jpratchi:
> Can anyone tell me how much backlash it tolerable on a Spitfire
> differential and what is the preferred method for measuring it on
> the car.
When you say backlash, I think you are really talking about play due to the
wear of the components. Backlash is a specific measurement of the space
between the teeth of the ring gear and pinion, when talking about diffs.
There are several places where play is present between the driveshaft and
the diff. There is the possibility of play in or between:
prop shaft U joint
pinion/ring gear mesh (a.k.a backlash, should be 0.005 in. max)
differential gears and their shafts
differential gears and their thrust washers
differential pinions and their shafts
differential pinions and their thrust washers
differential gears and the differential pinions
differential gears and the stub axle splines
halfshaft U joints
So the first thing to do is make sure the U joints all are tight, and
all the flanges are bolted securely. Then you can hold the wheels with
the parking brakes, or by having the back of the car on ramps, and then
rotating the driveshaft, gearbox in neutral. Of course, how much play
is tolerable is hard to measure. If the play is all in the pinion and
ring gear mesh, the gears will heat up and fail, after complaining for
some time. If the thrust washers on the differential pinions and gears
are toast, there will be lots of play and you'll small hear clunks as
the gears get forced from one end of their travel to another. If there
is too much play in the stub axle splines, you'll also hear clunks, until
the end of the shaft twists off, leaving the car pretty much unable to
move under its own power, though nothing will look wrong from the
outside.
So basically it is hopeless, I'll give you $50 for the Spit as it sits!
mjb.
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