M1078 LMTV planetary hub setup

steve6x6x6 said:

Working with the FMTV hub it is very important to setup up the clearance of these gears after removing the hub and reinstall. When the bearings are replaced of cleaned and repacked you need to check the gear clearance. I use a tool to check the clearance of these gears, this clamps it down so you do not get a false reading. . Min. .010 to .020

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Steve, I hate to be a moron (but apparently I am) -- How or where are you measuring the .010 -- .020 clearance with either this, or your opened-up cover methods for restraining the spider? I can see how you could measure lash with a DTI with these setups, but apparently I'm too dim to imagine how you can use a feeler to measure clearance?

Dial indicator is the only way, no way that I can see to get feeler guages in there. With the modified hub cover method you can really just feel for it. I have re done all my hubs and all but one needed more shims. On a positive the hubs now are much quieter and run a ton cooler.

Clearance check with depth indicator

I made a tool like the military uses out of aluminum. I will remake the pedestals for the stand out of steel, since the aluminum I bought seems to vary with temperature. I will have a machinist mill the steel pedestals to 2.170 for the mean measurement when the depth indicator is on the stand.

This tool is very easy to build. I bought the depth dial indicator from Amazon for around $64, and some aluminum from Industrial metals. I find that this is the easiest solution to get the correct measurement.

My biggest problem with the military way is it does not take into consideration any wear or variances in machining. With steves ring tool method you are no longer hoping but know. Also the lash of the end gear is not adjustable, unfortunately.

agazza2 said:

I made a tool like the military uses out of aluminum. I will remake the pedestals for the stand out of steel, since the aluminum I bought seems to vary with temperature. I will have a machinist mill the steel pedestals to 2.170 for the mean measurement when the depth indicator is on the stand.
This tool is very easy to build. I bought the depth dial indicator from Amazon for around $64, and some aluminum from Industrial metals. I find that this is the easiest solution to get the correct measurement.

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I agree, this tool and approach is trivial. A halfway competent person with decent measuring tools could make a passable version with a bit of ground bar stock, a couple NF bolts, a file and an appropriate tap. Could make it adjustable for different setting depths too.

Don't even really need the indicator for a poor-man's version: Just make the tool bridge the spindle instead of going beside it, instead of the indicator put in a pair of 3-4" long threaded bolts that can drop down and touch the nut. Fasten the thing tight to the hub face, drop the long bolts down until they contact the nut at diametrically opposite points, then take it to your pedestal stand, stand it on the long bolts and build a shim pack that fits between the 2.170 pedestal and the bar.

Still...

DiverDarrell said:

My biggest problem with the military way is it does not take into consideration any wear or variances in machining. With steves ring tool method you are no longer hoping but know.

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This seems like a good argument for setting it up based on the lash, rather than based on the depth of the pocket to the nut.

The counterargument is that 10 to 20 thou lash gives a pretty large margin for error, and the spider and/or gears would have to wear a /lot/ to change that measurement significantly. With a bit of hand-waving, and potential math errors induced by inadequate coffee so far this morning, the lash should change by roughly

(some constant) * sin(gear pressure angle) * change-in-pocket-depth * sin(bevel angle) [for bevel angle taken as zero in planar planetary configuration)

As a result, a 10-thou change in pocket depth makes much less than a 10-thou change in lash, and I'd call 10-thou of wear pretty extreme. Still, the lash method eliminates a whole bunch of variables...

The inside face needs re-set every time the hub is apart because the nut can change positions. If the nut always clocked to the same place, the shim pack wouldn't (almost ever) need to be changed. This is probably why they didn't bother making the outside adjustable.

I wonder how critical the lash is. I have a growl at have off throttle. I repacked bearings and worked my way out with two new gear sets in 2 of the 6 hubs. Set it by eye and feel using a cut off old hub to Steve's 10/20. No noise change at all and when I first opened them up there was a lot more then 20 thousands. My problem is the front end chunk so that will have to come out after the Ga. rally. Point being I would bet no special tools needed just cut off top of scrap hub and set by eye/feel.

I have a cut off old hub I used and if someone needs to use it and be willing to pay shipping both ways just pm me. Have old not cut hub and I could put it in the classified's if I thought it would sell.

Floridianson said:

....... Have old not cut hub and I could put it in the classified's if I thought it would sell.

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Will a cut hub from front or rear suffice to make this measuring jig out of?

Yep that is what I did. I had to have a machine shop cut it for me at 95 bucks. I did not have a horizontal band saw to cut the face off. Any hub will do.

I still have a little growl left as well. Only at coasting. Seems like par for the course on this type of hub reduction. I may later this year check them all again for giggles. It's a lot quieter than previously. The locker has made checking the rear harder. No more being able to rotate the hub with one side jacked. Now have to jack both sides, and drain oil from the center first (easier drain location) and then drain the hubs. With the homemade tool the hardest part is waiting for the RTV to dry so you can fill and test drive lol.

