[TR] Controversial subject...

John Macartney john.macartney at ukpips.org.uk
Wed Mar 26 11:20:34 MDT 2014


I think one of the things many may tend to overlook about Laycock overdrive
units is that the oil used in them is only part of the whole scenario. In
the days when Laycock were supplying the A and D types to a variety of
vehicle manufacturers, the weight of the oil used in O.E. gearboxes was
variable. Some, like Standard-Triumph recommended 80W/90, others straight
SAE 30. One of my old chums from Laycock has said more than once in my
presence that depending on what vehicle the O/D unit originally came from
(as we're now very much into using displaced units from other makes) Laycock
themselves set the primary pump pressure appropriate to the make and model
of car to which the O/D would be fitted. Allen Hess says his unit engages
with a 'bang' and Allen, it shouldn't. At worst it should be a gentle thump
and more particularly a smooth slurred engagement as on an autobox.  I don't
know John Esposito's views on this but IMHO if the oil being used is a
lighter weight than 80W/90 and especially when hot, it could be the primary
pump pressure is too high. Sadly, I don't remember what that pressure was so
can't offer further comment. I had a number of issues with the O/D on 'uncle
jack' (Stag) I drove in 2009 and it wasn't until I reached Texas that we
found the operating pressure was too low and this resulted in intermittent
engagement and under power kick-out. Once the pressure was adjusted to suit
the oil we were using, everything was fine. Just my two pennyworth.

Jonmac


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