new 4wd uprated gearbox and uprated viscous lsd
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25-09-2006, 12:41 PM
#202
lol, this problem was definatly on the cards as soon as i read about it, but azrael you description/useof a vc is wrong, the vc unit is purely only there to allow a take up of differance of speed between front and rear axles, it has no action on torque split this is done in the actual centre diff annular ring assy.
i have seen a group a sapphire on a rally many years ago loose drive slowly but surely due to a centre vc overheat, for those of you who have not had one apart, the maishaft from the gearbox slips into splines to the centre diff, there are a small set of three planet like gears inside the outer annular ring, the front propshaft via the drop gears is actually fed from the front of the centre diff not the rear as some people think, the centre diff is splined into the front driver drop gear then chained to the driven, then the inner part of the annular ring is then splined onto the output shaft through the centre vc to the rear prop, as long as the wheels are rotating at the same speed the vc does absolutly nothing, only when a differnce of speed between front and rear axles is noticed that tahe vc with heat up and its voscosity and pressure will increase to try to compensate for the incorrect speed tolerance, once these reach approc 120deg c (iirc) the diff will effectivly lock, affter a period of time the vc will melt its own seals losing any intial setup load, the car will then effectivly lose drive as the drive path through the box ( remember its done by equal load bewtween front a rear axles) is then lost and all you will do is pin the centre diffs planet gears thus no drive !!!
the same effect will happen if you break a shaft, for a while you will have drive, maybe even several miles, after that no drive - i did it my self in an old 4x4 sierra
hope this helps and that ive wrote it down as i mean to explain it !!
i have seen a group a sapphire on a rally many years ago loose drive slowly but surely due to a centre vc overheat, for those of you who have not had one apart, the maishaft from the gearbox slips into splines to the centre diff, there are a small set of three planet like gears inside the outer annular ring, the front propshaft via the drop gears is actually fed from the front of the centre diff not the rear as some people think, the centre diff is splined into the front driver drop gear then chained to the driven, then the inner part of the annular ring is then splined onto the output shaft through the centre vc to the rear prop, as long as the wheels are rotating at the same speed the vc does absolutly nothing, only when a differnce of speed between front and rear axles is noticed that tahe vc with heat up and its voscosity and pressure will increase to try to compensate for the incorrect speed tolerance, once these reach approc 120deg c (iirc) the diff will effectivly lock, affter a period of time the vc will melt its own seals losing any intial setup load, the car will then effectivly lose drive as the drive path through the box ( remember its done by equal load bewtween front a rear axles) is then lost and all you will do is pin the centre diffs planet gears thus no drive !!!
the same effect will happen if you break a shaft, for a while you will have drive, maybe even several miles, after that no drive - i did it my self in an old 4x4 sierra
hope this helps and that ive wrote it down as i mean to explain it !!
25-09-2006, 01:42 PM
#203
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I fail to understand your explanation. Why would the car loose drive without VC action if everything else is working fine in drivetrain?
You are 100% right with broken driveshaft of course, but if all shafts and diffs are OK VC is not required to have drive. I know it from experience too - mine VC was totally and completly dead whenI bought the car, I also experienced it on other Escos with failed VC - absolutly no locking action in centre diff but those drove fine.
Marco - I never ment any offence I think you misunderstood me.
You are 100% right with broken driveshaft of course, but if all shafts and diffs are OK VC is not required to have drive. I know it from experience too - mine VC was totally and completly dead whenI bought the car, I also experienced it on other Escos with failed VC - absolutly no locking action in centre diff but those drove fine.
Marco - I never ment any offence I think you misunderstood me.
25-09-2006, 02:07 PM
#205
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Good discription Markk
Here are some pics of the standard gearbox I loaned to SiB for Ford Fair..........only the centre VC was damaged and he lost ALL drive on track.............
The transfer box with it's cover and most internal bits removed, the long splined shaft is the gearbox output:
The transfer box cover and it's internal parts:
This is the centre VC, notice the splined inner hole, and also the outer drive teeth:
The VC fitted:
Here are some pics of the standard gearbox I loaned to SiB for Ford Fair..........only the centre VC was damaged and he lost ALL drive on track.............
The transfer box with it's cover and most internal bits removed, the long splined shaft is the gearbox output:
The transfer box cover and it's internal parts:
This is the centre VC, notice the splined inner hole, and also the outer drive teeth:
The VC fitted:
25-09-2006, 02:34 PM
#206
Originally Posted by Azrael
I fail to understand your explanation. Why would the car loose drive without VC action if everything else is working fine in drivetrain?
