Wiking

Tell me what is the A/T future with this bypass? Feeling is sehr gut.

A. Gives new kick to so sooooft 1 >to> 2 gear change,

B. Kickdown, which has been gradually 'falling asleep', is now fully awake. Works always, also from higher rpms.

The schema below:
- Original Resistor stays intact, wire is cut as shown, connected to a WOT switch.
- needs new add on bypass switch at throttle body
- One new 5kΩ resistor is in series only at WOT, normally sitch bypasses the resistor.
- The new resistor is used only at WOT. Normal drive = no change.

My guess is that servo etc seals at 15 yrs, are leaking. This can be compensated for a while with the higher pressure - regulated normally through the 12Ω drop down resistor.

see http://www.cardomain.com/ride/748507/15


Edit: updated, better pic

Matt93SE

iTrader: (44)

Doing that will greatly accelerate transmission failure by running the transmission pressure too high at WOT. too much stress on the bands and etc. If you're doing a top speed run, the transmission will keep shifting out of OD into 3rd gear because of the line pressure. eventually it'll start flashing tranny codes when you start the car and the transmission will slip worse and worse.

What happens next, I haven't experienced, but I'm sure you can figure it out.
My GXE was at the point above when I "unfortunately" totalled it.

Wiking

Few yrs ago, I got new 'leased life' via cleaning all supply etc connectors, 60k. My guess is that then seals were in better condition, and the small voltage increase gain helped solenoids to have again their designed portion of juice = higher voltage. Then the soft 1 >to> 2 gear change vanished and kickdown response became really better...

Day by day, this sooooftness has gradually returned. At WOT, sooofty slipping lasts ½-1 seconds after 2nd gear has been engaged, (now 90k.). Voltages have not changed. So it must be smtg else. It cant be the band wear, because it works perfectly w/o slipping with no resistor. My theory is the old servo seals are leaking (upgrade pack hopefully coming).

When the drop down resistor is completely out, second gear kicks really hard, both wheels screech (at around 40mph), and feels like all horses will jump out. That feels really destructive.

However, testing with various resistor, with the R5k, gear change doesnt seem to kick the tranny, but slipping is gone. Feeling is healthy.

Typically my tranny WOT abuses lasts seven seconds (60mph), maybe 200x per year. Is this and big issue?

We all die one day: Slipping is bad - this is bad - which enjoyment lasts longer? I think I let it die with this one... but will review the situation after upgrade kit.

Objections?

Matt93SE

iTrader: (44)

As long as it's not shifting at full line pressure, you should be okay. firmer shifts are fine, but once the shift is done, you want to take all that stuff out of the equation and let the computer and valving do its thing.

Wiking

The actual need for pressure increase is like for 'one' second only: to 'get' the kickdown, then firmly to engage the gear. Maybe I could use a time-delay-relay to cut out my pressure increase feature (increase now +50%?) but for the crucial seconds.
Lets see when the 'upgrade' kit arrives; if that doesnt help, then I'll build smtg to also take that mentioned OD issue into account.

Worst thing for me, is when kickdown isnt there when I have decided to pass a vehicle. This used to occur once during a 4hour trip... and I traced it into hydraulics (the solenoids do get ctrl as this no-kickdown uccurs).

Matt93SE

iTrader: (44)

Yeah, that's always annoying. Nissan's 4 spd autos are all sluggish like that. the 5 spd auto they put in the 2004+ was MUCH better, but still upshifts too quickly upon normal driving and doesn't kickdown easy enough when you put your foot in it. What I really hate is when I'm trying to turn onto a busy road and the tranny shifts into 2nd while I'm still rounding the corner and can't accelerate. then once you're going straight and want to get moving, it's stuck in the wrong damn gear and won't go anywhere. so you mash your foot to kick it down and it takes 2-3 seconds for the computer to figure out what you want. by that point you're going 20mph and the kickdown is severe enough to bark the tires. GRRRRRRR

for that reason, I just use the O/D off button or kick down to 2nd on the shifter. easier than goosing the gas and waiting for the computer to figure out you want to downshift.

Wiking

That delay can kill... My intermittent kick down failure is definitely hydraulic. Now this pressure increase gives kickdown back?, I should go and test it w/o my features again... Shall see if this holds, this story is just one day old. (I am ordering the valve upgrade from TRANSMISSION EXCHANGE CO, OR. They dont accept visa on line, so its donkey -age shopping.)

CapedCadaver

iTrader: (8)

not to mention sometimes you make it kick down to 2nd then lift suddenly for a split second and the stupid thing goes back into 3rd! which means you're only halfway there.

internetautomar

iTrader: (30)

manually downshift when needed. I used to do it all the time in my camaro since I had the detent cable disconnected.

