Pete Lund asked:
>I feel like a young child asking to hear that scary story again! I have a
>new Clunk from the rear somewhear.
>How does one diagnose the dreaded differential clunk again??? Is there a
>definitive test? What do I need to fix it?
Well Pete, how long is a piece of string, or more to the point, how fat is
your chequebook??
Seriously though, here are a few simple checks you can make. Wheel centres
moving on the hubs give only a small click, and you get this every time you
reverse out of the garage (which slightly untightens the spinners) then move
forward (which tightens them up again). Nothing to worry about.
More likely to give a clunk is one (or both!) halfshaft loose in its hub
splines. This will only get worse with time, and every quick and dirty
solution to the problem has not worked! Years ago splined inserts were
available, but new hubs are as cheap as inserts (even if you could still get
them) plus the machining, and you will need new shafts anyway. So you are
looking at new hubs and shafts, either splined or taper fit, as supplied by
Bob Grunau and myself. Splined 95GBP/US$180, taper fit 150GBP/US$285 plus
postage from England. Pull rear hubs and inspect: you might also find the
hub full of oil, which you can keep in the diff. with my hub nuts & lip
seals (25GBP/US$48 a pair.)
A rather rare problem is the whole end of the axle casing getting loose:
this has the square flange that the brake back-plate is bolted to so there
is quite a lot of torque on it. It should be a very tight interference fit
in the tube of the casing (which was probably heated to install it) with six
rivet-like pegs as back-up. All can get loose,and even fall out (which can
lead to loss of diff. oil) so check by jacking up the wheels, then with the
handbrake hard on, try to rotate the wheels: if the back-plate moves, you
have a problem!
If all that checks out OK, start looking at the diff. Bearing break-up
usually occurs gradually but if the front thrust bearing allows the pinion
to move too close to the crown wheel, one or more teeth could be damaged.
Grab the pinion flange with both hands (from underneath, or more easily by
lifting the parcel shelf) and see if it moves in-and-out or sideways (should
be virtually no movement), also how much it rotates (obviously, the
handbrake is on.) A small amount, say 1/4" or just over, is the normal
back-lash of the gears. Any more could be excessive back-lash, or the half
shafts tuning in the hubs. Now with the rear of the car off the ground,
rotate the flange slowly at least six times, feeling for any signs of
damaged teeth, indicated by cogging, or tight spots. If in any doubt, it is
easy to pull the diff. unit (or "Pumpkin") for closer inspection. All diffs
with many years of hard use which still have the original bearings, are on
borrowed time: I have lost count of the number I have fitted taper-roller
bearings to in the last seven years, including three of the T-Racers here in
the UK, without a single failure.
While you are looking at the flange, check the four bolts, originally with
split-pinned castle nuts: use new HT bolts with Aerotights or Philidas
all-metal self-locking nuts. Other bolts to check are the eight holding the
axle to the springs: they could be stretched and loose, or the axle
mountings broken. Its possible a Hardy Spicer joint is breaking up (how many
of us ever grease them?) and also that the gearbox RHS back plate has
broken, but that is more obvious as a clunk when you let in the clutch.
Happy Hunting!
TCRoger, Devon, Olde England
PS: I will be giving a seminar on the TA/B/C back axle at the T-Register
Rebuild day next week, although it is probably too late now to get a place.
I keep in stock every part for these axles, including my latest creation,
the new, improved drain plug with magnet!