You are 100% right with broken driveshaft of course, but if all shafts and diffs are OK VC is not required to have drive. I know it from experience too - mine VC was totally and completly dead whenI bought the car, I also experienced it on other Escos with failed VC - absolutly no locking action in centre diff but those drove fine.
Marco - I never ment any offence I think you misunderstood me.
You are 100% right with broken driveshaft of course, but if all shafts and diffs are OK VC is not required to have drive. I know it from experience too - mine VC was totally and completly dead whenI bought the car, I also experienced it on other Escos with failed VC - absolutly no locking action in centre diff but those drove fine.
Marco - I never ment any offence I think you misunderstood me.
25-09-2006, 02:39 PM
#207
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So far I can't make any sense of it. At least I need to know why my car would have drive and SiB's wouldn't.
Also if he run wrong dif ratios then VC's were nearly instantly fucked anyway so all his milage must have been done with no VC action whatsoever.
Also if he run wrong dif ratios then VC's were nearly instantly fucked anyway so all his milage must have been done with no VC action whatsoever.
25-09-2006, 05:43 PM
#208
Advanced PassionFord User
Spot on Mark, centre diff failure put me out of the RAC in 1996..something ive composed to try and explain the centre VC
The viscous coupling is a small sealed drum filled with a measured quantity of silicon fluid. Inside the drum are two sets of interleaved plates. One set of plates is splined to the outer drum and one set is splined to the inner shaft.
The viscous coupling is installed in the transfer-case to act as a limited-slip. The outer drum is attached to the front output shaft, for example, and the inner shaft is attached to the rear output shaft. As long as both front and rear output shafts turn at the same speed, both sets of plates in the viscous coupling turn at the same speed and there is no relative motion between the plates.
If the front shaft were to begin turning faster than the rear output shaft, indicating front wheel slip, the two sets of plates would develop relative motion and begin slicing through the silicon fluid. The silicon fluid would heat up and solidify, momentarily locking the sets of plates together and counteracting an open differentials tendency to transfer only limited amounts of power. With the plates locked together, relative motion stops; the silicon fluid cools down and returns to its liquid state, freeing the plates, but if the plates were continually slipping, or the locked state was overridden by continual abuse they would eventually overheat in a catastrophic fashion and lose drive completely.
The viscous coupling is a small sealed drum filled with a measured quantity of silicon fluid. Inside the drum are two sets of interleaved plates. One set of plates is splined to the outer drum and one set is splined to the inner shaft.
The viscous coupling is installed in the transfer-case to act as a limited-slip. The outer drum is attached to the front output shaft, for example, and the inner shaft is attached to the rear output shaft. As long as both front and rear output shafts turn at the same speed, both sets of plates in the viscous coupling turn at the same speed and there is no relative motion between the plates.
If the front shaft were to begin turning faster than the rear output shaft, indicating front wheel slip, the two sets of plates would develop relative motion and begin slicing through the silicon fluid. The silicon fluid would heat up and solidify, momentarily locking the sets of plates together and counteracting an open differentials tendency to transfer only limited amounts of power. With the plates locked together, relative motion stops; the silicon fluid cools down and returns to its liquid state, freeing the plates, but if the plates were continually slipping, or the locked state was overridden by continual abuse they would eventually overheat in a catastrophic fashion and lose drive completely.
25-09-2006, 09:27 PM
#210
Originally Posted by markk
lol, this problem was definatly on the cards as soon as i read about it, but azrael you description/useof a vc is wrong, the vc unit is purely only there to allow a take up of differance of speed between front and rear axles, it has no action on torque split this is done in the actual centre diff annular ring assy.
i have seen a group a sapphire on a rally many years ago loose drive slowly but surely due to a centre vc overheat, for those of you who have not had one apart, the maishaft from the gearbox slips into splines to the centre diff, there are a small set of three planet like gears inside the outer annular ring, the front propshaft via the drop gears is actually fed from the front of the centre diff not the rear as some people think, the centre diff is splined into the front driver drop gear then chained to the driven, then the inner part of the annular ring is then splined onto the output shaft through the centre vc to the rear prop, as long as the wheels are rotating at the same speed the vc does absolutly nothing, only when a differnce of speed between front and rear axles is noticed that tahe vc with heat up and its voscosity and pressure will increase to try to compensate for the incorrect speed tolerance, once these reach approc 120deg c (iirc) the diff will effectivly lock, affter a period of time the vc will melt its own seals losing any intial setup load, the car will then effectivly lose drive as the drive path through the box ( remember its done by equal load bewtween front a rear axles) is then lost and all you will do is pin the centre diffs planet gears thus no drive !!!
