Newbie
I have a 2003 Druamax/Allison combo and was wondering if it came stock with a limited slip diff, or is it an option. If it was an option is there any way of finding out if my truck has it. I can't seem to find the paperwork on it and I also did a search but it didn't come up with any answers. Thanks for the help...Bob
Administrator
Look in the glove box for the RPO sticker. The locking rear axle code is "G80".
You won't have "limited slip", in any case. The OEM option is an Eaton Gov-Loc, which is a locking axle, not limited slip. No matter which you have, be sure to use quality synthetic lube, as recommended, and NO additive.
Newbie
Just found my paperwork. It always takes the wife to find that kind of stuff. I did get the Locking Diff. So can anyone tell me the difference between a limited slip and a locking diff? Which is better. I will also do a search on G80. Thanks gain
Administrator
The RPO code "G80" has been GM's designation for any rear end that has either limited slip or locker, on all models, for as long as they've had RPO codes.
Limited slip is just that. Limited slip. The left and right axles always have friction between them, and allow power to be applied to a lesser traction axle, but not "positive" power.
A locker, on the other hand, in our case, stays open, like a traditional differential until wheel spin happens. Then the carrier locks both axles together, giving 100% power to both axles equally.
Limited slip is subtle and is always engaged. A locker is ON/OFF, depending on traction at the wheels.
The Eaton Gov-Loc on our newer trucks (1995 and up) acts like a Detroit locker, only not as violent or persistent. In my experience with the OEM lockers since 1995, they have been very durable and reliable.
Limited slip on the other hand is a different story. I've always had problems with OEM limited slip (pre 1995). They are weak and don't offer much performance gain. I've upgraded several to Auburn limited slip (auburngear.com) in those cases, and have been happy with them.
As far as which is better?
Depends on your needs. For most people, it doesn't matter. If you get off the beaten path, the locker will help you out of a sticky situation, where a stock L/S won't do much. There are performance limited slips (Auburn) that work better, but still not as positive as a true locker. The absolute best to have is a selectable locker. They are selected by a switch in the passenger compartment, and are operated either pneumatically or electrically. Eaton has a new setup for our trucks called an E-Locker (aftermarket). It is an electric switched locker for either the front or rear end. Looks like a nice setup.
Newbie
Thanks for all the info. i just bought a boat and don't have 4WD so I am hoping it will be able to get up the ramp without a problem. We'll see tomorrow. Thanks again
Bob
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