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#1
08-01-2009, 06:29 PM
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Manual transmissions transmitting power in neutral?
So I've tried and failed to replace the transmission in my 240d (due to missing parts).
While doing so, I noticed that the output shaft still spins even in neutral. It's not directly connected, since I can grab it with my hand to stop it even when the engine is running. Afterwards I compared both transmissions on the floor, by hand (turning input shaft and output shaft). The original transmission also does the same, but with less resistance. So does this mean anything, or is it normal? 
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#2
08-01-2009, 06:54 PM
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Remember that the input shaft drive gear meshes with the countershaft drive gear which drives all the counter shaft gears which then meshes with and turns all the speed gears. So the output shaft has all the speed gears moving on it any time the input shaft is moving.
In Neutral the hubs aren't connected to the speed gears via the synchronizer rings and sleeves so the output shaft moves but can be stopped with your hand. It's simply inertia and momentum that drives the output shaft in Neutral.
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#3
08-01-2009, 07:19 PM
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Viscous drag between parts.
__________________
 Gone to the dark side - Jeff
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#4
08-01-2009, 08:11 PM
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Yeah, it's just minor friction, it's normal.
__________________
1983 240D 3.0T 4-speed manual, now sold  1989 Subaru GL Wagon 5-speed Touring Edition
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#5
08-02-2009, 02:18 AM
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My outboard boat motor does the same thing. When it's sitting on the deck getting flushed in neutral the propeller slowly spins. If I rev it up it spins faster, but if I put my foot in the way it stops easily.
__________________
Dale http://i52.photobucket.com/albums/g1...MG_2277sig.jpg 1990 300D 2.5 Turbo -155k 2000 E430 - 103k 2014 Jeep Grand Cherokee Ecodiesel 4x4 - 11k 2014 VW Passat TDI SE - 7k Bro's Diesel 2006 E320 CDI - 128k Pop's Benz Pre-glow - A moment of silence in honor of Rudolph Diesel
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#6
08-02-2009, 04:21 AM
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Normal, internal friction.
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#7
08-02-2009, 11:49 AM
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I think a diagram is in order here
 I started typing a description, but I the above is about as descriptive you can get without pictures. Are those journal bearings or roller bearings that the gears on the output shaft ride on? The differences you noticed between the two transmissions could be differences in the lubricating oil or differences in wear in the bearings.
__________________
1985 300TD-euro 352,000 mi 1974 240D (1?)52,000 mi - has a new home now
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#8
08-02-2009, 04:31 PM
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In neutral, the transmission acts something like a torque converter--the input gears turn the oil and the oil turns the output gears. The effect is most noticeable when the transmission is cold and the oil stiff.
__________________
 "Buster" in the '95 Our all-Diesel family 1996 E300D (W210) . .338,000 miles Wife's car 2005 E320 CDI . . 113,000 miles My car Santa Rosa population 176,762 (2022) Total. . . . . . . . . . . . 627,762 "Oh lord won't you buy me a Mercedes Benz." -- Janis Joplin, October 1, 1970
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#9
08-03-2009, 11:08 PM
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Quote:
Wikipedia has a good sequence of schematic type of images, lifted from here: http://en.wikipedia.org/wiki/Manual_transmission Here's the neutral position, I don't want to post a pic of every gear, but they're all at the above link. In this pictures, the orange shaft at the upper left is the input shaft and the yellow shaft is the output shaft. 
__________________
1985 300TD-euro 352,000 mi 1974 240D (1?)52,000 mi - has a new home now
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