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LEGACY VENDOR
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Discussion Starter #1
Forum member ‘gyrogypsy’ has asked me to post up the basic physical dimensions of the problematic rotary potentiometer in the shift motor of the NV225 transfer box :



The hexagonal recess on the underside :



engages with a hexagonal boss attached to the motor casing :



which not only locates the potentiometer to prevent it rotating but also provides the angular reference against which the rotating shaft in the centre can be measured.

Also, the slot in the shaft can be seen (in the photo above) which engages with the key in the rotating part of the potentiometer :



I suspect that this potentiometer is a bespoke design just for this transfer box.

I’ll also post up the relationship between the potentiometer angle, the transfer box range (high, low, neutral) and the resistance measurement – hopefully tomorrow.

Phil
 

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This site would be so lost without you Phil.
 

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That's Great Phil. Like you say I will need the angular relationship with resistance, but also the relationship angle between the notch and the wiper.
 

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THis is an interesting thread. I'm curios as to the significance with the measurements. Is this potentiometer something that perhaps Gyrogypsy can attain? I ask because I am pretty sure my potentiometer is the cause of my bad shift motor causing the trans failsafe prog, and I don't really want to shell out the $1500 for a new one just yet.
 

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Discussion Starter #5
I’ve added some more information about the transfer box shift motor potentiometer below.

Regarding the potentiometer’s three electrical pins, the end pins are the supply & earth for a 5 volt reference supply from the ECU and the centre pin sends a voltage signal back to the ECU which varies depending on the angular position of the drive shaft i.e. it is this signal that the ECU uses to decide where the shift fork is and therefore which range is engaged.



The relationship between the drive key (which engages in the slot in the shaft) and the wiper position is shown below, together with the wiper’s angular position in each range. Defining a line from the centre of the middle pin to the centre of the potentiometer, in high range the drive key of the wiper seems to line up pretty much exactly with this reference line. Note that the potentiometer is being viewed from the underside (hexagon side) in these sketches :





 

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Discussion Starter #6
The equivalent resistance measured between the earth pin and the centre pin on the potentiometer for each range is shown below, and the angular position of the slot in the shaft can also be seen :







The potentiometer’s resistance at the extremes of angular movement (end pin to centre pin) are 1.26 kilohm to 4.84 kilohm on the particular one that I measured, though clearly there will be a manufacturing tolerance on this.

This photo shows the (carbon?) tracks on the fixed part of the potentiometer, around which the wiper moves taking the voltage from the ‘outer track’ – connected at its ends to the two outer pins – to the ‘inner track’ which is connected to the centre pin :



Phil
 

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Phil - that's great. That is all the information I need - and more.

It seems from your description that the full sweep of the track is used going from High-Neutral-Low which makes life very easy when sourcing as the track will be a standard 0-5k potentiometer. Personally, I don't think the track is bespoke, however the housing maybe. Lets see what comes back from my sourcing agents and take it from there.

Will revert as soon as I get a lead.

Thanks again... I hope by doing this we can benefit this community.

S
 

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I hope prety soon will be people , rebuilding this units for fare price , and saving rovers owners of hefty expense of 1k dollars for new unit !
 

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The concept here is to source the potentiometers and make them available for the community - instead of like you say having to shell out stealer money for a whole new unit.

I have people sourcing these potentiometers right now, so hopefully in about 2 weeks I will have some feedback and hopefully a source.
 

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Any progressess? For those who don;t use the high go out of high range I would think it may be easy enough to make a bypass or test plug. Any thoughts on placing a 4.5 Kohm resistor between the yollow and red lead?

Thanks
 

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Discussion Starter #11
Hi qtcrowe and welcome to the forum :)

I had thought about that i.e. I wondered if people might be happy to lose low range (especially if they never used it) for the sake of saving £1200 on a new shift motor, by fitting a permanent ‘high range’ resistor to by-pass the faulty potentiometer and kid the system into thinking it knew where the shift fork was.

Here comes the ‘but’ …

Each time the ignition is switched on the transfer box ECU powers up the shift motor until the shift fork hits the mechanical stop that corresponds with the range that was engaged when the ignition was previously switched off, and then uses this position to calibrate itself. My concern is that by fitting a fixed-value ‘by-pass resistor’ the ECU will realise that it has lost this closed-loop positioning system and will throw an error each time the ignition is turned on.

