Transmission care
 

Ok, we've got a '92 with 190K on it, and would like to make sure it keeps running. Can you folks tell me the best way to make the tranny last? Should we replace the fluid, or leave it alone? Any other tips? Thanks.

Re: Transmission care
 

If that is the original gearbox, and the ATF is still clean, you have done well.:) Just drain and top up the box every 20k, and drive it in 3rd around town.

If the oil is dark and smells burnt, look for another box. :(

Harvey.

Re: Transmission care
 

Replace the fluid but don't bother dropping the pan and changing the filter. It isn't really a filter; it's a wire screen and it doesn't get clogged. It's a waste of a pan gasket and screen. I like to use genuine Subaru transmission/power steering fluid. It's a quality fluid with good additives (subaru coolant is real good too but that's neigher here nor there). Add to it one bottle of lubegard atf protectant. This will make the fluid work better and last longer. Both the red bottle and the platinum which is a silver bottle are good--other brands and products are not equivalent. http://lubegard.com/~/C-113/LUBEGARD...ATF+Protectant
Upgrade/update your TCU with firmware with higher line pressure in 3rd and 4th gear to prevent high clutch and brake band slipping and eventual failure which otherwise plague SVXs.

Re: Transmission care
 

So, really, the internal filter only acts as a filter when the tranny is already failing and throwing off parts big enough to get caught in the screen. Is that correct?

Re: Transmission care
 

that is correct.

Re: Transmission care
 

Oh well, I guess that filter kit was a waste of money then. At least it wasn't too expensive.....

Re: Transmission care
 

You guys can pamper your autos all you like, I can't wait for mine to let go, but sadly, it seems to have been well taken care of.

STI 6 speed FTW!!!:lol:

Re: Transmission care
 

Don't agree with this bit on the trans screen. There have been a few that I have heard of that have had the trans fail due to the blocked screen.
http://www.subaru-svx.net/forum/show...+filter+screen
There are probably others that replaced the box due to this happening.


The slipping that destroys the band and high clutch, is a combination of high torque and low pressure. The low pressure is really due to the low rpm that the transmission pump runs at, when driving in 4th at low road speeds.
This combined with the high torque that the band and high clutch have to transmit, causes the slipping.

The line pressure can be increased, to add clutch pressure, by increasing the resistance of the dropping resistor. The resistance is 12 ohms increasing this to 25 ohms, by using two dropping resistors connected in series, will raise the pressure by about 30%. Increasing the pressure excessively will cause C and B solenoid binding, and hard changes.

The high torque is instantly reduced by 30% by shifting back to 3rd gear, this changes the overall ratio from 2.4:1 to 3.5 :1, the ATF output is increased by the same amount, and the heat produced by the torque converter is also reduced. It is the excessively high US ratio that has caused so much trouble. This is why fitting on trans that has a lower final drive ratio, like a Legacy 4.11:1 or an Outback 4.44:1, reduces the load on the box by about 17%/26%, results in a longer lasting, better preforming SVX.:)

Harvey.

Re: Transmission care
 

Na, there's no way a screen can get clogged. Aside from it being a very large surface area of a not very fine mesh I've never seen a clogged screen and I've rebuilt a lot of blown 4EAT transmisisons. I've had maybe half a dozen full of chunks of frictions that have fallen apart and maybe 4 full of chunks of bearings but I have never seen a clogged one. Even most blown 4EATs have clean screens.

The pump actually pumps a very large volume of fluid even at low RPMs. It incorporates a hydraulic feedback mechanism controling the volume of the vane pump so that the volume per rotation is higher at low rpms and lower at high rpms so that the actual volume pumped is equalized across the RPM spectrum. The sole reason for low line pressure at light cruise is the programming of the TCU. The stock programming has a very high solenoid a duty ratio under light cruise which bleeds of a whole lot of line pressure; there is no lack of fluid flow volume preventing a higher line pressure. That is easily accomplished by adjusting the main line pressure maps for each gear. Reprogramming the TCU with more line pressure in light cruise in 3rd and 4th gear or any gear's main map for that matter doesn't cause hard shifts or transfer clutch binding either. There are seperate maps and routines dictating the line pressure during gear changes and turns.

Re: Transmission care
 

[QUOTE[QUOTE]]Well I would like to help you , have a look here.
http://www.subaru-svx.net/forum/showthread.php?t=53883
This was the cause of the problem.