Wiking

The A/T stick doesnt behave like manual: theres the danger dropping it to N, past D. While passing a car and rpm at redline while 2nd engaged... then what happens? Dont want to know... With manual, u can throw it eyes closed and it will go where intended.

internetautomar

iTrader: (30)

worked fine for me on the camaro. haven't done it since. I'm lazy

Matt93SE

iTrader: (44)

these cars aren't really fast or bumpy enough to have to worry about that. just click it from 2 to D and you'l be okay.
the computer prevents it from manually downshifting into 'unsafe' gears. i.e. you can pull the shifter into 1st at 80mph and it'll downshift to 3 rd gear. as you're decelerating, it'll drop to the next lowest gear when it will be around 5000rpm in the next gear. so on so forth.

when upshifting, it'll just run up to redline and bounce off the rev limiter in whatever gear you've selected.

CapedCadaver

iTrader: (8)

when downshifting i still used to use the accelerator to help rev-match sort of.. basically to take strain off the friction materials. unfortunately i had a really bad motor mount up front so it shook the car when i did so.

Wiking

Upshifting, from 2 >to> D, lever can easily slip to N. At least w/o the US-std shift lock mechanism... Unhealthy.

CapedCadaver

iTrader: (8)

even then it can slip into N. You can push it from L all the way to N without pushing the button, then you have to push the button to get into R, and push it more to get into P. USDM shift lock only affects leaving P.

Matt93SE

iTrader: (44)

the shift lever lock only goes down gears. you can shift between N and D without using the button. There's enough throw in the shifter that it shouldn't be a problem tho. I did it for pretty much all of the 4 years I had my GXE and never put it in neutral by accident.

1992maximase30

hmm..too much line pressure.
thats odd.
this is what us gm guys did to help our trannys
this is what us honda/acura guys did when our trannys was about to go out.

i had that slow down shift and sometimes i would have to step on the gas twice.
but the battery cable came loose stayed like that till 3pm.

the the shifts are somewhat perfect.
like when cruising want to speed up she'll down shift right away.
on the highway doing 60-80mph wanna pass someone she'll down shift to 2nd.
not like before:
unlock t/c, then 3rd, then sometimes 2nd.

i might do that mod

CapedCadaver

iTrader: (8)

er... huh? how does that work?

1992maximase30

well i did'nt know then it dawned on me.
it's possible nissan's tcu has like a program where it "remembers" your driving habits.
like when i hooked the cable back up.
i was'nt driving like gramma.

now when i say somewhat perfect she still has that "delay" in confort mode.

but upshifts in power mode...fine.
downshifts are now fine.

CapedCadaver

iTrader: (8)

the delay in comfort mode is the entire purpose of comfort mode actually. so it will take more throttle position to make it shift.

1992maximase30

well i mean @ wot.

at light throttles it'll shift quick.
but @ wot it rev then stay there then shift...like it's confused to shift into the next gear or not.

power mode will shift into the next gear but at a higher rpm.

there's no slipping in either mode...

CapedCadaver

iTrader: (8)

must be placebo or something very wrong with your car. according to multiple resources, at 7/8ths throttle and upward, Pwr/Cmf switch is bypassed and the car shifts at 5800 if VG and i dunno what RPM if VE, regardless of setting. and the switch has NOTHING to do with line pressure, shift speed, w/e. any of those changes are byproducts of how the TCU calculates everything at any given point in time.

1992maximase30

yea i was told too.
i have a vid of her performance.

they said she does'nt show any signs of a tranny going but there kinda baffled as to the rpms difference between cmf/pwr.

on the ve i noticed that when in auto the pwr light would come on almost all the time.

on the vg it would'nt come on like it should.
i'm starting to suspect a failing tcu.

you want the link for the vid??

CapedCadaver

iTrader: (8)

or a bad TPS. bad TPS can cause laggy shifts and stuff. better for you is just a miscalibrated TPS.

Wiking

Bad TPS makes TCU, driving, definitely asthmatic. Theres three ways to tst the TPS, from self diag to resistance measurement, check out: http://www.cardomain.com/ride/748507/6

Have to add about the pressure mod: if anybody does it, I guess its good to get resistors 1, 3, and 5k Ohms, test each, then select the 'best'. If this issue is related to old worn rubber o-rings, then each tranny is individual... use what fits in to your tranny. You can use cheap smaller wattage resistors than the original - if connected to be used for few seconds a time. My resistor was 1W (eh... was it, have to check?)

LvR

Sorry Viking but I am not sure what it is you think you are achieving with this mod. With the std line pressure resistor being around 12Ohms, I cannot see a parallel modification with a few KOhm having any significant influence on the actual measured resistance and therefore line pressure due to the modification. (FSM says normal is 11.2 to 12.8Ohm)

While I agree that increasing the line pressure may indeed influence (improve or not) the speed/severity of actuation of clutches/bands etc I am not sure how such a small decrease in line press drop resistance can even be detected ................ I would say parallel resistors to be used for this mod should be more in the 100Ohm range in order to affect a measurable seat-of-the-pants affect on the feel of the auto.

