View Full Version : G80 doesn't seem to lock in reverse
I found myself in a position today where I had to back up a muddy hill. I was in 4LO and was having some issues moving. My front driver side wheel was spinning, but the driver side rear wasn't.
Does the G80 only lock going forward or do I have an issue with my unit?
I was eventually able to back up the hill, but it sure would have helped if the G80 had locked up in reverse. I was positioning myself to pull out a F150 with my winch, btw. :D
I'd love to gain manual control of when the G80 locks up as opposed to the current 'automatic' method.
I'm also wondering if there is a kit available to lock up the front diff?
huntindog
02-15-2003, 18:59
I know for a fact that mine locks in reverse.
I too was in some mud, with a trailer attached.
If mine hadn't locked I'd probably still be there!!
Seriously, My "spotter" told me that they were both spinning.
GMCTRUCK
02-15-2003, 19:58
The G80 uses inertia to lock. One wheel has to spin for the locker to engage. Problem is with this Eaton locker the wheel usually has to get spinning pretty good before the other will lock in. Some trucks seem to take more wheelspeed than others for it to work. Definitely not the slickest set up. The factory locker in my 79 locks much faster and stays locked.
Actually you'd be surprised at how little difference in rpms between the two driveshafts it takes to lock. The spec is 100 rpm. That is not much at all. Remember, it is the velocity that locks it and it usually occurs within less than a revolution. They had a sample rear setup at the Power Launch tour here local a few years ago. It had knurled handles that you could turn like drive shafts. You hold one and turn the other briskly and it lock instantaneously.
hoot's correct - the locker engages with at least a 100 RPM difference between the rear wheels. Also, it is does not lock above about 20 MPH.
Additionally, if you were in 4 low the one wheel may not have been spinning fast enough. We have a very low reverse gear.
Steve
CPMac632
02-16-2003, 13:17
ARB makes a locker for the front as well as the new ELock is also available. That might not be all I don't know of any others.
YZ, I think you're right. I was trying not to tear things up too much so I probably wasn't even going 100 RPM with the rear that was spinning.
Been out playing in the snow/ice today (we're getting pounded here in Central VA), and verified that I had no problem spinning both rears in 2 Hi reversing into my driveway.
I'll check out the ARB stuff as I'd really like to manually control when my diffs lock, like when trying to slowly ease out of a situation where I don't want to get to a 100 RPM differential before locking occurs.
C5dura
From the Eaton G80 Page:
The differential is set up with a flyweight governor that responds to differences in wheel speeds, and disc packs that are mounted between the side gear and the case.
Whenever one wheel is spinning substantially faster than the other, the governor spins rapidly, causing the flyweight to open. That flyweight then catches on a latching bracket and the lockup process begins.
During lockup, a self-energized clutch system causes a cam plate to ramp against a side gear. This ramping action compresses those disc packs mentioned earlier. The ramping continues until both axles - and therefore both wheels - are spinning at the same speed. This is full lock, and it prevents any further wheel slip. (Note: Axle lockup can only occur at speeds below 20 mph.)
The entire lockup process takes about a split second, and is virtually unnoticeable by the average driver. When both wheels regain traction, unlocking occurs and things go back to normal.
----------------------------------------------
Some info on the Detroit Electrac Locker:
The Detroit Electrac Locker operates as either a helical-gear, Truetac-like limited-slip or fully locked differential, depending upon which mode the driver selects. The shift from LSD to locker happens at the push of a button. A shift fork engages a trigger ring to either lock or unlock the unit.
The first Detroit Electrac Lockers, for Dana 44 axles, hit the dealer shelves in late 2002. The next application, for Dana 60's, should be available by February, 2003.
http://www.tractech.com/WhatsNew.htm
PDF brochure- http://www.tractech.com/docs/DetroitElectrac.pdf
I can sure tell when mine locks up. If one wheel is on snow and the other on pavement, it gives quite a slap in the back when it locks. You know it's there! It would be nice to have an electrically controlled engagement but overall I really like it. It's also good that it disengages above 20 mph or so. For the average driver who is not aware, if both are locked and spinning, you can loop it in a hurry as you guys know.
Steve
c5dura,
The G80 only pertains to the rear axle, not the front axle.
btw-I have a PPT file of the engagement curve for the Eaton Locker. If you are interested, shoot me an email.
wangotango
02-20-2003, 00:23
I assume that this locking will take place weather or not you are in 4wd.
Correct?
tks -- w/t
Forced Induction
02-20-2003, 10:40
When going around a turn, and lay into it when the road is wet my truck will sit there and spin one when thru the gears. The only way I can get the truck to slide around a corner is to have tension on the rear before entering the turn and then lay into it. If I coast around the turn and get in it while differential action is taking place it will not lock up. Is this normal?? It would see to be, but i'm not sure. My other truck has a Moroso Brute Strength carrier (clutch type posi) in it and it is locked whenever I hit the throttle, no matter what.
JA
battmain
02-20-2003, 19:32
"When going around a turn, and lay into it when the road is wet my truck will sit there and spin one when thru the gears. The only way I can get the truck to slide around a corner is to have tension on the rear before entering the turn and then lay into it. "
Check your speed when it wont lock up. I'm usually doing over 20mph when one wheel spins. Yeah, it's a great stress relief to see the tailgaters back away when you do that in the wet. smile.gif Some of them are so close you can't see their headlights.
wangotango
02-21-2003, 00:40
c5dura - thanks
w/t
I was up north this weekend and had to put the truck into 4wd four times becouse the rearend would not lock up forword or reverse , I had both rear tires on snow/ice no lock up, one (right rear) on ice and the left on pavement and still no lock up. I had the dealer do a rear end service about 4k miles ago since then I noticed more one wheel spin, they put the gm synthetic gear oil $28 a qt. did they mess up the rear end ?
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