Reversing up an steep incline!!!

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DawidT
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Reversing up an steep incline!!!

Post by DawidT » 29 Jul 2013 07:50

Hi All,

I need some advise please :pray: This week-end we participate in the Wildevymanne 4X4 day. One of the challenges was to reverse up a steep embankment, stop halfway up and then continue to the top. I could only make it halfway :redface: The Patrol just did not have enough "power" in reverse to go up, revs went to about 2500rpm and that was it. I used my 2010, 4.8 GRX (Automatic). I had to turn the car around and drive up the next embankment wich was steeper with no problems - The gearbox was in low range! I did the power valve mod a couple of months ago and it makes a big differance in normal driving. Did I do something wrong or is the Patrol computer set up to limit the power in reverse? :helpsign:

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Re: Reversing up an steep incline!!!

Post by Clem » 29 Jul 2013 08:29

Power valve mod?

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Bruin Beer
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Re: Reversing up an steep incline!!!

Post by Bruin Beer » 29 Jul 2013 08:46

David,
This is an effect of the torque converter stall spead (design of the automatic) and has nothing to do with the power mod.
The ratio of reverse is about equal to second forward.
Your best option would be in low, as you were and "binding" of the drive train when in 4x4 personally I would try and do it in as a straight line as possible not to lose even more power due to drive train binding when turning.
I have heard about this down-fall of the Patrol from a few sources and I am not sure there are a way around it.
I am interested to see what this topic deliver.
Rest asure. No harm done with the power mod.
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Re: Reversing up an steep incline!!!

Post by David » 29 Jul 2013 10:05

Dawid,

I have been experiencing that similar feeling of 'slippage' at times in reverse but struggle to pinpoint why. Every morning I reverse out of my driveway which is quite steep and some days it just feel 'pap' and other days it is fine. All fluids are fresh and on the right level and there are no error codes.

This only happens in the mornings when it is cold which makes me think the ECU/TCU is trying to protect the gearbox and diffs by limiting power or torque converter slip :think: Only problem: it is not constant!

I know the ECU limits power when your foot is on the brake and wonder if it is not doing the same due to some sensor malfunction??
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Re: Reversing up an steep incline!!!

Post by Stefan » 29 Jul 2013 11:32

I've heard from guys much more mechanically minded than myself that reversing up a steep incline under power is not great for the crown & pinion ? gears. Apparently the teeth are designed & engineered to mesh and bite into one another under load when driving forward, but in reverse they want to jump out.

Not sure if this is applicable to an auto-box?

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Re: Reversing up an steep incline!!!

Post by David » 29 Jul 2013 12:03

Hello Stefan

This is not a mechanical issue as there would have been some mechanical noise which is not the case here. This is just giving it gas and not going anywhere
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Re: Reversing up an steep incline!!!

Post by Chris Skinner » 29 Jul 2013 14:54

I have also noticed less than expected power while reversing my boat, especially on the beach where its difficult to move in the sand. In fact after getting my 4.8 after having a manual 4.5 I always maintained that I preferred the manual when in thick sand.
I did the 'power valve mod' and have noticed some improvement although this is somewhat subjective and some claim that it makes no difference anyway.
I think it is something NIssan has designed into teh gearbox and engine management software to protect the drive train - why, I would not know!

There is exactly this discussion going on right now on the Aussie forum with some additional interesting info:


http://www.patrol4x4.com/forum/nissan-p ... ost1141432
Last edited by Chris Skinner on 30 Jul 2013 07:52, edited 1 time in total.

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Re: Reversing up an steep incline!!!

Post by Peter Connan » 29 Jul 2013 17:30

I am not sure if this is the only reason, but I do know that in most cars reverse gear has a lower ratio than first, but in the Patrol this is not the case, and I believe it is even worse in the autos than the manual cars.

Whether there is any ECU intervention, I do not know.
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Re: Reversing up an steep incline!!!

Post by Tinus lotz » 29 Jul 2013 21:08

This is getting very interesting. ..

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Re: Reversing up an steep incline!!!

Post by Clem » 30 Jul 2013 05:19

First is 3.540
Second is 2.262
Reverse is 2.370

So the reverse ratio is pretty close to that of second.

That's on the 4.8 GRX tiptronic box.

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