the same effect will happen if you break a shaft, for a while you will have drive, maybe even several miles, after that no drive - i did it my self in an old 4x4 sierra
hope this helps and that ive wrote it down as i mean to explain it !!
i have seen a group a sapphire on a rally many years ago loose drive slowly but surely due to a centre vc overheat, for those of you who have not had one apart, the maishaft from the gearbox slips into splines to the centre diff, there are a small set of three planet like gears inside the outer annular ring, the front propshaft via the drop gears is actually fed from the front of the centre diff not the rear as some people think, the centre diff is splined into the front driver drop gear then chained to the driven, then the inner part of the annular ring is then splined onto the output shaft through the centre vc to the rear prop, as long as the wheels are rotating at the same speed the vc does absolutly nothing, only when a differnce of speed between front and rear axles is noticed that tahe vc with heat up and its voscosity and pressure will increase to try to compensate for the incorrect speed tolerance, once these reach approc 120deg c (iirc) the diff will effectivly lock, affter a period of time the vc will melt its own seals losing any intial setup load, the car will then effectivly lose drive as the drive path through the box ( remember its done by equal load bewtween front a rear axles) is then lost and all you will do is pin the centre diffs planet gears thus no drive !!!
the same effect will happen if you break a shaft, for a while you will have drive, maybe even several miles, after that no drive - i did it my self in an old 4x4 sierra
hope this helps and that ive wrote it down as i mean to explain it !!
25-09-2006, 09:27 PM
#211
Originally Posted by sibster
...if the plates were continually slipping, or the locked state was overridden by continual abuse they would eventually overheat in a catastrophic fashion and lose drive completely.
Good explanations Mark and Ian
Continual abuse? CHECK!
Catastrophic? DEFFO
Lose drive? YEP
Hopefully my funky new Mullit Rear diff and MATCHED RATIO front diff will seem me manage more than a few laps next time!
I'm surprised my borrowed box lasted 75+ miles on track at National Day with this problem though - seems they can take a bit of imbalance, but not a lot.
Still, glad we have got to the bottom of things, and now we can move forward with more testing.
All going to plan I should have the diffs and box back tomorrow or weds night, ready for refitting and road and track testing!!
Si
25-09-2006, 09:28 PM
#212
Originally Posted by sibster
Spot on Mark, centre diff failure put me out of the RAC in 1996..something ive composed to try and explain the centre VC
The viscous coupling is a small sealed drum filled with a measured quantity of silicon fluid. Inside the drum are two sets of interleaved plates. One set of plates is splined to the outer drum and one set is splined to the inner shaft.
The viscous coupling is installed in the transfer-case to act as a limited-slip. The outer drum is attached to the front output shaft, for example, and the inner shaft is attached to the rear output shaft. As long as both front and rear output shafts turn at the same speed, both sets of plates in the viscous coupling turn at the same speed and there is no relative motion between the plates.
If the front shaft were to begin turning faster than the rear output shaft, indicating front wheel slip, the two sets of plates would develop relative motion and begin slicing through the silicon fluid. The silicon fluid would heat up and solidify, momentarily locking the sets of plates together and counteracting an open differentials tendency to transfer only limited amounts of power. With the plates locked together, relative motion stops; the silicon fluid cools down and returns to its liquid state, freeing the plates, but if the plates were continually slipping, or the locked state was overridden by continual abuse they would eventually overheat in a catastrophic fashion and lose drive completely.
The viscous coupling is a small sealed drum filled with a measured quantity of silicon fluid. Inside the drum are two sets of interleaved plates. One set of plates is splined to the outer drum and one set is splined to the inner shaft.
The viscous coupling is installed in the transfer-case to act as a limited-slip. The outer drum is attached to the front output shaft, for example, and the inner shaft is attached to the rear output shaft. As long as both front and rear output shafts turn at the same speed, both sets of plates in the viscous coupling turn at the same speed and there is no relative motion between the plates.
If the front shaft were to begin turning faster than the rear output shaft, indicating front wheel slip, the two sets of plates would develop relative motion and begin slicing through the silicon fluid. The silicon fluid would heat up and solidify, momentarily locking the sets of plates together and counteracting an open differentials tendency to transfer only limited amounts of power. With the plates locked together, relative motion stops; the silicon fluid cools down and returns to its liquid state, freeing the plates, but if the plates were continually slipping, or the locked state was overridden by continual abuse they would eventually overheat in a catastrophic fashion and lose drive completely.
