Yes, there are three shafts involved with the gearbox internals. Actually
4 if you want to count the shaft on which the reverse idler gear rides.
Hmm, if I could find my blue TRF catalog, I could give some part number
references here. Oh well, maybe later. Maybe I'll add some pictures and
diagrams and add this note to the tech articles on the Team.Net wiki. Yep,
RealSoonNow.
OK, when the input shaft is turning, all the gears, other than the reverse
idler, are turning. The input shaft is directly "connected" to the cluster
gear, so the cluster gear, or laygear, moves when the input shaft moves. And
the 1st, 2nd and 3rd cluster gears are directly connected to the
countershaft, so they always move when the countershaft moves. So the 1st,
2nd and 3rd gears on the mainshaft rotate whenever the input shaft rotates.
But unlike the cluster gear, the gears on the mainshaft are free to spin on
bushings. So they are all turning when the input shaft is turning, all at
different speeds. When you shift gears, what you are actually doing is
making a mechanical coupling between a splined hub on the mainshaft and one
of the spinning gears. And the shift forks, synchros and such should be
set up such that at most only one of the gears is selected at any given time.
So when you "change gears" you aren't moving any gears, you are moving one
of the two hubs into or out of engagement with the gears. The gears
themselves don't move, other than whatever endfloat is present.
When you select 4th gear, the hub connects the input shaft directly to the
main shaft. But the input shaft is still spinning the counter gear cluster,
they aren't doing anything, just going along for the ride.
When one selects reverse, you do actually move a gear, the reverse idler
gear mentioned earlier. The shift fork pushes the gear into contact with
the reverse gear teeth on the cluster gear and the reverse teeth on the
splined hub. So all the other gears are still spinning in the forward
directon they always turn, but the hub on the mainshaft is turning in
reverse, and since the hub is splined onto the mainshaft, the mainshaft
goes backwards along with the hub, and the car goes backwards.
The layshaft is the part that the counter gear, cluster gear or laygear, which
ever name you call it, spins upon. Unless the layshaft bearings are toast, in
which case the gearbox makes lots of noise as the various parts become
crude cutting tools. I should take some pictures of a few, uh, choice
layshafts I have laying around, now used as "suitable drifts" on occasion.
Gee, now that I mention it, I have to find a new 17 tooth laygear for a
customer car that had badly trashed bearings, and really destroyed the
laygear. I better make some phone calls in the morning.
Hopefully this will help you better understand how the transmission works.
--
mjb.
http://fatchancegarage.com
"Where you've been is good and gone, all you keep is the gettin' there."
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