Rear Diff. Question

[gophergunner]

If I'm not mistaken, I was told that the rear diff. on the newer gmc/chev trucks is an AAM 11.5"

I'm curious if there are any aftermarket lockers available for this axle?

Preferrably something mechanical, like a Detroit Locker.

Thanks

[DmaxMaverick]

Check your RPO sticker in the glove box. If you see a "G80" code, you already have a good locker. The OEM locker in these is the Eaton Gov-Loc. Unless you need a serious locker for serious off roading, you won't do any better. If you want a manual locking diff, there are electric and air lockers to choose from. A Detroit locker is a very poor choice for a daily driver. The Eaton works similar, in that it is a positive locker (not "limited slip"). Only it is unlocked until wheel slip, while a Detroit is locked until there is a differential wheel speed (like in a turn). A serious downside of the Detroit is it may not unlock when you need it to most, like on an snowy/icy highway in a turn.

Try a search of the Drivetrain Forum (where you posted this thread) for more info. Use search terms G80, locker, Eaton, Gov-Loc, E-Locker (or variations). Lots of previous discussion.

[gophergunner]

Is the gov-lok in these axles anything like the gov-lok used in the older 14-bolt 10.5" axles? Because didn't those things break due to the way they actually functioned?

I know the thing is supposed to lock with something around 100 rpm difference between the 2 rear wheels. When i have my truck lifted on the jack i can even get it to lock, but there are times when it will not lock on the street and only one tire will spin. That really bugs me, especially since i'm noticing it more and more.

[DmaxMaverick]

Similar, but not the same.

The Gov-Loc isn't really "dumb". It will not engage if the wheel speed is above a set speed. I don't know what exactly it is, but 25 MPH is close. If your wheel (vehicle) speed is high, locking could be disastrous. Not just possible damage to the locker, but it could cause you to lose control of the back end (soon to be the front end) of the truck. The Gov-Loc in these trucks have proven to be very durable, effective, and reliable. If you can get it to lock while on stands, it's working. 100 RPM differential isn't really that much, but enough for the locker to safely engage when it needs to, and just as important, not engage when it doesn't. It is a passive system, but will work as advertised. We've heard of very, very few issues with them. Even those that spend a lot of time at the track don't break often.

[gophergunner]

Hey thanks, this is all really good info actually. I'm thinking maybe my driving habbits don't exactly agree with how the gov-lok works. It's not very often in the summer that i have trouble, unless its a gravel road or wet pavement, but in the winter on ice and snow is where I get frustrated the most. Driving in 4x4 of course usually eliminates any trouble, but I don't want to be driving around in 4x4 all the time.

I may still have to reconsider....

But thanks for the info.

[DmaxMaverick]

Suit yourself, but you have to be very careful with what you think you need or want. The rear diff should be "open" during 99% of your driving. You do not want it locked with normal driving. If you are losing traction at one wheel, locking them usually causes loss of traction at both wheels. It's not just about getting both wheels spinning to go forward, but reduced traction at both wheels removes your ability to drive straight. If you've ever "lost it" on snow/ice, you know it happens quickly, and is difficult to get back to a straight line. Even driving around in town on slick roads with a Detroit type locker will keep you and your insurance agent busy, more often than not. Bear in mind, I'm not trying to tell you what works best for you, but in most cases, it is much better for you to adjust your driving habits to the conditions, rather than trying to adjust your vehicle to your driving habits. The former will help keep you out of situations, while the latter will usually get you into them.

[93GMCSierra]

For me the locking would be required for deep snow and or mud, but again that is not "On Road" at least not most of the time, though there are times it is.