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Thread: brute4c : Front axle teardown q's

  1. #1
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    Default brute4c : Front axle teardown q's

    Front axle teardown q's
    Post by brute4c on Sept 6, 2006, 11:16am

    OK....after the fire, I found my diff lube to be very dark bluish in color...smoky blue I have been calling it...recall that I had a brake fire and lockout hubs were on the truck...the grease I had in the knuckles was black....my thought was that the grease had at least liquefied if not vaporized, toasted the seal inboard of the knuckle and made its way to the diff thus contaminating the fluid. Since the diff wasnt turning and the heat source was so far away and the lube is synthetic, I very seriously doubt that it could have gotten enough heat to the center section to boil the 3 plus quarts of lube for a long enough time to cause such a dramatic color change....we arent talking a little difference...but major!

    In ordering parts, I wanted to get the seals that go between the knuckle and the axle tube....I thought they were just inboard of the knuckle to keep the grease in there...well no....there is a bushing just inboard of the knuckle that the axle shaft passes through and the seal is actually far inboard almost at the differential...just a bit outboard of the bearing caps.

    In this view, #9 is the seal in question and #11 is the bushing.


    Not having torn into one of these before...I am wondering how much clearance is there between the bushing, #11 above, and the axle shaft? I am guessing not much...enough for a bunch of grease to migrate past on its own or not? Thinking back to Brians axles, he had a ton of grease down in there but that was done under pressure....seems that bushing should make a pretty fair restrictor or what good would it be....something like .1 inch or less maybe?

    Also, with the seal being at the inside edge, the only way to change them is to take out the differential right?

    I have to wonder if that was the source of my discoloration or not...so far away from the heat source, I doubt the seals got that hot...maybe the passenger side due to the offset of the housing but not sure that would happen....

    I would like to have all the parts on hand and do the job once....but dont want to spend more than I need to or make more work than necessary....though it would really suck to get it together and find those seals leaking...

    I take it those seals are there more to keep the lube in the center section than to keep the grease from the knuckles out?

    THANKS!!

  2. #2

    Default robertcowan :

    Re: Front axle teardown q's
    Post by robertcowan on Sept 6, 2006, 11:32am

    BRUTE, SOME LUBES I,VE SEEN HAVE A BLUE COLOR TO EM. AND FOR CHANGING THE INNER SEALS YES YOU GOTTS PULL THE CARRIER-RING GEAR ETC. TO GET TO THEM MOSTLY TO REINSTALL THEM. I,D PULL THE COVER AND CATCH THE FLUID AND IF ITS NOT COMTAMINATED ESPECIALLY SINCE ITS SYN. LUBE IT ISNT HURT. I KNOW OF SEMI TRUCKS WHICH RUN CONSTANTLY AT 225 -250 DEG. ALL DAY LONG FOR 250K MILES. OUR END PROBLEMS WONT EFFECT THE DIFF. MAKE SURE YOU GOT ALL PARTS TO REASEMBLE IT BEFORE YOU TEAR IT DOWN. SOMETIMES THERE HARD TO COME BY NOW. YOU OTTA WATCH EBAY AND PICK YOU UP A USED POWER LOCK AND INSTALL IT IF YOU TEAR IT DOWN. YOU WONT BELIEVE THE DIFFERENCE IT MAKES. 100.00 WILL GET YOU ONE PLUS S&H.
    BOB

  3. #3
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    Default brute4c :

    Re: Front axle teardown q's
    Post by brute4c on Sept 6, 2006, 11:44am

    This lube was translucent before the fire with no visible blue in it...Eaton synthetic 75W90 for semi axles....after, it was certainly not...not even close. Like a large amount was added to make it that dark and light impenetrable...
    Due to it being synthetic and so far from the heat source, not to mention is was all in one big "vat" in the center section thus requiring a major amount of heat for a long time to raise its temp versus a small pool, it seems it must have been contaminated somehow....I just cant figure how....