25-09-2006, 10:48 PM
#216
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sibster I understand very well how VC works, I had untill recently one taken out of my car for keeping papers on my desk in place. Still I fail to understand how no-limited slip action would cause no-drive condition. Maybe I'm too stupid. What's more I know at least two cars that are driving proofs that it won't happen (if we go into non-Fords I know at least comple Imprezas that sufered centre VC failure and still had drive). Can someone please explain that in simple terms? I know how planet gears etc look like and why would they require VC to transfer torque to wheels when none of the wheels is slipping I fail to understand :-/
26-09-2006, 08:37 AM
#217
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Originally Posted by marco polo
Originally Posted by Andreas
Need a swedish reseller?
you never know i might get over there aswell
26-09-2006, 08:55 AM
#218
Advanced PassionFord User
Originally Posted by Azrael
sibster I understand very well how VC works, I had untill recently one taken out of my car for keeping papers on my desk in place. Still I fail to understand how no-limited slip action would cause no-drive condition. Maybe I'm too stupid. What's more I know at least two cars that are driving proofs that it won't happen (if we go into non-Fords I know at least comple Imprezas that sufered centre VC failure and still had drive). Can someone please explain that in simple terms? I know how planet gears etc look like and why would they require VC to transfer torque to wheels when none of the wheels is slipping I fail to understand :-/
The explanaition wasn't entirely aimed at you my friend, I get the idea you already understand how the V/C works, the point I was trying to make and one which I hoped would sum up the debate was that the drive from the box to the rear does act upon the V/C and if the V/C had failed catastrophically it would slip, like an overheated clutch slips, dont forget the power from the box passes through the casing of the V/C, acts upon the epicyclic first, then back through the V/C itself before it drives the hub for the front diff take-off. Nothing has to physically snap or shear to prevent eventual loss of drive to the rear. I think to fully appreciate the concept we would have to have the debate with the parts both good and failed on the bench.
As I said I have first hand experience of this phenomenon and it gives all the signs of a failed clutch, you would not even has any suspicious sounds before the car stopped driving.
Thats probably made it even cloudier now..lol
Ian
26-09-2006, 09:02 AM
#219
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Most probably parts on bench would help. As I know I have first hand experience of cars with completly burned out VC's driving just fine in normal road driving. When I bought mine it was winter and when pulling off from traffic light it would spin rear wheels endlessly and understeer cathatrophically spinning fronts if you applied any throttle whatsoever in corner entry phase but it still drove just fine and pulled up to 230km/h with no problems.
It should be epicyclical diff making the torque split and VC only providing LSD action. If it is not then I am really feeling stupid and don't make any sense of it all.
It should be epicyclical diff making the torque split and VC only providing LSD action. If it is not then I am really feeling stupid and don't make any sense of it all.
26-09-2006, 09:24 AM
#220
Advanced PassionFord User
Azreal,
I do actually believe we are all singing from the same song sheet...
Yes you are correct the epicyclic does decide torque split.
I agree with you to a point, with a badly worn/weak V/C the car will still drive, but drive badly, as SiB endorses, but lots of the rally cars we see never have any maintenance done on the V/C's centre or rear, and as you know, they are lifed and in competition the life expectancy is quite short, when they are examined and found weak, refreshing the gel and renewing the plates transforms the handling of the car, but if the diff fails catashrophically i.e. no drive through the diff whatsoever you will lose drive....and the car will stop....
Ian
I do actually believe we are all singing from the same song sheet...
Yes you are correct the epicyclic does decide torque split.
I agree with you to a point, with a badly worn/weak V/C the car will still drive, but drive badly, as SiB endorses, but lots of the rally cars we see never have any maintenance done on the V/C's centre or rear, and as you know, they are lifed and in competition the life expectancy is quite short, when they are examined and found weak, refreshing the gel and renewing the plates transforms the handling of the car, but if the diff fails catashrophically i.e. no drive through the diff whatsoever you will lose drive....and the car will stop....
Ian
26-09-2006, 01:52 PM
#222
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Originally Posted by sibster
Azreal,
I do actually believe we are all singing from the same song sheet...
I do actually believe we are all singing from the same song sheet...
Yes you are correct the epicyclic does decide torque split.
I agree with you to a point, with a badly worn/weak V/C the car will still drive, but drive badly, as SiB endorses, but lots of the rally cars we see never have any maintenance done on the V/C's centre or rear, and as you know, they are lifed and in competition the life expectancy is quite short, when they are examined and found weak, refreshing the gel and renewing the plates transforms the handling of the car, but if the diff fails catashrophically i.e. no drive through the diff whatsoever you will lose drive....and the car will stop....
