Reprogramming ECU for bigger wheels??

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Lord Farquaad
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Reprogramming ECU for bigger wheels??

Postby Lord Farquaad » Sat Nov 09, 2013 11:42 pm

Sorry if this has been discussed before, but my search was fruitless. Anyway, I had bigger wheels fitted when I purchased my Pathy. As most others did when putting bigger wheels on, I fitted 265/70/17 BFG A/Ts. What I did not realize back then was that the bigger tyres influenced the auto gearbox. I was never happy with the way the gearbox operated, but learned to live with it. What irritated me was the fact that it would never lock up in 5th when cruising. That all changed about 3 months ago and I could not figure out why it started to lock up in 5th. I kept quiet as I did not want to jinx this bit of luck.

I started Googling for an answer and stumbled upon this article: http://www.4wdaction.com.au/articles/2012/pathmaker What caught my eye was this:
"I did get a bit too excited fitting KM2s in 285/65 (32in) sizing, Brendan explains. These seem to put a bit of strain on the car and its attraction to service stations.
Brendan also found that the five-speed auto started to hunt through the gears and didn't want to lock up in fifth"
So now I had the possible reason for the gearbox not wanting to lock up before and the tyres wearing down to almost standard size (That is after 3 years of driving and 70 000km) made the gearbox locking up again.

Well, I chatted with some people about this and some mentioned that the ECU of certain vehicles can be reprogrammed so as to calculate torque converter settings for larger tyres. Does this sound plausible or am I barking up the wrong tree?

I have not gone to my local Nissan dealer to hear if this can be done for the Pathfinder as I would like to go there armed with the appropriate info. Have any of you guys asked your local Nissan dealer if the ECU can be adjusted for larger tyres?

TIA


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doctahjones
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Postby doctahjones » Mon Nov 11, 2013 10:22 am

as far as i know the ecu cannot be reprogrammed for different tire sizes (like jeeps can, etc).

the bully dog gt tuner can change what speed is displayed (you can tell it how many% more or less mph you want displayed), but that's just for display and doesn't affect shifting/etc.

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NVSteve
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Re: Reprogramming ECU for bigger wheels??

Postby NVSteve » Tue Nov 12, 2013 9:27 am

Lord Farquaad wrote: Have any of you guys asked your local Nissan dealer if the ECU can be adjusted for larger tyres?
Yes, I've asked at multiple dealers (service departments). The Pathfinder can't be programmed/adjusted for different tire sizes. Pretty dumb on the part of Nissan.

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doctahjones
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Re: Reprogramming ECU for bigger wheels??

Postby doctahjones » Tue Nov 12, 2013 9:49 am

NVSteve wrote:
Lord Farquaad wrote: Have any of you guys asked your local Nissan dealer if the ECU can be adjusted for larger tyres?
Yes, I've asked at multiple dealers (service departments). The Pathfinder can't be programmed/adjusted for different tire sizes. Pretty dumb on the part of Nissan.
ehhhhhhhhhhh, i mean i'm not going to say they -weren't- dumb....

but what % of pathfinder/nissan owners do you think put large enough tires on to warrant that kind of option?

now the same question for jeep owners?

and when out on trails/etc, how many nissans vs other makes do you see?

so, i don't think they were being -dumb-, i just don't think they thought there would be enough need to have to build that into the ecu.

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NmexMAX
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Postby NmexMAX » Tue Nov 12, 2013 10:19 am

My experience is/was weird. I had 33.1's and changed the diff gears to 3.36's from 2.94's and the speedometer was spot on.


Which is a significant difference (8% or so) from stock tire size. Currently I've got 34.6 and it's off by only about 3.5%. Not sure how to explain either of those numbers.

Doesn't the Titan have the ability for a speedo recal? Maybe not, I don't recall. In any case, yeah, very little aftermarket support for the Pathy.

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akley88
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Postby akley88 » Tue Nov 12, 2013 10:34 am

NmexMAX wrote:My experience is/was weird. I had 33.1's and changed the diff gears to 3.36's from 2.94's and the speedometer was spot on.


Which is a significant difference (8% or so) from stock tire size. Currently I've got 34.6 and it's off by only about 3.5%. Not sure how to explain either of those numbers.

Doesn't the Titan have the ability for a speedo recal? Maybe not, I don't recall. In any case, yeah, very little aftermarket support for the Pathy.
i just wish i could find new gears for the v6

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NmexMAX
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Postby NmexMAX » Wed Nov 13, 2013 7:45 am

I believe you have the R200 in the rear and the R180 up front. Both of which have different R&P gear options. The front diff (R180) has many options since it's the same unit used in the Frontier/Xterra world. And the R200 is the same unit used in 300ZX's.

And of course, you could also upgrade to the R230/M205 combo, but you would then be limited to 3.36 as the lowest gear ratio (numerically highest).

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akley88
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Postby akley88 » Wed Nov 13, 2013 8:05 am

NmexMAX wrote:I believe you have the R200 in the rear and the R180 up front. Both of which have different R&P gear options. The front diff (R180) has many options since it's the same unit used in the Frontier/Xterra world. And the R200 is the same unit used in 300ZX's.

And of course, you could also upgrade to the R230/M205 combo, but you would then be limited to 3.36 as the lowest gear ratio (numerically highest).
is it the r200a by any chance cause then i can find some new gears. i was hoping for 4.111 gears front and rear so when i go to a 315 tire i will be better off.

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NmexMAX
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Postby NmexMAX » Wed Nov 13, 2013 8:18 am

R200 is for the rear and R200A is for the front. I believe you still have the R180A in front.

In any case, there are quite a few gears available. I'd go with 4.56's. I've been in contact with RuggedRocks about possibly fitting the R230 in the V8 (rear) for some possible options.

I'd get a hold of them, they're fast, responsive and informative.


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