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Old 07-15-2011, 07:17 AM   #51
MadDog_945
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Could someone explain to me why my G80 unlocks while spinning?

Everytime i do a drift it unlocks @ about 25mph and the lightdrift turns into a straight.. kinda boring...

Is this normal funtion?

If yes, do i have to cut this weight to get the unlock speed higer or what?
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Old 07-15-2011, 07:34 AM   #52
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Hi
Read the whole tread, the answer + explanation + cure was given earlier.
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Old 07-15-2011, 09:00 AM   #53
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Quote:
Originally Posted by Turbeam View Post
That is true, but I was making the assumption that the initial engagement had already taken place. REDUCING the mass would have no effect on the engagement speed.
If you reduce the mass of the flyweight (the big one) then it will not swing out at high speed - that mass swinging out at high speed is what disables the engagement.
If it swings out then the hook is not in place to catch the small flyweights and engage the ramping action.
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Old 07-15-2011, 09:13 AM   #54
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Quote:
Originally Posted by Turbeam View Post
As for the calculation to increase cut-off speed by reducing the mass of the big centrifugal weight, I don't think this takes account of either the fulcrum length from the pivot axis of any removed mass, or even the fact that the weight doesn't have a uniform section but tapers towards the end furthest from the pivot axis. Material removed from near the tip of the mass will have a much greater effect than any removed from closer to the fulcrum.
If you support the centrifugal weight by its mounting shaft/fulcrum while weighing, all this is taken care of. The acting weight that the whole mechanism sees is the same that you are weighing with the scale. I agree, finding the center of mass by calculation would be very difficult at best, but the weighing method takes the calculation out of that part of it.

Keep in mind that the centrifugal weight is not rotating at any speed around its own shaft, so it's just a simple static weight, not a dynamic one, that is needed for this part. It is purely the mass of the part of the counterweight that you can statically weigh, rotating around the centerline of the whole differential, that is the disengaging force.

The smaller spinning weights, they are another story. But the only thing they control is the beginning lockup threshold, not the unlock threshold, and I don't think anyone really cares to modify that.
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Old 07-16-2011, 05:21 AM   #55
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Quote:
Originally Posted by kildea View Post
If you reduce the mass of the flyweight (the big one) then it will not swing out at high speed - that mass swinging out at high speed is what disables the engagement.
If it swings out then the hook is not in place to catch the small flyweights and engage the ramping action.
Again, that is correct, and this is exactly what I plan to do. The question is .... how much mass from the tip of the big weight needs to remove to only increase the disengagement speed by, say, 20mph. (or as Sstory correctly points out, the overall mass as long as it is measured in an end-over-end method similar to weighing conrod ends).

For actual practical weight reduction purposes though, removing a fixed mass from closer to the tip (furthest from the pivot point) will have a greater effect than removing it from closer to the fulcrum, as although the diff rotation generates the centrifugal effect on the big mass it is the big weights rotation around the pivot/ fulcrum which is responsible for the disengagement action (and as Kildea says, also the non-engagement at higher speeds should there be a difference in half shaft rotational speeds) and mass x distance also comes into it.

I think we are actually all agreed on the principles and even goals, but some confusion is arising in the descriptions and wording.

To recap then:-

1) The factory locking function is designed to operate only between 0-25mph (0-30kmph)to get the car moving initially on slippery surfaces.

2) Welding up or removing the large counterweight mass either partially or right back to the pivot/fulcrum will delay the disengagement function, either a little or indefinately depending on at what diff rpm it is allowed to move outwards to disengage the lock-up ....if at all against spring pressure by the centrifugal force acting on it.

3) If the weight is removed or otherwise prevented from moving outwards the diff will also be capable of locking up at any speed providing that the half-shaft speed difference is present. (ie, if the disengagement point speed is increased to 50mph by mass removal, the diff will also continue to be able to lock-up at speeds of up to 50mph).

4) Removing mass from the big weight will have no effect on the units engagement at lower speeds (below and up to the new disengagement speed even after increasing it). While the hook end of the mass remains in the 'in' position, the unit will be capable of engaging and operating the lockup function.

5) The smaller rotating barrel centrifugal weights are only there to register the half shaft speed difference in the first place and bring lock-up into engagement. Do not attempt to modify or alter any parts of these components.

6) At this time no real information exists on the effect of removing different amounts of material from the end/tip of the big mass with regards to change of its operating speed. (no matter how we plan or attempt to weigh, calculate or remove that mass)
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Old 07-18-2011, 04:56 AM   #56
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So do i understand this right that when i just want to increase my delockspeed from lets say 25 to 40 mph i just have to dewalt my flyweight. Keeping all other functions as they are?



