Tom
Having recently had the gearbox apart on my 2500S...
The overdrive comes off as a unit, but as it shares the oil with the rest of
the gearbox, there will be spillage... You will need to remove it to
complete the gearbox rebuild anyway.
The usual cause of overdrive failure is electrical - ask me how I know...
The switch on top of the gear lever is the first place to look, followed by
the general state of the wiring. The wires are placed in a hot environment
and tend to become brittle with age. Added to that is the vibrations that
they are subject to. The solenoid itself and the relay could also be
damaged. The Haynes book for the saloons includes a wiring diagram (Figure
6.12) which they curiously omit in their Stag manual.
Make very sure that the isolator switch is included in the wiring. This
prevents the overdrive being selected in 1st, 2nd and reverse gears. Damage
as indicated in other posts will result if this is ignored.
The Haynes manual for the Stag details tests that can be done using a
suitable oil pressure guage - ie. it must be capable of reading pressures of
up to 550 lbf/inē. There is a plug next to the solenoid that is removed and
the guage installed. With the rear wheels raised and the front wheels
adequately chocked, run the engine and the gearbox in top gear at an
indicated speed of 25 mph (40 km/h). With the overdrive switched out, the
pressure reading should be 20 lbf/inē. When switched in, the reading should
be 550 lbf/inē. This testing procedure is (equally as) curiously omitted
from their Saloon book...
Having detailed the testing process though..., my friend (an A-grade
mechanic and fellow Triumph nut) who did most of the work on the gearbox,
tested everything while the car was still on the stands. He did not rev the
motor hard (doing so can be dangerous, especially if the car fell off the
stands), but tested it sufficiently to make sure all the various ratios
worked before doing a real road test. Having a tachometer to guage the
changes of ratios helped.
Hope this helps
David Greed
1974 Stag Man O/D
1979 2500S Man O/D
Email: Home: greed@wave.co.nz
Work: david.greed@telecom.co.nz
.
----- Original Message -----
From: Tom Parker <parkert@ihug.co.nz>
To: <triumphs@autox.team.net>
Sent: Tuesday, 14 September 1999 18:55
Subject: Gearbox Problems.
>
> Thank you to everyone who offered advice on the gearbox jamming in
reverese
> gear.
>
> The problem turned out to be 3/4 of the teath on the reverse idler gear
are
> stripped off!
>
> So it would seem to be a straightforward(!!) replacement of the idler gear
and
> the first/second syncro hub which is missing a tooth, and whatever else is
> broken.
>
> The other problem, unrelated is the overdrive that doesn't work.
>
> What can be done for that now that it is off the car?
>
> I've looked through the haynes manual and it covers a few things. Is it
> possible to test the overdrive while it is off the car? Presumably it
needs to
> be spinning quite fast and be full of oil before it will engage?
>
> How easy is it to remove the overdrive from the gearbox in situ should it
> still not work after the checks covered by the haynes have been performed?
>
> --
> Tom Parker - parkert@ihug.co.nz
> - http://www.geocities.com/MotorCity/Track/8381/
>
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