At 04:37 PM 10/26/98 -0800, PHILIPPE TUSLER wrote:
> Since shortly after I had the tranny in Tintin ('66 MGB-GT) rebuilt, it
sometimes balks at going into second gear. No grind, it just won't go in.
Brute force will put it in. Wiggling it back and forth will also. This is
most often from a standing start when I try to put it into second before
first (non-synchro). What could cause this?
One possibility. and a nice story here. Some years ago a friend needed a
gearox for a 1275 Midget, and some club member gave us one for free. Story
was that it was supposed to have been freshly rebuilt, but shortly after
being installed in the car it decided never to go into 3rd gear again. So
it was removed and replaced by another unit, and it sat for a few years
until we were inquiring and it was bestowed upon us rather uncerimoniously.
Thinking it might need a rebuild, we removed the side cover for a look
inside. Everything looked perfect, except the 3rd gear balk ring was stuck
on the steel cone surface. If we would pry it loose with a screw driver
the thing would shift properly into 3rd once or twice before hanging up
again. Upon disassembly we found a thin layer of carbon adhearing to the
steel cone where the balk ring would mate. Rather than slipping a bit on a
thin film of oil, the balk ring was getting stuck securely on the carbon
coated surface. We were able to clean the steel cone surface with a piece
of emery paper and a little oil in a few minutes, and upon reassembly we
had a perfectly good freshly rebuilt working gearbox (and the price was
right too).
My best appraisal of the situation (WAG) was that the parts were oiled
during assembly, then the gearbox was installed in the car and maybe driven
without being filled with oil. Heat from the friction of the balk ring
against the steel cone soon cooked the oil film onto the steel cone,
causing the balk ring to stick in place. So, I suppose checking the oil
level in the gearbox regularly is a good idea. And if something is
sticking, an oil change may help. And It might be worth the cost and
effort to treat it to a fill with Redline MTL fluid to see if it shows some
appreciation.
>In my mind, I see an asymetrical ball-spring. I sometimes also feel a
little *pop* vibration in the shifter a moment after taking it out of
third. Almost as though that asymetrical ball- spring just popped out of
where it was jammed.
It could be that the three selectors on the back ends of the shift rods are
getting well worn, along with the mating selector lever. Perhaps the
selector lever and/or selectors are not achieving the proper full travel as
demanded by the hand shift lever. When you shift out of 3rd gear, the hand
lever and remote control shaft may think the motion is finished, while the
3rd/4th shift rod still has a little ways to go to get to the center
detent. If the small engagement teeth on the 3rd speed gear and the
sliding hub are not quite fully disengaged, they will give a little axial
kick as soon as there is a bit of torque available, like as the clutch disk
and input shaft are coasting down to speed for the next gear. Solution may
be to renew the selector parts, either with better replacement parts, or by
welding up and filing the working surfaces back to the original profile.
>Twice I've had the tranny rebuilt by others, badly. Next time I will do
it myself and have only myself to blame, but at least I'll be able to
afford the beer to drown my sorrows.
The second time I went through a gearbox rebuild I was much more meticulous
than the first time. I spent some time getting to know the function and
working relationship of all the shifter parts, and particularly where the
accumulation of freeplay was coming from. I then replaced some of the
selector parts and some of the brass forks with some slightly less worn
parts from a donor gearbox. The end result was a surprisingly improved
shifting action and feel for the driver.
I am a firm believer in doing it yourself. When you learn how the gadgets
work, you will better understand what may be going amiss and what to do to
improve it. A lot of "professionals" rebuilding a gearbox may just replace
the obvious wear parts like bearings and balk rings and put it all back
together with little regard to the shifter parts. When you do it yourself,
you may not just know who to blame, but also who to thank for doing such a
nice job of it.
We should all enjoy the tinker toys.
Barney Gaylord
1958 MGA with an attitude
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