Alternatively - Perhaps I am missing something obvious, in which case please set me straight.

Wiking

The Illustration tries to implicate that TCU 'sees' a resistance of 5012Ω - while briefly at WOT - both resistors in series. Normally the 12Ω rules.

The effect is radical, real, causes pressure rise. I tested with series of resistor in series, 50, 100, 200, 1k, 1.5kΩ etc resistors... settled with this 5kΩ ... it doesn't burn rubber at 2nd ... I am really frightened that my horses would all escape if there was NO resistor as some ppl suggest (maybe they have tame engines

This is NOT needed in fully functional tranny, only old age remedy. But what is actually the problem, dunno, some kind of internal leak? I am just working like real doctors, casting lots witch pill$ to throw unto unsuspecting patient...

Btw, ppl with similar problems may test the effects just by unplucking the pictured connector: with stock tame hp that might be all u need...

Why only at WOT?
1. I dont understand enough... to keep the 5kΩ always ON, throw original 12Ω out...
2. A thinny R5kΩ from toolbox is ok, no need to go shopping for the big ones.
3. Normal driving is currently all nice and ok
4. Only kickdown had grown lazy, 1>to>2 change WAS too soooooft.

-------------------------------------------------------

Current test settings:

see http://www.cardomain.com/ride/748507/15

LvR

OK - if they are actually in series (12R+5000R) rather than like what I assumed to be in parallel, then fitting the 5000R is a complete waste............. effectively - simply removing the existing resistor with a switch would accomplish the same result

According to the FSM and under fully warmed up conditions only, pin2 on TCU supplies the line pressure modulating voltage (14V and thus high current implies low pressure while below .5V implies high pressure because of low/no current) while pin1 actually monitors the pressure modulating signal (voltage on line pressure solenoid).

................ the net result of either the additional switch being open or closed in the diagram of yours is exactly the same at the time of WOT operation (since pin2 at WOT supplies no voltage anyway) ................ and since the switch bypasses any affect the whole mod can possibly have under non-WOT conditions, the whole thing is technically useless and can serve no purpose.

If you are saying you do have and experience a difference in the auto's reactions with this modification fitted, then I don't know what to say other than IMO its not because of this particular suggested modification ALONE

Wiking

Nope.

With my hp (230?), just disconnecting the original Resistor, WOT acceleration, gear change to 2nd is about to rip my tranny to pieces. Burns rubber on both wheels. No way!

This resistor here adjust the pressure for nice firm operation ... maybe my tranny doesnt understand FSM ?

LvR

................ or perhaps I don't?

......... or on this particular aspect of the design whoever wrote the manual didn't know what he was talking about?

FWIW only - Is it your opinion that my understanding of what the FSM is saying is right? ............... I can offer the fact that unplugging the drop-down resistor apparently (according to those that have done it anyway) feed full mechanical-valve limited only pump pressure to line circuits to actually make me think the manual is in fact correct in its description and thus my statements




Wondering here ................You quite sure that switch you fitted is actually bypassing the resistor during non-WOT operation? ................ if eg it wasn't, then it could explain why you are saying you do have a measurable effect because the auto would then run at full pump pressure

Wiking

As said, I am no A/T specialist. I've been figuring out how all the RE4F02A 19 valves/pistons and five solenoids play the symphony. I am baffled with the information - cant decipher, I guess there are some fundamental confuzean error(s) for example in the FSM AT-9 info...

I just recently read about dropping that resistor off (=disconnect), then started testing. This is what came out, cant explain more. Test/try to disconnect, tell what happens...

The FSM is so called level III -manual. It doesnt really explain issues, just R&R.

To answer any those questions, I need level II or level I manual, one week time to study...

Wiking

Lifetime job experience is at stake.

LvR

I am no AT specialist either but I have a bit of related experience and training - ITO AT9 in particular I don't have a problem - the line pressure solenoid in the configuration shown there, seems to work as per the test procedures in the other parts of the FSM and tallies with my current understanding of the workings of the animal - ie - applying current to the line pressure solenoid will modulate/decrease the line pressure in proportion to the current while no current on the solenoid will leave maximum pump pressure to reach the line circuits.

As I said - if your newly fitted switch is funky or inadvertently wrongly connected, and then if it doesnt bypass your added resistor, you will and should indeed expect to experience a change in box behavior because you effectively have the 5000R resistor in series with the 12R resistor (simulating removing the original 12R resistor altogether)

Wiking

No... no flying bird electrons here

The heavy burden to fit theories (I havent none) into practice lies with theorists, not me

What is the underlying problem? Nobody knows which valve leaks if any - this has deciding part in flow directions. Before that is known, 'all' is guesswork.

