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Re: [Mgs] Flat towing

To: "Paul Hunt" <paul.hunt1@blueyonder.co.uk>, <mgs@autox.team.net>
Subject: Re: [Mgs] Flat towing
From: Barney Gaylord <barneymg@mgaguru.com>
Date: Fri, 17 Dec 2010 09:34:30 -0600
Quaint thought, but no.  The oil is shared, so to speak, but I seem 
to recall the OD unit will not drain unless you remove a second drain 
plug.  But as long a ther s oil inside, it's a mute point.

The OD unit had two modes of operation, engaged or not engaged.  To 
be engaged requirees electrical switch on and motion to create oil 
pressure.  In either case the OD input shaft is always driven by the 
output shaft when towing.  OD input is close coupled to the gearbox 
mainshaft so both turn together, and both oil pumps operate.

For the gearbox input to be stationary when towing, the clutch/brake 
lining must be worn away to nothing or some gearing must be broken, 
resulting in not driving the OD input shaft.  If the OD unit is 
broken in any way that omits driving the OD input shaft, then nothing 
in the main gearbx turns and no damage there.  Of course the broken 
OD unit will not heal itself, so needs to be repaired 
anyway.  Perhaps you can speculate if more damage might acrue to the 
broken OD unit if towed.

One thing is for sure in any case of normal operation or towing. If 
there is no oil in the gearbox you're just screwed, so check and top 
up gearbox oil before moving the car.


At 08:57 AM 12/17/2010 +0000, Paul Hunt wrote:
>The oil is shared between OD and gearbox.  The OD has its own pump 
>and that and the gearbox 'pump' will be driven when towing as long 
>as the OD is working correctly.  If there is a fault which means the 
>car free-wheels with OD switched out then neither pump will be 
>driven.  Oil level also needs to be correct.
>....
>
>----- Original Message -----
>>The MGB overdrive unit has separate oil reservoir and has it's own 
>>internal lube system.  This is also okay with flat towing, and has 
>>no effect on the 4-speed mechanicals.
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