DiverDarrell said:

The locker has made checking the rear harder. No more being able to rotate the hub with one side jacked...

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This doesn't seem to make sense. The locker is not supposed to be permanently locked - you could get /that/ effect a lot cheaper. If I understand the design of our "locker" properly, it should allow either side to freewheel forward while the other side is stationary. Is there something that prevents this if it's functioning properly?

The Detroit style locker keeps them always locked until one wheel free wheels faster than the other , like the outside in a corner. To do this you have to overcome all the lockup caused by the spring pack. I'm sure it can be done with a long enough cheater bar, but I know for fact you can't overcome it by trying to just turn the axle, and you can no longer just turn the pinion to rotate the one wheel when the other is on the ground. So the easiest way is to jack up both sides of the rear, let some fluid out of the center to get level below the axle tubes, drain the hubs and do the lash adjustments both sides. Or cheat like I did and drive the truck so one side of the axle is higher on an incline, drain the hub and service, just understand the everything on splines has to index back where they were to line up since you won't be able to rotate the axle anymore. If your going to touch the hub nuts than you have to jack both sides. I probably don't explain this well but if you have a locker and do this service you will quickly learn.

DiverDarrell said:

The Detroit style locker keeps them always locked until one wheel free wheels faster than the other , like the outside in a corner. To do this you have to overcome all the lockup caused by the spring pack. I'm sure it can be done with a long enough cheater bar...

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Right - I just would have guessed that the fairly ginormous tires would provide enough lever arm to get it to freewheel forward. Average guy ought to be able to put a couple hundred ft-lbs on there without much trouble. I've never touched a locker this big, but that's a whale of a lot compared to what's necessary to unlock light-truck-sized detroits. This risks getting a bit afield of the planetary setup topic though, and is entirely speculation on my part as I don't have the vehicle or axles in my possession yet, so I'll accept that I'll be living and learning!

A year ago I had little knowledge on all of it as well. Being one of the first to write about the locker install as there was not much info on it. Learned a lot about the hubs here, and until you open one up first hand, they seem more complicated than they are. If your serious about the truck I recommend making the tool to set actual gear lash, get the big hub nut socket, as well as the seal driving tools. And first thing when you get it home, open one up and check it out. It will only cost the lube and some RTV to put it back together. I had a leaky oil seal on a hub that got me to first open mine up.

DiverDarrell said:

A year ago I had little knowledge on all of it as well. Being one of the first to write about the locker install as there was not much info on it. Learned a lot about the hubs here, and until you open one up first hand, they seem more complicated than they are. If your serious about the truck I recommend making the tool to set actual gear lash, get the big hub nut socket, as well as the seal driving tools. And first thing when you get it home, open one up and check it out. It will only cost the lube and some RTV to put it back together. I had a leaky oil seal on a hub that got me to first open mine up.

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Are there any "little" parts (springs, pins, washers) to fall out and get lost and lose track of, when you open up the hub?

In other words what is the Pain-in-the=A** (PIA) index involved in opening up the hub?

No small parts. Two on the PITA scale.

DiverDarrell said:

Learned a lot about the hubs here, and until you open one up first hand, they seem more complicated than they are. If your serious about the truck I recommend making the tool to set actual gear lash, get the big hub nut socket, as well as the seal driving tools. And first thing when you get it home, open one up and check it out. It will only cost the lube and some RTV to put it back together. I had a leaky oil seal on a hub that got me to first open mine up.

Click to expand...

Another Ahab said:

Are there any "little" parts (springs, pins, washers) to fall out and get lost and lose track of, when you open up the hub?

In other words what is the Pain-in-the=A** (PIA) index involved in opening up the hub?

Click to expand...

Floridianson said:

No small parts. Two on the PITA scale.

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It sounds like a "No-Brainer".

It was a lot easier than expected for sure. If you know how to use a torque wrench and correctly tighten bolts in a pattern, your skill level is higher than needed for the hub. Figuring out shims with steves methods is simple, and may need a degree and a lot of luck to do it the army way. I would say a u joint replace may be more difficult.

it is not hard to check the lash, I take a piece or 1/4X 2" aluminum bar, then I took a piece of sheet metal and riveted it to the bar. I took my dial indicator and used the back side for the depth. the bar goes across the hub, I take the measurement off the sheet metal which is attached to the bar( or the top of the hub to be measured to the shims) very easy and accurate.

800summit said:

it is not hard to check the lash, I take a piece or 1/4X 2" aluminum bar, then I took a piece of sheet metal and riveted it to the bar. I took my dial indicator and used the back side for the depth. the bar goes across the hub, I take the measurement off the sheet metal which is attached to the bar( or the top of the hub to be measured to the shims) very easy and accurate.

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picture adds more cents to the sense.

Will a regular mechanic be able to do this? I don't have dial indicators, lathes or any special tools, I'm mechanically inclined, but this seems next level