Rear Diff Fluid

[On_3_Go]

i have an 02 Tahoe with the g80 code. I have read in a bunch of threads about LS additives being used and unused. My question is, people talk about using the Mobile 1 75w90 full synthetic. The only one I can find is one that has “ls” additive in it. Can that be used? Or should a fluid that doesn’t contain ls additive in it be used. Thanks in advance

 

[swathdiver]

I'd use the factory fluid, it's synthetic and has the additive already in it. 10-4016 or 89021677 Comes in 1 quart bottles.

 

[02Lightning]

Yes, that can be used.

 

[ScottyBoy]

I have the Mobil 1 fluid in mine. I had the Amsoil Severe Gear in it previously, but I noticed a leak and I had to grab some diff fluid locally. The Mobil1 was the only synthetic fluid I could find, plus Advance had them on sale for $7.99 a quart.

 

[On_3_Go]

I have the Mobil 1 fluid in mine. I had the Amsoil Severe Gear in it previously, but I noticed a leak and I had to grab some diff fluid locally. The Mobil1 was the only synthetic fluid I could find, plus Advance had them on sale for $7.99 a quart.

Does the mobile 1 you run, have the “ls” written on the front of the bottle? Seems even online I can’t find any without the additive in it.

 

[02Lightning]

The “ls” is for limited slip additive. It’s just a conditioner so the clutches won’t chatter, the only way you would notice a difference is if you had a limited slip differential and you didn’t have the additive. The differential would groan and chatter from the clutches slipping going around corners.
The gears and bearings in the differential don’t care if the additive is there or not. I think manufactures are making it easier now days and just putting it in everything.

 

[RED TAHOE LS]

The “ls” is for limited slip additive. It’s just a conditioner so the clutches won’t chatter, they only way you would notice a difference is if you had a limited slip differential and you didn’t have the additive. The differential would groan and chatter from the clutches slipping going around corners.
The gears and bearings in the differential don’t care if the additive is there or not. I think manufactures are making it easier now days and just putting it in everything.

Times two.
David g.

 

[corvette744]

The “ls” is for limited slip additive. It’s just a conditioner so the clutches won’t chatter, they only way you would notice a difference is if you had a limited slip differential and you didn’t have the additive. The differential would groan and chatter from the clutches slipping going around corners.
The gears and bearings in the differential don’t care if the additive is there or not. I think manufactures are making it easier now days and just putting it in everything.

Times 3 and all the new mobil 1 synthetic bottles have the LS on the front the older ones didnt.

 

[Z15]

The only truck and SUV (GM) to use a limited slip differential was the Quadrasteer as it was a (G86) Dana Axle. All SUV"s and trucks with a G80 use an Eaton Locking Rear Differential. A locker is not a limited slip so additives are NOT required and can actually have adverse effects so avoid lubes stated for use in Limited Slip or any limited slip additives. Note-The G80 code was used for both types of axle so it does not necessarily mean one or the other, you have to look at the vehicle line to determine.

¨ Optional Equipment (G80 Order Code) on all GM two-wheel and four-wheel drive light trucks and sport utilities.

Benefits

¨ Improved traction differentiates the vehicle relative to other rear wheel and four-wheel drive vehicles on the market.

¨ Maintenance free; requires no lube additives.

¨ Enhanced towing and off-road performance.

¨ Patented carbon friction disc technology enhances performance and durability while reducing warranty claims.


Principles of Operation

¨ Wheel speed difference (left to right) in excess of 100 RPM will cause a flyweight mechanism to open and catch a latching bracket.

¨ The stopped flyweight will trigger a self-energizing clutch system, which results in the cam plate ramping against a side gear.

¨ Ramping increases until both axles turn at the same speed (full lock), which prevents further wheel slip.

¨ At speeds above 20MPH, the latching bracket swings away from the governor and prevents lockup from occurring.



Technical Specifications

¨ Automatic locking takes place within a fraction of a second, so smoothly that it is unnoticed by the average driver.

¨ Unlocking occurs automatically, once the need for improved traction is gone, and is unnoticeable to the average driver.

¨ Compatible with anti-lock brake systems.

Chatter is essentially the build-up and release of energy between the differential clutch packs in a limited slip differential during operation. This phenomenon often occurs when torque is transferred between the clutches or when rotational speeds change. During the stick-slip phase, energy is built up to a point where contact between the clutch plates change between static friction (stick) and dynamic friction (slip), resulting in noticeable vibrations. It is this vibration that causes an audible chatter or ratcheting to be heard within the differential. While certainly an annoying characteristic, there is typically no mechanical damage occurring to the differential. It is most often noticed in parking lots or slow driving while turning where the outside wheel turns faster than the inside wheel.

In an effort to control this chatter, friction modifiers are often used. These additives result in a smoother transition between the two states of friction: static and dynamic. Static friction occurs when the clutches physically lock together, while dynamic friction occurs as the clutches are slipping, ergo Limited Slip Differential.

