• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

G80 locker, a few questions for those who have modded one.

Above a certain speed the ENGAGEMENT is disabled, yes, but it is also disengaged if it was previously engaged as well. The video does not show this happening, but in my experience it is, in fact, disengaged as well. Kildea, I know you said previously that the angle of the pawl-engagement "hook" doesn't seem to be sufficient to allow disengagement, but there's no other way to explain what some of us are experiencing. When my diff unlocks, it is not progressive. You can instantly hear one wheel spinning up faster than another, and you're not going sideways anymore. The locking action is very good. If any wear was present in the diff, wouldn't the lockup "quality" be affected?
 
Above a certain speed the ENGAGEMENT is disabled, yes, but it is also disengaged if it was previously engaged as well. The video does not show this happening, but in my experience it is, in fact, disengaged as well. Kildea, I know you said previously that the angle of the pawl-engagement "hook" doesn't seem to be sufficient to allow disengagement, but there's no other way to explain what some of us are experiencing. When my diff unlocks, it is not progressive. You can instantly hear one wheel spinning up faster than another, and you're not going sideways anymore. The locking action is very good. If any wear was present in the diff, wouldn't the lockup "quality" be affected?
 
sstory0626 said:
Kildea, I know you said previously that the angle of the pawl-engagement "hook" doesn't seem to be sufficient to allow disengagement, but there's no other way to explain what some of us are experiencing. When my diff unlocks, it is not progressive. You can instantly hear one wheel spinning up faster than another, and you're not going sideways anymore. The locking action is very good. If any wear was present in the diff, wouldn't the lockup "quality" be affected?
Click to expand...

Sure there is - the thing that keeps it locked is the static friction between the plates, when the ramp sandwiches them together the increase in normal force is abrupt. If the wheel that initially had traction looses traction - the ramp mechanism will be disengaged. If the threshold (dictated by the normal and the surfaces of the plates) is lower, due to worn out plates, it will be easier to un-sandwich the ramps. I explained this above I think, if you don't see why then watch that video again - the ramp backs off and the flyweights disengage when the direction of rotation of the spiders changes. If the threshold is lower the torque required to do this will be lower.

Maybe the best thing would be to measure the lever arm of the hook contact point vs the moment of the weight and produce some numbers, that will answer this question one way or the other, since speculating about it isn't really very useful anyways - I'll do this on the weekend and report back. That angle of engagement should tell us a lot, it may pull the pawl back after all - it's silly of me to try to determine that by looking at pictures.
 
Last edited:
A bit of analysis:
If you want to, say double the speed at which the diff disengages/is prevented from locking, you would want to have the same amount of action by the counterweight but at the higher speed. Since the counterweight is generating centripetal force, you could go about it like this:

Fc=(mv^2)/r,
where FC = Centripetal Force,
m = mass of acting part of the counterweight
v = rotational velocity, or just the speed since the units on this cancel anyway
r = radius from center of the diff to the center of mass of the counterweight

Since we want to keep Fc the same, we can set two equations equal to each other:
(m1 v1^2) / r=(m2 v2^2) / r
where m1 = initial counterweight mass
m2 = modified counterweight mass required for diff unlock at desired speed
v1 = initial unlock speed
v2 = desired unlock speed

And solve for the second mass:
m2 = (m1 v1^2) / v2^2

As a quick example, you could look at a an unlock speed of 50mph, or 2x the original unlock speed . Since in this case v2 = 2 x v1, we can substitute it in and solve for m2:
m2 = m1 / 4

So you can see that the amount of mass required to disengage the diff at twice the speed would be 1/4 it's original weight. Now you can't go just hacking off 3/4 of the length of that large counterweight, because the pawl acts as a counterweight. You would need to set up the pawl so the shaft was frictionlessly supported (kind of like when balancing an R/C airplane prop), and have the large counterweight resting on a fairly precise scale. Re-weighing as you go, cut off progressively more of the counterweight until the desired mass is achieved.

Practically, I'm not sure how many of us: A. Do enough of our own work like this and B. Have access to a scale sensitive enough for this requirement?
And also, I know this is all theoretical talk its function in the real world will vary a bit from theory, but I think the ability to weigh the counterweight is key to being able to tune it.

And as for my DD, it has an open diff. My racecar, it will probably have a welded diff because I'm too cheap to get a decent limited-slip, and I don't have the time for all the junk mentioned above:)
 
As for wear and the unlock function, think of the ramps like this: as the side gear moves up the ramps, the contact area between the two becomes less and less, while the amount of force between the two becomes more, wearing the tops of the ramps like a cam lobe. I would venture that if anything wears out (besides the clutch packs), it would be the tops of these ramps. If the ramps are worn, the angle relative to the clutch packs decreases, and the force between the two becomes higher. Therefore, wouldn't the tendency to stay locked after release be increased with wear? And if the clutch plates wear, they would allow the "ramp washer" to sink farther away from the side gear, exacerbating the problem? Or are you seeing another area of wear that I'm not?
 
