I was watching Motor Week a while back and they were testing the new Chevy Silverado. Then they had another segment where they had a 4x4 F250 with a limited slip rearend and a C1500 4x2 with the new locking rearend. They never used the 4 wheel drive because they were comparing the the Chevy and Ford rearends. I can't remember who makes the rear end that Chevy uses, but they were at that companies testing facilities. Anyways the Ford did fine with one tire on wet pavement and one tire on dry pavement. Then they went up a hill with one tire on rollers and the other on dry concrete. The ford couldn't make it up. The Chevy spun for a second or two then the locker kicked in and it made it up fine. They said the Chevy locker will automatically lock when there is a difference of 100 or 300 RPM between each wheel (I can't remember which it was). The Chevy did alot better than the Ford with limited slip in the mud also. They were trying to make the point that a 4x2 with a locker is better than nothing if you don't have 4 wheel drive.

 

In all probability that is nothing new, but just the same locking differential that GM has offered for a decade or two rather than a conventional clutch-based limited slip. If I am correct, it is made by Eaton, and sometimes goes by the name of "gov-lock". I think it is not particularly strong, and is sometimes nicknamed the "grenade locker" due to a tendancy to not stand up well to abuse.

 

Well whatever it is, it outperformed the Ford LS rear end. Chevy is touting it as something new. After seeing it demonstrated on TV I wish Ford would offer something similar.

 

IIRC, the new Chevy rear axle is an electric locker made by Eaton. IIRC, it's fully selectable, and automatically controlled and can be manually locked. IIRC, it's similar in design to the Eaton ElecTrac, but proprietary to GM axles.

IMHO, it's a waste of money. It's not really necessary for everyday use, and a pretty expensive option on the GM trucks. You could retrofit a Ford rear end with any number of selectable lockers (Eaton E-locker, ARB Air Locker come to mind) or automatic lockers for far, far less money.

-Joe

 

GIJoe,

According to Chevy's website, '07 Silverados can be equipped with an optional automatic locking differential, which is almost certainly the Eaton Gov-Lok. There was no mention that I could find of a selectable locker.

I know that a selectable electric locker is available on some GM products such as Hummers, but so far I can't find where it is available on Silverados.

If you have other information, point it out...I'm not bashful about eating crow.

 

An automatic locker sends 100% of the drivetrain power to both axles in the the third member whenever torque is applied (ie., gas pedal pressed). The best automatic locker that comes to mind is the Detroit Locker.

What is being described in the post above is not an automatic locker. Chevrolet has been using the 'gov-loc' limited slip for many years. Maybe they are just trying a new ad campaign on the same or slightly modified product.

 

Straight from Chevy's website: http://www.chevrolet.com/silverado/features/

Automatic Locking Rear Differential
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When rear-wheel slippage is detected at lower speeds, the available GM segment-exclusive(1) automatic locking rear differential allows additional traction on snow,mud and ice, or even a wet boat ramp. If one of the rear wheels has traction while the other does not, the locking rear axle automatically sends power to the wheel with grip to move the vehicle. Locking rear differential benefits include:

Enhanced performance for on- and off-road driving and towing.
Full lockup for maximum drive power to both rear wheels.
Fully automatic engagement.
Speed-sensitive actuation, which provides axle lockup when one wheel spins faster than the other.
Based on 2006 GM Large Pickup segment and latest available competitive information.

From Eaton's website: http://www.traction.eaton.com/prod6.htm

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.

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.)

I don't think this is the same thing as a GM Posi Trac. See my first post. This rear end was tested against a Ford LS rear end and the Chevy would slip for a second then the rear end would lock and both wheels would turn. The Ford would spin a tire on one side and the tire on the other side would barely turn.

 

This is an excellent advertising campaign with slick wording. If you want to 'change' the definition of an automatic locker than yes, this is a new definition.

An auomatic locker provides 100% of the engine torque to the axles whenever torque input is sensed (stepping on the gas). It disengages when there is no torque on the axles and RPM change in the axles is detected (going around a corner). What is being described in the article you site is a fancy limited slip, not an automatic locker. Automatic lockers do not lock up when there is a difference of a few hundred RPM. That is a recipe for broken axles. broken ring gears, broken pinions, etc. View a rock crawling competition sometime to see why.

Notice the wording in the Eaton article. It does not state 100% torque to both axles, it states full lockup, I guarantee you full lock up is not 100% torque to both axles.

Call an Eaton engineer, not a sales rep. You will get the proper low down on what an automatic locker verse a limited slip differential is and not a play with words like is being cited above.

 

Well great it's a slick new advertising campaign. However that still doesn't address the fact that I watched this rear end being demonstrated against the Ford LS rear end.

Both vehicles were driven on pavement where one wheel was on dry pavement and the other wheel was on wet pavement. The Ford LS worked just as well as the Chevy.

Next they had a hill with rollers on one side i.e. one wheel was on the pavement the other on the rollers. The Ford got to the rollers and stopped. One wheel spun while the other wheel didn't do much of anything. The Chevy got to the rollers, the wheel spun for a second or so, then the wheel on the other side kicked in and it made it up the hill.

Finally they tested it in on uneven terrain like going across a ditch. When the Ford got one wheel off the ground it stopped and the other wheel wouldn't engage. When the Chevy got one wheel off the ground that wheel spun for a second or so then the other wheel kicked in and it started moving again.

Slick marketing campaign or not, the demonstration was very convincing.

 

I am not doubting the demonstration. Quite sure there have been improvements in limited slips over the last 50 years. I know many people in my old Jeep club would run straight gear lube in the third member to 'tighten up' the limited slip differential. It shortened the useful life of the limited slip, but it sure worked.

Check out this months issues of Four Wheeler and Petersons Off-Road magazines. Both of them have the yearly shootout for which manufacturer has the best new 4WD vehicle. If memory serves me correctly there were 5 GM/Chevy trucks in the tests. They were all equipped with a limited slip. All the editors commented they wish Chevy/GM would equip the trucks with lockers.