After seeing the posts on the drop resistor mod, I emailed Nissan Performance Mag to ask. They posted my question in this months online 'Ask Sarah' section. Here's the question and response for those interested:

"Recently on Maxima.org someone posted about a 'drop resistor mod'. When a sensor is disconnected, it allows the full line pressure in the auto tranny which makes shifts faster and more abrupt. I tried this myself and it makes an enormous difference in shift times. Is it harmful to the transmission? Derek Michaels"

Full line pressure will be slightly easier on the transmission because it reduces slippage (typically 2-8% for autos) and shift overlap (being in two gears at once when upshifting) due to stronger application forces being directed via the servos to the bands and clutches. This locks up the bands and clutches harder and gives firmer shifts. By reducing slippage, it also decreases the amount of heat produced by the clutches and bands and locks the clutch in the torque converter up harder in the higher gears to increase fuel economy. The heat produced by slippage contributes to wearing out the seals, bands and clutches in an automatic more quickly. However, since the transmission controller is programmed to give full line pressure at wide open throttle, this mod just gives rough shifts at part throttle. It's similar to using an HKS ALC (Automatic Line Controller) box. Other ideas to improve shifting with an auto tranny could be to shim the PL solenoid regulator springs to increase peak pressure or to shim the shift accumulator springs to firm up and speed up the shifts. Or you can just swap in a manual!

 

They should've also answered the issue on what other parts may experience accelerated wear+tear due to this mod.

Judging from the harsh shifts at partial throttle, i'm sure something in there is being abused pretty bad.

 

I agree. As I read their answer, I was hoping something would be mentioned about abuse on engine mounts or something, but they didnt say anything. But they did give a few ideas to increase shifting speed in the last sentance...

 

Who ever answered that is wrong by stating that at WOT the trans goes to full line pressure. There is a big difference at WOT in the line pressure with the drop resisitor removed from the circuit vs having it in.

The reduced wear on the clutches etc is true and of course harsh shifts at part throttle. Thats why I have it hooked up to a WOT switch, its just way to harsh for normal driving.

Just because it was answered there doesn't make it the Gospel.

I disconnected the drop resistor on a 2003 Sentra recently with the same results under WOT, big difference.

Sarah is FOS. Some guy who doesn't know WTF he is talking about gave Sarah those answers. If it didn't make any difference at WOT I wouldn't need to use a WOT switch. Stop reading that sheit that women write.

 

 

i was more interested in the other ways of decreasing shift time... and of course i'd trust the guys on this board more than an editor

 

How do you perform the drop resistor mod. Where is it located?

 

I just tried out the mod and I wasn't very impressed. I could only tell the slightest difference between shifts at part throttle. At WOT there was no difference at all. I could possibly see how it would help if you were boosting like in Jime's case, but for my 01 auto i didn't feel that it was worth it.

 

You're the first person who barely noticed a difference. Everyone else has felt a harsh shift from 1st to 2nd, and when WOT it performs a lot better.

Jime: Where did you get the 'WOT switch', or how did you make it? Thanks.

 

I actually i think blubyu2k2 had a similar experience with the mod. I didn't chirp into second or anything. I plugged it back in after i did a run at WOT and did another and felt no difference. There was a slight thud without the resistor from 1-2 at part throttle but nothing as drastic as what i've heard.

 

Where do you unpug this thing, I want to try it out on the way to work tomorrow.

 

It's the only sensor located on the driver-side front strut tower.

 

Thanks for they quick reply Y2KSESteve!!!!!!!

 

Help!!!!! I pulled out the sensor that was closest to the drivers side front strut tower, and the car was staggering, then I took it for a spin and it would not go into 2nd gear, and now my ses light is on and I have never seen it on until I pulled the sesor. So now i unpluged the batterey and will start it up tomorrow to see if it comes off. Do you think I pulled the wrong thing. I didn't see any other things to pull. Please help!!!!!!!

 

The switch I am using is identical to a WOT nitrous switch (NOS and NX use the same one) except it has 3 terminals. This switch can be used in Normal Open (NO) or Normally Closed (NC). In order for it to work properly for the drop resistor it has to be normally closed and then when you hit WOT it goes to NO to open the circuit, just the opposite of what you would do for nitrous.

You should be able to get one at an appliance repair store. They are used in microwaves, dishwashers etc. I will post a pic tomorrow if you don't know what a WOT nitrous switch looks like.

http://www.slickcar.com/productdetai...ProductID=1805

 

That is why I did not try it when this first came up....I'm all for easing things on my tranny, shifting-wise, but this sounds pretty drastic, and if it sets off the SES light like it seems to, I think I'll just steer clear of that and wait for a better alternative down the road. I don't want to harm anything.

