Yes! It helps to have two people also.
Basically, you need a drill which will allow you spin up to at least 2500
RPM. You need to fashion a "bit" which will grasp the input shaft of the
gearbox and then insert the bit into the drill. Next, connect a
speedometer. Also make sure you have a circuit setup so that you can engage
and disengage OD with the flick of a switch. Position the speedometer so
you can view it easily. Before you begin spinning the input shaft with the
drill, make a mark (using whiteout or something) on the input shaft and also
make another mark on tailshaft, align these two marks... and then engage it
in which ever gear OD works in.
You can begin to spin the input shaft with the drill. Once you have reached
full (constant) speed; engage the OD. Within a second or two you should
notice a drop in speedometer reading (it will be minimal a you aren't
spinning it terribly fast, but a drop none the less). If that fails, you
can revert to the backup measurement... if the OD did not engage your
whiteout marks should still be aligned. You may wish to repeat this a few
times, to verify that it is engaging and staying engaged each time.
Like I said, the drop in the speedometer reading will be minimal. It should
read ~18mph with a late MGB gearbox without O/D engaged, once engaged it
will drop to about ~15-16mph.
Original idea for this tool is Tim Dumhamel's (sorry if I messed up the
name), Max Fulton and I spent quite a bit of time trying to figure out to
accurately measure the effectiveness of the O/D. If you're wondering why we
didn't use a tachometer rather than a speedometer, I can not recall, but at
the time there was something that made us decide against it.
I'd also suggest flushing the oil in the gearbox prior to doing this, and
then replacing with new oil.
Other helpful hints; have the gearbox secured well... sometimes the kickback
from the drill won't be absorbed by the person holding it ;-) (this can be
solved by spending lots of time making sure the bit, inputshaft, and drill
are aligned as well as possible!). Make sure to ground the gearbox housing
also. The faster your drill can spin, the better.
When I go home on fall break, I'll take some photos of this tool (or
adapter, whichever name you prefer) for anyone who wishes to make one.
--
Kai M. Radicke -- kradick1@ic3.ithaca.edu
'74 Triumph TR6 -- '66 MGB, both @home
> Is there an effective way to "bench test" an OD tranny? I have purchased
> a parts car with an OD tranny so I can't drive the car to determine if
> it works properly Inspection of the gears and synchros in the gearbox
> is pretty straightforward thru removal of the side inspection cover but
> I am at a loss as to determining whether the OD engages and disengages
> properly.
> Frank "Swamp Yankee" Krajewski.
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