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Old 03-14-2018, 12:41 PM   #1
LeedomtoFreedom
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Default G80 Making a Fuss?

Only recently has a rumble occurred in my car, it seems central the the rear passenger wheel and ONLY happens during right hand turns.

All of the bushings have been replaced very recently, which leads me to believe it's related to the g80 acting up.

It almost seems like the g80 is engaging too quickly and because I have summer tires on, it makes a lot of noise and vibration.

any thoughts?
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Old 03-14-2018, 01:06 PM   #2
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Jack it up, spin the wheels, see what happens.

It's basically an LSD with a very VERY low preload, that tightens once you exceed 100 rpm difference side to side (flywheels swing out, engage, it clamps down on the clutch pack).

On mine, it's barely noticeable as anything other than a normal open diff until you spin it fast enough.
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Old 03-14-2018, 01:10 PM   #3
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I jacked it up and couldn't get it to lock with my hands by spinning it. When I spin one wheel, the opposite wheel spins slightly. I couldn't notice any substantial play in the whole axle that might cause this.
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Old 03-14-2018, 01:13 PM   #4
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Quote:
the opposite wheel spins slightly
correction, it spins slightly in the opposite direction.
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Old 03-14-2018, 01:18 PM   #5
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As it should. If you leave it in park or in gear (AT or MT) then the driveshaft won't turn and it will maximize the RPM difference. It's 'around' 100 rpm, on mine I had to really get it spinning pretty good before it would engage.

Although if you're not hearing any weird noises out of it from what you did, you probably don't have any issues with the G80 in turns. It's designed specifically to not engage unless there's a very significant wheel speed difference.

As well as being prevented from engaging at all, regardless of wheelspin, over roughly 25 mph.
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Old 03-14-2018, 01:21 PM   #6
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The flywheel has been cut from my g80, allowing it to engage whenever.

I have no place to start then, trying to figure out this rumble.
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Old 03-14-2018, 01:42 PM   #7
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There's still a smaller set of flyweights that kick in to engage it at the 100(ish) RPM difference.

Wheel bearings?
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Old 03-14-2018, 01:49 PM   #8
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Just put your floor jack under either trailing arm and jack up one side of the rear axle. Make sure the jack is pointed in the same direction the car can roll. Start the car, put it in gear and ease your foot off the brake. After a couple of revolutions of the rear wheel that is up the G80 should lock and move the car forward. If it doesn't lock, something is broken or severely worn.
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Old 03-14-2018, 02:47 PM   #9
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So you want me to let the car roll on the jack on one side? like a crutch or something ?
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Old 03-14-2018, 02:49 PM   #10
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You should be able to do it by hand.

Although in this case, we're not diagnosing if the G80 works, we're diagnosing a rumble in tight corners. The G80 isn't trying to kick in in a tight corner unless you're stomping on that gas pedal and spinning a tire.
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Old 03-14-2018, 02:59 PM   #11
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It usually doesn't happen going through quicker, longer corners. Just tight ones.

I recently had the thread about the vibrations in the drive-train. While I've basically sorted that, I'm curious if it's somehow related, even though I can't think of how it would be.
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Old 03-14-2018, 03:00 PM   #12
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Quote:
Originally Posted by JohnMc View Post
You should be able to do it by hand.

Although in this case, we're not diagnosing if the G80 works, we're diagnosing a rumble in tight corners. The G80 isn't trying to kick in in a tight corner unless you're stomping on that gas pedal and spinning a tire.
I've had several that wouldn't lock when turned by hand, however, would almost instantly lock when one side is jacked up. I know you are trying to figure out a rumble. It could be a spider gear problem. It also could be that something broke in the G80. They supposedly get noisy when damaged.

OP, yes, like a set of training wheels, crutch, however you want so see it. If the G80 is working properly, it will lock and move the car forward. If you then put it in reverse and do the same thing, the wheel up in the air should turn 1-2 turns and the G80 will again lock, going backwards. If it behaves like that, it is working like it should.
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Old 03-14-2018, 03:13 PM   #13
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Interesting, both of the ones I have are trivial to engage by hand on the car or out of the car on axle stands - you can clearly feel the "knock" of the inertia of the other side attaching to your side.
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Old 03-14-2018, 03:17 PM   #14
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Yep, jack it up, leave it in gear so it doesn't spin the driveshaft, spin spin spin clunk.

The junkyard G80 I got is apparently somewhat worn, it never really locked up all that solidly on the road, but you can really 100% feel it engage when spinning it by hand. Freely spinning *clunk* - can't budge it by hand.

And again, if it's not making noises while you spin it, you should probably start looking elsewhere. Regardless of it finally engaging or not.
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Old 03-14-2018, 03:19 PM   #15
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Alright guys, after I jacked up the car an hour ago, I went to drive it in my neighborhood making only right turns like a UPS truck, and found that it didn't happen a single time.

I'm not saying I've got the magic touch, but maybe I do? If anyone needs my services, my rates are reasonable.
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Old 03-14-2018, 03:21 PM   #16
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I'm obviously not convinced it's gone, but I'll wait and see. If it comes back, I'll test the g80 trying both methods.
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Old 03-14-2018, 05:03 PM   #17
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Quote:
Originally Posted by JohnMc View Post
Yep, jack it up, leave it in gear so it doesn't spin the driveshaft, spin spin spin clunk.

The junkyard G80 I got is apparently somewhat worn, it never really locked up all that solidly on the road, but you can really 100% feel it engage when spinning it by hand. Freely spinning *clunk* - can't budge it by hand.

And again, if it's not making noises while you spin it, you should probably start looking elsewhere. Regardless of it finally engaging or not.
After selling you that one that didn't lock up hard, I test them all the way I'm describing, only, I block the front wheels and leave my foot on the brake a bit. They will lock hard and spin the tire on the ground when working correctly. I know that doesn't make you feel any better. The 740 we used to autocross would leave two stripes black as coal when the turbo hit if you weren't paying attention. It finally was abused enough it wouldn't even leave a mark on the outside tire when cornering. That locker has since been replaced with another one.
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Old 03-14-2018, 08:38 PM   #18
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Did you sell me that one? I forget. I sort of half thought I'd grabbed it from a junkyard around here. I did grab one from a fairly low mileage 940 a few years ago, I've just been too lazy to sap them.
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Old 03-14-2018, 08:46 PM   #19
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Yes. I sold it to you and once installed, you mentioned in another thread that you were underwhelmed with G80 locker performance. It made me examine their performance much closer before pulling them. I encountered a couple of them that had so little power transfer I didn't bother pulling them. I've probably pulled and sold 20+ so far.
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Old 03-14-2018, 08:52 PM   #20
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The condition probably depends more on the way they were driven than the miles the car has.
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Old 03-14-2018, 10:14 PM   #21
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I would think you could purchase new plates and restore it's function. I swapped some less worn ones from a rusty g80 into the one in my car when I installed it.
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Old 03-15-2018, 08:15 PM   #22
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I've made a liar out of myself. But in light of it's return, I had a thought.

My shocks are completely blown, rusty, and 40 years old. Could the combination of the shocks not dampening the wheels when they try to stick in a turn, like wheel hop?

Does this make sense ?
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Old 03-25-2018, 12:52 AM   #23
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Liar
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I've got a real issue with you Wilford
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Old 03-25-2018, 12:49 PM   #24
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Liar
I've got a real issue with you Wilford
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Old 03-25-2018, 12:57 PM   #25
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I've got a real issue with you Wilford
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