FMTV High Speed Gears

wheelspinner said:

somewhere in here is the dip switch settings that need to be changed.

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This is for an A0...... I thought an A1 was done in CAT software.




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Yes I think so to, I already looked in the Cat ET software but I couldn't find it. The TCM ( transmission control module ) sends the speed signal to the ECM ( engine control module ) and the ECM sends it to the Speedometer.

I have the feeling the settings have to be changed in the Allison Doc software. I don't think there are pins on the back of the A1 or A1R speedometers but I will check tomorrow to make sure.

We used these tools :

Forklift
U-joint puller
Axle plug wrench
HD air impact wrench with socket 33mm for the kingpin bolts
Height adjustable table to take out / install the pumpkins

That's pretty much it for the " special tools "

Remove the airlines ( brakes & CTIS )
Disconnect ABS sensor connector
Remove the 8 bolts that hold the kingpins in place
Remove the Upper and Lower kingpins
Pull the whole hub with drive shaft away from the truck
Remove pumpkin

That's pretty much it, really easy not much more to it.

Thanks for the reply.

So you left the shafts attached to the hubs the whole time? How hard was it to re-insert the splines into the pumpkin?


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Looks like a really nice garage.

I think I see what they did! By pulling the plug on the end cover, they were able to use a bolt into the end of the drive shaft to retain it (or push it into the center diff housing). The drive shaft is independent of the bearing and hub assembly, and only rides in bearings and the splines into the cross-joint (spider) on the outer end of the drive shaft. Same as pulling the rear drive shafts to tow an LMTV but for the front.
That's why the photos do not show the drive shaft in the hub/brake assembly (photo 2), but show it sticking out of the axle housing (photo 1). Brilliant!!! I'll bet you don't even need to drain the oil from the axle end hub assembly.
I'm thinking that if you use a long piece of threaded rod (all-thread) into the outer end of the drive shaft, you'd be able to fully control the drive shaft as you remove/install the brake/hub assembly.

More on their procedure (I'm guessing):
Remove wheels/tires
Remove brake drum
Pull the cap (plug) on the outside of the axle
Insert the all-thread into the end of the drive shaft to control the drive shaft
Remove air brake/CTIS lines, tie rod and drag link
Support the brake/hub assembly (forklift) or maybe engine hoist?
Pull upper and lower king pin assemblies and shims
Guide the whole brake/hub assembly off the end of the axle housing while controlling the drive shaft (using the all-thread)
Slide the drive shaft a foot or so out of the axle housing to release it from the diff
Pull the prop shaft (u-joint) from the diff
Pull and replace the diff
Put the drive shaft back into the axle housing and into the diff
Use the all-thread on the end of the drive shaft to guide it back into the brake/hub assembly as you put the assembly back into place. Rotate hub as necessary to align the drive shaft outer splines into the spider assembly
Insert and fasten the king pins
Reconnect air brake/CTIS lines, drag link and tie rod
Reconnect the u-joint on the prop shaft
Reinstall brake drum
Reinstall axle end plug
Reinstall tire/wheels
Bob's your Uncle!

ramdough said:

Thanks for the reply.

So you left the shafts attached to the hubs the whole time? How hard was it to re-insert the splines into the pumpkin?


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Click to expand...

Considered that route but figured it was worth doing as everyone else does cause could set the hub spacing and know it is good...... that and had heard puting King Pins back in is no easy task. guess we will soon see

We left the driveshaft in the axle and not in the hub. When the hub was free we pulled out the driveshaft from the axle. Like "Wandering neurons" says" the driveshaft is independent in the axle it like in the back. While pulling the hub away just hold the driveshaft in place with your hand so it stays inside the axle or pull it out together with the hub assembly. Doesn't really matter both ways are easy.

Installing is a little bit harder, we found out this is the easiest way : make sure the hub is level and aligned with the axle very important. Insert the driveshaft in the axle/diff first. Than pull back the driveshaft so that its barely in the diff . Maneuver the hub against the axle but not over the flat piece where it sits on. Now you can also align the splines in the hub with the driveshaft splines. Once everything is aligned it slides in easy and you push the hub over the axle.

Having a bolt in the end of the driveshaft helps maneuvering the driveshaft in the hub but there is also room in the knuckle for your hand to turn and maneuver the driveshaft into the splines of the hub.

