maxi drive locker actuator fork wear

**MLD** · 13th September 2015, 04:39 PM

Has anyone come across this before with a maxi drive locker. What i'm trying to ascertain is if this is simply a case to replace the actuator unit or it is representative of something more sinister. I'd like to know the cause too so i can avoid that behaviour. Hoping for feedback before i approach MR Automotive so i can talk to them with a little background info. I also don't want to be oversold by a local diff mechanic.

What you are looking at is the brass actuator fork that is attached to the actuator unit on a maxi drive locker. The end of the fork sits inside a housing on the axle and when the locker is engaged or disengaged is the moving force to engage or disengage the dog.

There is scoring on the brass fork on the diff housing side only. It's a few millimetre deep so its been a problem for a while. There is no scoring or material loss on the axle. The fork appears to be slightly bent but i'm not familiar with a new fork so i do not know if its bent or normal.

It came to my attention when i engaged the locker and drove in a circle and heard a metallic click but no squealing of the inside wheel as one would expect. With the wheel jacked the dog on the locker would engage but when under load while driving it would release. The light was bright when first engaged but immediately after the metallic click the light would go dull as if the actuator was not making solid contact to complete the circuit. The light could be a symptom of the bent fork but its the lack of depth of engagement of the dog and the ease in which it is forced out that concerns me of something more sinister.

If anyone is familiar with maxi drive lockers, this problem etc your comments are welcome. Please refrain from turning this into a locker manufacturer comparison or telling a story about the failure of another locker manufacturer.

MLD

**Bearman** · 13th September 2015, 05:27 PM

Certainly looks like there is a problem there as the wear indicates. It should be flush with the locking dog on the axle. You say it looks bent so that possibly is the problem - it should be straight. Is the mounting block welded evenly on the axle housing. By the sound of it the diff is not locking properly.

**brendanm** · 13th September 2015, 05:58 PM

Hi Mark
Brad over at KLR (Windsor) would be vey familiar and knowledgeable with Maxi Drive products.

**MLD** · 13th September 2015, 06:24 PM

Brain - I didn't fit the locker and it was built by a LR knowledgeable mechanic and it's been in situ since late 2010. If the welding of the housing was the problem I would expect it to be a problem prior to now. I had the actuator apart about 2 years ago so I know it's relatively recent.

I suspect I shock loaded the locker most likely while engaging which explains the bent fork and more I shock loaded it thinking it was engaged the more it stressed the actuator and fork.

Fingers crossed it starts and ends with the fork actuator being bent.

Anyone else? MLD

**Blknight.aus** · 13th September 2015, 08:27 PM

too much operating pressure is the usual suspect the fork bends when you try to engage with the teeth out of mesh or retract it with the diff loaded.

you dont get to see it much on teh stuff thats vac operated but when the "slow and difficult to engage" problem is solved by adding 100 psi of actuating pressure....

**MLD** · 13th September 2015, 10:10 PM

Thanks Dave - when you say operating pressure are you referring to the pressure under vacuum or the pressure of forcing 2 pieces of metal to mess under load.

Your answer seems to confirm my suspicion that it's a failure caused by engaging when under load or disengaging under load.

I'll see how it goes with replacing the actuator unit, fingers crossed.

If anyone has another insight I'm still keen to read it. And thanks to Brian and Dave for they insight.

MLD

**roverrescue** · 14th September 2015, 01:08 PM

Obviously not too easy to check insitu but do the locking dog . axle splines and crown wheel broached splines appear clean and mesh smoothly. They could / should be the actual source of the issue. The actuator bending and subsequent uneven wear are the symptom.

S

**MLD** · 14th September 2015, 04:18 PM

Thanks Steve, unfortunately checking the locking dog and crown wheel spines involves pulling the diff centre out. The diff was out earlier this year for new carrier bearings. I was told locker would require some replacement parts as they were wearing but foolishly didn't ask for specifics. Having checked with the mechanic today he was referring to the actuator fork showing scoring which is in the photo.

MR Automotive had not seen wearing of the like and was not aware of a prior incident of like. Always nice to be a first of something.

Replacement selector/actuator fork on its way. Mechanic said to test the locking dog manually by sliding the locking dog from the actuator first before pulling the diff cover off. If it doesn't engage with a little effort something is wrong. For completeness I'll update the post when I've worked through the issues.

MLD

**roverrescue** · 14th September 2015, 04:28 PM

Is it possible the pneumatic cylinder rod has a whoop in it ???
You could try cycling the actuator and check alignment. The maxi design with the floating collar on the dog would mean that for that angled wear on the fork there has to be some mid alignment between cylinder / actuator and locking dog

S

**MLD** · 15th September 2015, 11:09 AM

Quick update, last night i pulled the actuator off again and did a manual engagement test. It engaged with a some force but I was unable to disengage the dog with the same force. I was lightly rocking the wheel hoping to find the sweet spot while trying to disengage. It eventually disengaged with an almighty heave.

Steve's prediction was right. It's either the splines on the dog collar or the spines on the dog itself or the dog engagement into the diff centre. The bent fork is the symptom of the force required to engage and disengage. Long and short, the diff has to come out to replace any or all of those parts.

Thanks to all for your help. Gotta go and fertilise the money tree.

MLD

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