M939 Front Axle Boot replacement.....how I did it.....

[MO MV man]

Hello all,

I have to say, that was a LOT less "painful" than I expected.
My 1984 M923 was oozing grease and the boots were "crispy" to say the least.
Anyway, I elected to replace both even though the driver side was barely leaking.....we all know it was on borrowed time.
The insides of my knuckles were beautiful. Thank goodness whoever took care of my beast put plenty of that tan goo in there. LOL

I used US Made new zipper style from Memphis Equipment.

Removing the oldies and cleaning the surface is very straightforward so won't go into that.

The only "tricky" part is getting the new seal AND the clamp into the groove.

Here's how it worked for me:

1. Wrap the new boot around the axle, zipper it and turn it inside out to better access the groove.
2. Open the new clamp up (screw removed) and wrap it around the axle and boot.
3. Install the clamp screw (at 12:00 as the one that came off was) and install the nut with just barely enough thread to safely hold it in place so it's able to open wide enough Step 5.
4. Slide the boot groove portion into the axle groove.
5. Work the clamp into the boot groove slowly around the circumference. Be patient, it does work.
6. Tighten the screw slightly just enough to hold it in the boot groove and the boot in the axle groove BUT loose enough that the boot can be rotated ever so slightly into position. Not tight enough and it'll all pop out of it's grooves and you'll be redoing Steps 4 and 5. "just tight enough" and you can safely rotate it. It's a "feel" thing.
7. Gently fold the boot toward a few of it's bolt hole positions to check position in reference to the screw holes in the knuckle.
8. If need be, gently rotate the boot to match.
9. Once you're happy with the position, tighten the clamp.
10. I put a glob of RTV on the thread to prevent the nut from backing off (as the one I removed was) and on the zipper as well as where the zipper mates up to the knuckle.
11. If your previous positioning was good, you should be able to pop the boot into position and install the metal retaining ring.
12. Install screws and tighten gently. Don't overtorque and warp the ring! If at all possible, safety wire them.

Maybe this has been posted before? Maybe not.

But since it was a painless process and the results are worth their weight in gold, maybe this post might get someone who is on the fence about tackling it to dive in and give it a shot.

 

[jonesal]

I bought mine from Memphis as well. I thought they were high quality units. I followed the TM and sealed the zippers and let them set over night, and then mounted. The TM calls for safety wire, especially at the torque of the retaining rings (which is very low). Note with proper safety wire technique, they should not loosen at all.

I took pictures of the boot I took off and the Memphis one - will try to find them and post. Same zipper manufacturer, different boot manufacturer, different attachment style - one was sown, one was heat bonded.

Al Jones
84 M923

 

[crasheej]

I've done mine this way on my own trucks and our uncles. Works just as said.

 

[73m819]

When I did mine on the m819, I SEWED the inner edge to the ring

 

[Neophyte]

Good post........as I'm in need of a new zipper boot. I did a pre trip inspection this morning and said to myself "What are those globs of grease under the truck?"....and then looked at the axle.

 

[Tornadogt]

I am getting a small puddle of what appears to gear oil leaking from my Passenger side front axle boot. Looks to be leaking from the seem on the top 12 o'clock position. Are you guys saying your getting GREASE from this area??? should there be grease or gear oil? Mine is a M931A2. Also leaking some from the pinion seal anyone have the part number for the front Zipper style Axle Boot and a Pinion Seal and best place to get them?


added: Also did you have to remove the shield in front of the axle to access all the axle boot bolts?

 

[Rkrug]

Got the one on the drivers side installed, It was single digit temperatures and below zero wind chill which made it impossible to get on with out heating it up with the heater but it does look nice now, old one had a hole your hand could fit through. So if you don't have a warm place to install this at or don't have a heater, I would probably wait for warmer weather to install new boots.
Also had a question, when I hook up my electric lincoln 18v grease gun to the bottom zerk it barley pumps anything at all and the grease just comes out between the bottom plate where the zerk is and the main housing any way to fix this? When I took the old boot off I did not see any new grease that I thought I was pumping in with the grease gun through the zerk? Is it just plugged up?

 

[Rkrug]

View attachment axle zerk.pdfZerk labeled K in the picture, was also wondering what the 2 labeled L are for on my truck there are just 2 plugs there, are there supposed to be zerks there?

 

[jonesal]

Also had a question, when I hook up my electric lincoln 18v grease gun to the bottom zerk it barley pumps anything at all and the grease just comes out between the bottom plate where the zerk is and the main housing any way to fix this? When I took the old boot off I did not see any new grease that I thought I was pumping in with the grease gun through the zerk? Is it just plugged up?

I asked the exact same question over the summer and didn't get s single reply. Let's hope you do now. I'm just as curious.

Al Jones
'84 M923

 

[M35A2-AZ]

The bottom and top grease zerks are for greasing the king pins.
To grease the ball part of the axle you need to remove the Allen screws in it and pump it in that way.
The LO page above shows it as "L"

 

[Rkrug]

can I replace the allen plugs with zerks to aid in greasing?

 

[M35A2-AZ]

I think you could replace them to put grease in and then put the Allen's back in.
If you leave the Allen's I think it would cut the boots when you turn.
Just my thinking.

 

[Rkrug]

Took off the boot on the passenger side and and all the grease gushed out like a water fall because it appears to have been mixing with gear oil making it a thin jello like stuff, more work and things to replace.

 

[M35A2-AZ]

Took off the boot on the passenger side and and all the grease gushed out like a water fall because it appears to have been mixing with gear oil making it a thin jello like stuff, more work and things to replace.

Sounds like the axle seal is leaking a little as you said.
I have one on my M931 that is leaking a little oil, more work to do on that.

Good luck with your repair!!

 

[Rkrug]

Got the hub and every thing taken off,in addition to replacing the outer seal is there another seal that could be laking?is there one in between the brake and boot area (shown in second pic)?Maybe this seal http://www.ccsurplus.com/content/front-axle-seal-5-ton-shaft-assembly ?

Thanks
for any help

 

[M35A2-AZ]

Got the hub and every thing taken off,in addition to replacing the outer seal is there another seal that could be laking?is there one in between the brake and boot area (shown in second pic)?Maybe this seal http://www.ccsurplus.com/content/front-axle-seal-5-ton-shaft-assembly ?
View attachment 405222View attachment 405223
Thanks
for any help

Thats the one that is leaking. It is inside the axle housing just inside were the u-joints are.
You have the remove, brakes, axle and spidle I think it is called that.
Getting the seal out in a bear, sometime you have to get it from the other side. So you end up doing both sides.

 

[Rkrug]

Found it thanks!
View attachment seal.pdf

 

[hotbox]

While replacing my steering wheel today, I notice my front drivers side axle is a greasy mess. Looks like that's next on my list. Thanks for the info MO MV man!

 

[hotbox]

Did you also change the seals? Is it possible to only need to change the boot? I don't see gear oil, only grease around the broken boot. I guess I will know more once I see the inside of the drum.

 

[Rkrug]

If you don't have gear oil leaking then you don't need to change the axle seal, and trust me you only want to replace it if you have to.