As for wear and the unlock function, think of the ramps like this: as the side gear moves up the ramps, the contact area between the two becomes less and less, while the amount of force between the two becomes more, wearing the tops of the ramps like a cam lobe. I would venture that if anything wears out (besides the clutch packs), it would be the tops of these ramps. If the ramps are worn, the angle relative to the clutch packs decreases, and the force between the two becomes higher. Therefore, wouldn't the tendency to stay locked after release be increased with wear? And if the clutch plates wear, they would allow the "ramp washer" to sink farther away from the side gear, exacerbating the problem? Or are you seeing another area of wear that I'm not?
 
sstory0626 said:
As for wear and the unlock function, think of the ramps like this: as the side gear moves up the ramps, the contact area between the two becomes less and less, while the amount of force between the two becomes more, wearing the tops of the ramps like a cam lobe. I would venture that if anything wears out (besides the clutch packs), it would be the tops of these ramps. If the ramps are worn, the angle relative to the clutch packs decreases, and the force between the two becomes higher. Therefore, wouldn't the tendency to stay locked after release be increased with wear? And if the clutch plates wear, they would allow the "ramp washer" to sink farther away from the side gear, exacerbating the problem? Or are you seeing another area of wear that I'm not?
Click to expand...


The ramps don't come into contact at their tops, so I do not think they are going to wear enough to change the angle of contact, however keep in mind the normal is also decreased when you change that angle (at a given lock-up wheel torque) so I'm not sure it would make a difference as you propose.
When I took mine apart there was no wear on the ramps - I'll do another disassembly on the weekend, I'm happy to get pics of all of the related parts.
I think you need to get your hands on one of these things, take it apart and spend time tinkering with it a bit, it's difficult to use text to explore the workings. I do understand what you are getting at, keep in mind the ramps are straight-lined, so getting deeper into the ramp you don't change the angle of contact - unlike with a cam lobe. It's just the ramps are a rather hard and smooth metal, and they only see any wear when the actual thing is engaged, since the nubs are there they are in their rest position at all other times.

picture.php


That's what they looked like before I started in with my initial hair-brained scheme - I have a fresh one though too, ready for disassembly (it's the new type from a v90). I was thinking similarly though, I thought if I could get the thing to have a progressively shallower angle that the ramps would wedge together easily and hold tight, I removed the nubs and added shims hoping it'd engage on its own and be more like an lsd - turns out it just constantly wore the clutch packs down until they wouldn't stay locked at all. Made for a rather embarrassing attempted donut in a (nearly) abandoned parking lot on the cape in fact.
 
Last edited:
Good stuff. Man, I wish I had more time. I have a two girls, 1 1/2 and 4 yrs old. Going back to school to finish my degree, working full time. 'Nuff said.
It is really nice to see all the discussion about this though!
 
Good stuff. Man, I wish I had more time. I have a two girls, 1 1/2 and 4 yrs old. Going back to school to finish my degree, working full time. 'Nuff said.
It is really nice to see all the discussion about this though!
 
kildea said:
Watch the video again, when the large outer weight swings out the hooks that catch the flyweights (stopping the spinning of the countershaft, and engaging the ramp mechanism) are out of reach - above a certain speed the ENGAGEMENT is disabled.
Click to expand...

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.

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.

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.

No doubt there will be a calculation to work out the mass/ distance from pivot that needs to be removed, but it is a much more complex one that is beyond my math.

This brings us back to the old-school laborious trial-and-error method of just removing a small amount of weight from the thin end (furthest from the pivot axis), reassemble, and 'such it and see' how much difference it makes before repeating the process.

This idea opens up the possibility of making an adjustable centrifugal system, by moving the same overall mass further from the pivot point to increase its centrifugal effect and vice versa. it could be done by an overlap and clamp bolt arrangement or possibly by screw adjustment and locknuts holding a two-piece mass together, but I don't fancy the thought of either failing in service and coming adrift.

The simplest and safest method (if the most time consuming) must be just slicing off a little material from the end and trying it out before taking a calculated guess at how much more weight if any needs to be removed the next time.

I guess there isn't too much data around on the effect of removing different smaller amounts of material from nearer the tip of the centrifugal mass?
 
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?
 
Turbeam said:
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.
Click to expand...

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.
 
Turbeam said:
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.
Click to expand...

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.
 
kildea said:
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.
Click to expand...

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)
 
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?
 
Turbeam said:
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.
Click to expand...
I disagree, there is no disengagement function or speed.
If it comes unlocked while under load, it is broken.

Turbeam said:
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.
Click to expand...
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;
261672450.jpg
 
Last edited:
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.
 
You must log in or register to reply here.
Back
Top