maxi drive locker actuator fork wear

[MLD]

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.

https://www.aulro.com/afvb/images/imported/2015/09/577.jpg

https://www.aulro.com/afvb/images/imported/2015/09/578.jpg

MLD

[Bearman]

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]

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

[MLD]

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]

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]

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]

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]

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]

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]

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. :censored: MLD

[Dervish]

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


Brad has just seen this thread and texted me to say that the probable cause is a bent diff case.

[roverrescue]

Is this likely in a sal?

Surely in a sal the cast case would have signs of fracture ??
If the axle tubes bent and axle bent with it (unlikely) the locking spilines would be onside of the issue ?

I thought when old sal fails you kinda sorta know it by the pile of busted steel wrapped around the truck and track ???

I guess a bending force may cause the initial problem but

S


S

[MLD]

Brad has just seen this thread and texted me to say that the probable cause is a bent diff case.

Is there an easy way to check the straightness of a sals diff housing and axle tubes? A test I can do at home. More important, how many mm of bending before it would affect the locking dog.

MR Auto suggested to remove the wheel hub with the axle and axle dog to check the splines on all. Damage on dog splines that mates to hemisphere could be suggestive of damage to the splines on the hemisphere. A burr on the axle splines could be resistance for the floating dog. MR Auto were adamant that damage to the dog to hemisphere splines was unlikely but can happen in the most brutal of mechanical mis-sympathy ie engaging the locker at 20 km/h.

In respect of the dog sticking requiring a heave to release, according to MR Auto, could have been the consequence of the dog being forced to engage deeper than the fork would engage in normal use, thus causing material to bind.

I'll check the splines first and a home test for straightness before pulling the diff centre out.

MLD

[Dervish]

Is there an easy way to check the straightness of a sals diff housing and axle tubes? A test I can do at home. More important, how many mm of bending before it would affect the locking dog.

MLD

There is a test you can do, Brad said to just give him a call. I'll PM the number.

[MLD]

quick update for those interested

Since my last post i stripped down the wheel hub to expose the axle and floating dog. The dog splines were burred up. The axle splines were in good condition. I filed the burred faces on the dog splines that engage the hemisphere and reassembled. The dog still would not engage smoothly under finger pressure.

I spoke with several LR indies and the preliminary thought was a bent housing. So it was down to 2 possible causes, bent housing creating a misalignment of the dog to hemisphere or the hemisphere was damaged.

Since then the diff has been stripped. The hemisphere splines that receive the floating dog are cactus and the floating dog has been pushed out of shape by a margin enough to cause an engagement problem. Add to that the hemisphere spline centre is loose in the hemisphere. New floating dog and hemisphere spline centre are on the way. The hemisphere needs to shrunk and lathed to press in the spline centre.

Likely cause is lack of mechanical sympathy by engaging or, more likely, disengaging under load.

MLD

[isuzurover]

...

Likely cause is lack of mechanical sympathy by engaging or, more likely, disengaging under load.

MLD

Or more accurately it is probably due to trying to engage the locker while one wheel is spinning.

[I Love My Landy!]

Good evening All,

A bit of a thread revival, but perhaps this information can be useful. I had an issue where my rear maxi-drive locker would not disengage fully. I pulled the actuator off the housing and noticed excessive wear on the actuator fork (see photos). This is in a 1984 110 V8 with 650,000 km. The diff lock was in the vehicle when we purchased it 2nd hand in the early 1990's. The vehicle and diff lock have been used very carefully in our ownership.

Out of interest, the locking sleeve on the axle slides pretty easily into and out of the diff using my fingers and moving one wheel slightly back and forth, so i could probably infer that that there is no major damage to the diff hemisphere or at the locking splines on the diff end of the axle.

I called MR Automotive in QLD who told me that this was one of the original Maxi-Drive lockers made, but they still had a spare steel fork. More importantly, they said that it looks like wear that would be expected considering the the milage of the vehicle. They say the locking sleeve spins on the axle and wears away at the fork over time. Perhaps owners with Maxi-drives should check the actuator fork periodically? The newer ones are made from sintered brass apparently, so perhaps they would be more wear resistant than what i have (which appears to be mild steel).

Anyway, i hope this info helps someone one day.

Edward :)