Playing around with the 2.7 software (ECU and TCU)

[JeanLuke]

The transfer case switch is a resistive sensor, not just a switch. It changes resistance which the ECU interprets and feeds to the TCU via the CAN bus. It does not only change the mapping. It is also used in back-calculating the gearbox output shaft RPM from the wheel sensors (which I think are connected to the ABS unit).

Attempting to fudge the transfer case switch position will result in transmission slip errors, unless you also adjust that part of the code.

[JeanLuke]

[RTB]

Originally Posted by JeanLuke

The transfer case switch is a resistive sensor, not just a switch. It changes resistance which the ECU interprets and feeds to the TCU via the CAN bus. It does not only change the mapping. It is also used in back-calculating the gearbox output shaft RPM from the wheel sensors (which I think are connected to the ABS unit).

Attempting to fudge the transfer case switch position will result in transmission slip errors, unless you also adjust that part of the code.

All good to know. Thanks for that. Regarding the switch. Is that the same switch on all WG's? I only have 4 high, neutral, and 4 low. Guessing it might just use the last 3 positions.

The TCU has wheel dia, diff ratio, transfer case ratios, internal gear ratios. Makes me think it might be mostly stand alone as far as the calculations are concerned. I think it does receive wheel speed from the ABS, but that is where I think the transfer case ratio in the TCU comes into it.

Maybe that would mean I might be able to get it working in high range only, but might throw a code in low range. The more I think back to other threads I have seen, I think this might be the case.

Thanks for the resistance values too.I will save that so I can emulate them if I do give this a go. Believe me, it is a long way down the track if I do try it. Just the brain firing up wondering how far I could go with this.

[JeanLuke]

Originally Posted by RTB

All good to know. Thanks for that. Regarding the switch. Is that the same switch on all WG's? I only have 4 high, neutral, and 4 low. Guessing it might just use the last 3 positions.

Yes, it's used across many Mopar vehicles. It only uses 3 of the positions on the WG. WJ Diag Pro tells you which.

[RTB]

Originally Posted by JeanLuke

Yes, it's used across many Mopar vehicles. It only uses 3 of the positions on the WG. WJ Diag Pro tells you which.

Well that gets me thinking more. The 5 position transfer case is Quadratrak 1 I think??? Does anyone out there have one? If so, would you know if your gear changes happen differently between when you are in 2H and 4H?

We have 3 shift change schedules in our TCU. All 3 are different.

Could it be that it is 2H, 4H, and 4L?

If that works out to be true, then this could be as good. Means I could emulate the 2H command to get 1 shift map, leave it standard to get the second shift map, and low range could be left untouched.

The less perfect bit of that is that I only get to use the one drivers wish map, but I think that could still be set up to work almost as well. Would just need to bring the mid throttle boost increase down a bit, but that is cool.

If anyone has the 5 position transfer case, your experiences with it would be great.

[RTB]

Actually, if you have the 5 position transfer case, could you let me know if the revs float when you take your foot off the throttle when driving in 2H, and if they do the same in 4H. If there is no change when doing this test then they both use the same drivers wish map.

Cheers, Rob.

[JeanLuke]

The NV245 transfer case was available in some countries. The CRD only got the NV247. I have read threads where the 245 has been swapped into the CRD with, I believe, no software issues.

Edit: The NV245 has the 5 positions:
H2
H4 full time (centre open)
H4 part time (centre locked)
N
L4