Rear Posi Problems.
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Freshman User
Joined: May 2005
Posts: 25
Likes: 0
From: Canada
Rear Posi Problems.
I have just bought a new F250. My friend has also bought a new F250. This past weekend we went fishing north of where we live and the lake was still frozen. The bush road in was pretty soupy and still had snow. At one point we got stuck and had to use the two four wheelers to tow us out. Here we noticed that only one rear wheel was turning. His truck like mine has the FX4 package and shows on the VIN to have the Limited slip rear end. Any one encounter this problem. So far the dealer hasn't found the problem. i need to make sure my truck doesn't have the same problem.
Postmaster
Joined: Dec 2003
Posts: 3,130
Likes: 3
From: Massachusetts
Ford's limited slip is a very marginal set up. There have been many posts about problems like these. The rear end need some torque to the rear wheels before getting it to lock. Mud, sand, snow, and wetness just does not do it. On perfectly dry road it will lock every time. Go figure HUH? IF the dealers states there is no problem, I bet there isn't. It is just the nature of the differential. Ford really needs to get more aggressive on this set up.
I took matters into my own hands and drained the rear gear fluid and refilled it and kept testing the proper amount of friction modifier to get the thing to lock quicker. I kept adding some a bit at a time and took it for a drive and and did some u turn on pavement until I got the right amount of modifier in there where it would slip on turns but lock on sand and such,
I took matters into my own hands and drained the rear gear fluid and refilled it and kept testing the proper amount of friction modifier to get the thing to lock quicker. I kept adding some a bit at a time and took it for a drive and and did some u turn on pavement until I got the right amount of modifier in there where it would slip on turns but lock on sand and such,
Post Fiend
Joined: Jan 2002
Posts: 5,859
Likes: 7
From: USA
first thing i'd do is get under the truck and make sure it has a ls unit.Don't go by the vin or code on the door tag.
should be a tag on the rear diff that says XLxx ,the L stands for Limited Slip.
Some ls units are not setup correctly from the factory
As said above too much or not enough friction modifier or improper shims in the unit itself will cause problems.
Sometimes lighly touching the brake while one tire is spining will cause both to lock
Rich
should be a tag on the rear diff that says XLxx ,the L stands for Limited Slip.
Some ls units are not setup correctly from the factory
As said above too much or not enough friction modifier or improper shims in the unit itself will cause problems.
Sometimes lighly touching the brake while one tire is spining will cause both to lock
Rich
Elder User
Joined: Jan 2003
Posts: 828
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From: Baltimore
The rear in my 2005 F250 CC 6.0L auto 4x4 doesn't lock up too early either. This is probably a good thing when my wife drives this truck in the rain. But, I was coming out of the woods with a 2000+ lbs load of wood in the bed and when I had to traverse some uphill muddy trails, that rear was locking up like a champ. It definitely needs to see some substantial torque before it locks up tight.
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Freshman User
Joined: May 2005
Posts: 25
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From: Canada
Thanks for all your info. it's starting to make sense. I'm still breaking in my new truck and then i'll give the rear end some testing. As for my friend, the dealership is still trying to get their head around things. Seems like Ford needs to do some work here, as well as to better train their technicians!
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 421
From: Long Island USA
In all my comments about the Traction-Lok I never mentioned this:
I found that a few hundred pounds or more of "stuff" in the bed helps the LS get slightly better traction.
And above all, match your tires to what you're putting them through
I found that a few hundred pounds or more of "stuff" in the bed helps the LS get slightly better traction.
And above all, match your tires to what you're putting them through
