Limited slip lubricant

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  #1  
Old 02-24-04, 11:13 AM
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Question Limited slip lubricant

The manual for my '88 3/4 ton Dodge 4 wd recommends limited slip fluid in the rear dif.
Some major brands of 80w-90 gear oil are labeled as being suitable for ltd. slip but the 20 liter (5 gal) pail of 80w-90 generic gear oil I have is not labeled as such.
It meets API, GL5 and MT-1 specs but this doesn't tell me if it can be used in limited slip.

Any ideas?
 
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Old 02-24-04, 12:06 PM
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it doesn't say because...

..it's not for limited slip. it used to be that you could use the regular gear oil for limited slip as long as you put in a limited slip additive (this was on GM)...i'm not sure on a dodge and I wouldn't take a chance because those lubes are NOT interchangeable. i'm sure mike in nj can give you the straight poop here on whether an additive is ok or not...for what it costs to buy a little gear oil (unless you use alot of it) i'd just pick up a couple bottles of LS lube
 
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Old 02-24-04, 12:31 PM
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I don't want to damage anything but........

This rig is a project truck that I just got on the road and I would like to use what I have to "top up" and maybe do a couple of complete changes and then pull the covers and clean and inspect the diffs.
I expect to go through a fair bit of fluid and wouldn't mind saving a couple of bucks if the fluid I have would be ok.

Castrol and Penzoil containers both say "good for limited slip" but at 3x what I pay for bulk.

The tranfer case on this thing uses Dexron III and I've gone through a couple of gallons so far by repeat changes to clean it up.
 
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Old 02-24-04, 12:40 PM
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it won't hurt the gears...

...it'll mess with the friction elements tho...the thing is that I couldn't predict how long that would take...probably not a big thing...i'd still wait to hear what mike has to say on it
 
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Old 02-24-04, 05:17 PM
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The dif's are Dana 60's.
 
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Old 02-24-04, 05:51 PM
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I have used the additive with reg diff fluid with no problems. It adds the friction modifiers that are in the limited slip oil making it the same as.
 
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Old 02-24-04, 08:32 PM
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My Ford traction-lock 8.8 needs a "friction modifier" added or it will chatter
I'm not sure I would want to run it for long without it
Even if I'm going to change it soon to "flush" it
 
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Old 02-24-04, 09:46 PM
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as long as the fluid is rated GL5, your gears and bearings will be protected with no problems. not all 4X4s are posi, (trac-lock in chrysler's case), if you're positive it's a posi, you would need a little bottle of friction modifier if you were replacing all the fluid. for a simple 'topping off', i wouldn't be too concerned.

if you did change all the fluid, and forgot to add the modifier, you might feel a slight shuddering as you made a full turn of the steering wheel, but if everything is original (15 years old), i don't think you'd even feel that. new stuff---definitely would feel it.

gear oil is good for 30,000 miles between servicing, unless you're pulling a house with it. then synthetic is for you.

the shuddering isn't even a bad thing, nothing is getting hurt, it's just an inconvenience for some people.

the front is definitely NOT a posi
 
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Old 02-25-04, 04:19 AM
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I always thought posi gear oil was "non-foaming" and regular was not. Does the friction modifier change that?
 
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Old 02-25-04, 06:32 AM
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I used to use "posi" and limited slip" interchangebly but now know they are two different things.
Posi uses a clutch pack in the diff that always has the two wheels "locked" together and when one wheel exceeds the break-away force of the clutches allow one wheel to spin.
Limited slip on the other hand will allow one wheel to breakaway when traction is lost in one wheel but in about a half revolution of the wheel a cam forces the clutch pack together locking the wheels together.

From what I understand posi is used in cars and some 1/2 tons and limited slip is used in heavier trucks.

Have I got this right?
 
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Old 02-25-04, 10:20 AM
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Terms Posi-traction (GM term), Sure-grip (I believe was Mopar), Traction Loc (Ford), Detroit locker (Used by Ford) can use clutches, cones, cams, and ratchets basically are used to apply power to both wheels but allow differential action to make turns.
 
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Old 02-25-04, 04:16 PM
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So, even though they work differently you are saying there is no difference in the terminology?
I've had both and also have had the diff's apart and could see how they work.

The set-up that uses a cam to engage the stationary wheel does not engage the stationary wheel until the slipping wheel makes about a complete revoution. There is no wheel lock-up when going around corners with this set-up.

I thought there was a different term for this type of diff.
 
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