Not quite right. The pressure regulator, regulates the line pressure by controlling the pumps output. The total pumps out-put is controlled by the pumps speed, minus the quantity lost through the operational leaks and drains.

Yes the TCU does reduce the pressure at low throttle positions.
It can be accomplished a lot cheaper, by reducing the dropping resistor's resistance.:)

So when you are driving in 4th at a low road speed, with the line pressure increased from 50psi to 150psi and do a tight turn, you say this line pressure is reduced, so that the percentage of line pressure sent to the C solenoid is the same, as it should be. Don't think so.

As I have said, the main problem with the std SVX trans is the excessively high final drive ratio.

Harvey.

Re: Transmission care
 

Ugh, kind of a pain dealing with these line by line quotes....so I won't use them

so anyway....You're saying that someone had a loss of line pressure....changed his screen...and got his line pressure again? I find this hard to believe. If that is the case please say so directly. A picture where someone says he thought his filter was dirty doesn't do much for me.

no, the pump's output is controlled by a cam which changes the volume of the vane pump per rotation. The regulation of line pressure performed in the valve body you are describing is beside the point. The one and only point of any consequence is there is plenty of pump output to have much higher line pressure at light cruise and the only reason it isn't higher is because the tcu is bleeding it off.

If you really want to argue that tampering with the electrical connections is a better method of controling line pressure than setting the data right in the TCU firmware I'll just have to aggree to dissagree with you right now and not waste any more time.

Re: Transmission care
 

Oh no, another tranny debate. I am a pretty damn good engineer and these threads make my head spin. Of course, I am not an automotive engineer but an electrical/optical engineer so trannies are not my specialty.

I'm surprised no one mentioned bypassing the radiator with a higher flow oil cooler. I bought, but have not yet installed, a 10,000 GVW flex-a-lite cooler which has a pretty small footprint and a low flow resistance.

I agree with Mike on Lubegard. I have had great luck with the stuff and the folks at BITOG rave about it. It is an ester based additive which should help reduce operating temperatures. It is like water wetter for your tranny. Although I like Lubegard, I personally opted for Redline with no additives over Subaru ATF with Lubegard but I think that is a great option too.

From what I have gleened from the many threads on the subject, increasing the dropping resistor would help the line pressure a little but Mike's TCU map changes would help it a lot at those critical low RPM, low throttle conditions.

If stupid little crap like valve cover gaskets and O2 sensors ever stop going, I may be able to get the wife to agree to letting me buy Mike's TCU upgrade or valve bodies or both. Maybe a group buy by 1996 owners for the TCU upgrade would help spread out the cost of Mike mapping stuff out for our newer TCUs. (hint...hint to 1996 owners)

Re: Transmission care
 

Michael, why did Subaru program the original TCU for such light line pressure in light cruise?

Re: Transmission care
 

Subaru used the same solenoid a map for all 4 gears. They probably used the same solenoid a map in all their other model cars and for every year since they first released the 4eat. It was probably generated by a perfectly reasonable formula that calculated the minimal line pressure necessary to hold the rated carrying capacity of the transmission. It obviously works fine in 1st and 2nd gear which use larger clutch packs and it obviously works fine in other model cars which aren't as heavy as the SVX and have a higher gear ratio than the SVX.

The reason solenoid A and the maps and routines controling it are included in the system to begin with is to minimize the pressure the pump has to pump against. Pumping against pressure requires power so minimizing the pressure increases efficiency. Increasing line pressure 15% during light cruise might be enough to stop slipping if all the seals in the transmission and the high clutch are still very good. Maybe a 40% increase would do it. It's not practical start low and see where transmissions stop burning up. Putting it close to max pressure in the main map is an easy way to definitively fix the problem and the amount of power it takes to spin the pump against the higher pressure really isn't significant--especially compared to the power loss from erroring on the other side where the high clutch still slips.

Re: Transmission care
 

I would much prefer an flashable OEM ECU to a TCU upgrade on my 1996. Let the autos die!

Re: Transmission care
 

If the automatic SVXi are allowed to die, what percentage of SVX owner will replace the transmission with a five or six speed?
Since the five speed costs the average SVX owner about $2500.00 and the six speed maybe $4000.00?
Now go to your room and THINK about what you have said.:mad:

Re: Transmission care
 

Yes, this is a great idea to replace the stock in radiator transmission cooler with SOMETHING.
The size of the cooler should be determined by your transmission temperature.
If you install too big of a cooler your trans will never have lock up.


