Middle axle only use in rear

[coachgeo]

if you have a middle axle with Power Divider but NO active axle behind it for whatever reason (rear axle broke, or no spare tire thus you pulled wheels and pulled that drive shaft ... orr... you don't have a rear axle installed at all such as my case ).....

. won't power divider's differential try to send all power to the missing axle?
. To drive that axle; would one have to lock the power divider ?
... If so... too lock it do you send air to the air solenoid???.... or send NO air to the solenoid??. Not sure how that solenoid works.
..... If send it air.... anyone got an educated guess on how many PSI of air one should send it?

 

[73m819]

The power divider drives the rear axle (#3), if there is a issue with the real axle, the power divider needs to be engaged to drive the middle axle (#2), it will NOT hurt the power divider to be run engaged , need air to engage, no air, it drops out, as far as pressure goes just the standard operating pressure of the truck.

 

[scottmandu]

. won't power divider's differential try to send all power to the missing axle?

In an unlocked state yes and you will go nowhere fast.

. To drive that axle; would one have to lock the power divider ?

Yes

... If so... too lock it do you send air to the air solenoid???.... or send NO air to the solenoid??. Not sure how that solenoid works.

Yes I belive air has to be sent to the solenoid to work.

 

[wandering neurons]

Ok, stupid question: why can’t a FMTV intermediate axle be used as a rear axle in a 2-axle LMTV to reduce the drive shaft angle, assuming that air pressure is used to engage the power divider all the time? Is there some fitment that wouldn’t work?

 

[scottmandu]

Ok, stupid question: why can’t a FMTV intermediate axle be used as a rear axle in a 2-axle LMTV to reduce the drive shaft angle, assuming that air pressure is used to engage the power divider all the time? Is there some fitment that wouldn’t work?

A few clarifications.. FMTV is the Family of Medium Tactical vehicles.. This includes the Light Medium Tactical Vehicle (4x4 LMTV) and the Medium tactical vehicle (6X6) MTV. Referring to an "FMTV" as a vehicle is incorrect.

You can't use an intermediate axle from an MTV because the mounting points are different amongst other things, and the power divider has to be defeated.

This whole driveline angle thing is a non issue. If your rear driveshaft is in good repair, you will be fine. Every driveshaft failure I've heard of has been related to the slip yoke and splines wearing out cause the shaft to wobble and fail.

 

[wandering neurons]

I grok the definition between LMTV and FMTV. Was just thinking about drive shaft angles. Didn’t realize that the 6x6 used different mount points for the axles.
Oh well, another theory shot.

 

[Suprman]

It’s been done before. With a little modification. Worked just fine.

 

[Suprman]

 

[wandering neurons]

But is it truly worth the trouble? If it’s not a simple bolt-in I’m outa luck. I use a torch to turn metal pieces into expensive scrap.

 

[Suprman]

The truck in the pic needed a rear axle. It had grenaded or something. Back when this was done all I had on hand were middle axles. Matt Vintageiron did the truck. The guy wanted the axle moved forward so he could turn better for plowing.

 

[wandering neurons]

Ok, that makes sense. The picture looked funny, thought it had been a 6x6 minus the rear axle initially. Matt really had to do something different and makes sense based on the owner’s need and your parts availability.
In the interest of expenses and trouble, I’ll pull my drive shafts and have them inspected rather than complicating my truck
Thanks to you and scottmamdu for the ‘splaining

 

[Suprman]

Lay under truck on cardboard. Wear gloves grab each driveshaft one at a time and try to shake hard. Any felt play and something is bad.

 

[coachgeo]

Pretty much all you got to do is same as a typical truck/jeep spring over axle conversion. You grind off the mounts off the intermediate axle.... and you fabricate weld/clamp the spring mount setup off the axle removed onto the intermediate. Granted shiat load harder in practicality than typing on a keyboard and mentally picturing it. So yes... not a bolt on thing thus for most purposes.... well maintained drive shafts with constant checking as per TM's and you should be fine with OEM setup.

 

[coachgeo]

The power divider drives the rear axle (#3), if there is a issue with the real axle, the power divider needs to be engaged to drive the middle axle (#2), it will NOT hurt the power divider to be run engaged , need air to engage, no air, it drops out, as far as pressure goes just the standard operating pressure of the truck.

Was reviewing this thread.... and in re-reading believe this to be a yes/no correct thing in the FMTV trucks. Both intermediate axle and rear axle are engaged all the time. The power divider's differential allows for slippage between the two.... unless of course the locker inside the Power Divider is activated locking the differential between the two axles together. So if rear axle is taken out of play yes as he says... you have to activate the locker's air solenoid.


Was still not confident the air locker in the Power Divider is actuated using operating pressure as 73m819 suggest . Finally got a hold of Matt/Vintage iron (company is A&H Recon Shop in Falmouth MA) whom Will/Suprman noted that he had done this conversion before. Matt confirmed that the one he converted.. he did use standard operating pressure in that fabrication. That is two sources saying same thing so ... thus far seems then that this must be way to go.

 

[coachgeo]

Be it good be it bad... the process has started on my swap. Being that it seems confirmed now to use Standard Operating Pressure got a couple questions

. Anyone got a recommendation on where to tap into an air line with a Tee for the air source to the solenoid?

. Any air lines I should AVOID using for this air source?

. Any brand or particular type plumbing parts I should use to tap into this plastic airline ?

 

[coachgeo]

bump for help in post above. thanks.

 

[scottmandu]

bump for help in post above. thanks.

The diff lock on the 6X6's get the air source from the same source as the fan, so I'd start there.

 

[coachgeo]

The diff lock on the 6X6's get the air source from the same source as the fan, so I'd start there.

gives me a great head start. Much thanks.

Will look close at that.

 

[coachgeo]

Be it good be it bad... the process has started on my swap. Being that it seems confirmed now to use Standard Operating Pressure got a couple questions

. Anyone got a recommendation on where to tap into an air line with a Tee for the air source to the solenoid?

. Any air lines I should AVOID using for this air source?

. Any brand or particular type plumbing parts I should use to tap into this plastic airline ?

one axle out.... other going in this weekend.......

As to airline parts?? some of this is now listed in Simps spreadsheet.

As to air source?? any other thoughts on options to source the full truck pressure air? Would assume it needs to be something whose source comes from the dry air tank? Scott mentioned fan air in this thread...... since then have read some of the 6x6 got this air from someplace else but they did not elaborate where; that I recall.

another question that never got completely answered previously...... is this solenoid/actuator.... need constant air??? or hit it once with air and it is switched and held locked till another blast of air pressure opens say an pressure release valve? inside the unit deactivating it?

 

[Floridianson]

If you look at when the diff lock is applied to the MTV it is when you put it in mode if I remember. Full power to all axles front/rear.
When I have used the diff lock in any truck it was only to come out of something nasty. It was then switched off as soon as the truck has reached hard pan. Myself I would not drive with the diff lock in gaged at highway speeds.