Hold Switch On The Automatic Gearbox

[Lum]

I know the switch will force the car to start in second, but what behaviour does it cause after that.

I found some documentation on the Subaru 4EAT (which is also made by JatCo, same as the Nissan boxes) that states that hold+2 will be permanent second, hold+3 will start in second, change up to 3rd as soon as possible and then basically stay there, and hold+d will start in second then drive normally other than not using 1st.

Is this also true for the A31's gearbox?

I'm asking mainly because I'm interested in taking the car on a dyno and if the Nissan box does behave in that way, it should be pretty easy to get meaningful figures.

[Nic_A31]

Don't think it forces higher gear starts.

The switch dictates where the gearbox shifts under normal driving.

If its on hold it'll shift earlier than normal, if the switch is off it'll shift whenever, if it's on Power it'll shift as late as possible but won't exceed the redline.

If the switch is on hold or neither, and you plant your foot, it will act as Power anyway and shift late.

The idea of the switch is to change the shifting behaviour between cruising and hard driving, but it makes little difference.

[Mr Eps]

serious? it makes HUGE difference... it's also known as "snow" switch...

basically in less than desirable weather ie: rain you flick the hold switch... car starts in second and configures the gears to keep low rev range, high torque, low power... so that the wheels don't spin and you don't lose control so easilly

it's basically an ancient form of traction control

[Lum]

Yes, I've used it in the snow to good effect but never really knew how it actually worked. Only problem I had in the snow was dealing with other people's stupidity, oh and finding out that the font diff is open thus managing to get stuck out in the Brecons with 3 wheels spinning and one still.

So will the switch be any use for getting a meaningful dyno run or not. Don't want to waste £60 if they can't get it to stay in one gear for most of the run.

[Mr Eps]

"power" would be best for that.... realistically they're a dyno shop should /they/ do the driving????

[Lum]

The only 4WD dyno that I can reasonably get to doesn't seem to think it's possible to dyno an auto as they can't control when it changes gear, resulting in a meaningless gear.

I'm just trying to find a way to make it a bit easier for them.

[Nic_A31]

Controling gear shifts in Auto is easy.

1

2

D

if yours has O/D that will also dictate 3rd/4th gear

[Mr Eps]

^^^was gonna say this but wasn't sure if it'd insult your intellect

you could also unplug the solenoid / fuse that controls power going to the front wheels too making it RWD only and just do an RWD dyno

wait a minute 4wd isn't the problem

well yeah you cant hold the gear like nic said

[Sarumatix]

My tuner showed me how to do it. You unplug something from memory.. maybe a fuse? It's very simple and then it will stay in 3rd. But em.. what that thing is.. hmm .

[funkymonkey]

its a 3 speed auto, which means there's 3 gear ratios to operate the car in.

Hold affects the point at which the gear ratio is changed, as does power.

The only thing that might affect the ratio is overdrive, which it should automatically switch to after about 60 km/h or thereabouts. This is kinda like 3.5.

Summary: Leave it in "Drive" and turn off "Overdrive". You will end up in 3rd gear at higher speeds. Dyno.

[Nic_A31]

I beleive late models used the 5 speed auto....not sure on AWD though ?

I know all the turbo auto's were 5 speed

[funkymonkey]

I beleive late models used the 5 speed auto....not sure on AWD though ?

I know all the turbo auto's were 5 speed

all turbo's come with a "4 speed auto", which is 3 forward gear ratios and a reverse.

n/a's came in a 5 speed at the end of production, when they introduced a 2.5L n/a.

[Lum]

Mine's a 4 speed which may or may not be implemented as a 3 speed plus overdrive. The gearlever would imply that, but it could just be they didn't want to confuse people by changing it to D321. It's the same box as fitted to S13s

Would be interested to know what you do to force it into 3rd, well other than knacker it enough that it goes into limp home mode I mean.

[Sarumatix]

As I said.. one of the fuses from memory will force the gearbox to stay in 3rd (or 1:1).

[funkymonkey]

Guessing that's the overdrive fuse?

[Sarumatix]

I'd love to give you the answer but I honestly can't remember it may have been R32 specific as well. Perhaps the easiest way is simply to PM 'URAS' .

Basically.. you can just drive it up to 80 with overdrive off and then use the throttle carefully.. but as pointed out it gives a pretty crappy dyno run and wont really show you anything. The OP I believe is asking how to lock it into 1:1 so that they can tune it.

[R334door(s2)]

As I said.. one of the fuses from memory will force the gearbox to stay in 3rd (or 1:1).

there is a bunch of plugs in the front left side down a little disconnect the brown plug will lock it in 3rd for dyno run so it dont kick back to 2nd

hope this helps

Edited April 21, 2010 by R334door(s2)

[Nic_A31]

CONFIRMED:

1 = 1ST

2 = 2ND

D (O/D OFF) = 3RD

D (O/D ON) = 4TH

[funkymonkey]

technically overdrive isn't a gear in itself. it's a modifier on the 3rd gear. But for the purposes of a dyno, it should be left off to be a 1:1 ratio.

[Nic_A31]

Final drive / 4th is a higher ratio than 1:1 so technically it doesnt count as a gear, which makes the box a 3 speed + O/D + Reverse

You can also splice into the transmission loom at the ECU end and do it that way.