[TR] TR4A overdrive transmission

[Greg Lemon]

Creig, always an interesting topic with differing opinions, factory 
recommends 90w gear oil, however, most 90w off the shelves these days is GL5 
spec, you want GL4, which you can still get at NAPA stores I think, most 
don't stock it but can get it.  The GL5 has additives that can cause 
corrosion in the brass components of the gearbox.

Craig Esposito at Quantum mechanics recommends a straight 30w non detergent 
motor oil, cheap and usually available at the chain stores or tractor/farm 
supply stores

Many swear by Redline synthetic MT90, I haven't tried it, but have also read 
that it will find any leaks you have in the tranny or overdrive and pour out 
faster than conventional oil, those are expensive leaks, so I have never 
tried it.

Some people run multi-weight motor oils, though this article recommends 
against it.

I have tried all except the MT90, in my opinion both the gear oil and 
non-detergent motor oil work fine, and I detected no noticeable difference 
in shift quality or overdrive engagement, I also used to put in multi-weight 
motor oil, I remember my old TR4A would drop out of O/D on a long run on a 
hot day sometimes, and am wondering if it was from cavitation or foaming as 
described in this article:  http://www.quantumechanics.com/qm-htm/topic1.htm 
(scroll down).  I think I may have been running multi-weight 20w-50 at the 
time.

Greg Lemon