<VV> Rear wheel bearing greasing options / observations

[Tony Underwood]

At 06:56 hours 02/16/2005, Robert Coffin wrote:

>I have repaired several of the LM rear hubs that were done by others ,
>drilling and tapping for fittings and them filling the cavity with grease
>until it came out the seals. The units were not disassembled to do the
>modifications.


There are a number of different ways to do this sort of thing, and several 
of them can backfire.


>It was done to perfectly good rear hubs as a "preventative" measure.
>The cars were brought to me for lack of braking ability.

...hub filled full of grease...?   It's not necessary to fill the hub IF 
you have that trusty air compressor on hand... the one used to clean the 
bearing hub assembly.



>You can guess why - the grease expanded when the brakes warmed up the hubs
>and coated everything in the rear brakes.


There's a way around that...


>Upon disassembly , I also found steel chips which had worked their way into
>the bearings and ruined them.


The trick is not to drill a hole into the hub.   The hole is drilled into 
but not through the hub.   Check closely along the way to make sure the 
drill bit doesn't go through the side of the hub.    Stop just short of the 
tip of the bit just breaking through the hole into the inside of the 
hub.   Then use a punch to push through and ream the hole out to accept the 
grease fitting.

I was under the presumption that this was how it was always done...  no 
chunks or chips get inside the bearings this way.   And with careful 
tapping of the hole, only small granular grains of metal remain to get into 
the bearings which are flushed and cleaned and blown clear with 
the  brake-klene and the compressed air.    A few cycles of the brake-klene 
and compressed air leaves the inside of the hub pretty well flushed 
clear.  Spinning the hub while doing all this helps a lot.


>SO , what started out as a way to save a little time and $ turned out to be
>a quite expensive re - repair.


Obviously someone did it wrong...


>I would not recommend this "fix", even thought it is shown in the Corvair
>Tech Guide, as there is no positive way to keep some chips out of the grease
>cavity.


See the comment about avoiding drilling chips and cleaning out any tapping 
residue.    It *is* important to make sure nothing metallic remains 
rattling around inside the bearing hub.



>And unless the cavity is totally filled with grease[ NOT NECESSARY]
>,no new grease will get to the hub bearings.


Yes it can.   Carefully orchestrated squirts of grease through the zerk 
fitting, followed by more air to blow it into the bearings.    It only 
takes a LITTLE grease on the bearing rollers to lubricate them for the 
duration.     The trick is doing it right...  and doing it this way makes 
for easy cleanup after, and a minimum of grease out the seals after you're 
done and everything is back together.



>If the rear hubs are PROPERLY rebuilt with the correct clearances, and the
>correct amount of premium synthetic grease - like Mobil 1- is used , the
>rear hubs should outlast the rest of the car...with no need for any grease
>fittings, as appealing as they might seem to be....

*And* if the modification was done correctly to begin with.

Obviously if it's done wrong or sloppy or without consideration, there will 
be dirt in the bearings, chips in the bearings, tapping grit in the 
bearings, dead grease clumps in the bearings, and no new grease in the 
bearings.

Again, the trick is in doing the mod right.   Then it works quite 
well.     I would wager that the tech tip in the Tech Guide was written by 
someone who had done it right previously.    I've done this trick more than 
once and I've not had any trouble out of it from any of the bearings I've 
done.

Then again, an effective argument could be made against including any such 
tips in the tech guide when such tips can backfire if not done just 
right.


>I put a pipe plug in the holes , with Loctite, to keep anyone from being
>tempted to "grease" the units when repair was completed.


I just left the fittings in my cars... since nobody else will be working on 
them anyway.

So far so good...  and it's been many years now.

And, as mentioned, compressed air is your buddy.



tony..