limited slip
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Laughing Gas
Joined: Feb 2006
Posts: 947
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limited slip
From the c1 code on my 2003 f250 and reading the codes on this site it is supposed to be a 3.73 limited slip axle. When the tires start to spin only the passanger rear tire will spin. Is my limited slip burnt out. If so like i suspect where can i get a good replacement at a decent price. I don't go off roading much but my 2000 f150 i bought brand new has limited slip and i love how it handles when the tires do break loose. Any advice is always greatly appreciated. Thanks
Lead Driver
Joined: Sep 2003
Posts: 5,844
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From: Albuquerque
Your 3.73LS might not be burnt out. I would recommend a gear change first. Then test it out...
To change the gear oil for a LS rear it calls for 8oz of additive friction modifier. TIP: Add 2 pints of 75w140 sync gear oil and then add 4oz of modifier. Add the rest of the gear oil until full (total needed: 6.9 pints)
Now test drive in an open parking lot. Do a figure 8 drive slowly and check for any noise in the rear. If no noise...then test in the dirt for both wheels to spin. If you hear chatter while testing, then you will need to add more modifier. Do that in 2oz increments.
Hope that helps some...
biz
_____________________________
2003 F250 SD SC 142" XLT FX4 V10 Auto 4x4 3.73s
To change the gear oil for a LS rear it calls for 8oz of additive friction modifier. TIP: Add 2 pints of 75w140 sync gear oil and then add 4oz of modifier. Add the rest of the gear oil until full (total needed: 6.9 pints)
Now test drive in an open parking lot. Do a figure 8 drive slowly and check for any noise in the rear. If no noise...then test in the dirt for both wheels to spin. If you hear chatter while testing, then you will need to add more modifier. Do that in 2oz increments.
Hope that helps some...
biz
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2003 F250 SD SC 142" XLT FX4 V10 Auto 4x4 3.73s
Joined: Jul 2006
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From: Capac MI
Hey, No limited slip means only one tire spins. Posi is when they both spin at the same time. You can check this by puting it in drive and turning it really sharp and going slow, the back should bounce. Im not sure about if u put it in 4 high or low because it might lock the rear axle. But you will definatly know, i wanted to see if i had a posi so i gave it to her on a dirt road and i came up with to, but the road was flat so my Dad said get on some uneven terrain and i did and spun em and i had to still, I still wasnt sure and i jacked up the rear end and spun on tire and it was two lol i checked it every way but the right one, so i pulled the number and it was 4 10 posi. Hopefully this sparks u some more help.
Thread Starter
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Laughing Gas
Joined: Feb 2006
Posts: 947
Likes: 1
Thanks biz. I thought the dealer told me that the diff fluid was changed when i bought the truck about 6 months ago but maybe not. Thanks for the help. Any advice on where to get the fluid and additive from without paying fords prices. Thanks
Lead Driver
Joined: Sep 2003
Posts: 5,844
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From: Albuquerque
Originally Posted by ponch37300
Thanks biz. I thought the dealer told me that the diff fluid was changed when i bought the truck about 6 months ago but maybe not. Thanks for the help. Any advice on where to get the fluid and additive from without paying fords prices. Thanks
Actually, you can use any brand gear and modifier oil you want. Just make sure it says it works with FORD LS. Castrol gear oil is high quality...IMHO. So...any parts store should do.
GEAR info:
75w-140 Synthetic
MODIFIER Info:
XL-3 or equivalent meeting FORD specification EST-M2C118-A
biz
_____________________________
2003 F250 SD SC 142" XLT FX4 V10 Auto 4x4 3.73s
Junior User
Joined: May 2006
Posts: 67
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From: Durango, CO
Originally Posted by ponch37300
From the c1 code on my 2003 f250 and reading the codes on this site it is supposed to be a 3.73 limited slip axle. When the tires start to spin only the passanger rear tire will spin. Is my limited slip burnt out. If so like i suspect where can i get a good replacement at a decent price. I don't go off roading much but my 2000 f150 i bought brand new has limited slip and i love how it handles when the tires do break loose. Any advice is always greatly appreciated. Thanks
Elder User
Joined: Dec 2003
Posts: 652
Likes: 1
Originally Posted by THE KING
Hey, No limited slip means only one tire spins. Posi is when they both spin at the same time. You can check this by puting it in drive and turning it really sharp and going slow, the back should bounce. Im not sure about if u put it in 4 high or low because it might lock the rear axle. But you will definatly know, i wanted to see if i had a posi so i gave it to her on a dirt road and i came up with to, but the road was flat so my Dad said get on some uneven terrain and i did and spun em and i had to still, I still wasnt sure and i jacked up the rear end and spun on tire and it was two lol i checked it every way but the right one, so i pulled the number and it was 4 10 posi. Hopefully this sparks u some more help.
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FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
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From: Long Island USA
OK, here's what to do when changing the gear lube.
