FMTV Highway Speed

[coachgeo]

I forgot the torque split wasn't 50/50. But I believe the added torque would be 43% not 30%.

According to http://www.allisons.org/ll/4/Stewart-S/FMTV/ and several other sources the split is 30/70 front to rear in Highway mode but I well could be missing some math based on rear end and/or tranny ratios affecting things or something like that.

 

[FMTV Truck Sales]

Coachgeo-
Correct - when in "Drive" torque split is 70/30, when in "Mode" torque split is 50/50. scottmandu is correct - if in 2WD, we would achieve a 42.8% increase in torque/HP to rear wheels (of course same torque/HP that went to 4 wheels before).

I don't see any reason to angle the axles. We asked Meritor about it two years ago (they are a partner)...they had the opportunity to sell us more parts but instead told us it was unnecessary. The early issues with A0's were driveshaft issues that were corrected (not axle angle issues). The A1 is the most reliable wheeled vehicle the U.S. Army has ever owned and the first to earn their "Ultra Reliable" status....with the axles installed as is.

 

[coachgeo]

....I don't see any reason to angle the axles. We asked Meritor about it two years ago (they are a partner)...they had the opportunity to sell us more parts but instead told us it was unnecessary. The early issues with A0's were driveshaft issues that were corrected (not axle angle issues). The A1 is the most reliable wheeled vehicle the U.S. Army has ever owned and the first to earn their "Ultra Reliable" status....with the axles installed as is.
....

When you get chance.... ask Meritor why the switch to what has appears to be a version of the Intermediate axle in 2008? For all we know it was simply due to thinning out their over supply of them? Curious.

thanks for passing on reliability info.

 

[FMTV Truck Sales]

Will do!

 

[scottmandu]

When you get chance.... ask Meritor why the switch to what has appears to be a version of the Intermediate axle in 2008? For all we know it was simply due to thinning out their over supply of them? Curious.
thanks for passing on reliability info.

I believe that change occurred in 2007.

 

[FMTV Truck Sales]

The change occurred in 2007 with serial number 100001. This production change was known as SO23 which succeeded prior PY4 and PY5 (A1) production runs.

 

[98G]

Will do!

Do you happen to have the numbers for M809 and m939 series trucks as well?

 

[Smike740]

We discussed an appropriate angle to make a wedge block at for the rear but far as I know.... no one has done it. Would have myself but decided to go with a 6x6 front (intermediate) axle instead. Mine should be installed by Feb.?? march?? Waiting for locker to arrive and get installed first. Was mailed out Monday 27th. So that's holding things up and now am having to drive LMTV daily cause the normal daily driver is down with a badly leaking Turbo Oil seal (aka...... best way to cause a run away engine)

Coachgeo,

Are you planning to swap the entire 6x6 intermediate axle into your truck or can just the center section be used? What else needs changed for the swap (driveshaft, exhaust....)?

Thanks,

Mike

 

[scottmandu]

You can't really swap the axle the spring perches are different you can swap the chunk. Use a chunk from a 2007 or up lmtv.

 

[coachgeo]

You can't really swap the axle the spring perches are different you can swap the chunk. Use a chunk from a 2007 or up lmtv.

"older" OEM A0, A1's with 4x4 rear axle pumpkin is offset driver side. Seems some have pulled 4x4 axle..... spun and flipped it 180degrees it to get the needed pumpkin offset on passenger side ... then installed the Powerdivider chunk. This requires remaking spring perches too. Spin and flip is cause power divider exits up and to the drivers side....... to keep drive shaft in line with tranny you have to have the pumpkin off set more to passenger side to accommodate this. Don't quote me..... take your own measurements.

Installing a new complete 6x6 also requires OEM spring perches ground off..... and complete new spring perches made. Either way a good fabricator should be able to do this....... . no different than doing a spring over axle conversion on a truck when it comes down to basics of the procedure..... just BIGGGER and heavier duty. The heavier is the issue..... shop having big enough forklift etc. to move the axle around; much less jack stands to support truck etc. Will probably need rear drive shaft modded too. Not sure on that yet. 6x6 and 4x4 use same rear driveshaft but not sure if the different OEM spring hang system of 6x6 has that axle sitting more forward or not thus allowing for same shaft to be used. 6x6 uses inverted leaf spring and one axle hangs on each end.

I am going NEW 6x6 axle route and having new perches made and then mounted. But honestly if I had known about the potential flip and spin then plug in Third w/attached powerdivider I might have gone that route. Would potentially have saved a massive amount in shipping cost. Power Divider is HEAVY but still much lighter than a whole axle assembly. Stock gearing. Will someday go to taller ties to drop engine RPM's some.

