. Dana
rear axles also contain a synthetic lubricant but do require a change.
Refer to your scheduled maintenance information for change intervals
on Dana rear axles."
meeting Ford Specification EST-M2C118–A for complete refill of limited
slip axles. Ford design rear axles contain a synthetic lubricant that does
not require changing unless the axle has been submerged in water. Dana
rear axles also contain a synthetic lubricant but do require a change.
Refer to your scheduled maintenance information for change intervals
on Dana rear axles."
Now, having said that, the general consensus is that 8 oz. is probably too much friction modifier. One of the more popular strategies is to add 4 oz. and take a test drive with the windows down & stereo off. If you hear the clutch packs chattering as you make corners, you need a little more modifier. Add in 2 oz. of additional modifier, and take another test drive. Lather, rinse, repeat.
Have a great weekend!!
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New User
Joined: Jan 2009
Posts: 9
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From: Yukon, Canada
ok, good to know. can i assume the LS is working if the wheels are turning in opposite directions (when i spin one) with the truck on a hoist or does that just confirm the diff is between the wheels? there is no friction modifier in the rear diff fluid as it is right now. i just took a little test drive to the high schools paved parking lot and turning as tight as i can with a crew cab long box dually, i hear nothing from the rear end. i never noticed any problems getting out of anywhere this winter - really have no idea if the LS is working or not...
Post Fiend
Joined: Mar 2009
Posts: 11,798
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From: Mt. Shasta California
Take it to a gravel/dirt road. Stop, put your foot on the brake, hit the gas and go back and look at your tracks. Sounds like you don't need modifier which you can overdo to where it is counterproductive.
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Joined: Jul 2002
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From: Long Island USA
Well, that's not entirely true.
With a stock Ford Traction-Lok limited-slip, apply about 25ft/lbs of torque to the wheel, and the clutches will slip and allow the other wheel to spin in the opposite direction.
Without applying that much torque, the other wheel should spin in the SAME direction with the transmission in neutral.
But with both wheels in the air, and the transmission in park (or a manual in gear), if you can easily spin one wheel and the other one spins the other way, either the clutches are TOAST or there is no stock Tracition-Lok limited-slip in there. (not going to get into gear-driven lockers that will allow that to happen)
Lead Driver
Joined: Jun 2007
Posts: 6,757
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From: Corvallis, OR
Come and test my limited-slip, you can't turn one wheel and have the other turn the opposite way with it in park
Well, that's not entirely true.
With a stock Ford Traction-Lok limited-slip, apply about 25ft/lbs of torque to the wheel, and the clutches will slip and allow the other wheel to spin in the opposite direction.
Without applying that much torque, the other wheel should spin in the SAME direction with the transmission in neutral.
But with both wheels in the air, and the transmission in park (or a manual in gear), if you can easily spin one wheel and the other one spins the other way, either the clutches are TOAST or there is no stock Tracition-Lok limited-slip in there. (not going to get into gear-driven lockers that will allow that to happen)
Well, that's not entirely true.
With a stock Ford Traction-Lok limited-slip, apply about 25ft/lbs of torque to the wheel, and the clutches will slip and allow the other wheel to spin in the opposite direction.
Without applying that much torque, the other wheel should spin in the SAME direction with the transmission in neutral.
But with both wheels in the air, and the transmission in park (or a manual in gear), if you can easily spin one wheel and the other one spins the other way, either the clutches are TOAST or there is no stock Tracition-Lok limited-slip in there. (not going to get into gear-driven lockers that will allow that to happen)
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Tuned
Joined: May 2008
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ok, good to know. can i assume the LS is working if the wheels are turning in opposite directions (when i spin one) with the truck on a hoist or does that just confirm the diff is between the wheels? there is no friction modifier in the rear diff fluid as it is right now. i just took a little test drive to the high schools paved parking lot and turning as tight as i can with a crew cab long box dually, i hear nothing from the rear end. i never noticed any problems getting out of anywhere this winter - really have no idea if the LS is working or not...
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From: Corvallis, OR
Tuned
Joined: May 2008
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Duh, its not rocket science brain child, the OP just simply wants to know if his LS is working. No jacks or lifts or any other needless equipment is needed just a good right foot and maybe a little left for the sickly 6.0s and 5.4s autos, where u can't hold her to the floor and dump the clutch. We call them 1 leggers or 2 leggers depending on how many black marks they leave on the road where i come from.