Put in only 2 ounces of limited-slip additive first instead of the 8 that Ford says!
Drive it in circles, you should hear some chatter from the limited-slip. If you don't, leave it and see if it works!
Keep adding additive in 2 oz increments until the chatter is gone, but the limited-slip still works.
I put in only 4 oz. in my Sterling 10.5 rear, and it now locks up MUCH BETTER than it did with 8 oz of additive.
Thanks Fredvon4!
Uh, 150ft/lbs of break-away torque? NOT! It's around 20-25 ft/lbs by Ford's spec! An Auburn HD LS will break-away at around 150ft/lbs.
One thing about the Traction-Lok, use the parking brake to keep it from rolling, apply throttle slowly, and then slowly let off the parking brake at the same time. This will give enough preload to the clutches to possibly keep it locked up. Ford even says something about this in my owner's manual I believe.
Put in only 2 ounces of limited-slip additive first instead of the 8 that Ford says!
Drive it in circles, you should hear some chatter from the limited-slip. If you don't, leave it and see if it works!
Keep adding additive in 2 oz increments until the chatter is gone, but the limited-slip still works.
I put in only 4 oz. in my Sterling 10.5 rear, and it now locks up MUCH BETTER than it did with 8 oz of additive.
Thanks Fredvon4!
Uh, 150ft/lbs of break-away torque? NOT! It's around 20-25 ft/lbs by Ford's spec! An Auburn HD LS will break-away at around 150ft/lbs.
One thing about the Traction-Lok, use the parking brake to keep it from rolling, apply throttle slowly, and then slowly let off the parking brake at the same time. This will give enough preload to the clutches to possibly keep it locked up. Ford even says something about this in my owner's manual I believe.
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Senior User
Joined: Feb 2005
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From: Pittstown NJ
<TABLE class=tborder cellSpacing=1 cellPadding=4 width="100%" align=center border=0><TBODY><TR title="Post 3819073" vAlign=top><TD class=alt1 align=middle width=125>THE KING</TD><TD class=alt2>Hey, No limited slip means only one tire spins. Posi is when they both spin at the same time. You can check this by puting it in drive and turning it really sharp and going slow, the back should bounce. Im not sure about if u put it in 4 high or low because it might lock the rear axle. But you will definatly know, i wanted to see if i had a posi so i gave it to her on a dirt road and i came up with to, but the road was flat so my Dad said get on some uneven terrain and i did and spun em and i had to still, I still wasnt sure and i jacked up the rear end and spun on tire and it was two lol i checked it every way but the right one, so i pulled the number and it was 4 10 posi. Hopefully this sparks u some more help.</TD></TR></TBODY></TABLE>
The only way the rear end will hop around turns is if you have a live rear axle aka a locker of some sort limited slip will not cause this to happen
The only way the rear end will hop around turns is if you have a live rear axle aka a locker of some sort limited slip will not cause this to happen
Thread Starter
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Laughing Gas
Joined: Feb 2006
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Do i need to add the modifier if i use 75w-140 Synthetic. Some where on here i read that you don't have to use the modifier with synthetic cause the synthetic already had some sort of modifier in it so you were sure that the synthetic and modifier were compatible. Just currious and would like to change the fluid but don't know if i need the modifier or not. thanks
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 421
From: Long Island USA
YES you need to use the additive.
The stock Ford/Sterling 10.5" has a tag on it that says 75w140 synthetic ONLY. And then Ford says in the service manual to add 8 ounces of additive.
So according to Ford, you MUST use it.
Unless the bottle of lube says "additive already inside" or something to that effect, I would make sure to add the additive - at least 4 oz of it.
The stock Ford/Sterling 10.5" has a tag on it that says 75w140 synthetic ONLY. And then Ford says in the service manual to add 8 ounces of additive.
So according to Ford, you MUST use it.
Unless the bottle of lube says "additive already inside" or something to that effect, I would make sure to add the additive - at least 4 oz of it.
Junior User
Joined: May 2006
Posts: 67
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From: Durango, CO
Originally Posted by krewat
OK, here's what to do when changing the gear lube.
Put in only 2 ounces of limited-slip additive first instead of the 8 that Ford says!
Put in only 2 ounces of limited-slip additive first instead of the 8 that Ford says!
Originally Posted by krewat
Uh, 150ft/lbs of break-away torque? NOT! It's around 20-25 ft/lbs by Ford's spec! An Auburn HD LS will break-away at around 150ft/lbs.
Oh well, I'm at the end of 2.5 miles of fairly level dirt roads now, we'll see how it handles the snow then decide what needs to be done.
Thanks
Senior User
Joined: Mar 2006
Posts: 103
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I just got my truck aligned and when it was on the lift and he rotated the rear tires they both spun at the same time in the forward direction is this right or do I have a problem with my limited slip? I thought one wheel spins the opposite direction when off the ground.
