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Old 01-23-2008, 08:55 AM   #1 (permalink)
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SAAB's (old) freewheeling manual transmission

elhigh posted this in a thread about P&G (pulse & glide):

About a thousand years ago my Dad had a 1970 SAAB 96, and one thing about it that always drove him crazy was the freewheeling clutch - it would keep popping between settings and that made it hard to drive.

But most significantly, that thing would've been the owl's howl for P&G - tap the gas to go, let up to coast. Is anyone making a slipper clutch that could be bolted into a modern app? Like an '87 Toyota truck?
And it reminded me of a post that someone had made at teamswift with more detail:

my personal driving technique comes, largely, from having driven vintage saab cars with "free wheeling" built into their transmissions. their operation included inherent coasting while you were off throttle, a vestige of the 2 stroke powered cars that had oil mixed with the gas. if you were off the throttle and used the engine for compression braking, the engine effectively had no lubrication and would sieze up. they used the same highly efficient front drive transaxle in the later model 4 stroke powered cars so the "free wheeling" mode remained and was just super for winter driving.

the point to my explaining the saab stuff is to illustrate the point that i have no compunction about coasting, out of gear, legal or illegal. the saab had an over running clutch that allow the input shaft of the tranny to disconnect from the engine (after the normal clutch) if the input shaft ran faster than the engine's crankshaft. if you let the engine drop to idle, the tranny just rolled along at road speed. the system allowed smooth re-engagement when you pressed the throttle and matched crank rpms with the input shaft speed.


the old saabs had a lock out lever way up under the dash. you basically had to stop the car and get out of the seat to engage or disengage the lock out.

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Old 01-23-2008, 03:32 PM   #2 (permalink)
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VW and quite a few other 70s/80s manufacturers had that setup. I bet it was from the same parts supplier and could be retrofitted, although I wonder if the tcc could be kept.

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