 

Ya its pretty drastic if you don't know what the heck you are pulling.

 

I finally found mine yesterday and disconnected it, didn't get an SES but the shifts were very hard under low RPM's. I live in a small town with two lane streets so it was shifting a lot. I drove about 2 miles and decided to reconnect it. I'll save up for the VB mod. I'm still interested in the switch that jime put on.

 

I remember you had issues trying to find it... so where is it located in the 2k3's?

 

It's on the drivers side strut tower, about 3-4 inches down from the top of the tower and centered on the tower, it is silver in color. There is only one connection coming out of the resistor and it travels, as you are looking from the front of the car, left to right, tucked right in the corner of the strut tower and the fender. I bent out the connection out a little to get to the release button, but be careful. Hope this helps. Good luck!

 

Sounds like it's in the same area as in that picture i showed you in the other thread. So is it just the connector-type that's different?

 

You are right, it was the connector that was different. Thanks again.

 

Thanks for the help.

 

Pic on my site
SES Light just a part of life

 

We both have a 2K3. I got an SES light and A/T check light immediately after starting the car. After a short drive I stopped and reattached the connector, the A/T check light went out, but the SES light did not and I finally performed the ECU reset procedure which did turn off the light. I've read posts from others with 2k2 and 2k3's that, like you, did not get an SES light... why? I assumed our cars shared the same control units and programming.

 

I have a 2k2, right after i disconnected the plug no light came up. Drove for a couple of miles and turned it off. Reconnected the plug and got an A/T Check light on my first start. Turned it off then on but just left the key at the ACC position for a couple of seconds. Started it and the A/T check light went away. No SES light at all.

Weird if anything.

 

I am the engineering editor of NPM and I check as many of the articles each month as I can for technical correctness. She did answer that question. When you increase line pressure, you reduce shift overlap and the attendant slippage that the clutches and bands experiance, thus reducing wear and tear on the transmission.

Reducing slippage also reduces heat and thus is easier on seals and some of the other heat senstive componetes in the transmission.

Harsh is relative, the shift shock is still mostly canceled out by the hydralic cushion of the torque converter and is nothing compared to the drivetrain shock that your typical manual transmission experiances.

The resistor mod is harmless even though it doesnt do very much.

Mike

 

How the hell do you know she is wrong? She seems to know about how the transmission works, As engineering editor for NPM, I edit what she turns in. I also know that she comes up with these answers herself and there is no guy telling her what to write, at least I don't. When she does need help I know her advisors are top industry people. You are lame to assume that because she is a girl, some guy must tell her what to write. She knows a lot about how cars work and she works on some very fast cars although SR20 stuff is where she is most knowlegable.

I know a little about the Nissan FO4A transmission. I do know that the PL solenoid that controls the transmission line pressure goes to 100% duty cycle at WOT as comanded by the ATECU. If you can get the PL solenoid to allow more line pressure than going full open please enlighten me! Adding resistors mearly has the PL solenoid at full duty cycle all the time and thus gives harsh part throttle shifts as the line pressure is high all the time. Why don't you tap the pressure port of the transmission and measure the pressure? I have when playing with transmissions and I tried this mod a long time ago, it doesnt have any affect on WOT line pressure, just part throttle!

Shimming the PL solenoid regulator spring can increase WOT line pressure or running the stiffest of the three avalible springs plus shimming will work as well. Shimming the shift accumlators and limiting their travel also makes for harder faster shifts.

Basicaly in my opinion the dropping resistor mod is sort of a rice mod because it really doesnt do much besides mess up the driveabilty of the car and perhaps make an incremental difference in how the transmission really performs when it is at less than WOT. Perhaps is is somewhat benifical in transitional heavy throttle stuff like you might do in autocross or something but in my opinion if you were really interested in the best performance, you should have bought an MT equipped Maxima.

Mike

 

Mike,

That's great information and much appreciated but my 2003 GLE shift is HARSH by ANYONE'S standard when that little component is unplugged!

I once owned a 95 Z28 that would easily bark the tires when it hit second at anything above 1/2 throttle, the shift was quick, solid, and firm, but not harsh. The shifts in my maxima are not like that at all... it literally pounds into 2nd gear with a bang that feels like the transmission will come flying out through the wheel well. Maybe some maxima's deal with this mod better than others.

I agree that the transmission's shift-smoothing components may benefit by reducing the slippage during shifting, but the absolute pounding MY car exibits when the resistor is unplugged is definitely not harmless.

btw... my comments are sent with respect for you and your car knowledge... please don't flame because I may not agree with your 'mod is harmless' statement.

