D or 3 ?

[2NI]

The SVX is my first automatic car (I live in €urope) & I must admit that the gear changing rule sucks on "D", especially while driving around town... It's really badly done, changes gears all the time, I don't like the feeling of it at all!

So you guys always drive in third gear? Even to start the car from a red light? Does it work? What's 1st & 2sd for then?

Tell me what's best, I'm here to learn (and if I could avoid to kill the transmission by the way... )

[budbaer]

If you start from a stop in 3 it will run through all the gears, it just won't go past 3rd gear. Just make sure you don't have the manual button pushed, because then it won't go through the lower gears.

[Trevor]

Originally Posted by zukiru

Huck told him it was a good buy. sounds good enough of a reason for me.

MY reasoning in full detail :-

DUTY SOLENOID VALVE "A". This is a pulse width modulated duty solenoid valve, ( Sometimes known as a pulsoid). The device is incorporated in the SVX transmission control system in order to adjust line pressure in the following manner :-

The fluid line is provided with a bleed or bypass via an on/off device, in the form of an electrically operated valve. This solenoid valve is opened and closed repeatedly, in a rhythmical manner by a control current which is turned on and off by the transmission control unit (TCU) at a very fast rate.

The valve is a normally closed device, and remains closed in the event of the loss off a control current. After passing through this modulated solenoid valve, the continually interrupted pressure is in the form of a pulsed flow. When the peaks level off with the troughs, there is a resulting overall steady reduced pressure.

The level of this pressure is adjusted by varying the on/off intervals. Most often the length of the on time is adjusted and the number of on/off pulses per second is kept constant. The usual rate is around 50 cycles per second. The resulting adjusted output pressure is therefore delivered as a rapidly fluctuating stream.

The system incorporates an expansion chamber as a smoothing element, which works as a sort of cushion. This device is usually in the form of a cylinder and piston or diaphragm, backed by a coil spring. In the SVX system the component is described as a Pressure Modifier Accumulator. The high pressure peaks in the stream press the piston outwards and become rounded off, while the low pressure troughs are filled in as a result of the piston moving inwards under spring pressure. The end result is a smoother level of pressure, such that controlled devices are not materially affected. An increase in the volume of fluid controlled, is achieved by transferring the solenoid regulated pressure, to a pressure modifier valve and a regulator valve.

It should be clear that by “chopping” the fluid supply in an adjustable way, pressure control is achieved economically using a simple poppet type solenoid valve, with few mechanical or electrical complications. However the valve remains in a continuous cycling mode, which imposes rather arduous mechanical stresses.

THE DROPPING RESISTOR CIRCUIT. It will be immediately apparent that a sudden on off cycle tends to cause what could be called a hammering of the valve seat, even though this is largely checked by the viscosity of controlled fluid flow. The dropping resistor introduces a second series of current pulses applied in parallel with the control signal. These shorter pulses are applied during the off cycles and timed to check the travel of the armature as it reaches the closed position, thus reducing both shock and noise. These secondary parallel signals in effect, “round off” the closing period and reduce the closing shock. This arrangement can be made even more sophisticated and configured so as to soften the opening cycle, as well as the closing of the valve.

It will be appreciated that increasing the resistance in the circuit, or opening the circuit by omitting the dropping resistor, has two outcomes. Firstly the relative electrical off time is increased thus increasing the line pressure and therefore makes shifts more abrupt. Importantly as a second issue, increased shock loads are applied to the valve.

The resistor should measure between 9 and 15 ohms to be within specifications. The usual is about 12 ohms.

It is a documented fact, that the line pressure control solenoid is the first to fail, due to having by far the most arduous duty to fulfill. Failure is usually mechanical resulting in the valve seat not closing properly and as a result line pressure is markedly reduced. The end results are drastic, especially in respect of transmission friction surfaces. The fault will not necessarily be registered as a fault code, as the armature of the valve can be in the fully closed position with the problem confined to a worn or obstructed valve seat. In the event of an electrical fault, which should register, the valve being normally closed, will fail safe and result in maximum line pressure.

[huck369]

Trevor,
That does make sense, but I'm looking at it from a mechanical point of view in the fact that by driving around at 30-50 with the transmission in 4th gear, there is a LOT of stress on the wear parts of the 4EAT due to the increased leverage against the transmission’s clutches, put on them due to them having to allow more slippage to do the same amount of work it could do in a lower gear more efficiently, thus causing excessive heat and wear to the clutches.

I hadn’t really thought of it in the hydraulic viewpoint, but after reading your post, I still feel the driving in the “3” gear for around town (sub-50mph) is less wear on the wear components, so even if it does shorten the solenoids lifespan a little…the solenoids are easier to replace than the clutches, and can actually be done with the transmission in the car (I think this is correct).

So even though I agree with your points, I still think it is better on the transmission to run it in “3” when you’re in slower conditions…can you see my point of view?

I’m definitely not a automatic specialist, but I do have a basic understanding of their workings….just putting my thoughts out there.

