In a message dated 1/8/98 4:47:36 PM Eastern Standard Time, boballen@sky.net
writes:
> I later was reading some hot rod magazines and it confirmed what I had
> discovered but disbelieved earlier. To wit, the Camaro and Firebird
> 6-speed trannys are less than desirable for the hot-rod retro-fitter set
> primarily because GM specified a wedge in the case casting specifically
> to offset the tranny a little closer to the driver. Why? So the shifter
> would poke up into the cockpit in the desired place.
Bob. Larry, and others,
Whatever did we do before the internet? After reading Bob's post, I went back
and re-read the January '94 article in Car Craft magazine on swapping the T56
tranny into Firebirds, Camaros, and Mustangs. Indeed, the shifter is relocated
to be closer to the driver, but it is done by rotating the entire transmision
around its center axis by 18 degree. This is accomplished by placement of the
mounting holes in the bellhousing. Nothing was mentioned about an angle
offset, and nothing was covered about this in the crossmember fabrication
instructions.
I think it is pretty reasonable to assume that the centerline of the
transmssion is parallel to the engine center line, although the output shaft
"could" be displaced laterally. I could see no evidence of this, but even if
so, the parallel requirements would still be met for the entire drivetrain as
long as the differential, transmission input and output shafts, and engine
centerline are parallel. If the transmission shaft angled with respect to the
engine, I would think all kinds of bad wear patterns would result. I think we
all know how critical it is that the pilot bushing is centered up with the
pilot shaft. If the transmssion is angled, then the engine would also have to
be.
As far as I know, there is no requirement that the pinion shaft be
perpendicular to the rear axle shafts, provided the ring and pinion were
machined properly, but I don't know of it ever being done any other way. Thus,
if the transmssions is angled, then the driveshaft cannot be phased properly.
I'll freely admit that I have no first hand knowledge of any of this, and I
have never knowingly ridden in a car with an improperly phased drivetrain. I
do know of one instance in which a person experienced severe vibration after
swapping a V8 into an older car. When asked if he phased the drivetrain, his
reply was "nah, that ain't got nothing to do with it!" I only know that for
the last 40 + years I have read countless articles expressing the need for
phasing, and don't recall any that said otherwise (with one big exception - on
very high powered drag racers, the pinion is purposely set low so that when
hit with the extreme torque of the 2000 - 5000 Hp engines, the uncontrollable
tendency of the pinion to climb the ring will put the pinion at the correct
angle).
This may be one of those myths that are perpetuated form time to time, but
just from thinking about how the u-joints work, I don't think so. Just trying
to rotate a u-joint in your hand, you can see and feel the variations in
rotational speed as it rotates. The larger the angle, the more pronounced the
variation. If one u-joint is running at a steep angle with a high variation,
and the other is running at a small angle with low variation, they could not
possibly cancel out. Of course, the real question is "how much is too much?"
Maybe there is enough rubber in the mounting parts in a Camaro that the whole
body is numb with respect to what's going on down under, so a slight vibration
in the drive train is not a bother. Remember the "odd fire" Buick V6? It
wasn't till they started putting those things into luxury cars that the
vibration was a problem - for us po' folk driving commoner's cars, it was good
enough. Sorta like losing sleep because some one put a pea under your mattress
- only a problem for a Little Princess.
If there were only a few electrons involved......!
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://www.sky.net/~boballen/mg/Masters/
'74 MGBGT---3000mile/year driver, original condition, slated for a V8 soon!
'68 MGBGT---organ donor for the '74
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