Rear Difflock Accuator

[AndyCook]

A couple years ago the rear difflock stayed on when i used it to get unstuck in deep snow.
nothing would unlock it - jacked it up, turned wheels, reversed it etc

at the time i didnt know about the end cap for the accuator rod on side of diff, and instead i proceeded to remove the difflock accuator motor assembly and it fell apart... corroded...

i got a nice new replacement one.

since then i have used the rear difflock in anger a few times a year - snow, laning etc
and always activate it once a month to make sure things still moving.

last week in Lakes I needed the locker to get up some tricky rockslabs, and even then had both back wheels slipping.
back on the road i soon realized the rear difflock was still engaged, even though i had turned it off at dial and lights had gone off..

this time i removed the rod end cap on diff (needed an Irwin stud extractor to remove one bolt after it rounded off head when cheap socket split...
i pulled rod out the last 5mm with mole grips.

I used the rear difflock again in Peak district and it disengaged OK (i had also bought a new accuator from milners that morning but not fitted it!)

back home and with vehicle on axle stands i tested locker and it stayed locked again, even with turning control dial off-on-off etc
i removed end cap and pull the rod the last bit again to disengage - since it was moving, enough to lock OK but not quite moving out enough to unlock,
carefully i removed the accuator unit OK, pulled the accuator rod all way to end stop in off and refitted accuator (after motoring it on-off-on-off etc
this time it still locked ok, but 1 in 6 attempts it wouldnt unlock. but this time if turned cab control on-off-on, it unlocked after a few attempts. so is still a bit unreliable, and i cant be sure it will unlock properly everytimg its used.
i fitted the new unit and it worked flawlessly
so am am painting the new unit, and will fit it.

i will probably open the unreliable one and try and see what can be stopping the thing from fully unlocking everytime,
any ideas? i seem to remember there is a spring in there, but its only used for the locking motion?

 

[BobMurphy]

Andy,

Just one spring - but it appears to work in both directions:

This was 'Pentland Cruiser's' Actuator - the business end got left behind when I removed the unit .

I suspect the problem is the thick yellow grease that turns to cheese with age. If you can strip the old unit carefully you may be able to clean it out and re-grease it.

The grease can also get onto the electrical motor reversing connections on the gearwheel and in the body so you may have a bad connection in there.

I still have all these bits. The actuator was running but the case had been cracked previously and dirt had go in so it was toast. If you want any bits (or the lot to play with) just PM me.

Good luck.

Bob.

 

[AndyCook]

Thanks for pics Bob
thats the spring i remember
thats what my first one came off like!
Actually i wonder if i kept the bits. I will look later, then maybe i can sort out mk2 one as a spare.
I wonder if the grease is clogged or it slipped a tooth inside. The external cog and rack teeyh in diff are fine.
I will open mkii locker when mk3 one painted and fitted,

after all the mkII one is only 2yrs old... the original mk1 was 10yrs old went it failed to unlock and disintergrated like yours when trying to remove it.

will keep you posted on developments

 

[Chris]

Typically it the motor inside that little tin can on top. The insides are fairly robust. But the magnets drop off.

Chris

 

[AndyCook]

not sure its the motor Chris - since the thing operates 100% most of the time, but occasionally only through about 90% of its movement range,
but i will check that too. i would have thought if magnets had moved it wouldnt work fullstop., or maybe the magnets are moving, just not everytime the thing is activated.

investigations will begin soon when i start surgery on it

 

[AndyCook]

looked at the mk1 original accuator bag of bits in garage just now.
and one of magnets was adrift in that -

the plastic cog part (which is turned by a worm screw from motor) looks like its a press fit onto the spindle, and on this old accuator it can be turned on the spindle easily, wonder if that is why it failed

havent opened up the mk2 one yet, as the new accuator needed another coat of paint

 

[BobMurphy]

the plastic cog part (which is turned by a worm screw from motor) looks like its a press fit onto the spindle, and on this old accuator it can be turned on the spindle easily, wonder if that is why it failed ?

The plastic cog doesn't turn the spindle .

The plate rivetted to the back of the cog turns the spring, which tensions the cam that also runs on the spindle, which turns the second plate that IS fixed to the spindle (the bit that was 'left behind' in my pics).

Most of the mechanism is just free-wheeling on the spindle.

Bob.

 

[AndyCook]

opened up the mkii accuator this evening. motor magnets OK and still firmly in place.
and the spring looks intact inside and no stripped teeth on wormdrive or plastic cog.
already corrosion working its way in, and caked grease.
i wonder if it has a electrical fault relating to the 3 sprung contacts that must register position of the motor and when to turn off/on
i will have to check

red stuff is grease i smeared on it when i refitted it , at the weekend

new one fitted and working OK

[attachment=5:3njil6t6]IMG_3908 (Medium).JPG[/attachment:3njil6t6]

[attachment=4:3njil6t6]IMG_3909 (Medium).JPG[/attachment:3njil6t6]

[attachment=3:3njil6t6]IMG_3910 (Medium).JPG[/attachment:3njil6t6]

[attachment=2:3njil6t6]IMG_3912 (Medium).JPG[/attachment:3njil6t6]

[attachment=1:3njil6t6]IMG_3914 (Medium).JPG[/attachment:3njil6t6]

[attachment=0:3njil6t6]IMG_3915 (Medium).JPG[/attachment:3njil6t6]

 

[BobMurphy]

And that's just two years old

It looks as though it should work after a clean-up

Bob.

 

[Gav Peter]

Jeesh Andy, with all that red stuff on it, looked like I'd been working on it!!!

 

[AndyCook]

No chainsaws or axes involve here Gav
its just some grease i put between accuator and axle when i temporarily refitted the unit

 

[AndyCook]

Think i wil remove new one annually to give a fresh coat of paint and check seals, probably needs RTV sealant as well as the orings

 

[AndyCook]

any ideas what type of grease is used or suitable for use in these accuators?, which must be a electrical conductor by looks of things...

 

[Justin_Elliott]

Its a non-conductive silicone based grease (dielectric grease)...

The three spring connectors tell the ECU whether the 'wait' springs have been preloaded in the locked or unlocked position. If you use a conductive grease the motor will fail to stop and could do some serious damage.