Overdrive cut out in 4WDLow

[Ian Sharpe]

Now that I have the 3.15 gears installed , it would like to try to get rid of the overdrive cut out in 4wd, this will bring the revs back a bit in 4WD low 3rd gear (auto).

As those with autos know the overdrive dont work in 4WD. Since the OD is activated electronically it must be prevented from doing so by means of a relay or something energised by the 4WD position switch.

I looked up my wiring diagrams but couldnt readily see anything that referred to a cut out switch for the OD whilst in 4WD Low.

Any of you guys know anything about this??

Or maybe there is a reason Mitsu did this, so perhaps I shouldnt mess with it.

cheers

[Bitsamissin]

Ian, mate I'd do a bit more research about this first.
There's a reason why they have done this.
Perhaps the 4th (overdrive) gear isn't strong enough for the torque multiplication generated in low range at higher speeds.
Maybe the torque converter wouldn't put up with it ?
Now you have the 3.15 gears the torque multiplication is horrendously more than what you had in low range.
I'd be talking to a few auto tranny experts about doing this to find out if the box will cope with it.
The NL has the V5A51 4sp auto which replaced the Aisin V4AW3 4sp which was a strong 4sp auto.
It would be interesting to know if the earlier (NJ & NK) V4AW3 had the same lockout function.

[Bitsamissin]

Actually it maybe to prevent the torque converter locking up in overdrive when in low range.
These auto's have lock a up torque converter that only works in overdrive for fuel economy.
Maybe with the torque converter locked (in overdrive) in low range is not a good thing ??

[Ian Sharpe]

Frank,

yeah my NK 3.5l had the overdrive lockout as well.

I agree , there is probably a good reason why Mitsu have done this & maybe I should leave it as it is

cheers

[-Scott-]

Frank

I understand your argument, and there is probably a very good reason Mitsubishi have done this.

I'm sure you'll correct me if I'm wrong but the torque converter is at the flywheel, and sees (multiplies) engine torque regardless of what the transmission is doing. Any torque mulitplication through the transmission/transfer case creates more torque at driveshafts/wheels and not at the torque converter.

My guess is it's to do with the lockup function. I've heard the lockup clutches tend to be pretty weak, which is why they tend to unlock at the slightest hill.

I'd look for some way to bypass the overdrive lockout, but also block the lockup.

Cheers,

Scott

[Bitsamissin]

Scott, I'm pretty sure the torque converter is a mechanical function which is triggered by the overdrive gear. I don't think the two are mutually exclusive in operation.
It certainly is the case for the earlier auto's (KM148 & V4AW1 in the Gen 1's) as it has been discussed at length on Trail Talk. The V4AW2 as in the NH/NJ 3.0 V6 still had a mechanical lockup converter in overdrive only activated mechanically.
However the V4AW3 (NJ & NK 3.5 V6) is fully electronic in operation (but I'm not sure if the torque converter is still mechanical) the V5A51 4sp auto (NL models only) are also fully electronic but again I'm not sure of torque converter application.
I'll do some research........................

[Alex Kogan]

Torque converter is the hydraulic motor-pump unit in front of at transmission behind the flywheel. Is and always will be mechanical. Also I believe OD works in 2Low. Just gain enough speed turn OD on and off it should be noticable.

[Ian Sharpe]

OD doesnt work in 4WDLo 2nd, well not in mine anyway.

The owners manual says that overdrive doesnt work below 45kph(or therabouts), so it looks llike it is speed governed, which means this it is driven by the ECU speed sensor & probably impossible to tamper with!. It also is driven by engine temp, so if the engine is still cold it wont work even over 45kph.

OD certainly works in 4H & 4Hc, i tried it this morning. I also called into the local Mitsu dealer & spoke to one of their mechanics about this. Talk about clueless, didnt have the foggiest what I was talking about.!!

So it may have been that I never ever got to 45kph in 4wdLo before & now that I have the 3.15 gears I doubt I ever will. I guess if you are doing that sort of speed in 4WD then you may as well shift into 4wdH/c since the motor will be screaming its head off!.

I should also add that gear changes arent as smooth as before & in fact do produce a bit of a surge. The changes now come in a lot earlier, especially first to second. I will play around a bit with the A/T switch in normal mode & hold mode. Hold mode basically eliminates first gear & starts you straight off in second. That could be handy as 2nd low now is roughly equivalent to old first gear low. It may also be amatter of adjusting the lead foot on the accelerator!.

IMO opinion these gears are for the serious off roader as they certainly do change the way the Pajero drives in 4WDLo.



.

[-Scott-]

So it may have been that I never ever got to 45kph in 4wdLo before & now that I have the 3.15 gears I doubt I ever will. I guess if you are doing that sort of speed in 4WD then you may as well shift into 4wdH/c since the motor will be screaming its head off!

5th gear 4wd Low my engine is turning 3000rpm at 40km/h - pretty much the same as 2nd gear high. And I've got the 2.85, not 3.15...

But I just love 1st low for crawling.

Scott

[Ian Sharpe]

NJ,

Fortunatley for you , your overdrive is user selectable, autos are based upon road speed. I'll do some more testing this weekend.

cheers

[-Scott-]

NJ,

Fortunatley for you , your overdrive is user selectable, autos are based upon road speed. I'll do some more testing this weekend.

cheers

Hmmm...

Anybody looked at the speedo signal? I presume its a digital pulse train sent from the transmission to an ECU somewhere. I wonder how difficult it would be to build a black box to double the frequency when the transfer is in low?

Would this be a good thing to do? With a 3.15:1 reduction AFTER the trans, load shouldn't be an issue - under most circumstances.

Would bugger the speedo and odometer accuracy, unless there's separate connections?

Just thinking out loud (figuratively speaking )

Scott

[Ian Sharpe]

Scott,

thats one for the 'too hard' basket!

[pickle]

Pretty sure mine does not go into overdrive in l/range. Says spose to limit speed to 50kph max whilst in 4wd lo in case bits come flying out from underneath.
Dave