[TR] TR4A overdrive transmission

[Randall]

> I haven't
> looked at my book yet for recommended oil.  90 weight?

90 weight GL4 was the factory recommendation (or 80 if you consistently drive in below freezing weather).  Lots of folks will tell
you 30 weight motor oil, and Triumph used to recommend that.  But they changed around 1960 to the GL4, so they must have had some
reason.  Rumor has it that the GL4 protects the gearbox better and reduced warranty returns.

GL4 is getting hard to find at FLAPS.  Personally, I use Redline MT-90, which is GL4 but also is designed specifically for manual
transmissions.  OD operation seemed about the same, but it definitely had a positive effect on shifting the main box.

> Is there anything else I can check or do prior to installing 
> other than
> getting someone to rebuild it?  

At a minimum, I'd get a pressure gauge and check the pressure, even if it does engage with more oil.  The accumulator spring seems
to get weak with age, leading to low pressure, which can allow the OD to slip under maximum load.  Jay Holecamp sells a pressure
gauge with the funky adapter (replaces the plug above the operating valve) for a reasonable price
http://www.geocities.ws/jholekamp/
Or you can build your own.

Probably also worth draining the old oil, even if it doesn't have very many miles on it.  Check the oil for swarf, and clean the
magnets and pickup screen inside the OD drain plug.  

I recommend building or buying a special wrench for the plug; hitting the ears with a punch & BFH can distort it and lead to leaks
that are hard to fix.  Here's my home-made one
http://goo.gl/cd21oS
In the background of that photo, you can see my previous attempt, just a bar of steel with two bolts at the right spacing and a
little filing on the sides of the bolts.  It worked well enough, but was tough maneuvering under my TR3A, so I made the one in the
foreground (out of a cheap socket sourced from eBay).  Or I believe Moss sells a tool.

Randall