I agree with you to a point, with a badly worn/weak V/C the car will still drive, but drive badly, as SiB endorses, but lots of the rally cars we see never have any maintenance done on the V/C's centre or rear, and as you know, they are lifed and in competition the life expectancy is quite short, when they are examined and found weak, refreshing the gel and renewing the plates transforms the handling of the car, but if the diff fails catashrophically i.e. no drive through the diff whatsoever you will lose drive....and the car will stop....
Maybe you mean that if centre differential (epicyclical) fails then VC will help to retain some drive for some time - on that I agree, but with working epicyclical and VC that lost all it's silicone fluid the car should still transfer torque to the ground normally, just loosing grip easily. Maybe different diffs front/rear cause something that I don't understand that makes the car loos drive without VC,a part from that I cannot find any reasons.
I belive we are far from main topic, maybe some moderator should move that VC part of this discussion to tehcnical forum? I belive that new uprated gearbox is more interesting in itself to general audience.
26-09-2006, 10:11 PM
#223
[quote="Azrael"]
Hi Azreal
The box is real quality honestly , the gears are very strong
Marco
Originally Posted by sibster
Azreal,
I belive we are far from main topic, maybe some moderator should move that VC part of this discussion to tehcnical forum? I belive that new uprated gearbox is more interesting in itself to general audience.
I belive we are far from main topic, maybe some moderator should move that VC part of this discussion to tehcnical forum? I belive that new uprated gearbox is more interesting in itself to general audience.
The box is real quality honestly , the gears are very strong
Marco
26-09-2006, 10:38 PM
#225
Originally Posted by Azrael
I bet they are. Maybe one day you'll make not-too-noisy dogbox and I can afford it.
To be honest when the box is proven and things are going well then in the future
i'll get loads of options eg
Big tooth helical normal ratio (road car quite)
Big tooth helical short ratio (quite)
Big tooth straight cut short ratio
big tooth straight cut dog engagement noraml ratio
big tooth straight cut dog engagement short ratio
big tooth straight cut longer ratio 5th gear
big tooth nelical cut longer ratio 5th gear
i can do MT 75 big tooth straight cut RWD (2wd) version aswell right now
no need to test them as they will work no problem i wont have to worry about silly VC packing up
Marco
26-09-2006, 10:43 PM
#227
Originally Posted by Azrael
I hope we see it, as well as other parts beeing remanufactured for Cossies so they can be maitained in runing order in future.
as for the 9" diff these are gen 909 motorsport moulds
I can also do any uprated VC for any car/truck/van any make/model as long as it got a VC in it i can do and all will be dyno tested to what ever
good init
marco
26-09-2006, 10:45 PM
#228
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You should think about front diff casings - maybe not thickwall, just reinforced with adding metal and welding but smething like this would find big market I think. Price on Quaife ones it a big barrier.
26-09-2006, 10:51 PM
#229
Originally Posted by Azrael
You should think about front diff casings - maybe not thickwall, just reinforced with adding metal and welding but smething like this would find big market I think. Price on Quaife ones it a big barrier.
I don't know if it would be cost effective
the R+D front unit is suppose to be very good it's 2way plated LSD
I have heard it's good never tested one tho
26-09-2006, 10:51 PM
#230
Originally Posted by Azrael
You should think about front diff casings - maybe not thickwall, just reinforced with adding metal and welding but smething like this would find big market I think. Price on Quaife ones it a big barrier.
The front diff is my main concern
At least I will have the full spec Mullit rear diff and box
I also want the Big tooth Straight cut close ratio Dog Engagement box when its ready!!!
Si
26-09-2006, 11:10 PM
#232
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Originally Posted by marco polo
I don't know if it would be cost effective
the R+D front unit is suppose to be very good it's 2way plated LSD
I have heard it's good never tested one tho
Is it whole unit with casing too?
2-way LSD sounds a bit extreme, I understand for gravel rallycar, but elsewhere 1,5-way or even 1-way. For road cars plated diff in front doesn't sound like good idea at all.
27-09-2006, 05:27 PM
#233
Originally Posted by Azrael
Originally Posted by marco polo
I don't know if it would be cost effective
the R+D front unit is suppose to be very good it's 2way plated LSD
I have heard it's good never tested one tho
Is it whole unit with casing too?
2-way LSD sounds a bit extreme, I understand for gravel rallycar, but elsewhere 1,5-way or even 1-way. For road cars plated diff in front doesn't sound like good idea at all.
yes it's a whole unit with casing too i don't know that much about it to be honest mate
marco
