Adding P38 actuator to Borg Warner transfer box?

[LiftedDisco]

So... good idea, or up there with the ‘most stupid of stupid ideas’ award?

 

By way of background, I’m currently building a Tornado (very slowly, some would suggest...) which is based on ‘92 RRC running gear, complete with a BW transfer box.

 

I will have to put the vehicle through IVA due to having taking 18” off the rear of the chassis so am keen to keep things as sensible and ‘normal’ as possible but am also able to build things to suit my own development ideas etc.

 

One challenge is that the transfer lever may clash slightly with the lower edge of the dash - I can reduce the lever / arm to eliminate the clash but given the BW operation, any movement on the lever is simply forwards and backwards which brings me neatly to the thought of the P38 actuator.

 

This would (subject to sorting the wiring) allow me to have a simple switch control on the dash to go to High / Low setting with the movement on the BW unit being controlled by the solenoid actuator.

 

So... vote of confidence - does this sound like a plan or am I simply creating yet more points of potential failure... keep it simple with an adapted lever or put it all on black with more electric gubbins and complexity?

 

Thoughts (and horror stories) welcomed...

[Bowie69]

Will you have air on board? If so, sounds a perfect job for a small push pull cylinder.

I don't see any issue doing what you suggest, only concern is whether the P38 actuator would even be suitable, just from a mount POV, as the box hangs differently in a P38 compared to RRC.

[landroversforever]

No idea whether the P38 actuator will work or not (if its the same as an ML merc I've got one here you're welcome to if its not yet made it into the scrab bin).

Other option is the D2 cable setup? Should be easy to find as you'll only be wanting the high/low version and not needing the much rarer Difflock version.

[elbekko]

Could be an option, but I don't think the motor will just bolt up to the older boxes? And I'm not sure you could just swap the rear housing over, probably a few differences there too (aside from the whole drops on the other side thing).

As for controlling it, @Escape is currently running an all-relay replacement for the transfer box ECU that seems to be working well, so no ECU needed, just a latching switch.

[Escape]

It would work, but wont be easy. The Borg Warner for the P38 has a different internal shift mechanisme, with a rotating selector shaft that has a spiral groove machined that moves the fork as the shaft rotates. This is a totally different mechanisme as on the older Borg Warner. Those have a small lever acting directly on the selector fork. You can not just fit a P38 actuator to it, you could possily use a small pneumatic actuator or even an electric one. I looked at doing it the other way around, replacing the actuator of the P38 with a simple lever system (never got as far as to where I would have to mount that...) but decided against it because the rotation required is around 270°, so not easily translated to a lever. On the older boxes there is much less rotation, but more force required, so much better suited for a lever. Adn as said with a push-pull cable you have some freedom where to put it.

I would have prefered a lever to be honest, but went for the next best thing to at least get rid of the ECU. If you're still interested despite the above, do read on. 😉

The P38 actuator itself is similar to one for a window, sunroof or even wiper: an electric motor with a worm driving a big gear that drives the shaft. It also incorporates a position switch. The way it is set up means high and low postions are not at the end of travel, so ideally you want to use the position switch. I briefly considered using just a 3 position momentary switch, but decided against it because you have no way of knowing the exact position of the selector. And you want the gears properly engaged, without stalling the electric motor at the end position. That works in an emergency, for example when the transfer ECU dies while in low and you use pigtails on the connector to get back to high. With the engine off you can hear the electric motor and even then you get sparks by the time you remove the pigtails. So not something to use on a regular basis.
With the proper controller, the motor stops where you want it and it will also allow feedback, so the motor engages (either way) until it reaches the preset position. With cyclic loads applied there is always the chance the selector would move and the gears could disengage. That happens when you remove the actuator completely, you can manually select high or low while under the car, but as you drive off it could slip to neutral. Not fun when on the road with a loaded trailer and no hard shoulder to pull over to. With a P38 actuator and an all-relay controller like I'm using it's easy enough to have the same feedback as with the standard ECU. But it's a lot more complicated than just adapting the lever.

Filip

 

[LiftedDisco]

@Escape That is perfect and thank you for providing such an insight...

 

I’ll stick to having the lever, as per the original RRC set-up.

 

Thanks to all who responded!