2013 Tahoe LTZ Rear Differential Fluid

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Mitch2013

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I changed out the rear diff oil with the owners manual AC DELCO 75w-90 synthetic recommended. A few days later I noticed that I was getting a moaning noise when turning sharp low idle turns and it was coming from the rear end. Contacted the dealer and my drivetrain warranty ran out on 10-29-17. (SWEET!!!). Anyway the dealer looked up my VIN and and confirmed the type of diff fluid I used was correct. He said the my hoe had posi rear end but just the synthetic was fine.

I took it upon myself to add LS fluid and the noise stopped instantly! Anyone else experience this issue before? Anyone know why the owners manual doesn't say to add it? Thanks in Advance.

Mitch
 

greenhornet

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I changed out the rear diff oil with the owners manual AC DELCO 75w-90 synthetic recommended. A few days later I noticed that I was getting a moaning noise when turning sharp low idle turns and it was coming from the rear end. Contacted the dealer and my drivetrain warranty ran out on 10-29-17. (SWEET!!!). Anyway the dealer looked up my VIN and and confirmed the type of diff fluid I used was correct. He said the my hoe had posi rear end but just the synthetic was fine.

I took it upon myself to add LS fluid and the noise stopped instantly! Anyone else experience this issue before? Anyone know why the owners manual doesn't say to add it? Thanks in Advance.

Mitch
I have had that problem sometimes and the LS fluid does help especially with synthetic hypoid. Sometimes it just grabs more than other times,just the clutches stick from straight line driving and jerk loose in a corner then it seems to be fine for a while.It happened with my 1976 C 10 ,2000 Tahoe LT which had Amsoil 75/90 synthetic for there whole life and sometimes with my 2015 LS with it's factory fluid.Annoying but never seemed to be a problem.Hope this helps.
 

dbbd1

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Does LS mean limited slip?
Then, yes, you should have added it. Limited slip require friction modifiers added. Unless it's already in the lube.
 

swathdiver

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The factory fluid already comes with the limited slip additive. Did you use part numbers 89021677/10-4016?

If you did and were still getting the chatter, then you did right to add just enough more to make it stop. You've got a little more wear than most.
 

Z15

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Trucks and SUV's DO NOT have a limited slip differential (aka POSI, short for Positraction), they have a Locking differential and you DO NOT NEED any limited slip additives. They can actually cause problems.

You would think the dealer would know this.

¨ 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.



Also, owners have no idea why Limited slip differentials even use the additive. Its to control chatter, i.e. noise.


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.


Locking differentials make noise when they engage, its the nature of the best. Average driver would likely not even notice but aggressive drivers will for sure.
 
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