One side take us about 15-20 minutes because we didn't have the hub perfectly level and aligned with the axle and to figure out what the best way was. The other side took us 1-2 minutes. Getting the Kingpins back is place is no issue at all. On the drivers side we didn't even take of the steering rod coming from the steering box.

In December we are going to install high speed diffs in another truck and we are going to do it the same way for sure.

Berend said:

We left the driveshaft in the axle and not in the hub. When the hub was free we pulled out the driveshaft from the axle. Like "Wandering neurons" says" the driveshaft is independent in the axle it like in the back. While pulling the hub away just hold the driveshaft in place with your hand so it stays inside the axle or pull it out together with the hub assembly. Doesn't really matter both ways are easy.

Installing is a little bit harder, we found out this is the easiest way : make sure the hub is level and aligned with the axle very important. Insert the driveshaft in the axle/diff first. Than pull back the driveshaft so that its barely in the diff . Maneuver the hub against the axle but not over the flat piece where it sits on. Now you can also align the splines in the hub with the driveshaft splines. Once everything is aligned it slides in easy and you push the hub over the axle.

Having a bolt in the end of the driveshaft helps maneuvering the driveshaft in the hub but there is also room in the knuckle for your hand to turn and maneuver the driveshaft into the splines of the hub.

One side take us about 15-20 minutes because we didn't have the hub perfectly level and aligned with the axle and to figure out what the best way was. The other side took us 1-2 minutes. Getting the Kingpins back is place is no issue at all. On the drivers side we didn't even take of the steering rod coming from the steering box.

In December we are going to install high speed diffs in another truck and we are going to do it the same way for sure.

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Would you consider doing a write up? It sounds very easy, but more pictures and such would help me feel better. I don’t think anyone has done one for this method. This is my plan for my truck right now. I don’t have a forklift, but planned on using two engine hoists.


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ke5eua said:

Yeah I defiantly wouldn't have had room. Are you in the truck in your pic or a mv?

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I was wonder if these pumpkins and transfer cases are still available in 2020. How much would the set me back and are they still coming out of Texas.

I am looking for a set for my 1078 as well

I still have about 120 new diffs

NevadaLMTV said:

I was wonder if these pumpkins and transfer cases are still available in 2020. How much would the set me back and are they still coming out of Texas.

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Pretty late to the party. The inexpensive "scrapped" ones from Texas are long gone. Now you're looking at a few thousand dollars per axle ($3500?), and up.

No, nowhere that bad, $2000 will buy you a new complete diff ready to be installed and installation is actually pretty easy.

NevadaLMTV said:

I was wonder if these pumpkins and transfer cases are still available in 2020. How much would the set me back and are they still coming out of Texas.

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What transfer cases are you referring to? The center diff for the 6 x 6?

So It seems to me that m-35tom has what folks need. So I am thinking out loud that I may be interested in 3 of these for my 1997 M-1083. Do you have them for the M-1083? are you offering complete axels or just the HSP gears? please let me know thanks.

for a 1083 the front and rear are the same as a 1078. The center axle is different and harder to find. https://www.lmtvtrucks.com/Drive Train/index.html

Any information on the disposables required for this job? 3.07 gear swap. Gear oil capacity, seals required, O rings for axle nut?

You can save the gear oil and reuse it if it is clear and clean. Otherwise, front 2 gal, rear maybe 2 1/2 gal. front no need to remove big hub nut in front so no oil loss. Rear must remove nut so very small loss but hub oil in rear comes from diff oil so it will refill itself. You will need some gear oil RTV. No other parts needed, just clean the kingpin seals and grease the kingpins when done.

m-35tom said:

You can save the gear oil and reuse it if it is clear and clean. Otherwise, front 2 gal, rear maybe 2 1/2 gal. front no need to remove big hub nut in front so no oil loss. Rear must remove nut so very small loss but hub oil in rear comes from diff oil so it will refill itself. You will need some gear oil RTV. No other parts needed, just clean the kingpin seals and grease the kingpins when done.

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Thank you.

m-35tom said:

You can save the gear oil and reuse it if it is clear and clean. Otherwise, front 2 gal, rear maybe 2 1/2 gal. front no need to remove big hub nut in front so no oil loss. Rear must remove nut so very small loss but hub oil in rear comes from diff oil so it will refill itself. You will need some gear oil RTV. No other parts needed, just clean the kingpin seals and grease the kingpins when done.

Click to expand...

Still looking for a write up on the kingpin method.


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