The resistor setting which is as described, enhances the solenoid resistance thus its valve operation. 'Behind' is the pump pressure... There is no magic: solenoids do work differently as current flow varies. Now it just barely is doing smtg... How TCU handles the I/O, no info available.

With the 5k, butt dyno registers real push 1>2 ... With 1.5k, no push but still firm...

Wiking

Maybe my illustration was not clear enough ... so I made a new picture.

The original Line Pressure Drop Down Resistor remains intact. Added 5kΩ resistor is normally 'closed out' =bypassed via the WOT switch. When throttle becomes fully open and current cant go through the switch, all current to solenoid has to run through both resistors = in series. Hope this helps...

see http://www.cardomain.com/ride/748507/15


The new 5kΩ works in series with the original resistor. It is used only when when gas pedal is fully pressed and the NC bypass switch opens. At Wide Open Throttle, WOT, the total resistance that TCU 'sees', is briefly the sum of all series resistors, 5012Ω.

LvR

Well - I understood that to be the case yesThis is where you are losing me when you say you actually feel a difference in auto response with the mode (at WOT only yes?)

The TCU has no current going to the solenoid from #2 pin at WOT already without this mod of yours (according to FSM) therefore your mod cannot affect that aspect .................. yet you still feel a difference.

Perhaps your WOT switch defines a new WOT point - ie - different (must be earlier) - to what the TPS is doing (both the TPS and your switch is not acting at the same relative throttle position to indicate WOT and hence your mod can via that switch affect the auto's feel )?

Wiking

Pull out the plug in your max, and test (=infinite R) ---> Effect on always. Yes/No?

I dont like that hard ripping the effect. I need smtg between those 'extremes'.

I based my trial on claims what I just read, not my invention. Tell me where this TCU ctrl would be explained in detail in the FSM. TCU is just a mystery 'brick', two wires to drop R...

Solenoids do behave like that, no mystery: the bigger the resistor value in series, the lazier the solenoid (and here its valve).

LvR

Sorry man - I have a VG with 300 000km on the original auto box (both doing fine atm) and imo doing that may well unnecessarily shorten the auto's life - if it was younger I would try it to confirm. If that is the sort of info you actually need to figure what happens then I would suggest a pressure meter able to do around 10bar connected to the line pressure port.

There is nowhere in the FSM that the exact engineering details wrt line pressure governing are grouped together.

My comments and understanding stems from the following scattered bits of related info in addition to the valve diagram on AT9:

AT18
At28 (line pressure duty)
AT58 (actual resistance values to figure currents with voltages applied from pin #2 TCU)
At77 (the output voltages measured on TCU #2 and the resulting feedback voltages to TCU #1 ............. use resistor in series voltage drop calcs and those values corresponds to the functionality)
AT86 (line pressure test)

That, and the fact that people disconnecting the dropper resistor reporting line pressure highs with non-WOT harshness and thus indirectly confirming the functionality at WOT.

Oh I agree completely - but imo the solenoid's valve sits on a return spring - iow you need a certain amount of force applied via the solenoid to even start making it move. Sure once its moving a very small change in current will affect the movement at that point, but with your suggested mod I have a problem seeing how the solenoid can see anything other than what the FSM already intends to happen (except in the case where your switch may possibly define a different WOT throttle angle to the TPS)- this is the problem


Note that I am not saying its a bad suggested mod - I am just trying to understand what exactly it is that one would actually achieve ito box operation and how its eventual durability (your thread title after-all) is going to be influenced at this late stage in its life - I am glad you do experience the desired effect, but I am willing to bet that today, here and now, any other vehicle undergoing the same mod will not show the same effect as I am at a total loss of explaining why you should be experiencing the effect you do - it just doesn't tally with the maths, with the hydro-dynamics, or with the current functionality before the mod gets applied.

sonicii

I'm with LvR here, the line pressure solenoid is powered through the 12ohm dropping resistor, chaning that to 5012ohms, would not supply enough current to the line pressure solenoid to move it at all, and will give the same effect as totally removing the dropping resistor, full line pressure. I am also at a loss to explain why there would be any noticable difference between a 5012ohm (or even 1012ohms for that matter) dropping resistor and a open dropping resistor.

Wiking

Life stays theory if no WOT

I've read the FSM 'few' times --> no explanation ... I cant see any mystics here, the TCU box just remains unexplained. Solenoid tuning = basic cause-effect law. My question was how tranny will take pressure mods.

Even the original resistor is just a pressure tuner, I wont do this: http://tatanko.boredmder.com/drop_resistor.html