Limited Slip Question

[pburchett]

I have a 97 GMC 2500 Light Duty truck (6 lug 3.73 gear ratio limited slip rear end).

I purchased the truck with 113,000 highway miles on it from a fleet company.  I serviced the truck and changed the rear differential fluid (almost 3 quarts + additive) with GM products.  Yes, it does hold this much.

 

Before the fluid change the truck would only spin one wheel a fraction of a rotation before the other wheel would lock in, and would stay locked in for a little while (50 to 100ft).  I could tell it was still locked in as I turned on dry pavement.  

 

Now the wheel has to spin 1,2 or 3 rotations (hard to tell) before lock up, if it even locks up.   I have drove it 3,000 miles since the fluid change and it seems to be a little better, but no where like it was when I first got it.  The fluid I removed from the differential was dirty, but it had a red tint to it.  I know the GM stuff I put back in did not have a red tint to it.  Does anyone have a clue as to what product they might have used?   Do I need more friction additive?

 

Thanks in advanced for any help.

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[dukbludvl]

what additive did you use for limited slip? I have a yukon with lim. slip rear diff. and did not put an additive in when I changed mine about 15K miles ago.  I'm just wondering b/c I wasn't aware I needed to put in an additive. Also, I used Mobil1 synthetic 75W-90 gear oil.

[RyanbabZ71]

DUK

 

the pre 99 trucks needed an additive.  The newer trucks do not need this because of the use of synthetic gear oil.

[Black02Silverado]

You need the additive for the rear with limited slip due to the noise you would get when you turn the vehicle. It is not needed, at least that is what I have been told by various others that work on limited slip GM products. It is just used to keep the noise down while turning. A limited slip has clutches in it that keep it locked up. The clutches are held into place by spring pressure. Sounds like the clutches are finally wearing after all the miles on them, which is normal. It can be rebuilt. You can go to the dealer to get a new set of clutches that will come with new springs also.

The new models have an eaton locker in them and does not use clutches like the limited slip. You can go to the eaton web site and it explains it all really well. This is off the Eaton web site.

 

 

Eaton's Posi Limited Slip Differential

 

Do stoplights remind you of drag strip Christmas trees? Do twisty mountain roads make your pulse quicken? Does steering with the throttle make perfect sense to you?

 

Then Eaton Posi is your friend. Muscle cars, hot rods and mild off-road vehicles should look to Eaton's limited-slip differential for their traction answers. And the fact is, Eaton's Posi units are virtually bullet proof.

 

We're talking precision forged gears for high impact strength and durability.

 

Formula One race-bred carbon friction discs for lifelong, chatter-free operation.

 

A spring pre-load pack combined with a field proven, high performance cast iron case for unbelievable durability.

A Quick Look At How It Works…

 

First, let's consider the open differential. Open diffs are designed to allow both wheels to turn at different rates so the vehicle can do things like turn corners. And when you're on clean, dry pavement, taking it easy on the throttle, everything is fine.

 

 

But, as soon as the drive wheel starts slipping, driveline torque follows the path of least resistance. That means the more power you give it, the faster the wheel slips. In other words, you're stuck…

 

With Eaton Posi, you prevent wheel slip before it can get started. To do that, carbon disc clutch packs preloaded by a central spring assembly are located behind each differential side gear.

 

When torque input increases (i.e., engine rpm's go up because you've got your foot in the throttle) the clamping load on the clutch packs goes up. That clamping load causes the clutch packs to grab, transferring power to the other wheel. The end result? Wheel slip is usually prevented.

 

The key here is that a limited-slip differential's power transfer is primarily based on input torque. So, with normal or light throttle applications on dry pavement, only the drive wheel receives torque, or power - just like an open differential.

 

While this is an excellent way to control traction in street rods, light duty pickups and all types of tarmac running racecars, it isn't the best solution for the serious off-road vehicle.

 

Why? Because it's input torque, not wheel slip that determines when power is transferred to the other wheel. So, what about the back-woods, two-track, gotta get over the mountain type? Enter the Eaton Locker…

 

Frequently Asked Questions

What is the Eaton Locker?

 

The Eaton locker is an automatic locking differential for rear wheel, and four wheel drive vehicles. As long as there is no wheel slip, the locker performs as a standard open differential which merely allows the vehicle's rear drive wheels to rotate at the different speeds necessary for cornering. However, when wheel slip occurs, the unit locks the rear axle together providing maximum torque to both the high and low traction wheel.

 

What does the Eaton Locker do?

 

During full lockup, the Eaton Locker provides maximum torque to the vehicle's rear drive wheels making it possible for the vehicle to maneuver over rough or slippery terrain.

 

Will Eaton traction modifying differentials go on my vehicles?

 

The Eaton locker is available on any GM light truck or sport utility while the limited slip differential is available on most GM rear wheel drive cars and trucks. (See our aftermarket information section.)

 

Is the locker a replacement for 4 X 4?

 

The locker is not intended to be a replacement for 4 X 4, in fact it performs equally as well on a 4 X 4 as it does on a standard rear, two-wheel-drive.

 

Why do I need this on my vehicle?

 

In today's fast paced world, people need vehicles they can trust in all kinds of weather and under all kinds of conditions. The Eaton Locker's unmatched performance inspires such trust. It provides traction in even the worst conditions and gives you the confidence to go where you want, when you want.

 

What type of lubricant and limited slip additive should I use with my newly purchased Eaton Limited Slip Differential?

 

Eaton strongly recommends utilizing an API-GL5 approved Mineral-Based 80W-90 Axle Lubricant and one 4-oz bottle of Limited Slip Additive (GM or Ford).

 

What is the spring pre-load in the standard limited slip differential unit and are upgraded spring pre-load packs available to consumers?

 

The standard spring pre-load for all Eaton Limited Slip Differentials is 400 pounds. We do offer 800 pound spring pre-load packs for high performance vehicle applications.

 

[Please Note: The 800 pound spring pre-load systems are offered for a limited number of vehicle applications, and the units have a higher propensity to produce chatter.]

 

Is the Eaton Limited Slip Differential currently available for my vehicle application?

 

The Eaton limited slip differential is currently available for several GM, Ford, and Import vehicle and/or light duty truck applications.

 

Is the Eaton Limited Slip Differential a drop-in OEM replacement part?

 

The Eaton Limited Slip has been designed to install as a drop-in replacement for most OEM vehicle applications. (Please consult your owners manual for specific vehicle replacement part requirements)

 

Is the Eaton Limited Slip Differential Rebuildable?

 

The Eaton Limited Slip Differential is rebuildable. Each of our aftermarket distributors offers service kits for the internal componentry of the unit(s) (springs, side gears, pinion gears, clutch packs, etc.).

 

Where can I buy a mechanical locker?

 

The Eaton locker is option code G80 Locking Differential on GM light trucks and SUV's. Go to Chevrolet or GMC.

 

Hope this helps.

 

[pburchett]

The additive was GM friction modifier