Thread: maxi diff locks @ axles now available

Originally Posted by Lotz-A-Landies

I don't know about the Ashcroft and Jackmac systems, but MaxiDrive are superior to ARB in their ability to remain locked.

The ARB are activated by pressure and require the pressure to be maintained to keep the hemisphere locked. If you lose the compressor or rupture an air fitting/line the ARB unlocks.

The MaxiDrive on the other hand only requires the air to change but then remain locked until the mechanism is commanded to unlock.

As far as I'm concerned, the last thing you would want is to be climbing over a steep obstacle, tear out an air line and then immediately lose your locker, with possible dramatic consequences.

Much better the have a MaxiDrive which stays locked until you can find a safe place to repair the loss of air.

Diana

You make a good point. most other lockers have a spring disengage. However, over the past 2 years my vehicle has spent most of that time plowing through Ti tree scrub up to the door sills, and I have never ripped an airline off, even though my diffs are upside down and the airline fitting is unprotected at the bottom, instead of the normal location near the top of the differential. My old Falcon air conditioning compressor hasn't failed either in the 10 odd years it's been fitted, ditto for the direct mechanical pneumatic switches.
Volvo portal axle difflocks are vacuum engage, spring disengage. I've often wondered how they would go on a long full throttle climb, where engine vacuum would be quite weak.Once the vac tank supply was depleted i'd assume the locks would disengage?
Wagoo.

Lotz a,
When going over an obstacle with the diff loaded would (I would have thought) bind up the diff gears and whilst loaded, remained locked together and not release until the load is then released. When a air line is comprimised it would have nil effect until the gears release.

Just a thought.

Regards,
PeterW

Originally Posted by TwoUp

Lotz a,
When going over an obstacle with the diff loaded would (I would have thought) bind up the diff gears and whilst loaded, remained locked together and not release until the load is then released. When a air line is comprimised it would have nil effect until the gears release.

Just a thought.

Regards,
PeterW

Peter

Yes that is true, but the pressure would only have to come off momentarily, like lifting a wheel, or lifting your foot off the accelerator before the diff would unlock.

Diana

Also with the Maxi's running on Vacuum, if you did tear a hose out, is there not a chance that you would lose the servo assistance on the brakes?

As Wagoo, I also have never ever ripped an airline out (over 6 years of abusing it now)

ETA, Diana I think you are correct. I believe they could be run on 15psi instead if required...

Originally Posted by isuzutoo-eh

Amongst the Jac Mac/TJM prolocker, ARB airlocker and Maxidrive, where does the Jac Mac bolt action stand in terms of strength and reliability? Assuming all are for the same ratio/diff type (ie Rover 4.7:1)...

Was it only that it required getting out of the car to operate it, that caused the move to air operation in Jac Mac's products?

(I am excited to have a bolt action locker to go in my 2a)

When I worked at Jac Macs back in the late 70s early 80s, before we got the correct heat treatment for the locking halfshaft sorted, there were a few instances of the splines twisting between the side gear and the cross shaft and the diff staying solidly locked.
Removing the halfshaft is a real problem. Driving around doing figure 8s all day on concrete failed to break the shaft.This was on a Salisbury Diff, so we ended up having to cut through the carrier bearing outer race in order to gain access to and cut through the halfshaft with an oxy acetaline torch. so to answer your question, strengthwise the old sliding axle difflock is pretty good.Milling the ends off the halfshaft splines is possible for impatient drivers who just remove the extractor bolt andstomp on the throttle straight away without giving the locker a second or 2 to engage.Generally,lock the diff once you leave the bitumen, and unlock it once back on it.
Wagoo.

Originally Posted by Psimpson7

Also with the Maxi's running on Vacuum, if you did tear a hose out, is there not a chance that you would lose the servo assistance on the brakes?
<snip>...

Philip

With "vacuum acumulator" tanks, it depends upon the plumbing and valving. Just like on the old trailer vacuum brake systems, the accumulator tank was supposed to be installed so that if a vacuum line disconnected the valve system in the tank would still provide for negative pressure to the brake booster (and keep the air induction/carburettor system for the engine working).

Diana

Originally Posted by Lotz-A-Landies

I don't know about the Ashcroft and Jackmac systems, but MaxiDrive are superior to ARB in their ability to remain locked.

The ARB are activated by pressure and require the pressure to be maintained to keep the hemisphere locked. If you lose the compressor or rupture an air fitting/line the ARB unlocks.

The MaxiDrive on the other hand only requires the air to change but then remain locked until the mechanism is commanded to unlock.

As far as I'm concerned, the last thing you would want is to be climbing over a steep obstacle, tear out an air line and then immediately lose your locker, with possible dramatic consequences.

Much better the have a MaxiDrive which stays locked until you can find a safe place to repair the loss of air.

Diana

And on top of that all the air lockers I've seen used in anger are wired so they unlock when the ignition is switched off. So when you stall out on an unsuccessful climb the diffs unlock

Tony

Originally Posted by Lotz-A-Landies

I don't know about the Ashcroft and Jackmac systems, but MaxiDrive are superior to ARB in their ability to remain locked.

The ARB are activated by pressure and require the pressure to be maintained to keep the hemisphere locked. If you lose the compressor or rupture an air fitting/line the ARB unlocks.

The MaxiDrive on the other hand only requires the air to change but then remain locked until the mechanism is commanded to unlock.

As far as I'm concerned, the last thing you would want is to be climbing over a steep obstacle, tear out an air line and then immediately lose your locker, with possible dramatic consequences.

Much better the have a MaxiDrive which stays locked until you can find a safe place to repair the loss of air.

Diana

I have only ever observed this problem once in the field. A cruiser with twin ARBs had either a dodgy compressor or an air leak. The ARBs kept unlocking. I agree, the MD locker has an advantage here, but the problem is extremely rare. Conversely, there are reports of vehicles sucking sand into the engine when MD vacuum lines developed a hole...