So to say the classical G80 Locker Mod?
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Old 07-18-2011, 06:59 AM   #57
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Quote:
Originally Posted by Turbeam View Post
2) Welding up or removing the large counterweight mass either partially or right back to the pivot/fulcrum will delay the disengagement function, either a little or indefinately depending on at what diff rpm it is allowed to move outwards to disengage the lock-up ....if at all against spring pressure by the centrifugal force acting on it.
I disagree, there is no disengagement function or speed.
If it comes unlocked while under load, it is broken.

Quote:
Originally Posted by Turbeam View Post
I can't imagine the ramps themselves wearing as such, and even the friction plates have a much easier duty than those in say a normal plate type LSD.
I don't know about easier life, less heat load, but it engages with a ferocious bang every time, and can scramble the splines on the clutch plates, especially if you have more power and/or grip than stock.
Or maybe a bowl of this;
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Old 07-18-2011, 09:44 AM   #58
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And you did what to your locker to fill the pic above with scrapmetal?
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Old 07-18-2011, 01:43 PM   #59
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Why are we still talking about this? Weld the damn weights in.
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Old 07-18-2011, 02:13 PM   #60
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This may be a dumb question (I am new to Volvo), but can you just pull the cover off and drill several holes into the weight?

You would not need to weld, or pull the axle shafts out and disassemble the diff, I would think that would raise the unlock speed.
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Old 07-18-2011, 02:46 PM   #61
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Quote:
Originally Posted by 940Orlando View Post
This may be a dumb question (I am new to Volvo), but can you just pull the cover off and drill several holes into the weight?

You would not need to weld, or pull the axle shafts out and disassemble the diff, I would think that would raise the unlock speed.

Once and for all, there is no unlock speed to a properly functioning G80. There is a speed above which it will not lock. Once locked, as long as increasing power is delivered to the G80, it will not unlock.
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Old 07-18-2011, 02:50 PM   #62
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Originally Posted by 2manyturbos View Post
Once and for all, there is no unlock speed to a properly functioning G80. There is a speed above which it will not lock. Once locked, as long as increasing power is delivered to the G80, it will not unlock.
is it possible that when the car shifts (auto) or the drivers shift (stick) this unloads the diff for a moment allowing it to unlock?
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Old 07-18-2011, 02:56 PM   #63
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Quote:
Originally Posted by Mueller View Post
is it possible that when the car shifts (auto) or the drivers shift (stick) this unloads the diff for a moment allowing it to unlock?
Yes, as soon as power delivery stops, it should unlock. An auto never stops delivering power when it shifts. It's in one gear, then, the next by grabbing the next planetary gear. That's the beauty of an auto for drag racing.
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Old 07-18-2011, 06:17 PM   #64
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Mine has stayed locked for as much as 300 feet of normal straight driving after regaining traction, then surprised me with as wild and noisy next corner.

I can come to a stop with a rear wheel airborne, and brakes locked idling in D is enough to keep it locked.

It does work on ice.

I think it is supposed to need to ramp the other way to unlock.
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Old 07-18-2011, 06:17 PM   #65
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Doubleposted for emphasis.

Last edited by 745 TurboGreasel; 07-18-2011 at 06:22 PM..
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Old 07-18-2011, 09:21 PM   #66
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Quote:
Originally Posted by 745 TurboGreasel View Post
I think it is supposed to need to ramp the other way to unlock.
this
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Old 07-19-2011, 03:03 AM   #67
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Quote:
Originally Posted by 2manyturbos View Post
Once and for all, there is no unlock speed to a properly functioning G80. There is a speed above which it will not lock. Once locked, as long as increasing power is delivered to the G80, it will not unlock.
Yeah.. but too many ppl have this issue, including me.. also some ppl say once and for all the G80 schould behave like this.. so.. whos got the right once and for all?

I dont want to piss you off... just want to clarify whats going on..


