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

well, following on from this thread: http://turbobricks.com/mods.php?content=art0027

i'm gonna mod my locker this week, provided i can get answers to the few questions i have.

firstly, if i cut the same amount off as has been done in the thread, any idea as to the speed that the diff will unlock?? if it unlocks at all?? ideally, i'd like it locked while at the redline in 3rd.. 80ish mph. possible? or am i askin too much of this diff??

secondly, anybody have an online manual/guide as to what torque settings each bit needs?? or did you use the one or two 'grunt' torque method? lol.

an finally, the replacement shim. any dimentions as to the size i should replace it with??

i've tried searching for these answers but i fail.

thanks.

Weld the weights in instead. You won't have to take it out of the housing.

I would assume "replacing the shim" means to put it back into place.

Cutting the weight allows it to start locking up at higher speed (or any speed). It does not dictate at what speed it unlocks. With an unmodified locker, you could start a burnout and run the wheel speed to 100mph and it would still be locked. But unmodified, you couldn't start spinning both tires above ~25mph. With the weight cut off, you should be able to get 2wd when slip starts happening over 25mph.

thanks for both replies fellas.

scotty: care to elaborate(sp) on this?

will it still unlock at all?? could you highlight exactly what to weld and where??

by replacing the shim, i'm following by this pic.



i'm assuming by 'shim' he means the thin washer in the pic. surely he said replace as in fitting a new 1 of slightly thicker material, instead of re-fitting the one already there. no? am i just getting mixed up by replacing and refitting?? sorry i just dont want to f*$k this up.

also, how do these diffs hold up against wheels being locked at highish speeds via hydro/handbrake lever, and igniting the rear wheels again? as you prob guessed i plan on using the car for local midnight drift clubbing and as a promiscuous lady of the track.

Doherty_340 said:

scotty: care to elaborate(sp) on this?

will it still unlock at all?? could you highlight exactly what to weld and where??

Click to expand...

if you already took it apart and removed the weight then there is no point in welding it - you'd otherwise have welded the weight to the case, at the gap at the tip of the weight ... would keep it from swinging out - same thing you are trying to accomplish with the cutting, but easier than taking it apart and cutting it.

i see, thanks! i haven't started working on the diff as of yet as i wasn't too sure about the shim and torque settings for the rebuilding.

the welding is looking the much easier option, but is there any draw backs??

ie: the unlocking again for 'normal' driving, or also in my area, police checks for welded diff's.

anybody on here went this route??

towerymt said:

I would assume "replacing the shim" means to put it back into place.

Cutting the weight allows it to start locking up at higher speed (or any speed). It does not dictate at what speed it unlocks. With an unmodified locker, you could start a burnout and run the wheel speed to 100mph and it would still be locked. But unmodified, you couldn't start spinning both tires above ~25mph. With the weight cut off, you should be able to get 2wd when slip starts happening over 25mph.

Click to expand...

Towery, I generally regard your posts as scripture, but in this case I would have to disagree.
I have a '92 745Ti with an LT1 that will absolutely not keep the diff locked above 25mph. Very frustrating when trying to destroy a set of tires before getting a new set. It will start off locked, all's well until it passes about 25-30mph, then blammo! One legged disappointment...
Were I keeping the car, cutting the weights would be one of the higher things on the list.

sstory0626 said:

Towery, I generally regard your posts as scripture, but in this case I would have to disagree.
I have a '92 745Ti with an LT1 that will absolutely not keep the diff locked above 25mph. Very frustrating when trying to destroy a set of tires before getting a new set. It will start off locked, all's well until it passes about 25-30mph, then blammo! One legged disappointment...
Were I keeping the car, cutting the weights would be one of the higher things on the list.

Click to expand...

do not want !!

tbh, i take 99.9% of the stuff posted on here as scripture.

are you refering to me and my car? if so, i plan on keeping, maintaining and driving the complete balls off it for as long as possible....

if not, you would cut the weight rather than weld??

sstory0626 said:

Towery, I generally regard your posts as scripture, but in this case I would have to disagree.
I have a '92 745Ti with an LT1 that will absolutely not keep the diff locked above 25mph. Very frustrating when trying to destroy a set of tires before getting a new set. It will start off locked, all's well until it passes about 25-30mph, then blammo! One legged disappointment...
Were I keeping the car, cutting the weights would be one of the higher things on the list.

Click to expand...

if it is unlocking then there is a problem (edit: i <i>assume</i> there is a problem rather, there were two versions of the g80, i just don't see how the version i disassembled could be unlocked by the pawl?), if you look at the design you'll see why ... someone posted a great video of how it works once, but get it apart and you will see.
if the pawl was what kept it locked then it would break with little effort, once locked the ramps have engaged and the clutch packs should be wedged together, you'd have to get the ramp to rotate opposite the direction of the "wedging" for it to unlock.
maybe your clutch packs wore out? i know mine did ... though there was likely another reason for that.

sstory0626 said:

Towery, I generally regard your posts as scripture, but in this case I would have to disagree.
I have a '92 745Ti with an LT1 that will absolutely not keep the diff locked above 25mph. Very frustrating when trying to destroy a set of tires before getting a new set. It will start off locked, all's well until it passes about 25-30mph, then blammo! One legged disappointment...
Were I keeping the car, cutting the weights would be one of the higher things on the list.

