Rear differential question

[hinton69]

Hello all,

I have a '98 5.0 AWD and am trying to figure out if it has the limited slip rear diff. The axle code on the door sticker is D4. From what I've read, a letter and a number means its a limited slip (standard diff uses 2 numbers). Searched here but didn't really find anything. Getting ready to change the fluid so I'm just trying to figure out if I need the 75W140 and friction modifier.

Thanks!

 

[deweyville65]

Jack up the rear end, both sides. Spin one of the tires. If the opposite tire spins the same direction, limited slip. If the opposite tire turns the opposite direction, or does not turn at all. open differential. Be sure trans is in neutral.

 

[R1dd1cK]

D4 is 3.73 limited slip.

 

[SoNic67]

All the AWD's have limited slip on rear. And in the center diff. It won't make sense not to be, otherwise the AWD would be worthless.
Only the front diff is open.
However, if you use the Mobil 1 75W140 LS fluid, it already has the friction modifier additive in it - read the description.
Only the Motorcraft fluid needs it.

 

[radman]

Sorry No Cigar

Not quite right. My 99 Eddie 5.0 AWD is 3:73 open 8.8 it came from the factory that way. I am the original owner.
Mike

 

[SoNic67]

Hmmm... that makes your AWD worthless. What's the point of having the VC in center diff if the rear and front are both open?
How do you know is open?

 

[radman]

I like you.........

do my own service and have checked the i.d. tag on the housing many times and the door tag is 46, I have also ask myself the same question, "why no Traction-Lock?"
Mike

 

[imp]

Awd connection?

Someone please explain to me why AWD is "useless" if both front and rear differentials are "open".

Thanks! imp

 

[X~FACTOR]

Same here. AWD = open diff.

 

[swshawaii]

There is no individual on Explorer Forum I trust less. Consistently gives misleading information and he's in this thread. Sorry. :thumbdwn:

 

[radman]

They are not worthless

that's an exaggeration. They still can pull through both front and rear in the same way that a two wheel drive vehicle can pull with an open differential. You will not get any assistance from the other side if there is no traction at either wheel and it will direct power to the wheel with the least amount of traction the same as with two wheel open differential rear-ends.

In the case of AWD in this configuration they do quit well in snow and mud. All though I have only had mine through 14 winters it has never failed to get me where I want to go. If I did not tell you it was an open rear I doubt that most folks would find issue with that omission.
Mike

 

[SoNic67]

99% or the time you will have more traction on one side than another. That's just because of the way other people drive, they make paths in the snow, ice before you get there. You cannot drive exactly on their marks and usually they don't have the same with cars like yours.
That's why you need that limited slip side-to-side.
In this way if only one rear wheel has traction and none on front, you can still move.
If don't believe it, that's your prerogative. Ask yourself why Ford used a LS diff in other models. Just because they had some on shelf?
Sure, you might be OK without it. I did drive with a 2WD in snow for years too, wasn't born in a AWD with LS. That doesn't prove that AWD is not needed, it just prove that I was cautions enough where I drove my car. And using winter tires (not 'all weather' ones).

PS: Some of the newer cars get away without LS by using the traction control and ABS - braking the fast spinning wheel. I think the 2004 'Advance Trac' does it, but I am not positive... Not so effective IMO.

 

[deweyville65]

Sonice, please tell me how come big trucks have power dividers between the front and rear drive axles and open differentials, and are able to have twice the traction when the power divider is locked. Only very few trucks have a locking (side to side) rear differential. When slippery conditions occur, the drive tires with the lowest traction will slip. Lock the power divider, and one of the drivers on each axle will then have power to them. They may both slip, but at least both axles are pulling. On trucks equipped with a locking differential, then you have three of the four drivers pulling. Appears the same with your AWD. Company I drove for bought new Kenworths in 2001 with a system that used the braking system to apply the brakes to a spinning driver for traction. All that did was to run the truck out of air. Then it was time to call for a tow. These trucks were single drive with tag axles. Worthless in slippery conditions. And don't try saying the principals are different, just because Kenworth vs. Explorer.

 

[SoNic67]

Locking differentials are NOT open differentials.
For example some GM axles have locking diff, it engages suddenly when differential RPM are over a certain limit.

And yes, ControlTrac/ABS braking the spinning wheel is not as effective as a LS or locking diff, but is much more cheaper (free if the car has ABS) so... Some manufacturers decided that's a nice marketing tool to have.

 

[bill06447]

All Wheel Drive trucks came standard with Limited Slip Diffs in 1996 and 1997. Maybe different in 99? Also the door tag isn't the final word for what's underneath, if someone changed the door on your truck, as they did mine, it's worthless. Pulling the diff cover is the only sure way to tell, as a tight open diff will rotate both wheels the same direction, and a worn out LSD will act like an open rear with wheels rotating opposite.

Bill

 

[bill06447]

Locking differentials are NOT open differentials.
For example some GM axles have locking diff, it engages suddenly when differential RPM are over a certain limit.

There's as many different types and trade names for limited slip axles as there are axles. True-Trac, Gov-Lok, PosiTraction, Equa-Lok, Sure-Grip, some use clutches, some springs, some cones, then you get into the realm of locking axles, culminating with the tried-and-true spools and "Lincoln Lockers". The garbage axle in my 2012 GMC 1-ton van sounds like the one SoNic67 is talking about, it's a G80 code Limited Slip on the sticker but it doesn't do anything until it spins over maybe 30mph then engages with a loud *bang* (waiting for an axle to snap next trip on the ice)

Bill

 

[hinton69]

D4 is 3.73 limited slip.

Thanks!

Didn't mean to start an argument I know the door hasn't been replaced so the sticker should be factory. Guess I'll find out for sure when I pull the diff cover.

 

[deweyville65]

Sonic, I am quite aware that locking differentials are not open diffs. However on big trucks the Peterbilt I drove had a locking differential operated by an air operated, driver controlled sliding gear thereby locking both rear axles together. Normal operation, open diff. Throw the valve, locked diff.

 

[bill06447]

Sonic, I am quite aware that locking differentials are not open diffs. However on big trucks the Peterbilt I drove had a locking differential operated by an air operated, driver controlled sliding gear thereby locking both rear axles together. Normal operation, open diff. Throw the valve, locked diff.

That only locks the front and rear screws together. When locked, the front right/rear left wheels will spin, and vice-versa.

Bill

 

[deweyville65]

That only locks the front and rear screws together. When locked, the front right/rear left wheels will spin, and vice-versa.

Bill

Bill, it is NOT the same thing as a power divider. Yes the power divider locks the front and rear drive axles together. And true only one of the drivers on each axle will will spin in slippery conditions. What I am talking about is a TRUE locking (side to side) of the REAR drive axle when the valve is locked. I think I know what I am talking about as I ran two different transfers with this feature. Both just happened to be Peterbilts. One was factory equipped, the other was added on by the previous owner. Many times in the mud and snow I used this feature to get out when only using the power divider would not do the trick. The actual name for this feature was Traction Lock.