    I did change it out to new lube and discarded the old....just dont trust stuff that I dont know what is in there...

  4. #4
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    Default barrman :

    Re: Front axle teardown q's
    Post by barrman on Sept 6, 2006, 12:06pm

    Jon,
    The outter bushing #11 is what holds the axle shaft in the center of the tube while the hubs are turned. Too much play in them and you will get vibrations and of course wear on your carrier and hubs. That bushing is what makes the axle full floating.

    The seal #9 is where the grease was oozing past on Brians axles. I took the stripped axle tube with the seals and bushings still in it to the car was to power wash. My students had already used brake cleaner to get everything they could reach clean. I ran out of money before I ran out of odd colored gunk coming out of the space between the bushing and the seal. I personally think that yours has 40 years of old oil, grease, rust, etc between the seal and bushing. Getting it hot just loosened that stuff up enough to mix in with your good oil.

    You have two options. Leave the seal and bushing alone, rebuild the ends, drive it and change the fluid after a hundred or so miles and see how bad it is.

    or

    You can tear it all down, clean everything, hope you got it set back up right, change the fluid after 100 miles and see how it looks and get rid of any new metal that has come off from the new parts meeting their new neighbors.

    Either way, driving with lockout hubs disengaged you should be ok. For flat towing just go the extra step and remove your brake drums next time and don't worry about it.

  5. #5

    Default porkchop :

    Re: Front axle teardown q's
    Post by porkchop on Sept 6, 2006, 12:14pm

    The bushing #11 will allow oil past it. If the grease liquified in the hubs, which it did in your case, then it would go past the bushing with no problem. The seal to stop the oil from mixing between the hubs and the diff is #9 which you have to pull the diff to change (I have spares, PM me). The black burnt grease then would mix with the diff oil from a bad seal and cause your discoloration. It took me a total of three hours from what I can remember to do both shafts on the front.

  6. #6
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    Default brute4c :

    Re: Front axle teardown q's
    Post by brute4c on Sept 6, 2006, 12:40pm

    So I take it there has to be enough clearance between the bushing and the axle shaft to send grease down there normally...not under pressure feed...

    So just driving around, the grease gets hot in the knuckle and will be thin enough to migrate to the other side of the bushing as well?

    That makes sense...so if the truck has 28,000 miles on it like mine and has been greased regularly, there is going to be grease past the bushing normally?

    I thought the grease would want to be contained in the knuckle and the gear oil would be allowed to go from the diff to the bushing area...thinking thats where the seal would be....wonder why the grease is the one that can migrate in that tube area, unlike the rear axle....

  7. #7

    Default tacomainoh :

    Re: Front axle teardown q's
    Post by tacomainoh on Sept 6, 2006, 12:48pm

    Jon, the inner seal is the only seal on the later 60's. There is a company making outer seals now, don't know if they'll fit the 715 or not, but they are a double seal design and cost $55.

    There shouldn't be anything in the axle tubes but the shaft. The bushing is just there to guide the shaft.

  8. #8
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    Default brute4c :

    Re: Front axle teardown q's
    Post by brute4c on Sept 6, 2006, 1:08pm

    Wont some of the grease, when it gets hot and runny when driving, make it past the bushing? Brian was pushing grease past the inner seal but that was under pressure....obviously not my situation but there must be some clearance there in order for that to have happened right?
    Cant be much though...

  9. #9

    Default tacomainoh :

    Re: Front axle teardown q's
    Post by tacomainoh on Sept 6, 2006, 1:15pm

    If all is well, nothing will make it past the inner seal. There shouldn't be any grease in the tubes unless those inner seals are compromised.

  10. #10
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    Default brute4c :

    Re: Front axle teardown q's
    Post by brute4c on Sept 6, 2006, 1:47pm

    Hold on here now.....

    the bushing is at the inboard edge of the knuckle....the seal is way down the tube by the differentail bearing caps....so some grease can get in the tube unless the bushing out there is so tight to the axle shaft that grease cant pass by....or what am I missing?

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