I drove my TR6 again last night. This is the car in which I installed a
rebuilt engine several weeks ago only to have the transmission fail, the
starter die, and a strange noise come from the rear end.
Despite Scott Paisley's advice that I give the transmission one more
chance, the exhaust pipe was still warm as I got on the phone with TRF
and ordered a rebuilt transmission. I appreciate your logic, Scott, but
with a fresh, souped up motor under the hood, I just didn't want a
transmission on it's last legs---I wanted something I could have
confidence in. And, after having had the transmission out of the car
four times in as many years for one reason or another, I wanted things
sorted out right for a while!
I had the starter rebuilt locally for $75---half the price that TRF
wants (plus core). I asked the grease-smeared gentleman at the counter,
"Did you replace the bushings?" "We went through the whole thing."
"Did you rewind the armature?" "We went through the whole thing." The
establishment doesn't actually have a dirt floor, but it wasn't much
more civilized looking than that. And the paperwork associated with the
transaction consisted of a single 3x5 yellow sheet with carbon
scribblings and "Paid" on it. But they gave me a year guarantee, and
they actually come highly recommended from other local motorists. So
I've got my fingers crossed, but the thing does spin the motor a hell of
a lot better now than it used to.
But then there was the noise from the rear end. The noise started after
about 5 miles of around-the-block driving, just after 2nd gear started
grinding and screeching on the old transmission. It was one "ka-chunk"
per revolution, and seemed to come from the vicinity of the right-rear
wheel. I immediately suspected that either I had failed to bolt the
half-shaft to the differential correctly or that a bearing cap had come
loose on a universal joint, allowing the web to slide out. This was a
substantial noise that started quietly and grew loud within about a
hundred yards. It persisted whether I was on or off the throttle in
gear or just coasting.
I disassembled all of the pieces of the drive train and examined them
all externally. It had all been bolted together solidly, all of the
universal joints were intact and tight (they only have about 3K miles on
them), and the wheel bearings were tight and quiet. A car builder/racer
friend suggested I examine the differential for a broken ring-gear
tooth. I examined it externally, holding alternate output shafts tight
and turning the input shaft, and then holding both output shafts tight
and turning the input shaft. There is a fair amount of play in the
differential, and I know from experience that unequal torque is sent to
the output shafts on smooth, dry, level ground. But the differential
was quiet, and there was no slip or "chunk" that you'd expect from a
broken gear.
So I lub'd everything, replaced the trailing arm bushings (the new
bushings have been sitting quietly in a box for 3 years, waiting for me
to install them) and put it all back together. This has been a long
project, and I just didn't have the stomach to start tearing things
apart and replacing parts that appeared to be in perfect order. Since
the noise was persistent, regardless of the load condition, the
differential seemed the least likely suspect, and I reasoned that it
couldn't be too difficult to tear a half-shaft or wheel bearing back
apart if I could later determine exactly where the noise was coming
from. Since I rebuilt the wheel bearings myself 3 years ago, they seem
to me to be the most likely candidates---although the "ka-chunk" was an
awfully severe noise to be coming from a smooth-turning, tight wheel
bearing.
So anyway, I drove it last night! I'm still waiting on some fiddly bits
associated with attaching the shift rod to the new transmission to
arrive from TRF, so I couldn't do any real driving---but I got it
together enough to select gears slowly and gingerly, and that suited the
way I wanted to test things anyway. The new starter sounds better than
ever, the new transmission is silent...
...and so is the rear end.
So, all-knowing friends, what do you think the noise was?
I only drove around the block once, because it was late, because the
shifter was so vague, and because, damnit, I wanted to have at least one
Triumphant night, not filled with angst. Perhaps I'll expand my travels
tonight, gingerly exploring the performance envelope, seeking---but
hoping not to find---the combination of conditions that evokes that
awful "ka-chunk ka-chunk ka-chunk ka-chunk ka-chunk".
Thanks for the advice and encouragement I received after my last TR6
saga posting. I'd still like to hear advice on tuning the stock ZS
carbs and the ignition for a Kent (S2 equivalent) Fast Road cam and
9.5:1 compression. The car runs rich, the idle is lumpy, and I can't
get it to idle lower than 1400 RPM.
Happy Motoring (at last!)
Kevin Riggs
(205) 730-3074
work@riggs.b30.ingr.com
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