Quick Change Shift Kit Question

[oab_au]

Originally Posted by b3lha

Maybe that's true. I think that firming up the shifts by recalibration of the line pressure is probably a very good idea and might help to extend the life of the transmission.

Phil the line pressure is set by the throttle position, you may raise be recalibration, but it is still lowered during the change.

But the less torque you apply to the clutches, the less they will slip and the longer they will last. It seems to me that reducing the torque during a shift must a good thing for gearbox longevity. Conversely, disabling the torque-cut signal must surely subject the clutches to more torque, more slip and more wear than leaving it alone.

The maximum amount of torque that is applied to the box is when you do a full throttle start in first. The torque is not cut, and the line pressure is not lowered.

I accept that the primary goal of the QS device is performance, rather than gearbox longevity. But it's stretching things a bit far to claim that it will definitely make the transmission last longer. Maybe in a few years time, when people have done 80000+ miles with a QC, we'll be able to look at the failure stats and say whether it is better or worse. But right now it's just speculation either way.

Well I don't think I made that claim. but what I can say is that preventing the lowering of the line pressure during the change, will reduce the wear on the brake band and clutches, and if we are going to do that we may as well let the converter do the work it is supposed to do

Harvey.

[oab_au]

The cutting of the engine torque during the change not only produces the ‘do nothing’ between gears, it robs us of the Torque converters action that should happen on the change. By cutting the engine torque the converter can only act as a soft coupling between the engine and box, the gear ratio changes and the engine has to pull that higher ratio, that can bog it down, eg 1st gears 2.78 to 2nd gears 1.54.

With the torque cut removed, the converter is allowed to handle the full engine’s torque, it will act as a variable gear ratio between the engine and the gearbox that can change the ratio from 1:1 down to 1.9:1. So that when the change is made from 1st to 2nd, instead of the 2nd gears ratio of 1.54, the converter can reduce this to 1.9 X 1.54, to 2.85 then as the converter brings the engine speed down to the lower gear, the converter will reduce this to 1.54. Because the converter reduces the gearing, it also multiplies the torque to give that surge on the change, that only a Quick Change driver can enjoy.

Harvey.

[y2daniel1981]

Originally Posted by NiftySVX

I do not have any experince with the quick shift product, and I do not personally believe it to be detrimental to any soft transmission parts, but it could be argued that the planetary gears or the lip seals could be damaged by it. I do not believe this is really relevant, because we don't see those kind of failures on these. What's more, what I have had done is surely more trying on those components than any electric mod, and I believe it to be within design limits.

Next time I'm in OKC I'll be more then glad to give you a ride in mine, not sure when the next time will be though (usually about every other month.) I will however be in Stillwater Saturday night

[oab_au]

Originally Posted by NiftySVX

I do not have any experince with the quick shift product, and I do not personally believe it to be detrimental to any soft transmission parts, but it could be argued that the planetary gears or the lip seals could be damaged by it. I do not believe this is really relevant, because we don't see those kind of failures on these. What's more, what I have had done is surely more trying on those components than any electric mod, and I believe it to be within design limits.
.

I'll have to find a QC member around your area for you to try it, I think you will be surprised.

MY OPINION, as a person who has extensive experience with this transmission (but again, absolutely zero with the QC product) is that the torque control signal was put in place to make the thing hold together AND to make it shift better, though I find it odd that it does not occur on the 1-2 shift which is where I think it is needed the most as far as feel goes. .

I disagree with you on the "holding together bit". The same box has done service in the turbo models that use it, without the torque cut. The torque cut and the pressure lowering is on all shifts.

I believe that a modification of the valve body to increase base line, apply pressure to the band, high clutch, drain from those areas to compensate for the added flow, and flow thru the cooler circuit could help with the longevity of the transmission, and that such modifications make the QC essentially unnecessary by achieving the same results.

Yes modifications to the valve body to improve the flow for cooling and lubrication, can only help the transmission, but the valve body mods won't prevent the TCU from reduce the pressure, regardless of the valve body mods, the engagement pressure will still be lowered to allow slipping. The QC does that.
Increasing the base line, line pressure will mean that the pressure applied to the B and C solenoids will also be higher that can cause lock-up clutch drag, and transfer clutch binding.

Harvey.

[NiftySVX]

For some reason I thought it was only on the 3-4. Hm, I can't remember everything but I don't know. I don't see it hurting transmissions is all. I'd put it on my car, but by 1-2 shift is already so hard it squeeks the mounts

[Trevor]

Originally Posted by oab_au

Phil the line pressure is set by the throttle position, you may raise be recalibration, but it is still lowered during the change.

Line pressure is not “set by the throttle position,’’ as you repeatedly claim. Line pressure is set as a result of the TCU computing several inputs, with throttle position being but one.

Obviously if the calibration is adjusted and the overall pressure raised, the “lowered” pressure must also be raised.

The maximum amount of torque that is applied to the box is when you do a full throttle start in first. The torque is not cut, and the line pressure is not lowered.

The situation prevailing when starting is in no way relevant. The point raised was the possibility of clutch slip, when clutches operate as a result of gear changing, at which point, torque reduction most certainly proves an advantage.

Well I don't think I made that claim.

Statement made within previous post 10. --- “If it is fitted to a normally good box, it can help to extend the transmissions life”

[Trevor]

Originally Posted by oab_au

The cutting of the engine torque during the change not only produces the ‘do nothing’ between gears, it robs us of the Torque converters action that should happen on the change. By cutting the engine torque the converter can only act as a soft coupling between the engine and box, the gear ratio changes and the engine has to pull that higher ratio, that can bog it down, eg 1st gears 2.78 to 2nd gears 1.54.

