Okay I have spoken with the owner of the 1963 Chevrolet Biscayne about his differential case
lateral run-out problem if you recall we had seven thousandths of an inch lateral run-out
which was way too much and in speaking with some of my colleagues here at the University we decided
that we would like to try cleaning up or truing up that lateral run out here on our procut,
I'm sorry Accu turn brake lathe the pro-cut is on car one but this is our a key turn a bench lathe
and as you can see I've got the differential but this is something you haven't seen before I've got
the differential mounted up on the arbor shaft our arbor shaft has about one thousandth of an
inch run out which is the maximum allowed for Arbor shaft run out on our brake lathe and so
of course that's going to no matter how straight and true this appears to be it's going to still
have a thousandth of an inch run out but the trick is trying to get the differential case perfectly
centered using bearing cones for disc brake rotors and I've played with that a few times in different
relationships with the case to the cones and the lowest amount of run-out I can come up with on
the dial indicator here's is six thousandths of an inch so I'm sorry the highest amount was six
thousandths of an inch so that's the one I'm looking for and we're gonna I've got it at
that point right now so we're going to try to clean this up with the disc brake rotor bit one
of the bits treat this like a rotor finish the rotor surface and see if we can take out some
of that lateral run-out let me get the camera position to where you can see the before run
out and then we'll do an after machining run out check ok I'm going to turn on the brake
lathe and we'll take a look at the run-out that we're measuring here with the dial indicator
so as you can see we've got some movement there and let me zoom in you see what we've got
get focused yeah right there okay notice we're going maybe mm below zero and it goes up and
touches maybe just slightly maybe goes over that five so there's there's six to seven thousandths
of an inch run out which one thousandth of an inch of that run out could be from the arbor
shaft at the brake lathe itself but like I say we're going to put the bit one of the bits for
cutting a disc brake rotor right on that surface the lateral surface there where the roller tip is
and try to clean this up okay I've got the brake lathe all set up here to machine this lateral
surface of the differential case and I've got it started I could not get the bit all the way
in to that surface where we measured the radial run-out but I've got a really really close but
it is taking its first pass here hopefully it's the only pass I'm just taking off a few
thousandths of an inch of material and so far it appears to have a nice clean cut but it'll
be a little more revealing as we get to the outer edge because that's where I believe most of the
run-out is towards the outside of that flange so let's continue watching this
looks like we're about third the way through
it's not making any unusual noises no screeching like some brake rotors do but we've got enough
mass here that hopefully won't do that it's looking good and sounding good so far
looks like we're a little more than halfway through
got some people working in the background here so I apologize for the extra noise
looks like we're almost out to that Ridge where the rust buildup was from the spacer
plate on the 456 gears that we had on there we've got cleaned that up
with a knife sharpening stone so that wasn't affecting the lateral run-out
looks like we're about 3/4 the way through
hopefully we'll be successful here if we're not then we're gonna have to find a different
differential case the owner of the vehicle I spoke with last night and he said that he
thinks he can round up another one but hopefully we won't have to he also told me that he looked
up the part number of that differential housing and it was for an open-style differential and
to fit this positraction differential case in an open-style differential housing they had to
grind out all that material that I discovered when we first disassembled the housing okay it
looks like it's done let's zoom in here we're all the way out and let's see if we need to do
another cut or if that was good enough looks like there's a just a tiny bit on that outer
edge that it did not clean up back it off here just a little bit we're really close but I think
I'm gonna run one more pass on that and then we'll take it back over to the differential
housing and check its run out oh I'll check its run out here too but let me do one more
pass I won't make you watch that one okay I've run the second pass here on the brake lathe for
this differential case and that cleaned up really well I've just mounted the dial indicator back up
to check for run-out and of course it's going to measure or it should measure zero right now
but then we're going to loosen this nut and hold the cones that Center it and turn the difference
of case half a turn and then re-measure the run out and that'll give us the true rent out
that we've machined in based on the centering cones but that's not necessarily based on the
side bearings so the end goal here is to have the runout when centered by the
side bearings in the differential housing be less than three thousandths of an inch so let
me reposition the camera so we can watch the dial indicator and we'll check this okay here
we go I've got the dial indicator hooked up I'm going to turn this on and we're going to expect
to see a zero run out at this point oops I just bumped the camera try that again okay here we go
looks like we're getting the tiniest little movement that's probably just dust or dirt
let me put a rag on this surface clean that up a little bit there we go all right so less than
two thousandths of an inch right there okay now we're gonna shut off the lathe
and as I said we're gonna rotate the differential case in its cone cones half a turn so you know
loosen this up right right there and excuse the phone call so I'm gonna hang on to the center
cone and the outer cone and turn the case half a turn right there and then we'll tighten the
nut back up we're gonna do a rolling tight on this not a pound pounding or impact tight and
now let's watch the run out again here it should be higher than it was initially after machining
and yes it is it looks like we have about three thousandths of an inch right there and of course
that's with the arbor shaft moving up and down a thousandth of an inch of that so we're less
than that, we're probably two to one and a half thousands of an inch by time we get it back in
the differential housing and centered with its side bearings so let's let's take that over and
put it in and try it and see what we get okay we are back to the workbench and we've got our
differential case off of the brake lathe and set up being centered by the side bearings now
and I've got the dial indicator all set up here and I'm very pleased with the results
the overall run out is just a little over one thousandth of an inch not even a complete
thousandth of an inch and I have to admit that's the first time I've ever machined
a differential case on a brake lathe but let me show you we are on 0 there as we rotate it
around it goes up to one just a little over one back to zero back up to one so this is
ready to put the ring gear back on and of course I had to gut the differential case I had to pull
all the clutches and side gears and differential pinion gears out of this case to be able to put
the arbor shaft through the middle of it there on the brake lathe but it did work really well
and we were successful in repairing this 1963 differential case so we can now proceed once I
find some grade 8 1 inch long fine thread bolts to put back in the rain gear that preferably
won't stretch at 53 foot-pounds so this has been a demonstration of measuring the lateral
run out on the differential case and that radial run-out would be measured on this surface here
but we've already done that in a previous video and it was around one thousandth of an inch also