I finally changed out the parking brake shoes on the M35 today. The hand
lever was scewed all the way out and the stop nut underneath was all the way
in and the parking brake would not hold the truck. Of course the friction
material on the shoes being 1/16" thick or less was obviously the problem.
I found some things that might make it a bit easier for anyone else who may
be doing this in the future.
The procedure in the manual (TM9-2320-361-20) is fine if you've got the
transfer case sitting on a bench but the way it's mounted in the truck you
have to sit on the ground and stick your head up between the drive shaft and
the frame. It's not easy to see what you need to be working on all the time
and most of the work was done while looking thru a small hole in the
crossmember that is in front of your face. If you were short it would be
easier.
It all comes apart pretty easy except it is a real PIA to get the stop nut
completely off of the end of the cable so you can take the lever arm off.
Do turn the top of the parking brake hand lever (in the cab) all the way CCW
before you start adjusting things after re-assembly.
Once you have your new or relined shoes ready I found it easier to do the
following (speaking of relined shoes, I had two sets done at a cost of $75
from the local truck brake shop). The book tells you to pre-assemble the
entire shoe set and arm etc. Instead, pre-assemble only the inside shoe and
the lever arm and it's "E" clip, of course have the stud already pressed in
for the adjusting wire thing (lower corner of inner shoe). Put the outer
shoe in first (by itself) , adjusting the large pivot pin (bolt) at the
bottom so you can just barely feel some axial play. Then adjust the top
stop bolt for the 0.015" clearance they talk about in the manual, in my case
I only had the clearance that small at the very top of the shoe, I assume it
will wear in later. It is much easier to do it this way than to try to
adjust that top stop bolt and get the spring on with that lever arm in the
way. So when the outer shoe is all set and it's small top spring is on,
then slide the inner shoe/lever arm assembly in and install the other "E"
clip, the lever arm return spring, and the entire adjuster assembly and
eccentric that goes down low on the shoes. Now you can put the cable stud
thru the lever arm and put the stop nut on till you get a uniform 0.015" gap
at both ends of the inner shoe, this translates to only about 1/4" to 1/2"
of free movement fo the lever arm. Then adjust the thing at the bottom of
the shoes such that the inner shoe has a uniform gap at the top and bottom.
The only thing left is to turn the hand lever (in the cab) CW and keep
flipping it up till you get some resistance and your done. I tried running
against the parking brake in L2 and it would not move and that was with what
I would call a pretty light pressure on the brake hand lever.
The "E" clips are catalog items from any bearing type distributor, IRR
#1000-X098 as I recall, $5 will get you almost 100 pieces, anyone need any
by the way? The other little clip, which they tell you not to reuse, can be
gotten from NAPA, they have a page in the brake parts book with life size
outlines, just match an old one to that, I forgot the number and don't have
a receipt handy.
Now on to the the rear brakes, bearing, seals, etc.
later
je
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