Outer Limits 4x4 Board

I'm looking at ways of fixing the 'run away' problem on steep descents.

I'm considering changing diff ratios or reduction gears, but I was just reading about manual torque lock ups.

It would cost $800+ to get this for my truck and it still wouldn't be fantastic as I have 33s so the gearing will still be worse than factory even fully locked up.

If I fitted reduction gears (maybe the new Marks 44% ones) will I get good engine breaking on hills? or will I still need a manual torque lock up to stop the slip in the torque converter.

Just after peoples thoughts/experiences really.

Thanks

Martin

Locking up an Auto:
http://www.outerlimits4x4.com/PHP_Modul ... hp?t=16478
http://www.outerlimits4x4.com/PHP_Modul ... hp?t=21798


Kingy

EDIT: that first link V8Pootrol put up is where it all began.

Or you could have it done the right way.... PM MQ080 on this board.
My torque convertor is locked permanantly under decelleration but work as per normal while accelerating. I dont have to worry about it EVER, its never let me down and the comment from a fello Rangie man was my car on 37" Creepys was as slow as his on 33" muds
And i hadnt changed any gearing.

Now ill have toy diffs with abit lower gearing (4.1) and hopefully the reduction unit.

I have put the auto through afair bit of punishment and so far its been no worry at all..... why more people havnt done this is beyond me

So far i am extremely impressed.

Cheers
Anthony

P.S. and if you dont like it, its a reversable mod. Or you could just get a new Torque Convertor.

Mmmm well I've read that and I don't like the sound of the modified torque converter to provide engine breaking, sounds too risky to me. I'm not convinced on the manual torque lock up switch either.

So if I fitted reduction gears, what sort of engine breaking can I expect? Can anybody who has reduction gears fitted to an auto comment on that? I mean if you are still getting slippage in the torque converter, how does that offset the advantage of the lower gears, if that makes sense?

Thanks,

Just read through the two links - my suggestion would be to use the tach output to cut the lock up. This signal could be used at a speed that corresponds to ~400-550 rpm in any gear.

Most standardish vehicles (35's, mid 4's:1 diff ratio, 2.5:1 tacse, 3:1 transmission = 3.5 kmh, 1m/s, at 650 rpm) this would be as fast as you would like to go, but with better tcase ratio could be made more managable.

About $10 in parts........

From my (simple) perspective, the torque converters only function after the lockup is engaged is to provide some hydraulic pressure to the rest of the transmission, the lockup clutch takes all the torque when cruising. It would seem that if the manual lockup was not used continuously off road (ie only when decending), there shouldn't be a significant problem with failure.

Auto + Crawler Gears =

cj wrote:Auto + Crawler Gears =

3.06 x 4.7 x 4.1 = 59:1

Option to go to 4.625 or 4.88 diffs instead of 4.1's too.....

When i fitted the V6 comm motor and trans to my surf i couldn't get the lockup to work for 1 reason or another so i bypassed the computer and hooked it to a button so i can operate it whenever i like which is hardly ever but i have accidently switched it on while 4wding and it seems to make a little difference going down hill as it takes the slip out of the equation.I don't think it's worth the chance of damaging an otherwise good trans as mine shudders when driving slow because the lockup is supposed to work after 70kmph!!Id spend the money on rockhoppers!!

Hey CJ so you are happy with reduction gears on your auto? what tyres are u running and have you changed diff ratios?

Thanx

Mabs,

MY GQ short comp truck is a 4.2L carby auto with rockhopper gears, i also changed form 3.9 to 4.11 diff gears, and i run 35's, i find it drived verry well, if you are at nissan trials, you will be able to see it in action,

Hey Ozy,

Yeah I'll be at the trials, I'll look out for ya, how do I recognise your truck?

Cheers,

mabsydney wrote:Mmmm well I've read that and I don't like the sound of the modified torque converter to provide engine breaking, sounds too risky to me.

risky? why?

just do it mang

mabsydney wrote:Hey CJ so you are happy with reduction gears on your auto? what tyres are u running and have you changed diff ratios?

Thanx

No, I haven't changed diff ratios and I went from a 26" to 31" tyre so that's a 19% increase. My crawl ratio is now 63 plus as a bonus I have the autos 2.5 torque ratio. In 1st Low it's real slow so generally I don't go below 2nd Low unless it's really needed. The downside is driving between the hard bits means I generally go back to High range as Low is now a bit too low for general cruising but my brakes do like me a lot better now that they don't have to work as hard downhills and I can pick my way instead of having to attack an obstacle so it's gentler on the car as a whole as well. Generally every choice you make is a compromise of some sort but I am happy with this choice.

26" tyres????? isn't that a 100 series in your avatar? 26" is a bit small isn't it?

mabsydney wrote:26" tyres????? isn't that a 100 series in your avatar? 26" is a bit small isn't it?

It's a Vitara