Transmission Mods

[oab_au]

Huskymaniac wrote.

On the power switch mod, someone mentioned that the TC will not lock up when this is engaged. Won't that defeat some of the purpose since the TC will generate more heat when unlocked? The oil will pump faster since the revs will be kept higher but the TC will generate more heat. Has anyone proven that the faster pump has more impact than the unlocked TC so that the net effect is positive which is to say lower operating temperatures? It would be nice to get the higher RPM map while still allowing the TC to lock up. I haven't installed the switch because I hate re-wiring cars. I am not even a weekend mechanic. If there is an easy way to re-wire the manual button to be a power button, I will do it.

The torque converter clutch still locks-up on my Liberty and SVX, when the Power mode is switched on.

Am I correct that you said the higher resistance will increase line pressure? It sounds like your box does so too. What exactly is the difference and how does one install your box?

No I don’t increase the resistance, in fact it has to be the original resistance, to allow the throttle position to set the level of engagement pressure. The TCU turns the line pressure down to reduce the engagement shock. I prevent the TCU from dropping the line pressure, when the change is made, to ensure a no slip engagement.

When the TCU cuts the torque for the change, the engine speed slows to the next ratios speed, this prevents the torque converter from working during the change.
By preventing the torque cut, the engine will drive the converter into a stall condition, to match the speed difference, and will multiply the torque.
This is most noticeable when down shifting to overtake on the highway. Instead of the car lagging there waiting for the change to take place and the power to come back, the change is instant, with the torque increase accelerating the car out and around, spending less time on the wrong side of the road.

Harvey.

[NeedForSpeed]

Originally Posted by oab_au

Huskymaniac wrote.


The torque converter clutch still locks-up on my Liberty and SVX, when the Power mode is switched on.

No I don’t increase the resistance, in fact it has to be the original resistance, to allow the throttle position to set the level of engagement pressure. The TCU turns the line pressure down to reduce the engagement shock. I prevent the TCU from dropping the line pressure, when the change is made, to ensure a no slip engagement.

By preventing the torque cut, the engine will drive the converter into a stall condition, to match the speed difference, and will multiply the torque.
This is most noticeable when down shifting to overtake on the highway. Instead of the car lagging there waiting for the change to take place and the power to come back, the change is instant, with the torque increase accelerating the car out and around, spending less time on the wrong side of the road.

Harvey.

The US TCU is not programmed to lock the TC in power mode until 92 MPH. If wired, best to turn off for freeway driving. If you need it for easier downshift, re-engage as needed. US power mode is perfect for selection 3, driving in town.

As for transmission protection, diff fluid is important. Change it. The diff is in a heat-sandwich, engine, transmission, and two drive axles. We bought both Pearls and the Teal with broken front diffs.

This last bit, explained by Harvey, less time on the wrong side of the road, is the most important thing to me. Saving lives is even bigger than saving transmissions, especially when its my life . Shift delay was a noticable problem the first week I owned my new 92 SVX, with a brand new car and transmission. I waited for an opening, nailed it, and waited. Showing off my new SVX a bit, I remember the pass, closer than I planned.

More recently, as a passenger in the Teal SVX, oldest driving it, he pulled out to pass. The shift delay is significant. It looks like you should have more than enough time for a safe pass, but too much time wasted without real power to the wheels. There was enough, but more than enough is better! Now, no more of this this type of downshift delay with QC installed. You are Quickly Changed into a lower gear before you hit the oncoming lane.

My second son calls his QC "insta-shift". He said it feels like 'power mode' to him. He complains about his worse fuel economy. He can't resist testing the shifts and Stebro, every time he drives it

[1986nate]

Turning the cruise control on will also override the power mode mod. And will lock the TC as normal.

[NeedForSpeed]

Originally Posted by 1986nate

Turning the cruise control on will also override the power mode mod. And will lock the TC as normal.

TRUE, good point,
use the cruise paddle to engage/disengage Power mode as necessary for freeway driving.

[Huskymaniac]

Originally Posted by NeedForSpeed

The US TCU is not programmed to lock the TC in power mode until 92 MPH. If wired, best to turn off for freeway driving. If you need it for easier downshift, re-engage as needed. US power mode is perfect for selection 3, driving in town.

Yeah but I don't like the idea of the TC not locking up, even for around the town driving. It defeats the purpose, to some extent, since more heat will be generated. And that heat is lost energy which hits your gas mileage. From what I have been told, the most important thing is to make sure the transmission is not shifting constantly and driving in 3rd does that. I also understand that some people believe that driving in lower gears, at higher RPMs also puts less stress on some tranny components like the bearings. So that's a good thing. But I still don't like that the TC doesn't lock up. Would be nice to get a TCU upgrade that allows the TC to lock up in power mode, at all speeds.

[tiv0]

Originally Posted by Huskymaniac

If there is an easy way to re-wire the manual button to be a power button, I will do it.

Sorry, I'm going a few posts back with this...

HERE is a link to the thread on how to do this. As much as you may not enjoy messing with wiring, it is fairly simple to do. I did it with my first svx when I was only 16 (and I was as big of a newbie as you could be when it came to wiring in cars).

Post #111 provides a decent "how-to" for wiring the manual button on the shifter to engage power mode, however you will need to refer to previous posts to view the pictures of the connector. It is as simple as removing a pin and replacing it 2 slots to the left.

