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Rear diff lube.

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Old Jul 25, 2007 | 10:28 PM
  #1  
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Rear diff lube.

I have a 8.8 with Ford posi rear end. I was wondering what kind of fluid to put in it. I put in Lucas 85w-140w. I was wondering if this is ok. Also I'm going to drain and add fluid to the front diff. Im guessing it is a dana 44. What fluid should I use for the Dana?
 
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Old Jul 25, 2007 | 10:52 PM
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I used 75w90 in both my differentials. I guess it all depends on your climate but 85w140 is pretty high in my opinion.
 
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Old Jul 25, 2007 | 11:22 PM
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use 80w90 for both and add posi additive to the posi 8.8 diff
 
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Old Jul 25, 2007 | 11:28 PM
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Yes, do not forget friction modifier.
 
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Old Jul 25, 2007 | 11:42 PM
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Well, if it's a posi, then you don't have to add the friction modifier, if it's limited slip you do.

Matt
 
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Old Jul 26, 2007 | 12:03 AM
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It was my understanding that posi is short for posi-traction, which is just another name for limited-slip used by other auto manufacturers. No?
 
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Old Jul 26, 2007 | 12:11 AM
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no, positive traction (or posi) means that both wheels get equal amounts of power all the time (like putting in a spool, or welding up spider gears). Their not practical for everyday driving because when you go around a corner, the tires squeal and put a strain on the axles.
The limited slip means there's clutches that kick in when one wheel spins a certain amount of times. This is better for a DD because you can go around corners and he wheels will turn at different speeds. That's why you have to add friction modifier to a limited slip, because the clutches need the modifier to grab each other, if not, they'd probably just burn up while rubing together and trying to give traction to the wheel that isn't spinning.
I don't know what kind of category a locker is, because its an open diff until you it locks, and also it uses gears to "lock" the two wheels together and making it a posi.

Their two different things, for sure.
Matt
 
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Old Jul 26, 2007 | 12:36 AM
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Ah' Mtthwvn73's Posi- Traction is a GM terminology and does have clutch's like a a Ford Limited Slip.

Same thing with a different name under different manufactures.
 
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Old Jul 26, 2007 | 12:50 AM
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Your 100% correct. I had to look it up, but your definatly right. So what would you call one with a locker, I found out welding up the spider gears is called a Lincoln locker (I guess for the Lincoln welder). Also FWIW, Eaton made the lockers for Chevy, didn't know that, just thought I'd throw that in.

Sorry for the mis-information, I'm definatly Chevy ignorant, lol.
 
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Old Jul 26, 2007 | 01:17 AM
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Woo I was right!! For once...
 
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Old Jul 26, 2007 | 02:55 AM
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im dumb. The rear is limited slip not a locker.
 
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Old Jul 26, 2007 | 03:42 AM
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You said it was posi, which technically is correct because its the same idea as limited slip. Either way, you need to either use a "limited-slip" gear oil or add a friction modifier. I know that Redline makes limited slip additive in a bottle about the size of a pill bottle, it doesn't take much.

After you change the gear oil, if there is clicking and chattering coming from the rear end then you need to add some friction modifer in increments until it goes away. Do not use too much or you clutches will slip all the time and render the limited-slip properties useless. If you have not used some kind of additive for the limited slip and you are not hearing clicking/chattering then your clutches for the LS are probably bad. The sure fire way to tell is to jack up the rear end and spin one of the tires by hand. If the opposite tires spins in the same direction then the LS works, if it spins in the opposite direction then your clutches are fried. Hope that helps!
 
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Old Jul 26, 2007 | 05:27 AM
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Your local Ford Dealer has:

C8AZ-19B546-A .. Friction Modifier Additive
 
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Old Jul 26, 2007 | 06:32 AM
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I thought the opposite wheel was supposed to spin the opposite direction if you have LS. You cant spin the wheel fast enough by hand to engage the clutches.
 
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Old Jul 26, 2007 | 09:35 AM
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Originally Posted by mrl390
I thought the opposite wheel was supposed to spin the opposite direction if you have LS. You cant spin the wheel fast enough by hand to engage the clutches.
I don't think speed has anyything to do with it.
 
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