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Discussion Starter #1
If you have done dune bashing or driving in the sand dunes, you know the Auto Transmission plain sucks for such usage !!! Even the manual shift function of the AT doesn't cut it.

Imagine you have a big dune to climb and you leave the AT in D, You floor the throttle with a good run up to the dune, it shifts through 1st - 2nd and 3rd gear and halfway through the climb, engine screaming at 5000rpm, you want it to continue in 3rd so you can make it, but the [email protected] AT, with a brain of its own, decides its better for fuel efficiency to be in OD at this engine rev, and shifts !!! You realise the [email protected]@kup and immediately manual shift to 2 while keeping the throttle floored but nothing happens because the AT does not want to shift now !!! All momentum lost, you are now precariously stuck, probably a bit side ways on a dune face ... If you were smart and kept the throttle floored while turning the steering full lock towards down hill, the AT will now realise that the vehicle has almost come to a stop and then shifts in to 2nd, giving you enough momentum to get back down, so you can give it another try....

This time, you decide to keep the AT in 2nd all the way but while taking the run up to the dune, IT STILL UPSHIFTS because the vehicle speed gets to around 50-60kmh (30-40MPH) and revs around 5500rpm..... the AT being intelligent again decides to override my selection because it wants to deliver better fuel efficiency !!! Who the [email protected] told the AT to shift after i left it in 2 ????

Another time i started in 2 and just when the revs got to 5000rpm, changed to 3 and got almost 3/4 way up the dune, just then it started slowing down and i knew a shift to 2nd would get me all the way, so, while keeping the throttle floored (remember, i can't stop-shift to 3rd-floor the throttle in the middle of climbing a dune) i shifted it into 2nd but nothing... no gear change ... so i had to turn downhill yet another time and abandon the climb because now the AT was overheating.

Pls help. My AT is driving me crazy. It leaves me stuck halfway up dunes that vehicles with manual (MT) are easily climbing. No amount of fiddling with the manual gear selection helps.

cheers
 

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Yeah, our AT is not very dune friendly when it comes to hill climbing. I've experienced this a few times wheeling around some dunes here in the US....but this is why I have this:



and this



:)

You are probably doing it already, but having VDC off helps a ton while climbing (ABS off for all around dune travel). I can typically make it up the tallest dunes once I have momentum with VDC off. Oh, and you will definitely want an auxiliary transmission cooler.
 

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I have held it against the limiter in 2nd gear and it will just stay there. No forced upshift beyond 2nd gear. Being that you are in a non-us market and get different stuff from us that may include different transmission programming.
 

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Discussion Starter #7 (Edited)
:notworthy: i'm not lucky enough to have such dedicated toys for dune bashing !!

I'm not sure if the Transmission programming is so widely different in other regions ? and don't know about UpRev transmission re-tuning but i did write to Levelten about the issue. Hope they reply.

Turning OD off simply stops the tranny from engaging 5th gear on the AT. I need to be able to hold it in 2nd OR 3rd gear, turning OD off isn't going to help much.

I've got no VDC on my X. Can you explain how turning ABS off (by removing the appropriate fuse ?) helps in holding a gear / climbing the dune. I know it certainly helps while coming down the dune face.

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ABS was just a general guideline for the dunes - not related to climbing (didn't mean to add it in with VDC, will edit). I wasn't aware there were Xterra's 05+ that didn't come with VDC?
 

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I go to the dunes all the time and always with VDC off and usually 4Hi (depending on the sand) but with some momentum I'll put in usually in 3rd and get up any dune without issues. If anything, keep it in a higher gear (3rd or 4th) and just downshift if you're struggling.

In super soft sand (like dunes down in CA) I've had to use 4Lo quite a bit on looong mellow dunes that I stop on, but usually 4Hi will get the job done thanks to the momentum I have when I hit the dune.

Otherwise, there are some complications with our tranny's shift, but they're at least consistent and it becomes easy to learn your way around those.