However, it would certainly be an interesting thing to try….

Phil
 

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Thanks Phil. Last week I had to have my transmission rebuilt. A bearing in the B clutch came apart which then cause a chain effect due to the excess clearance. While I was trouble shooting before accepting that it was an internal issue I did check the transfer cause motor by removing it and running it through the the range while checking the resistance vary from 4.5 to a.5 K ohm. It appeared to be all with in range. I had put it back in and the once when I got a trans failsafe when I had switch it to low and could not get ti back out so I unplugged the connector and put 12 volts to the 9 and 10 pin to move it back to high. This works but I think it may take it to far and cause the ECM to see a resistance that is out of range and set a output sensor or canbus fault.

Any way I got the car back and 5 mile down the road it goes into trans fail. The transmission works find otherwise until the fault is detected. I took it was trip the output shaft senor general fault and can bus fault. They replaced the sensor and it was still there so next the harness which did not correct it. So they took it to Range rover to have them read the codes and after reviewing the codes with a ZF technician they said it is the transfer motor. Although they have no test plug or way to confirm other then put a new one on and see if that fixing the problem. I picked it up and pulled the motor again to verify the operation and it checks OK based on the information I have found.

We I moved the moved to move it from high to low across pins 9 and 10 I believe it gets out of sync because it will almost immediately set the trans fault when you start the car. I cleared the codes and cycled it a few times and it seem to put it back in sync but will still periodically set the trans fault code. I suspect I may be getting an intermittent resistance reading. The transfer case module is also detected a shorted sensor to battery fault. Have you seen this type of fault before while troubleshoot a transfer case motor?

Thanks

Quentin
 

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Phil's threads are great any I have learned so much. At this point has "gyrogypsy" or anyone been able to source a supplier of potential manufacturer of the seemingly simple potentiometer? Phil has provided the physical and electrical specs. it would be great to perhaps contract with someone or do the research to find out who supplied them to New Venture Gear-> New Process Gear which is now owned by Magna Powertain.
 

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Standby - the future is bright. I should have a test piece within 3-5 weeks. FYI - this is a custom piece manufactured in China.
 

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gyrogypsy / RRPhil, regarding the '03-05 transfer case potentiometer and see that gyrogypsy may have something sourced from China. It is too bad we cannot find who makes the existing part, but this should be interesting. In the interim, does anyone know of a good source for the transfer case motor. I would like to replace mine and replace the potentiometer on the old one when it comes out.
 

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there is a company in the US located in Pennsylvania called Dorman Products and they manufacture a nearly identical part in China for the US market that fit many GM truck models. In speaking with Dorman, It has the same 5V reference and functionality. I just ordered on from my local advanced auto parts store and am going to give this a go. I will revert back on results!
 

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Thank you so much for sharing such a valuable information. Finding alternatives, more long lasting and better built than horrendously expensive not-fit-for-purpose parts is a bonus. Maybe the potentiometer remanufacturing just experiences an unexpected boom

Best regards from Spain
Robert
 

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Unfortunately could not deal with the trans box neutral and transmission fail safe dings and warnings ANYMORE!!! I broke down and bought a new transfer case shift motor for $1600.00 (Atlantic British) (didn't want used) and will wait until gyrogypsy comes through with a spec potentiometer. hope he lets me in on the first production so I can sell my used motor on eBay before the value drops to the cost of the potentiometer itself.

used RSWSolutions.com All Comms software, cleared all codes, re-calibrated suspension and wallah...I have me car back.

BTW, the stealer wanted $2250.00 for the part ;-)
 

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First post here...

Purchased my first RR last month - a 2004 HSE w/ 36k miles on it. It's been a dream to drive until this past weekend when I received the dreaded "Trans Failsafe Prog" message and subsequent limp mode...which has persisted the last few days. It is in an indi shop now to have the error codes pulled, but after reading countless threads on the subject I suspect that the pesky potentiometer may again be the culprit in my case...

Any update on the Chinese prototype? This would be a Godsend...
 

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Most probably is the inhibitor switch in your case.
 
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