Click to expand...

Mine worked like this too... it would stay locked till over 25mph and then bam, right tire fire. The *only* time i could get it to keep both going if it was wet and both tires never found anymore traction than the other.

I bent the shaft the weight rides on, so I did what was needed then... Had my friend weld all the gears together from both access holes... Hasn't let me down yet!

sstory0626 said:

Towery, I generally regard your posts as scripture, but in this case I would have to disagree.
I have a '92 745Ti with an LT1 that will absolutely not keep the diff locked above 25mph. Very frustrating when trying to destroy a set of tires before getting a new set. It will start off locked, all's well until it passes about 25-30mph, then blammo! One legged disappointment...
Were I keeping the car, cutting the weights would be one of the higher things on the list.

Click to expand...

that's how it's supposed to work. it's probably toasted like the one in our lemons car. the diff housing was REALLY hot after the race. had quite a bit of inside wheel spin from the mod'd G80. I suspect the clutch plates just aren't gripping anymore and it just slips and spins a tire and creates heat with no added benefit.

So if it were toasted, it would still lock to begin with?
To be fair, I've only disassembled a GM positraction and a GM Cone-type--never a governed one.

So if it were toasted, it would still lock to begin with?
To be fair, I've only disassembled a GM positraction and a GM Cone-type--never a governed one.

Other than checking to see if mine gets hot, that's what mine does. If you jack up the rear end you can spin one wheel fast enough by hand to feel it engage, but apparently once engaged it doesn't really transmit enough torque to even break the inside wheel loose on a rain-slicked street.

I need to check at the dealer for clutch packs for a rebuild. Or are they available anywhere else for less???

There was a 940 turbo at the PnP Saturday when I got my remote-reservoir power steering setup, but the cursed thing was in a 2 - 3" deep puddle, and I don't want another G80 bad enough to lay in filthy mosquito laden water in a junkyard long enough to pluck it out of the axle.

http://www.youtube.com/watch?v=tTGZOJQQBeE&feature=related


At around 3 minutes you get so see how the governor works, it just governs engagement, once engaged it needs to back off to disengage, you'll notice that swinging the weight out (at speeds over 'x' mph) requires action ... well it requires the pawl to back-off, notice the angle of engagement vs the pivot point. This is why i figured something would likely be fouled up with the ones reported to not remain locked - or maybe you guys are shifting?

I'm going to take one apart soon and see what can be done about shimming it tighter. Looks like all the clutch plates are flat, so maybe I'll try a bellville shim from a dana powerlok if it happens to fit.

towerymt said:

With an unmodified locker, you could start a burnout and run the wheel speed to 100mph and it would still be locked. .

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You sure?

When i have slip, the lock of both wheels unlocks @ exactly 40Km/h~25mph.. rly pisses me off in drifts... its like ADS then... anti drift system

Posi tive

That is a very informative video!

I think the point may be missed, however, that the pawl that engages the spinning weights is itself counterweighted on the bottom. So even though the spinning weights have stopped spinning relative to the carrier, the pawl is spinning relative to the case and the counterweighted bottom is being pulled outward towards the case. At a certain speed, the pawl will be pulled out of engagement with the spinning counterweights and unlock the diff. If you cut the lower counterweight off of the pawl, it would still retain the requirement for a difference in axle speed to lock, but would not unlock after a certain speed. Weld the spinning weights to the case, and you have a standard clutch-type limited slip. Remove the weights, and it will never lock up,

I think that unlocking action at speed is the whole reason for this type of diff to exist. If it merely locked with a difference in relative axle speed, how is it different than a standard Eaton clutch-type limited slip without counterweights? As a matter of fact, the standard type will lock with only a TORQUE difference, but this one requires a SPEED difference as well.

Thoughts?

sstory0626 said:

I think the point may be missed, however, that the pawl that engages the spinning weights is itself counterweighted on the bottom. So even though the spinning weights have stopped spinning relative to the carrier, the pawl is spinning relative to the case and the counterweighted bottom is being pulled outward towards the case. At a certain speed, the pawl will be pulled out of engagement with the spinning counterweights and unlock the diff.

Click to expand...

No, that was also part of my point, however my issue is with the angle of engagement of the hook at the end of the pawl relative to the direction of motion of the weight upon disengagement.
From my observation during disassembly/reassembly, and from the video, it appears to me that the plane in which the hook engages, and the tangent to that lever arm are not anywhere near parallel ... oops ... so i'm not clear on how the disengagement occurs without the pawl 'backing off'. The angle of that hook may be sufficiently steep to allow the weight to pull the mechanism back out of the locked state, however with those clutches wedged together I don't see it being the obvious intent of the design, it would take significant effort from the weight - if it were designed to work that way I'd expect to see a steeper angle to the hook.
Now if the clutches were worn I could see that 'pulling back' of the pawl to be somewhat more realistic, but since mine never let up 'above 25mph' I'm just not seeing it.


edit: and please, don't assume you'd have a standard clutch-type limited slip without the mechanism - get the thing apart and you'll understand why - there would need to be significant tension on that clutch pack for it to behave that way - hence the ramp - the spring simply holds everything in place