The mysteries of the "surge" of my 72B continue. But to recap -
About five or six weeks ago, I was driving down a hill in 3rd gear and O/D
and when I downshifted out of o/d, the car acted like the o/d was
engaging/disengaging in maybe two second motions. To determine if it was
the overdrive or the switch, I disconnected the yellow wire from the
coupling to the wire that leads to the transmission. The problem went away
so I was started to contemplate ordering another stalk switch.
Then a few weeks later, on the same road, same time, same place, the surge
returns briefly. Since there was no power to the overdrive, I figured it
couldn't be the overdrive disengaging/engaging. Maybe it was carbs or
vacuum advance?? But the problem disappeared again for a few weeks.
Then last week, another related problem occurred after a fair bit of city
driving under level terrain - I lost reverse gear or actually it was barely
functional - it just didn't quite catch. No problem though as I could push
the car backwards easily enough. A few hours later, the car was fine, as if
nothing had happened. I did a quick search on the list archives and found
someone who described very similar symptoms where he described losing
reverse after the car was driven extensively, also with od tranny. This was
a year or two ago - anyone recall this one or the solution?
This brief loss of reverse happened right before I left on a weeklong
backpacking trip to the Yellowstone Park backcountry so I didn't have time
to work on it. After I got back earlier this week, I drove the 72B to work
the next morning. And once again the surge occurred - same hill, same spot,
same time,same duration (maybe two blocks). But when I accelerated, it
accelerated just fine and smooth. The surge or gear slippage or whatever
seemed to be mainly a de-acceleration thing. But just to test another
issue, I checked reverse shortly after the surge symptoms appeared and it
was out. But then after the car sat for a few hours, everything was back to
normal.
Based on a few suggestions on that posting from a year or two ago, I
drained the oil and removed the filter. But alas, the filter was clean. I
believe I was running 20/50 Castrol and plan to replace with the same.
Also relevant - I have owned this OD transmission since 1983 or 1984 and
have put maybe 200k miles on it. I have had it overhauled twice, the last
time was three or four years ago but it likely has less than 4k miles since
the last overhaul as it sat for nearly two years between its use in my
71BGT and now in my 72B. This is the LH-type. Although I have done a lot of
work on my cars including several engine overhauls, I have yet to really
delve into the transmissions. Both overhauls were done at transmission
shops. In both cases, I had to find adventuresome shops since I was in
remote areas (Wyoming and Montana). I figure British mechanics are fairly
simple and couldn't be too different from American technology. But I
provided the Haynes manual to both shops and also acquired all the parts
they needed.
So I'm at a bit of a loss here. Any words of wisdom out there? Any
experience or knowledge on say the relief valve or other parts accessible
underneath?
David Councill
67 BGT
72 B
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