A1R rear axle locker (intermediate axle from MTV) questions.

GeneralDisorder

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I've done some searches here on the forum but I haven't found any discussions about this......

So my A1R has the high-pinion rear axle. Basically the intermediate axle from the MTV with the output blocked off.

So if I get a complete 3.07 intermediate third member...... don't those have some kind of locker/power divider in them already? Can I transfer that into the case of my third member that has the output disabled and make use of it? If not will the detroit locker that fits the A0/A1 rear axle fit into the A1R third member?

Trying to get a handle on what parts I need to buy for this swap to end up with 3.07's and a locker in the high pinion third member.....

Thanks!
Rick
 

coachgeo

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the OEM Meritor locker your thinking of in the 6x6 axle is NOT in the third member.... it is inside the PDB (power divider box - the big jug that juts up off pumpkin that front drive shaft attaches to, and rear drive shaft attached too in a 6x6. ...... The high pinion box (HPB?) shares the same case and "some" of the internal design of the PDB used in 6x6. Likely this locker is not inside the HPB ... Its not needed.

BTW locker your speaking of in 6x6 does NOT lock left and right wheels together as your assuming anyway- it locked middle and rear axles together....

PDP is essentially a differential sitting sideways between the front and rear axle..... it does its differential-ing thing between those two ...... similar to a differential between two wheels.
 
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coachgeo

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Yes that will fit
the R&P is slightly different inside the middle third of 6x6 compared to the LMTV's.... hence why it has different part numbers to the LMTV's.

Question for you Tom do you think:

> that likely it is still true.... the R&P is still not same between the High Pinion and the previous OEM LMTV axle?
> also do you figure that likely the R&P remained the same between the thirds of the Middle axle past/present MTV.... and the thirds of the High Pinion axle? Especially since High Pinion Box shares some design with the Power Divider Box?
 

Ronmar

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Yea I dont know if locker is the right term for the mechanism in an intermediary axle. As I understand, It doesn't lock the axle shafts together to drive both wheels equally.

The center axle normally freewheels, and when engaged(in mode) it uses air and couples the driveshaft torque passing thru it to the rear axle, down to the differential of that middle axle so you go from 2 driven axles to 3, or 4x to 6x…
 

GeneralDisorder

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I understand better now. So the Detroit locker will work. Got it.

Now it's just a matter of figuring out the ring and pinion. Can I use the R&P from an intermediate MRAP axle in my high pinion axle?

Rick
 

ckouba

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The center axle normally freewheels, and when engaged(in mode) it uses air and couples the driveshaft torque passing thru it to the rear axle, down to the differential of that middle axle so you go from 2 driven axles to 3, or 4x to 6x…
In my perusal of the forum (admittedly, not the TM's), I had come to believe the opposite- that it was the intermediate axle which was powered and the rear was the one which was added upon engaging "Mode". Am I mistaken?
 

coachgeo

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In my perusal of the forum (admittedly, not the TM's), I had come to believe the opposite- that it was the intermediate axle which was powered and the rear was the one which was added upon engaging "Mode". Am I mistaken?
you are mistaken....... sorta

there are trucks..... with it as you describe... both commercial and military.... but that would be maybe early 90's and older.

... butttt that way of doing it both commercial and military again has begun to be superseded by the way others and myself described above. Pretty much all; USA at least, 6x6 has gone to both axles working..... with a slip built in between them (aka side ways differential) and maybe a locker that locks out the slip. Seems like the phasing out started with any newly designed/manufactured 6x6's in the mid 90's?
 

Ronmar

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In my perusal of the forum (admittedly, not the TM's), I had come to believe the opposite- that it was the intermediate axle which was powered and the rear was the one which was added upon engaging "Mode". Am I mistaken?
yea I didn’t word that very well. Like in a all wheel drive vehicle both axles are driven with the power divider functioning like a center differential.

The problem arrises if you roll up over uneven terrain, you can lift one or the other axle off the ground and all your torque will escape thru a now lifted wheel. The same thing happens on the 4X truck in AWD mode when you lift a wheel. When you go into mode a solenoid valve sends air back to that power divider and disables the differential in it so both axles receive equal torque. Same as the center diff in the transfer case shifts from a 70/30 torque split in AWD to a 50/50 torque split when you go into mode…. Without the power divider differential, you would have to lift one wheel on each axle to let all the torque escape…
 

ckouba

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When you go into mode a solenoid valve sends air back to that power divider and disables the differential in it so both axles receive equal torque.

Ah-hah! I thought it was the opposite- I thought they addressed the need for a differential in the tandem pair by sending no drive to the rear axle. I get the traction implications and how things would slip, etc... without the locking function, and that the air solenoid locks the two diffs (xfr case and inter-axle) to provide traction at all three axles.

With lockers in the rear axles, it would seem that I am 5 wheel drive all the time, not just in Mode? Or I guess not because one of the 4 rear tires could slip, which would absorb all the distributed torque. With the interaxle diff open, no locker in the front, and one rear wheel in the air, the truck is effectively 2 wheel drive- one front wheel and the grounded wheel of the axle half in the air. Right?

I see a big problem if both tires of a rear axle lose traction without Mode engaged....

Sorry to have talked my way through that out in the open, and if I am still off-base, please advise.
 

coachgeo

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@ckouba, at present there is only one axle (wheel to wheel) locker available so it is a bit mute (Detroit soft locker type design is all available right now).
 
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