 

The solution is don't do this mod, it reallydoesnt do much or put a swtich in line so you only have part throttle full line pressure when you want it.

The converter should not be locked at the 1-2 shift so I don't understand why the harshness is super bad. Have you ever driven an older domestic non electronic A/T like a Turbo 400 or 350 with an agressive shift kit or a full manual racing valve body? The harshness should be on par with that.

Belive it or not, it actualy doesnt hurt the tranny but come to think of it, it may put more stress on CV joint, motor mounts ect, especialy since stock Nissan motor mounts suck.

Mike

 

She is wrong because it does change the line pressure at WOT, you are wrong if you assume is doesn't also. It even works on a 2003 Sentra that I tried it on a couple of weeks ago. I wouldn't even use it except at WOT.

All the rest of the gobblygook about the shifting etc is correct and I don't fault that.

You can call the drop resistor mod rice if you want but that does not change it effectiveness. It does increase the line pressure at WOT whether you believe it or not and its easily checked by running it at WOT disconnected and connected.

I run it on a WOT switch so it is does not even come into play at part throttle and I remind people all the time its a WOT mod only.

I am not sure if it works on all Nissan's or not but it sure works on the 4th Gen Maxima and the 2003 Sentra.

Also, if I had wanted a manual I would have bought one, I happen to have the fastest 60' time on this board and I do know a little about what I am saying.

We aren't going to get along I can see that but I hate when magazines make false statements and then some engineering editor makes it worse by trying to backup some lame brained female who can't backup her statements.

If you don't think the drop resistor mod increases the line pressure of a 4th gen Max at WOT you are FOS too. There are lots of people on this board who have tried this mod at WOT and will testify to its effectiveness.

We have people on this board that make statements that aren't true, me included sometimes but when the editor of a mag proclaims falsehoods its much worse. I know you probably aren't doing it purposefully but you are still wrong.

 

What disconecting the resistor does is kill the power to the PL solenoid which is a PWM (pulse width modulated like a fuel injector) solenoid that controls the transmissions line presssure. When you kill the power, the solenoid fail safes to a fully open condition and the transmission sees maximum line pressure and hence the application pressure of the clutchs and bands inside the transmission increses, so you get a harder shock, less slippage and faster shifts.

On every Nissan I ever checked the PL solenoid goes to 100% duty cycle at WOT which means its fully open which is the same result as unplugging it. There is a chance that perhaps on this year of Maxima the PL solenoid is not at 100% due to ATECU programming or something but thats unlikely because no Nissan (U30 Altima, A32 Maxima, P10 G20, Z32, S13) I have bothered to check did not work by this logic.

So tell me what line pressures you measured before and after then to prove me wrong! Which test port did you measure those pressures at?Tell me how the line pressure is going to increase once the PL solenoid is wide open?

How much faster did you car go once you did this mod? How does your ability to cut a fast 60 foot time have anything to do with how this mod works when the 1-2 shift is after the 60 foot point?

Lets see some data.

Tell me how do you know that someone is stupid because they are female? That is a real dumb assumtion.

Mike

 

Pressures were measured at the D,2 and 1 positions test port, the reverse is much higher. Pressures were in the 150 range with trans operating normally at WOT, with the resistor removed from the circuit the pressure increased to over 200 at WOT. I didn't measure at part throttle because I don't use it a part throttle its hooked to a N/C WOT switch.

Line Pressure solenoid is not wide open at WOT, thats where you are wrong but disconnecting the drop reisistor does do just that.

How much faster did I go? Was never measured because I did this mod to save the trans clutches by shifting faster at WOT not to help 1/4 times.

The 60' has nothing to do with this mod, it was to show you I am serious about my racing and I have a faster 60' than any of the manual transmissions you are saying I should have vs my auto.

Now lets see your data. You are saying that my 4th Gen Maxima doesn't increase line pressure over stock at WOT with the drop resistor removed. I say it does. PERIOD. This is much easier to prove by just doing it, the difference at WOT shifts is dramatic its not questionable.

Anyone who backs up a female who makes false statements and believes them himself is obviously in the same IQ arena.

BTW I have been a mechanical P. Eng for over 30 years what are your credentials?

 

If find it hard to belive that a fellow engineer would have such a condensending attitude toward women, especialy one that I find to be quite intellegent! I also find it amazingly stupid that you could call someone who wrote a response like that stupid especialy when you put stupid and woman together as if they are connected! Then again you are calling me stupid without even knowing me or what my background is which is another careless assumption.