To grep your explanation.. what could be wrong with my diff? And ! Could it be possible that this ramping sometimes is reached while drifting when playing with the throttle to stabilize it?
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Old 07-19-2011, 03:23 AM   #68
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Transitioning from drive to coast will unlock it.
You can weaken the holdback springs against the small weights to engage lock easier. This will doubtless increase wear, but possibly reduce shock, as there will be less time to build differential rotation. When it comes down to it, you will still ave a unit that is by its nature unsuited to any sort of performance driving, on or off road. I'm not hating, used gently , it is damn good for not getting stuck in a near stock vehicle, especially at PnP prices.
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Old 07-19-2011, 03:46 AM   #69
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Quote:
Originally Posted by 745 TurboGreasel View Post
Transitioning from drive to coast will unlock it.
You can weaken the holdback springs against the small weights to engage lock easier. This will doubtless increase wear, but possibly reduce shock, as there will be less time to build differential rotation. When it comes down to it, you will still ave a unit that is by its nature unsuited to any sort of performance driving, on or off road. I'm not hating, used gently , it is damn good for not getting stuck in a near stock vehicle, especially at PnP prices.
Mine has lived for quite awhile behind a 400whp 16v motor. It just recently nuked the locking mechanism but seems to me that its a reasonably good part fore even moderately powered volvos.
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Old 07-19-2011, 04:25 AM   #70
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so 2? years with stock wheelwells? How much time on slicks? Your car weighs how many hundred pounds less than a fully dressed 940?
But really what I take issue with is the way engagement requires substantial wheelspin, then just shocks the other tire loose.
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Old 07-19-2011, 04:55 AM   #71
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Well the G80 was the first mod on the car. 3 years of performance only driving. I have a dozen or so 1.6-1.7 60' time slips on slicks and have slid the car around streets of willow, Adams kart track, let several people co-drive it at Davis auto-x the last two years and constant street abuse. We will see how long g80#2 lasts at this power level.

My full weight 245 has had one for ~5 years. Not nearly the power of the 242 but plenty of torque and huge loads. I have had this car/diff offroad in Baja with 1000lb of gear in the back (diff doing its thing hours on end), flat towed my 242 to the track, launched boats (slick launch ramps definitely make use of the locker). The g80 is still holding up fine. Makes the car so much more useful and for a minimal investment.

There are better diffs out there, they just cost a hell of a lot more than the $30~50 a moded g80 does. Bang for the buck is pretty damn good.
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Old 07-19-2011, 05:04 AM   #72
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Quote:
Originally Posted by 745 TurboGreasel View Post
Transitioning from drive to coast will unlock it.
it just pisses me off that it unlocks while drifting.. so.. you do think it comes from playing with throttle? Mh.. normally when im in a drift the tires are spinning, sometimes faster/slower but never stop.. so there shouldtn be a transition between driving and coasting...

Naahh...
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Old 07-19-2011, 05:52 AM   #73
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The one in my truck might be 25 years old. My contact patches are as much as a foot wide, and nice gear oil cost more than the axle I put it in. I don't go out of my way to thrash on it, and it hasn't broke yet. I have no regrets, it's a whole lot better than an open diff.

Maddog, could it be your tires are still sliding because you are going sideways and your wheel speed is momentarily less than ground speed?
But you are going over 25, so it won't lock up again.
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Old 07-19-2011, 05:52 AM   #74
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Really? again.
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Old 07-19-2011, 06:02 AM   #75
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Originally Posted by 745 TurboGreasel View Post
I disagree, there is no disengagement function or speed.
If it comes unlocked while under load, it is broken.


I don't know about easier life, less heat load, but it engages with a ferocious bang every time, and can scramble the splines on the clutch plates, especially if you have more power and/or grip than stock.
Or maybe a bowl of this;

This has not been my experience of the unit, but much of the difference in their operation may be down to the very different usage that they get between our cars.

In mine, it is certainly disengaging, but that is under cornering loads and with a manual transmission and up to 12" slicks. It may not be under such constant loading as with an auto, but that may also be because the speeds where slip begins to occur is already above the 25mph stock 'engagement/ disengagement' maximum speed, and if much below that speed a gear change would be needed before very long.

No doubt you will also be starting off from full throttle from 0mph onwards and not lifting off at all, where on a circuit the throttle could be rolled on and off or feathered to the suit available grip and cornering radius so the load fluctuates.

The first step for me then is still to increase the engagement speed a little by reduction of the big mass.


The ferocity of engagement is a valid point, but even so I believe the shock loading on the half shafts and across the diff forging itself is the real issue. The clutch friction plates will only see this very briefly until the force on the ramps locks it all up when there will be no significant further slip.

It would be interesting to see if any of the shock load could be reduced by softening of the springs controlling the rotating weights to reduce the required half shaft speed difference that activates engagement?

I'm curious as to the cause of failure of the G80 in the photo. Was this diff already modified to allow engagement at higher speed.... it looks unmodifieed in the photo? Did it fail on initial engagement at low speed or when moving faster? I don't personally believe that either the G80's clutch packs or its ramps will be the weakest link in the chain.

The fracture of the main diff body forging looks like a material failure around the big mass pivot pin bores? I take it that it failed during actual lock-up?

If serious wheelspin was to occur on a high-output car running big slicks and a modified G80 at higher road speed and rpm, the shock torque load across the axle immediately as the diff locked could be huge. There might even be an argument for reducing the clutch pack friction area and introducing more slip during lock-up to try to 'soften' the engagement?

We can't really complain too much about a unit failing like that that if we are asking it to do much more than it was ever designed or intended to, but for some uses it could still be a useful and low cost option with only minor mods.
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