Well, excuse me <g>. I know perfectly well how the OD switch functions,
but doesn't it strike you as odd why it is called a 3rd-4th "lockout"
switch when it does not "lock out" the OD in 3rd-4th, it "locks out" the
OD in all other gears, speaking functionally (not mechanically). I left
out reverse because, well, "duh"...
As for the oil issue, don't you think it might be relevant to the
problem? I believe I have previously heard reports of OD problems caused
by using too light or too slippery a lubricant. At least one respondant
claimed changing the oil solved his problem.
paul.hunt1@virgin.net had this to say:
>The chat about the oil is rather by-the-way for the original poster, and the
>switch closes in 3rd and 4th rather than opening in 1st and 2nd. I suppose
>it could be taken to be like the old glass half full/half empty thing, but
>in that case you would need to include 'reverse' with '1st-2nd',
>particularly since disabling the o/d in reverse it the most important
>function of the gearbox switch.
>
>If you can make the o/d cut in and out by pulling the gear lever around a
>bit while in 3rd or 4th it is almost certainly the gearbox switch. Do you
>have the gear-lever mounted manual switch? If so be aware that the wiring
>to these can give trouble because of the continual waggling about.
>
>PaulH.
>
>----- Original Message -----
>From: Max Heim <mvheim@studiolimage.com>
>To: MG List <mgs@autox.team.net>
>Sent: Wednesday, June 21, 2000 4:40 PM
>Subject: Re: Overdrive woes
>
>
>> Hmmm, could it be temperature related? My understanding is you should use
>> single weight motor oil in the OD transmission. I use 30wt. Or...
>>
>> ...possibly the 1st-2nd lockout switch is flaking. Either the switch or a
>> wire connecting to it is opening temporarily, maybe related to vibration
>> at that RPM. Tough to get at the switch in a '77, though...
>>
>> delling3 had this to say:
>>
>> >I have a MGB fitted with a LH type overdrive. I recently started having
>a
>> >problem with the overdrive "cutting out", and am looking for some help.
>> >
>> >Symptoms are noticable in either 3rd or 4th while in overdrive. While
>> >cruising under moderate load - not accelerating hard, or lugging at low
>> >R.P.M., the overdrive will begin to drop out. It is an intermittant
>> >situation, the engine will load up momentarily as the overdrive drops
>out,
>> >then the RPMs fall again just as quickly. The symptoms occur only in
>> >overdrive (the clutch isn't slipping), and seems to be possibly
>influenced
>> >by either R.P.M. (around 3500 R.P.M. engine speed) or temperature (more
>when
>> >car has been run for a while).
>
>
>
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.
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