As to replacing the pan filter I personally am in favor of it for several reasons.
1)First of all they are like $30.00.
2)When the pan is removed you can check and remove the accumulated debris on the magnet.
3)By dropping the black cross flow tube you get about two more quarts out of the transmission.
4)When I replace transmissions I am REQUIRED by the transmission vendor to replace the filter on a used unit or there is no guaranty!
5)It couldn't hurt.



Geez, another engineer.:rolleyes:
:p
Husky, I have mentioned it in another thread! ;)
http://www.subaru-svx.net/forum/showthread.php?t=56310

Re: Transmission care
 

Sure, can't hurt as long as the person doing it owns a torque wrench and also invests in a new oe gasket so they aren't just creating leaks or a huge mess for the next go around. We all know how much we love taking a pan off someone has installed with that pink stuff.

Re: Transmission care
 

:eek::eek::eek:
The pink stuff,
the taker of life,
the scourge of the pan!!!!!:eek::eek:

Re: Transmission care
 

I don't want to cause you any pain.:)

"If that is the case please say so directly." Yes that was the case.:)

I don't want to waste your valuable time either, but.

No I didn't say it was a better method. I said it was cheaper.

Tampering with either the electronics, or tampering with the vearables, will produce the same results.
The only difference is the cost.:) $20.00 compared to $xxx.xx.:eek:

Harvey.

Re: Transmission care
 

Well in that particular document you linked to and are sighting as a replacing the filter brought line pressure back instance he went from a long filter to a short filter so maybe his pan was dented--that causes a loss of line pressure. Anyway, a clogged filter is so contrary to everything I have seen I would have to suspect some sort of unaccounted for coincidence that was the true reason for a return of line pressure after a filter change if it did in fact happen.

I wired my air compressor into the 240 outlet for the the dryer the other day. I went to dry some clothes later the same day and the dryer didn't work. I figured I must have messed up a connection--too much of a coincidence for the dryer to break the same day. I checked the outlet poles with a multi-meter and they were all good but man it was just too much of a coincidence to accept the dryer broke at the same time--maybe a connection isn't tight enough so it has voltage but the dryer can't draw enough current. I took the outlet apart and retightened all the connections but the dryer still didn't work. To make a long story only medium long I did finally open up the dryer and find the switch that turns the dryer off when you open the door was bad. Not having a switch on hand and not caring if the dryer turns off I popped a crimp cap in place of the switch and my dyer works.

Moral of the story is coincidences do happen and it will take more than one reported case of changing a filter restoring line pressure to convince me the screens clog. That's just me though. Others will of course make up their own minds.

Re: Transmission care
 

Yes I am sure they will.:)

Harvey.

Re: Transmission care
 

Tampering with the wiring is a long way away from changing the map that dictates what line pressure is in a particular gear. For one, tampering with the wiring effects line pressure at all times which according to your earlier statements must make you worry dreadfully about transfer clutch binding and what not. For two, when the line pressure is changed by tampering with the wiring the TCU does not know about it and can not take it into account in other routines like it can if the map is changed and a different solenoid a duty ratio is calculated. For three, tampering with the wiring defeats or partially defeats the signal/system which cushions the solenoid valve from fully seating and causing wear to the valve which will in the long run cause a loss of line pressure.

Re: Transmission care
 

Hope you don't mind, but I will have to divide this into 3 sections.:)

No, increasing the dropping resistors Resistance to 25 ohms does increase the overall line pressure by about 30%, this leaves the TCU to vary the line pressure, with throttle position.
Doing a flat increase of 50psi to 150psi, a 300% increase, inhibits the throttle position from controlling the pressure at all, in 3rd or 4th.

The TCU won't know if either type of tampering has been done. It works the throttle position control of the pressure, assuming that the specified amount of current is sent to the A solenoid. Changing the resistance alters the result.
Changing the specified variable number, that the program is looking-up, alters the result. The TCU does not know, that you have tampered with this specified variable, it just uses that number to produce the pressure.

Oh I can't believe you have written this crap.:eek: This is the same bull $hit that Trevor tried to infect us with. Shows a complete lack of understanding of the transmissions mechanical operation.:rolleyes:

Harvey.

Re: Transmission care
 

Very little of what you just said is correct but I don't intend to get drawn into a harvey/trevor dynamic so I'm going to drop it now.

Re: Transmission care
 

Damn it, you BOTH are wrong! It works by focking magic!!!:lol:

Re: Transmission care
 

With the greatest of respect Harvey, your method of tampering with the wiring will never produce a result comparable to a proper TCU remap.