As I posted, my testing has not involved a A33 but I have tested A32's and every Nissan that I have ever tested (Ieven listed them in my last post) does not incresese pressure when the PL solenoid is taken off line. The peak line pressure is controled by the regulator before the PL solenoid. As I also said there could be differences in the programing of the controler and it doesnt go 100% on your vehicle.

As far as my credentials, I might not be the smartest person in the automotive world but I am an Automotive Engineer for a major OEM, an ex race support Engineer for a major factory backed race team and a ex high performance parts engineer for the factory performance division for a large major OEM. I have been an Automotive Engineer for 18 years. I hold or have held SCCA, IMSA and NASA compition licences and currently race SCCA and NASA sanctioned events. Most of the cars I have supported have been consistant winners, lap record holds and national champions. I also have built some pretty powerful Nissan street cars including a 575 whp 300ZX, a 430 WHP Sentra SE-R and a 176 whp NA Sentra SE-R. The NA SE-R won its class in the inagural SCC Ulitmate Street Car contest.

I am definaly not the smartest person out there but I am qualifed to make statements on how this particular transmission works.

Mike

 

Pics of the afore mentioned sensor on a 2003 A33 Maxima...

 

God I should have known better than to ask an engineer's opinion of himself.

I agree you are not the smartest person as well but I disagree that you are qualified on how this particular transmission works. I spent a whole career trying to simplify things my fellow engineers tried to make complex. I don't care how many transmissions you tested or what magazine you lie for but we are talking about a 4th Gen auto Maxima and the drop resistor mod does increase line pressure at WOT when its removed, regardless of what you or Sara may think or say.

I also did not make careless assumptions on you or your background, I recognize *******s right away. You qualify.

Now you are saying you haven't tested an A33 but yet you are very qualified to make assumptions based on the others. Well I will let you back out if you want but you are still WRONG about the 4th Gen Maxima auto and so is Sarah.

I did a little video a few minutes ago, just wish I had a Max with a little more HP and exhaust to amplify the results better but you can still hear the difference. It feels much faster than it sounds. The 1-2 shift is much faster than the 2-3 because of the gear ratio, the 3-4 is even less but when you are running 300 HP + the difference is much greater.

http://members.rogers.com/mrjimedwar...p Resistor.wmv

Regardless if you want to go on thinking it makes no difference, (which you probably will) go ahead but don't try convincing Maxima enthusiasts because they are smarter than that.

I have spent enough time on this subject and I don't really care what you think or say so this is my last post, the Org folks will make up their minds based on the facts.

PS Give my regards to Sarah. Tell her next time to check out her facts and her boss a little closer, it will enhance her career.

Have a nice day A$$hole

bigdo26 I will also remember you for going and getting this jerk. He is one of the reasons I retired when I was 48, got sick of listening to verbal diarrhea.

 

Hey Jim...your video link isn't working

 

morepower2 and Jime PLEASE tone it down a bit. No need to have a d!ck size contest.

morepower2-
Question for ya:
When you measured the line pressure solenoid valve duty cycle, what was the throttle position?

 

Ok off the top of my head typicaly the WOT line pressure of a FO4A in the foward gears is around 80-100 psi give or take a few. In reverse its typcialy a little higher. At stall it is around 200 psi. You said its 150 psi in the foward gears stock and 250 psi with the solenoid disconnected. Usualy the stall pressure is the max a tranny generates.

Unfortunalty the FSM for the 03 Maxima does not include the pressure under driving conditions like the old manuals do but the line pressure at stall which is typicaly 50 percent of WOT is around 180 psi which means the pressure at WOT in the foward gears should be a little more than 100 psi if the 03 acts like most Nissan transmissions, a bit less than your measured 150 psi. The stall pressure in reverse which should be the peak pressure posible to generate in the transmission is 278 psi which is close to your measured peak. The foward stall pressure is 179 psi which should be around what you see with the PL disconnected.

It cracks me up how you from the start have made this a personal issue with no provocation and your attitude towards women. In calling me stupid you also call Clark Steppler of JWT stupid who I called to make sure that my experiance was in line with his tuning experiance as well on this subject. I mearly want to qualify the jornalistic integrity of the websight I edit and defend the qualifcations of our writers. You may be a good engineer but whatever, unlike what you have done with me I don't have enough information to make a call on what sort of person you. I have nothing to prove to you anyway so this is my last post in response to you.

I don't need to call you names or insult you, I think the nature of your posts shows how much class you have.

Mike

 

I don't have an issue with **** size, mine is very small and that's the reason why I build fast cars to make up for it :-)

For diagnotic purposes you measure it at idle and stall.

Mike