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Discussion Starter · #1 ·
I had my dealer replace the pinion seal in my rear end. I bought the Mobile 1 synthetic with the friction additive and told them to use that. Since the replacement I have the shimmy in light turns. Do I just put more friction modifier in it? How much? Can you add too much?

I did notice one thing they did. They filled the axle with the rear wheels ~18" off the ground. Fluid might be a little high.

BTW, my dealer did this job for $160 including the updated $45 seal. What a deal. Hunt Ford, Franklin KY. Great bunch to deal with.

Thanks in advance,
 

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If the truck is on a rack, it doesn't matter how high in the air the wheels are.

As a rule if you pull the Diff cover or axles, when you refill, you fill until the oil drips out the hole. Then you need to jack up one side at a time to get the oil into the axle tubes. Then check again.

Since you've driven the truck, just pull the fill plug and add oil with modifier as needed.
 

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Add more friction modifier. These rears need two bottles usually. One bottle is good for car and light truck rears that hold maybe 2quarts or less of oil, but the 10.5 holds a lot more than that. I'd add like half a bottle and drive it around, see if it goes away. If so you're good, if not add the rest of the bottle.

You don't want too much, it could cause less limited slip action. The idea is to get it just right, just past no chatter.
 

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Discussion Starter · #4 ·
if the back of the truck is 18" off the ground and the front tires are on the ground, the filler plug is tilted up...

TKO,
Mine is the Dana 80 with the 11.25" ring gear. How many ounces is your said bottle?
I'm just really not sure why it is shuttering in the first place. Others here have used the Mobile 1 with the additive without issue.
Thanks,
 

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I know this thread is a month old now, but just wanted to share my experience;

Had to get pinion seal work done about 2 months ago. I'm on a bit of an Amsoil bandwagon right now so I had the shop doing the work replace the old oil with Amsoil 75w-140. Bottle said no additives were required for the LSD.

I've never had the LSD work so perfectly before. Given it was cheaper for me to buy the Amsoil fluid from Bumper-Bumper vs. Motorcraft + Additive from Ford, I don't think I'm going to go back. If you ever have to change your fluid again I'd suggest giving the Amsoil a shot.
 

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I have used the Mobil 1 fluid that already contains the limited slip additive successfully. I have not had to add anything else to it.
 

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How many quarts does the F250 rear hold if you remove the cover to drain it?
 

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I used Amsoil in my prior '99 truck and had to add the additive after about 6 months use as the rear end began to chatter in turns. With my present truck I added the additive with a fluid change as I didn't want to deal with it again. Amsoil is a bit wishy-washy in their directions about the additive, but I really like their gear fluids.

Ford06- if you have the stock cover, you will need about 3.5 quarts. If you have the newer aluminum cover it will hold a bit more. I bought 4 quarts and the additive and used it all.
 

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Anyone know torque specs for rear diff cover and drain plug 05 350
I am also wondering if perma Tex high temp red rtv is ok for diff gasket
 

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Probably, just make sure you let it set for 24 hours before filling the rear.
 
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