Dave and Jeff,
The Isolator switches on the TR gearboxes are permissive switches, not
lockouts. Every "A" type overdrive since the early TR2's had a pair, one
for second gear on the right and the other, for third and fourth, in the
center. If the remote assembly on your gearboxes does not have drilled
and tapped holes for these two switches, it was not originally an
overdrive remote assembly, but a remote for a standard gearbox. Am I
correct in assuming both of your cars are not original overdrive cars?
The standard gearbox remotes (cover assembly) had a "boss" in the
casting for these switches which needs to be milled, drilled and tapped
to fit the isolator switch. Bypassing the isolator switches can cause
bad things to happen for two reasons:
1. Too much torque for the overdrive in first gear
2. The well known problem of having the o/d engaged while in reverse
which is tough, to say the least, on the unidirectional clutch.
Have you priced overdrive units lately? The underground market
consisting of gearheads and hobbyists like us, is drying up so the
$300-$600 overdrive units (as is, where is of course) are getting hard,
if not impossible, to find. The dealers are already in the $1200 and up
range for a rebuilt overdrive unit. So unless you have unlimited sources
or unlimited funds, you'd better do whatever you can to preserve what
you have.
Just my .02
Ed Woods
'60 TR3 with overdrive
'54 MGTF in need of overdrive
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