The TCU uses a very complex algorithm to determine the optimum line pressure to suit a whole variety of driving conditions. It is not simply proportional to the throttle position.

I am in full agreement with LAN here. The transmission is a relatively modern software-controlled system. The only correct way to recalibrate it is via remapping the TCU.

As Trevor cannot be here to defend what you call his bull$hit, I'm going to restate my conclusion that neither you nor Trevor have a complete understanding of how this system works.

Re: Transmission care
 

I replaced the TCU with a flux capacitor. The car only goes when it is struck by lightning.

Re: Transmission care
 

Can you write up a how to?
And is it switchable?

Re: Transmission care
 

1.21 gigawatts!!!

Great Scott!

What the hell is a gigawatt!?

I have to say though that really, while a lot of the things in this thread are debated, one thing is clear: a transmission cooler that replaces the stock one is a 100% good idea.

Re: Transmission care
 

Ok no problem, I was only interested in the technical points.:)
Don't mean to cause anybody any problems.

In addition, I would like to apologise to Trevor.
I see that I have used his name here in a derogative maner.
It was not intended to be, it just come out that way.


But,,,,,,,,,,,
I would like to take this up again with Phil, in another place, There is a lot to be learned..:D

Harvey.

Re: Transmission care
 

Why do you say that!:mad:
They are being discussed!
Or we are just having an intelectual discord about,
,,,things!
But a debate, NO, I must protest!






















:rolleyes:

Re: Transmission care
 

Tonight I had a chance to get under "Pete's Pearlie", now mine.:DTEEHEEHEE!
A beautiful 230,069 mile SVX with an aftermarket trans cooler, Subi fix trans filter, a 4.44 installed years ago, with now maybe 150k on it.
I removed the trans filter, disconnected the stock in rad cooler, and did a "transfusion" of Dexron to BG Products, with the engine running, the car in park.
To watch the two/three year old fluid exit the trans through the clear hose, a clean but dark red, and watch the bright red BG enter through a similar hose was very, very cool!
After a roadtest, I "think" that the slow 2/3, 3/4 shifts were better, but they were still too slow.
I see a valve body for this one too.:o

Re: Transmission care
 

Harvey, I apologize for speaking very affirmatively and being more instructive in tone than convincing. I could have been more affable and amiable and wish I had been. I will endeavor to do so in the future.

Re: Transmission care
 

Thats OK Micheal, posts don't always convey the meaning as we intend. Interpretation is the readers domain.:)

Harvey.

Re: Transmission care
 

Reguarding transmission cooler size;
"I had to take a long drive today in 24-26°f weather, driving a
1)4.44 SVX with
2)a huge transmission cooler,
3)no external filter,
4)factory trans cooler bypassed, and
5)BG Products synthetic fluid in it.
All five of these changes lower the transmission temperature.
The highest trans temperature that I saw was 140°f even though I was driving at 3000rpm, about72 mph.
When the temp dropped to 138°f, it would unlock the torque converter.
The cooler in this SVX is a 15,7/8"total width, and 7,1/2" tall.
It is a Hayden/Imperial #242016 that has six passes.
For a summer car, or a Southern States car its might still be a little on the big side"

Re: Transmission care
 

I think that is the same Hayden I was looking at. I talked to the technical folks at Summit Racing and asked them which cooler had the lower flow resistance, the Flex-a-lite 4110 or the Hayden 676. They said it was the Flex-a-lite 4110. I think the 4110 also had the smaller footprint. It has less cooling capacity but, as you said, larger cooling capacity may not be a good thing. I could only imagine how cool my tranny would be running in our -18F mornings with a large Hayden cooler.

Re: Transmission care
 

A word of caution... When working as it is designed to work your dryer has a heating system that pulls the air through either the heating coil if it is electric and through a chamber that is heated by a flame if it is gas. The blower does not force air over the heat unit. If the dryer is accidentally ran even for a short amount of time, which will happen if the door is opened with it running with the door switch not functioning, bad things can happen. Worse things can also happen and they can be a lot worse than simply replacing a small, inexpensive part.

You can probably get one here at a reasonable price.
http://www.appliancepartspros.com/

Keith:cool:

Re: Transmission care
 

a gigawatt is a billion of those little rascals:)

Keith:cool:

Re: Transmission care
 

The footprint has never shown itself to be a problem to me.:o