4EAT shift kit

[jeremod]

Don't know if anyone has seen this but I'm thinking it may work on a Legacy 4EAT.

Dunno how much different the SVX trans. is from the Legacy but being a Subaru it shouldn't be that different.

http://cgi.ebay.com/ebaymotors/Subaru-S ... dZViewItem (http://cgi.ebay.com/ebaymotors/Subaru-SVX-Stage-1-Shift-Kit-SVX-Automatic-1992-97_W0QQitemZ280049761410QQcmdZViewItem)

[ryankenn]

I'm all for anything that helps my 4EAT shift more crisply. Someone just needs to see if the 4EAT from the SVX is the same. We should just all chip in for that price and try it out on a car.

[backpack09]

I have zero experience with autos (autos are for girls :lol: ) but the as long as you can find the resister pack they show in the pictures, this should work for any subaru. What it actually does, I do not know...

[badbasser98]

Well, the SVX's has a completely different engine and tranny from the EJ series which is in your cars. This being so, I would have to make an assumption that the internals are not the same and not compatible.

[jeremod]

Alright this is gonna be a long one. I'm a bit of a geek so this could get kinda technical but I'll try to make it understandable. I started out as a mechanical engineering major before I decided engineering is too much of a desk job.


I've been doing a lot of research today on the possibility of installing this shift kit on a Legacy 4EAT. I am fairly positive it will work. I found the resistor that controls line pressure in the transmission. It's located on the front right side strut tower kinda above the ABS solenoid. (I'll get pic soon)

We'll start with a little background info on automatic transmissions. Feel free to correct me if I'm wrong on anything here. If you don't really care how it works then you can skip this part. :grin:

Automatic transmissions are almost entirely hydraulically controlled. Power is transmitted from the engine to the transmission via hydraulics as well as the shifting of gears. The speed at which the transmission shifts is controlled by the Duty A solenoid. Solenoids are basically on or off. When the solenoid is off the valve closes and the line pressure is high. The opposite is true when it is on. The only way to variably control the pressure is by pulsating the solenoid so that the amount of time that the valve is open is varied. The solenoid usually pulses about 50 times a second but how long it stays on with each pulse is changed. All of this is controlled by the TCU. The problem with the pulsing is that the solenoid would cause a hammering effect on the valve. That's where the resistor comes in.

The resistor in the engine bay is wired to the solenoid so that it produces a very short pulse during the off stage. This in effect slows down the valve just before it closes, and reduces shock and noise. Removing the resistor does two things. 1.) The valve spends more time in the off position therefore raising line pressure and making shifts faster. 2.) Increases shock loads on the valve.

(I found all of this info here: http://www.svx-iw.com/svxiw/article/?article=212)

Basically what the sift kit does (as far as I can tell) is use engine vacuum to trigger a pressure switch that basically removes the resistor from the circuit during acceleration. This momentarily causes an increase in line pressure which equates to crisper shifting. The same can be done by unplugging the resistor but this apparently causes poor downshifting when coasting (like stopping at a light). It also causes rough shifting when driving slowly which can be annoying. This shift kit basically allows the transmission to shift normally under "gentle" driving but when you put your foot down it disconnects the resistor and the transmission shifts faster.

I really can't afford this kit right now, but later this evening or tomorrow I will try pulling the resistor and see if there are any noticeable improvements in shifting.

This could be the answer for all us poor people stuck with a slow shifting 4EAT.

[jeremod]

Results!

With the resistor unplugged there is a VERY noticeable change in shifting. The car shifts MUCH more quickly and almost kicks you in the a$$ esp. when accelerating hard. It shifts very crisply.

The down shifting problem is very noticeable though. When slowing down from highway speeds the car doesn't seem to want to down shift at all. Even if you do it manually with the gear lever. It took about 10 seconds from when I changed from D to 3 before it shifted and then I seems like it couldn't decide which gear it wanted to be in. Seems like the kit is the way to go here since when coasting it would essentially reconnect the resistor.

I think I am going to make a manual switch mounted somewhere inside the car for when I want faster shifting. Kinda like a sport mode. Just need to turn it off when you slow down.

[badbasser98]

Mine shifts pretty hard when I'm on it anyway. I guess I am not really seeing a benefit to doing this.

[ryankenn]

I would say ( baddasser ) try disconnecting that resistor and see how much harder it hits. I did the same thing and it works like a charm. However, like he mentioned, the downshifting leaves something to be desired.

Its too bad you can't replicate the problem the other way, ie having the car hold 3 through a corner instead of shifting up to 4. I just manually shift mine all the time, which isn't the best ( or so I've heard ) for the tranny.

What could be done is trying different values of resistanct to reach a happy medium of crisp shifting with workable downshifts.

Does the kit say where it gets its vacuum reading from to determine whether your WOT or coasting? I'm assuming somewhere on the Legacy is a hose that performs the same function. You could also just add a switched relay to the gas pedal that performs that function when the pedal is on the floor.

[jeremod]

Looks like it just taps into a vacuum line and has a pressure switch in it.

[ryankenn]

I'm just curious which vacuum line they use. The only thing I can think is that the ONLY time I'd want that resistor in, is during foot off throttle, anytime I have any gas on, I'd want the crisp shifts, even for city driving. The vacuum line may not do that, but something relying on the pdeal would.

I wonder if this guy will ship to Canada.

[scottzg]

why not just stick a relay with a switch under the gas pedal? break the circuit when the gas is floored.

[sansMYSTi]

My RalliTek tranny mount makes the 4EAT feel a little more crisp, though noise and vibration increases. Might be an easier way to get the slush box to "feel" better.

[jeremod]

I'm just curious which vacuum line they use. The only thing I can think is that the ONLY time I'd want that resistor in, is during foot off throttle, anytime I have any gas on, I'd want the crisp shifts, even for city driving. The vacuum line may not do that, but something relying on the pdeal would.

I wonder if this guy will ship to Canada.

I agree. The point at which the switch is activated is adjustable so you could probably make it more sensitive. I'm not sure how adjustable it is.

Here's the link to the actual product.
http://smallcar.com/svx/tsk.htm