[Manarius]

Originally Posted by Huskymaniac

Yeah but I don't like the idea of the TC not locking up, even for around the town driving. It defeats the purpose, to some extent, since more heat will be generated. And that heat is lost energy which hits your gas mileage. From what I have been told, the most important thing is to make sure the transmission is not shifting constantly and driving in 3rd does that. I also understand that some people believe that driving in lower gears, at higher RPMs also puts less stress on some tranny components like the bearings. So that's a good thing. But I still don't like that the TC doesn't lock up. Would be nice to get a TCU upgrade that allows the TC to lock up in power mode, at all speeds.

I wouldn't want to the TC to lockup during town driving. In town, it constantly locks and unlocks, so I don't know how that would be beneficial.

[1986nate]

Originally Posted by Manarius

I wouldn't want to the TC to lockup during town driving. In town, it constantly locks and unlocks, so I don't know how that would be beneficial.

Really? Mine only lock up over 50 mph and will stay locked to around 45 as long as the brake isn't hit. I put it back into 3 if i'm not at steady speeds of 50mph or higher.

[Huskymaniac]

Based on the responses here, discussions I have had offline and research of old threads, here is a list of mods that most or everyone agrees are safe. They are in the order in which people believe they benefit transmission reliability in this particular car:

1. Upgrade valve bodies
2. Replace stock ATF cooler with a low flow resistance cooler
3. Upgrade TCU with unit from ecutune.com
4. Switch to synthetic ATF and do a partial drain and fill every 2-3 OCIs
5. Increase the resistance of the transmission resistor to 15-20 Ohms
6. Add switch to engage power mode

I specified a low flow resistance cooler because most people agreed that heat is not the problem but lack of fluid flow and pressure is. There was strong agreement that high ATF temps were a symptom of an already failing tranny and not the cause of a failure. However, high ATF temperatures can cause other parts to fail even before the actual problem causing the heat fails itself. So, increase pressure, increase flow, change to a good ATF and/or use a good ATF additive, change the ATF regularly and keep it cool.

[svxwill]

why you drop QC from the list? it seen that's a good value mod and it's by OAB_AU

[Huskymaniac]

Originally Posted by svxwill

why you drop QC from the list? it seen that's a good value mod and it's by OAB_AU

Nothing personal intended toward OAB as he is a great source of information and help. When I researched it I found several people that were concerned about the bypassing of the torque control signal. I like the other aspects of the design but that scares me. If I were looking for performance, it would be a different story but my concern is exclusively for improving reliability. Not sure if I should have included the power mode switch mod. I was thinking that running higher RPMs and lower torque had some reliability benefit. Not sure if that is accurate.

There is also opinion that #5 may do as much damage as good. Again, I was thinking that a small resistance increase would increase line pressure slightly. But there are trade-offs.

[oab_au]

Originally Posted by Huskymaniac

Nothing personal intended toward OAB as he is a great source of information and help. When I researched it I found several people that were concerned about the bypassing of the torque control signal. I like the other aspects of the design but that scares me. If I were looking for performance, it would be a different story but my concern is exclusively for improving reliability. Not sure if I should have included the power mode switch mod. I was thinking that running higher RPMs and lower torque had some reliability benefit. Not sure if that is accurate.

There is also opinion that #5 may do as much damage as good. Again, I was thinking that a small resistance increase would increase line pressure slightly. But there are trade-offs.

Yes you might like to ask any of the 100 people that are using it, what they think.

Harvey.

[Huskymaniac]

Originally Posted by oab_au

Yes you might like to ask any of the 100 people that are using it, what they think.

Harvey.

I'm sure there are lots of people happy with it. I am just being cautious. This is my daily driver. That was probably a stupid choice but what's done is done. At this point my focus is doing things that I am sure will help reliability. Any doubts, even if misguided, will scare me away at this point. The only things everyone agreed on were the cooler change, the valve body change and frequent fluid changes. I even had one person tell me driving in "3" around town is not necessary. I don't drive fast around town so I do it anyways. I figure it couldn't hurt.

I got my first fluid change yesterday. The mechanic said the fluid looked and smelled good so I am cautiously optimistic. He only got 4 quarts out of it though. He had it flat on a lift. I will be going back at my next oil change and have him do a second drain and re-fill.

[svxwill]

good luck on long life for your trans.
my first svx had it rebulit 2 times and on 2nd time when i added the SmallCar kit with subaru external filter, which made it die faster (there wasn't as much info few years back). when i got the 92svx this year, i just changed the internal filter and put new oem atf. not sure i will do any mod to this trans.

[NeedForSpeed]

Originally Posted by Huskymaniac

At this point my focus is doing things that I am sure will help reliability. Any doubts, even if misguided, will scare me away at this point.

If the above statement is your only true objective, you should immediately delete your entire list. You can not be 'sure' of any of it. Items 1,3,5,6 are considered 'performance' mods, usually for those that drive accordingly. Items 2 and 4 are considered reliability/maintenance mods, but not everyone agrees on the cooler or on synthetic You clearly and correctly stated, the list is based on 'what people believe'.

To my knowledge, other than maintenance, none of the six items you listed has ever been proven to add reliability to a ’96 SVX transmission under normal road use. Most items on your final list have been tested sparely, and for relatively few miles, with mixed reviews.

You have taken the biggest step known and observed in increasing transmission reliability in an SVX, namely, driving a post-92 SVX. I believe that nearly everybody agrees on that. These later transmissions, when properly maintained according to Subaru, will easily approach 200,000 miles without failure. In fact, how many here have had a 96-97 transmission fail?

By 96, Subaru engineers had enough years and miles to correct early reliability concerns in the SVX. That is what you risk by making changes to a car you consider a 'daily driver'. I do not believe that any advice given here regarding reliability, other than periodic fluid change, is conclusive.

If you are looking to change the performance of your transmission, the 'safe' question is a different question entirely, with many opposing opinions.