With the torque cut removed, the converter is allowed to handle the full engine’s torque, it will act as a variable gear ratio between the engine and the gearbox that can change the ratio from 1:1 down to 1.9:1. So that when the change is made from 1st to 2nd, instead of the 2nd gears ratio of 1.54, the converter can reduce this to 1.9 X 1.54, to 2.85 then as the converter brings the engine speed down to the lower gear, the converter will reduce this to 1.54. Because the converter reduces the gearing, it also multiplies the torque to give that surge on the change, that only a Quick Change driver can enjoy. Harvey.

It is proposed that it is desirable to have full engine torque, which is further increased by the torque converter, suddenly applied to the transmission “as a surge on the change”. Apparently this added shock load is a sort after and enjoyable feature, “that should happen on the change.”

By contrast, the very reason for including torque reduction feature, is made clear.

[immortal_suby]

Originally Posted by Trevor

It is proposed that it is desirable to have full engine torque, which is further increased by the torque converter, suddenly applied to the transmission “as a surge on the change”. Apparently this added shock load is a sort after and enjoyable feature, “that should happen on the change.”

By contrast, the very reason for including torque reduction feature, is made clear.

Do you care to address the lack of torque control on turbo models using the same transmission? Or would you rather sidestep that point and just pick apart every single thing that Harvey does.

[92 SVX]

Originally Posted by b3lha

Maybe that's true. I think that firming up the shifts by recalibration of the line pressure is probably a very good idea and might help to extend the life of the transmission.

But the less torque you apply to the clutches, the less they will slip and the longer they will last. It seems to me that reducing the torque during a shift must a good thing for gearbox longevity. Conversely, disabling the torque-cut signal must surely subject the clutches to more torque, more slip and more wear than leaving it alone.

I accept that the primary goal of the QS device is performance, rather than gearbox longevity. But it's stretching things a bit far to claim that it will definitely make the transmission last longer. Maybe in a few years time, when people have done 80000+ miles with a QC, we'll be able to look at the failure stats and say whether it is better or worse. But right now it's just speculation either way.

I am not an engineer, but some common sense coupled with a smidgen of knowledge leads me to think a higher torque applied will cause less slip.

Take it this way if you try to stop something spinning, if you hold light pressure it takes longer to stop, but if you apply hard pressure it takes considerably less time to stop.

[Trevor]

Originally Posted by immortal_suby

Do you care to address the lack of torque control on turbo models using the same transmission? Or would you rather sidestep that point and just pick apart every single thing that Harvey does.

Your sarcasm is noted. When I side step a questions as does Harvey, you will have grounds to complain. Meantime please confine yourself to stating fact.

In point of fact, your reference to the different models proves the need for the features incorporated in the SVX transmission. Not by contrast, that the features are superfluous.

The SVX is a much heavier car than the models to which reference has been made, and also includes a higher final drive ratio. Comparison on the grounds suggested is in no way valid and is in fact stupid.

[Trevor]

Originally Posted by 92 SVX

I am not an engineer, but some common sense coupled with a smidgen of knowledge leads me to think a higher torque applied will cause less slip.

Take it this way if you try to stop something spinning, if you hold light pressure it takes longer to stop, but if you apply hard pressure it takes considerably less time to stop.

A smidgen common sense applied correctly will assist in understanding what is involved.

It would appear that you are thinking of the power involved in closing and holding the friction surfaces in secure contact. The torque referred to is that which must be transferred by the clutches.

The more torque having to be transferred when a clutch closes, the greater the wear. Reducing this torque during gear shifts, therefore has a very real advantage.

[immortal_suby]

Originally Posted by Trevor

The SVX is a much heavier car than the models to which reference has been made, and also includes a higher final drive ratio. Comparison on the grounds suggested is in no way valid and is in fact stupid.

You are much more intelligent than to bring final drive ratio in as a factor. Weight difference is negligible considering cargo and passengers or lack thereof.

[b3lha]

Originally Posted by 92 SVX

I am not an engineer, but some common sense coupled with a smidgen of knowledge leads me to think a higher torque applied will cause less slip.

Take it this way if you try to stop something spinning, if you hold light pressure it takes longer to stop, but if you apply hard pressure it takes considerably less time to stop.

I think you are looking at it upside down. Using your analogy, the torque is the "spinning force", not the "resisting force". The "resisting force" is the friction of the clutches being pushed against each other by hydraulic pressure. The greater the torque, the more friction you require to resist it.

Increased pressure results in less slip for the same amount of torque (as you correctly said). But increased torque results in more slip for the same amount of pressure.

What Harvey does is increase both torque and pressure but not necessarily by the same amount. So it's hard to say whether there is more or less slip during the very short time period of the gear change.

[Trevor]

Originally Posted by immortal_suby

You are much more intelligent than to bring final drive ratio in as a factor. Weight difference is negligible considering cargo and passengers or lack thereof.

Again a post limited to sarcasm.

A study of the relationship between RPM, torque and power, will provide an understanding of what is involved. It is also necessary to be conversant with the terms, net and gross, in respect of weight.

Only then can one consider and be aware of the parameters overall, as were presented to the designers of the SVX.

[Trevor]

Let it be very clear that when a “QC” is fitted, immediately after more than one third throttle is applied, regardless of any other function, all control of transmission line pressure via the TCU ceases; i.e. the operative signals from the TCU are locked out and maximum line pressure prevails.

What is more, the “QC’ does not in any way act progressively, as has been claimed. The action is complete and immediate. As soon as a set degree of throttle opening has been applied, from that point on, the operative signals from the TCU are immediately, completely locked out, resulting in continuous uncontrolled, maximum line pressure.