[Ricochet]

I'd neutral bomb into 2 and peel out then cruise the freeways in second gear so I can hear my baby scream weeeeeeeeaaaaaaaaaaaaaahhhhhhh

[richardstanley]

Originally Posted by Ricochet

I'd neutral dumb into 2 and peel out because I'm cool then cruise the freeways in second gear so I can hear my baby scream woo woo

For real?
I can't imagine ever neutral dropping an svx... Askin to pay out the a$$ for that one haha

[Ricochet]

nooooooooo you quoted before my ninja edit weeeeeeeeeaaaaaaaaahhh!

[Ricochet]

oh and I did pay a lot, got a 5spd swapped while I'm here in this great wonderful place.

(no I never neutral dropped I was kidding)

[ItsPeteReally]

Originally Posted by huck369

........but I'm looking at it from a mechanical point of view in the fact that by driving around at 30-50 with the transmission in 4th gear, there is a LOT of stress on the wear parts of the 4EAT due to the increased leverage against the transmission’s clutches, put on them due to them having to allow more slippage to do the same amount of work it could do in a lower gear more efficiently, thus causing excessive heat and wear to the clutches.

I'm sorry, but I think you've got the whole thing upside down, there is less leverage in 4th than in 3rd gear. The only time the clutches slip a little is at the instant of gear changing. If they slip at any other time then your transmission is either broken or seriously maladjusted.

Now the torque converter, until it locks up in 4th, is slipping all the time!. Whilst the torque converter is unlocked it absorbs most of the shock loads, but conversely, the torque multiplication effect increases the loads on the clutches and gears too.

The easiest time the gearbox has is when the car is in 4th with the converter locked.

At lower speeds, it's anybody's call whether it helps or not, but I know I would spend a lot more on fuel driving around in 3rd.

[svxistentialist]

Originally Posted by budbaer

If you start from a stop in 3 it will run through all the gears, it just won't go past 3rd gear. Just make sure you don't have the manual button pushed, because then it won't go through the lower gears.

Manual Mode is to avoid wheelspin when starting off in muck-slush-snow-slippy conditions.

It does two things; it denies the use of 1 range only [i.e. not lower gears, plural] and it also denies the Power Mode.

When Darren says he uses it in stop-start traffic, I know what he means. As he normally drives around with Power Mode on [his car is JDM, so he can ], by switching to Manual in traffic, he is starting off in 2 range, plus Power mode is denied, so driving is smooth as silk.

However, I'm willing to bet because of torque convertor use in this fashion, his ATF will heat up more than when using 1-2-3 under Normal mode, with Power mode switched out.

So I'm saying using Manual will give you smooth progress OK, but could lead to overheated ATF problems in hilly areas or hot cities in midsummer.

None of which happens for long in the UK or Ireland.

Joe

[Trevor]

Originally Posted by ItsPeteReally

I'm sorry, but I think you've got the whole thing upside down, there is less leverage in 4th than in 3rd gear. The only time the clutches slip a little is at the instant of gear changing. If they slip at any other time then your transmission is either broken or seriously maladjusted.

Now the torque converter, until it locks up in 4th, is slipping all the time!. Whilst the torque converter is unlocked it absorbs most of the shock loads, but conversely, the torque multiplication effect increases the loads on the clutches and gears too.

The easiest time the gearbox has is when the car is in 4th with the converter locked.

At lower speeds, it's anybody's call whether it helps or not, but I know I would spend a lot more on fuel driving around in 3rd.

The issue is becoming confused and the salient point lost in the process. The concern is that with the transmission in D, the car running at intermittent slow speeds and varying engine loading including light and even coasting, the TCU will be signaling constant gear changes, all to no avail. This useless hunting up and down causes unnecessary wear and tear.

[richardstanley]

Originally Posted by Trevor

The issue is becoming confused and the salient point lost in the process. The concern is that with the transmission in D, the car running at intermittent slow speeds and varying engine loading including light and even coasting, the TCU will be signaling constant gear changes, all to no avail. This useless hunting up and down causes unnecessary wear and tear.

This is basically how i would imagine it goes down. And how much gas mileage could you really be using not switching to fourth? not that much i wouldn't imagine

[Trevor]

Originally Posted by richardstanley

This is basically how i would imagine it goes down. And how much gas mileage could you really be using not switching to fourth? not that much i wouldn't imagine

Right on Richard.

There is no saving, as immediately the throttle is opened, there will be a shift down from D. If anything the delay could result in the negative.

[ridered777]

Sorry to bring this thread back from the dead...

But I have a question which no one asked, and I'm surprised it didn't come up.

I hear from... someone... *Cough*David(Seraphinwolf)*Cough* that all Subaru trannies have this neat little thing where if you put the gear selector in "3", it over-rides the usual torque split between the front and rear wheels and makes it CLOSER to 50/50. He said the exact number of slip varies by tranny/car I think...

Any thoughts or ideas? I've never seen anyone say anything about it, and I've done a few tests in my car in "low traction situations", and though I don't THINK it's changing the split (that is, when the wheels slip, then AWD split kicks in, giving more power to rear wheels), it's obviously (as I'm sure Trevor will point out ) not a reliable scientific method by any means.

Craig

[Wikedjuggalo]

What about FWD cars? what effect does this have? Does it matter if driving in 3 will do anything? I mean I guess the same thing? Also I don't do this as I usually get over 50 often but damn stop lights get in my way J/k.