I don't really seem to have many issues in the sand and love the dunes. :D
 

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Discussion Starter #12
Air pressure is the big thing. @ o.p. what pressure are you running? I usually have run 12psi in the sand.
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I run 12psi too. Sometimes with the result of tyre pop outs !!!



I go to the dunes all the time and always with VDC off and usually 4Hi (depending on the sand) but with some momentum I'll put in usually in 3rd and get up any dune without issues. If anything, keep it in a higher gear (3rd or 4th) and just downshift if you're struggling.

In super soft sand (like dunes down in CA) I've had to use 4Lo quite a bit on looong mellow dunes that I stop on, but usually 4Hi will get the job done thanks to the momentum I have when I hit the dune.

Otherwise, there are some complications with our tranny's shift, but they're at least consistent and it becomes easy to learn your way around those.

I don't really seem to have many issues in the sand and love the dunes. :D
I guess i'm not able to give you the right picture of how the dunes here are, and how soft the sand is. The sand dunes of US probably don't compare. 4Hi will never work here as it puts down too much torque with very less momentum gain. We always drive in 4Hi except for when we get stuck and need to get the x out.

anyways, i tested the manual selection of the AT today and it works fine. Dont know why it behaved that way in the dunes.

thanks for all your inputs.
 

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Get a programmer that has WOT delete. I drive in Florida 'sugar sand' all the time. It's very fine, much finer than west coast sand. I thought my X sucked in the sand (which it did) until I got the hypertec and was able to keep all power down in lower gears and higher RPM's. Of course having VDC off and lower pressure helps in addition to but the way I understand it, you need WOT delete.
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Hey bro,

Just leave your trans in 2nd it will bounce off the rev limiter. Ive driven in Sweihan/ Fossil rocks/big red etc..the trans will not move out of the manually selected gear. In the dunes you hardly come out of 2nd for most of the time, why did you even have it in "D" in the first place. Anyways happy offroading..
 

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Imagine you have a big dune to climb and you leave the AT in D, You floor the throttle with a good run up to the dune, it shifts through 1st - 2nd and 3rd gear and halfway through the climb, engine screaming at 5000rpm, you want it to continue in 3rd so you can make it, but the [email protected] AT, with a brain of its own, decides its better for fuel efficiency to be in OD at this engine rev, and shifts !!!
5000 RPM in 3rd gear up a dune? In 4 Hi?

That would be over 90 mph... I'm a bit confused.
 

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Discussion Starter #17
Hey bro,

Just leave your trans in 2nd it will bounce off the rev limiter. Ive driven in Sweihan/ Fossil rocks/big red etc..the trans will not move out of the manually selected gear. In the dunes you hardly come out of 2nd for most of the time, why did you even have it in "D" in the first place. Anyways happy offroading..
Yeah, i know i should never have left it in D.... anyway, lesson learnt the hardway ...

by the way this was in Liwa, where the sand is softer than Big Red if i'm not mistaken. Fun.. Fun...
 

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not when there's only wheel spin to have in the soft sand !!
I've been driving off road vehicles in sand dunes (Imperial Sand Dunes in California) for almost 30 years and I have yet to see a stock or slightly modified vehicle spin its tires like you're describing. Either the hills you're climbing are not steep, or you're not in the middle of a hill at 5000 rpm in 3rd gear. The X simply doesn't have enough hp for that. Plus, once you're up on top of the sand, there is very little wheel spin, especially in 4WD...

The below is a hill called Oldsmobile Hill in Glamis, CA. In 4 Hi, my stock motored X could only manage topping out in FIRST gear... Any steeper than this hill and the X will sink - even running 33" tires at 10 psi. So, pardon me for being confused at what you're telling us. I'd believe it if you were in 4 Lo and going about 35 mph... not 90+ in 4 Hi.... at least in the middle of the hill... If you were getting a run at the hill (and it better be REALLY flat and smooth), then sure, you could top out in 3rd...

BTW - I tried this hill in 4 Lo and didn't do any better than 4 Hi.

 
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