 

[swathdiver]

All SUV"s and trucks with a G80 use an Eaton Locking Rear Differential. A locker is not a limited slip so additives are NOT required and can actually have adverse effects so avoid lubes stated for use in Limited Slip or any limited slip additives. Note-The G80 code was used for both types of axle so it does not necessarily mean one or the other, you have to look at the vehicle line to determine.

I thought the GMT800s had the same differential as the GMT900s? See below Mike, from my service manual:


The optional locking differential (RPO G80) enhances the traction capability of the rear axle by combining the characteristics of a limited-slip differential and the ability of the axle shafts to "lock"together when uneven traction surfaces exist. The differential accomplishes this in 2 ways. First by having a series of clutch plates at each side of the differential case to limit the amount of slippage between each wheel. Second, by using a mechanical locking mechanism to stop the rotation of the right differential side gear, in order to transfer the rotating torque of the wheel without traction to the wheel with traction. Each of these functions occur under different conditions.

Limited-Slip Function

Under normal conditions, when the differential is not locked, a small amount of limited-slip action occurs. The gear separating force developed in the right-hand clutch pack is primarily responsible for this.

The operation of how the limited-slip function of the unit works can be explained when the vehicle makes a right-hand turn. Since the left wheel travels farther than the right wheel, it must rotate faster than the ring gear and differential case assembly. This results in the left axle and left side gear rotating faster than the differential case. The faster rotation of the left-side gear causes the pinion gears to rotate on the pinion shaft. This causes the right-side gear to rotate slower than the differential case.

Although the side gear spreading force produced by the pinion gears compresses the clutch packs, primarily the right side, the friction between the tires and the road surface is sufficient to overcome the friction of the clutch packs. This prevents the side gears from being held to the differential case.

Locking Function

Locking action occurs through the use of some special parts:

A governor mechanism with 2 flyweights
A latching bracket
The left side cam plate and cam side gear
When the wheel-to-wheel speed difference is 100 RPM or more, the flyweights of the governor will fling out and one of them will contact an edge of the latching bracket. This happens because the left cam side gear and cam plate are rotating at a speed different, either slower or faster, than that of the ring gear and differential case assembly. The cam plate has teeth on its outer diameter surface in mesh with teeth on the shaft of the governor.

As the side gear rotates at a speed different than that of the differential case, the shaft of the governor rotates with enough speed to force the flyweights outward against spring tension. One of the flyweights catches its edge on the closest edge of the latching bracket, which is stationary in the differential case. This latching process triggers a chain of events.

When the governor latches, it stops rotating. A small friction clutch inside the governor allows rotation, with resistance, of the governor shaft while one flyweight is held to the differential case through the latching bracket. The purpose of the governor's latching action is to slow the rotation of the cam plate as compared to the cam side gear. This will cause the cam plate to move out of its detent position.

The cam plate normally is held in its detent position by a small wave spring and detent humps resting in matching notches of the cam side gear. At this point, the ramps of the cam plate ride up on the ramps of the cam side gear, and the cam plate compresses the left clutch pack with a self-energizing action.

As the left clutch pack is compressed, it pushes the cam plate and cam side gear slightly toward the right side of the differential case. This movement of the cam side gear pushes the thrust block which compresses the right-hand side gear clutch pack.

At this point, the force of the self-energizing clutches and the side gear separating force combine to hold the side gears to the differential case in the locking stage.

The entire locking process occurs in less than 1 second. The process works with either the left or right wheel spinning, due to the design of the governor and cam mechanism. A torque reversal of any kind will unlatch the governor, causing the cam plate to ride back down to its detent position. Cornering or deceleration during a transmission shift will cause a torque reversal of this type. The differential unit returns to its limited-slip function.

The self-energizing process would not occur if it were not for the action of one of the left clutch discs. This energizing disc provides the holding force of the ramping action to occur. It is the only disc which is splined to the cam plate itself. The other splined discs fit on the cam side gear.

If the rotating speed of the ring gear and differential case assembly is high enough, the latching bracket will pivot due to centrifugal force. This will move the flyweights so that no locking is permitted. During vehicle driving, this happens at approximately 32 km/h (20 mph) and continues at faster speeds.

When comparing the effectiveness of the locking differential, in terms of percent-of-grade capability to open and limited-slip units, the locking differential has nearly 3 times the potential of the limited-slip unit under the same conditions.

Locking Differential Torque-Limiting Disc

The locking differential design was modified in mid-1986 to include a load-limiting feature to reduce the chance of breaking an axle shaft under abusive driving conditions. The number of tangs on the energizing disc in the left-hand clutch pack was reduced allowing these tangs to shear in the event of a high-torque engagement of the differential locking mechanism.

At the time of failure of the load-limiting disc, there will be a loud bang in the rear axle and the differential will operate as a standard differential with some limited-slip action of the clutch packs at low torques.

The service procedure, when the disc tangs shear, involves replacing the left-hand clutch plates and the wave spring. It is also necessary to examine the axle shafts for twisting because at high torques it is possible to not only shear the load-limiting disc, but to also twist the axle shafts.