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Old 07-11-2011, 10:10 AM   #1
Doherty_340
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Default 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.
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Old 07-11-2011, 11:19 AM   #2
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Weld the weights in instead. You won't have to take it out of the housing.
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Old 07-11-2011, 11:22 AM   #3
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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.
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Old 07-11-2011, 12:48 PM   #4
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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.
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Old 07-11-2011, 01:09 PM   #5
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Quote:
Originally Posted by Doherty_340 View Post
scotty: care to elaborate(sp) on this?

will it still unlock at all?? could you highlight exactly what to weld and where??
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.
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Old 07-11-2011, 01:46 PM   #6
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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??
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Old 07-11-2011, 01:48 PM   #7
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Quote:
Originally Posted by towerymt View Post
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.
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.
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Old 07-11-2011, 02:14 PM   #8
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Originally Posted by sstory0626 View Post
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.
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??
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Old 07-11-2011, 02:43 PM   #9
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Quote:
Originally Posted by sstory0626 View Post
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.
if it is unlocking then there is a problem (edit: i assume 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.

Last edited by kildea; 07-11-2011 at 03:11 PM..
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Old 07-11-2011, 03:41 PM   #10
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Quote:
Originally Posted by sstory0626 View Post
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.
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!
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Old 07-11-2011, 04:17 PM   #11
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Quote:
Originally Posted by sstory0626 View Post
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.
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.
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Old 07-11-2011, 04:30 PM   #12
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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.
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Old 07-11-2011, 04:31 PM   #13
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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.
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Old 07-11-2011, 04:31 PM   #14
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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.
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Old 07-11-2011, 04:52 PM   #15
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http://www.youtube.com/watch?v=tTGZO...eature=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?
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Old 07-11-2011, 04:58 PM   #16
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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.
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Old 07-12-2011, 03:34 AM   #17
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Quote:
Originally Posted by towerymt View Post
With an unmodified locker, you could start a burnout and run the wheel speed to 100mph and it would still be locked. .
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 :D
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Old 07-12-2011, 04:18 AM   #18
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Old 07-12-2011, 09:14 AM   #19
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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?
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Old 07-12-2011, 09:48 AM   #20
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Quote:
Originally Posted by sstory0626 View Post
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.



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

Last edited by kildea; 07-12-2011 at 09:57 AM..
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Old 07-12-2011, 09:58 AM   #21
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The problem is that of the two locking wedges, one is the side gear and the other side is a glorified washer with a set of wedges on it that are not locked to the case in any way except for the spinning counterweight shaft. As soon as the spinning counterweights are allowed to spin again, the whole locking wedge piece disengages and is allowed to spin relative to the case, completely disabling any lockup.
There was talk of two types of G80--maybe yours (@kildea) is another type that does not unlock at high speed? I'm sure this is the type mine is, as well as anyone else whose diff unlocks above 25mph.
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Old 07-12-2011, 10:03 AM   #22
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Quote:
Originally Posted by Doherty_340 View Post
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??
Sorry--I was referring to what exactly my car does.
I would probably weld the weights to the carrier. You will have to completely disassemble the diff (I think) to get at the pawl to cut it. It really wouldn't be a good idea to try to cut the pawl while it is still in the car--too many metal shavings and such.
But that is my opinion. Maybe those with more experience disassembling/reassembling these diffs would comment?
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Old 07-12-2011, 10:10 AM   #23
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some very helpful/informitive replies...thank you all.

tho, some new questions have arised....

i've watched a computer generated video on youtube of this diff, how it works, and it in 'exploded' views. ( i guess its the video posted? i haven't tried it as the media player on this laptop is rubbish. plays videos in robotic/ strobelight type jumps.)

if i go the welded weights route, and i suffer slip and a hot housing, can i still get it split to replace my clutchpacks??

could it be possible to install a single extra 'disc' to the worn pack to tighten them up? or best replacing all of the pack? i'd guess even with the extra 'disc' in the worn pack, the worn discs could still slip against one another but grip the single new 1, thus still giving slip/possibly more heat??

if the weights are welded, they still have to rotate to generate the lock-up, right? and if i just weld the pawl to the casing, the weights would still expand and...lock-up?? or bust into pieces?? lol.

at first, i'd thought about shaving/champhering the weights at each end, increasing the centrifugal force needed to expand them out...then i thought that would just heighten the difference in speed needed between the wheels to achieve the lock-up?? am i understanding this correctly??

sstory: i'd prefer to do this mod right, ie dissamble/cut the pawl/reassemble. tho only if its a better option. if welding the weights has the exact same outcome and is obv the quicker/easier option, then i'l do that...

also to clarify, the complete axle is out. i bought it on its own as my 940 is non locking. after upping the boost to 0.8 bar its funny, but not much 'fun' leaving 70ft long 1 wheeler lines. i like 11's and arse out achshun.
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Old 07-12-2011, 10:12 AM   #24
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You will have to completely disassemble the diff (I think) to get at the pawl to cut it. It really wouldn't be a good idea to try to cut the pawl while it is still in the car--too many metal shavings and such.
absolutely.
there really is no way to get at a narrow section of that weight, and it takes a while to cut through with a cut-off wheel anyways. if you don't want to open it (a hassle from my perspective) then cutting the weight is not an option, in this case welding is the way to go.

i ruined one of mine by (after cutting the weight) replacing the spring with a hefty wave spring and grinding off the nubs on the ramps in an effort to turn it into something of a limited slip - i failed miserably, though it worked well for a couple of weeks, the clutches were worn completely smooth eventually and i was back to an open diff.
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Old 07-12-2011, 10:23 AM   #25
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Doherty - You are not welding the small flyweights, just the one large weight. Look at the operation again and work through the stages with the video and you'll see why. You'd just bridge that gap between the weight and the case with a small chunk of metal and weld it at both sides - don't go crazy and you'll be able to grind it off if you need to get into the diff.
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