[Mgs] Overdrive Noise/Shifting Problem

Paul Hunt paul.hunt1 at blueyonder.co.uk
Wed Jan 30 01:54:47 MST 2008


Firstly there definitely should not be slippage in 2nd gear, as OD should 
not be engaged in that gear and drive is through the locked one-way clutch, 
not the linings. However if the one-way clutch has been damaged, which 
happens if OD is still engaged when reversing, then it could well be 
dependant on the linings which will tend to slip in the lower gears.

With some of the other symptoms it could well be that the lock-out switch is 
bypassed or has been in the past and damaged the OD, or possibly sticking 
closed occasionally but this latter would be extremely unusual.  It's easy 
to check the lockout switch - simply drive along in 1st or 2nd flipping the 
manual switch in for a few seconds and out for a few seconds.  If the revs 
change as they should in 3rd and 4th, then the lockout switch is not doing 
its job, pure and simple.

Max is correct in saying there is only one lockout switch, which only allows 
OD to be engaged in 3rd and 4th (4th only on later American cars) and locks 
it out in all other gears.  On a 71 is should be on the left side of the 
gearbox, with the reverse light switch (nothing to do with OD) on the right.

If the lockout switch is functioning correctly all this is highly unlikely 
to be oil level.  It could be caused by dirty oil and blocked filters. 
Drain the oil from the gearbox and clean the filters.  Then refill with ATF, 
which is said to have cleaning properties.  If that seems to fix things, 
possibly after a while, drain, clean and refill again.  20W/50 engine oil is 
the norm, although again some say that ATF works better in a marginal 
gearbox i.e. one with some problems.  Failing that, it will need removal, 
stripping and rebuilding as there would appear to be a major mechanical 
problem.

PaulH.

----- Original Message ----- 
> for the second time in about 6 months or so, i've put it in reverse, let 
> out
> the clutch and all i get is a loud whine, no movement. 


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