PS.. pretty sure powerdivider and third member of 6x6 is all one unit.

 

[coachgeo]

The change occurred in 2007 with serial number 100001. This production change was known as SO23 which succeeded prior PY4 and PY5 (A1) production runs.

Did you ever hear from Meritor about if they had any clue why TACOM requested the change to the High Pinion Axle?

 

[Smike740]

Coachgeo, Scottmandu,

Thank you for both of your replies. I didn't think about the R/L offset. I just looked at Meritors website and found some info, It looks like the newer A1 RR axle has the chunk offset 1.17" to the drivers side vs the original A0 RR axle was offset 6.67" to the drivers side. From this flipping the housing will put the chunk to far towards the passengers side but still may work. Also although the A1 chunk may fit the A0 axle this option would put the driveshaft flange to far towards the drivers side. It looks like the best option would be to find an entire RR axle from a 2008+ LMTV which likely is difficult.

PS the newer meritor axle number looks to be RH-15-611, the original looks to be RS-15-611

 

[coachgeo]

.... It looks like the best option would be to find an entire RR axle from a 2008+ LMTV which likely is difficult....

or as Im doing, use a full 6x6; be it A0 or A1, intermediate axle and modify it's spring perches to mount into the M1078 leaf system. It will already have the proper off set since it was used with matching chassis, engine and tranny anyway.

 

[Smike740]

Coachgeo, that option also seems doable, what is your plan for spring perches? It looks like they could easily be fabed using steel. Do you plan to weld them to the housing? I would probably not weld to the housing since its cast iron and would rather sandwich the housing with the spring perches and u bolts similar to how the M939 5 ton front axles are mounted.

I have the tools and equipment to do the modification and swap, I wanted to make sure there wasn't an easy bolt in solution first.

 

[tennmogger]

or as Im doing, use a full 6x6; be it A0 or A1, intermediate axle and modify it's spring perches to mount into the M1078 leaf system. It will already have the proper off set since it was used with matching chassis, engine and tranny anyway.

Pictures?

 

[coachgeo]

Pictures?

Just got my car back from shop thus I can stop daily driving the 1078 soooooo hopefully sometime in next month or so the fellow I've lined up to do my conversion can start on that. Will try to get him to shoot pics.

Coachgeo, that option also seems doable, what is your plan for spring perches? It looks like they could easily be fabed using steel. Do you plan to weld them to the housing? I would probably not weld to the housing since its cast iron and would rather sandwich the housing with the spring perches and u bolts similar to how the M939 5 ton front axles are mounted.

I have the tools and equipment to do the modification and swap, I wanted to make sure there wasn't an easy bolt in solution first.

Fellow am teaming up with has equipment and experience to weld to cast housing but feels won't need to do to much of that cause the OEM 4x4 perch system coming off appears to be mostly a clamp around system already. Thus we should just be able to move that over to the new axle 6x6 axle once we shave its perches off. Think there is only a slight raised flat surface on top of axle tube the 4x4 we would have to fab up. Might can make that slip over instead of welding to housing too. I've not looked at TM of 4x4 axle/spring set up recently so am forgetting the full details.

 

[FMTV Truck Sales]

coachgeo-

Do I understand you are planning on replacing a 4x4 rear axle with a 6x6 rear axle to achieve high pinion differential gear set?

If so, we can order a new high pinion gear set (in any ratio, with or without locker) new from Meritor with a warranty. They're not cheap, but perhaps worth the ability to simply swap.

Let me know if interested.

Thanks!

 

[coachgeo]

coachgeo-

Do I understand you are planning on replacing a 4x4 rear axle with a 6x6 rear axle to achieve high pinion differential gear set?

If so, we can order a new high pinion gear set (in any ratio, with or without locker) new from Meritor with a warranty. They're not cheap, but perhaps worth the ability to simply swap.

Let me know if interested.

Thanks!

yes, using NOS 6x6 for high pinion. toatal with shipping and fabrication around 2500. New is what... twice that if not more??

 

[scottmandu]

yes, using NOS 6x6 for high pinion. toatal with shipping and fabrication around 2500. New is what... twice that if not more??

It sounds like alot of money for something with no demonstrable benefit.

 

[coachgeo]

It sounds like alot of money for something with no demonstrable benefit.

May just be peace of mind... but then again...what was it that made TACOM feel it had a demonstrable benefit?