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trouble getting 5sp into first

  #1  
Old 02-08-2008, 12:08 PM
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Default trouble getting 5sp into first

most of the time only when im down shifting and rolling at a good speed tho. i had the master cylinder checked out when i got my last oil change and dude said it was fine...

is the some kind of safety feature so you dont over ref the motor?

wuts going on?
 
  #2  
Old 02-08-2008, 02:18 PM
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Default RE: trouble getting 5sp into first

The rev limiter will not allow you to over rev the motor.
Do you double clutch when you downshift to 1st?
 
  #3  
Old 02-08-2008, 02:38 PM
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Default RE: trouble getting 5sp into first

nope dont double clutch... never thought of it, i'll give it a shot. thanks
 
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Old 02-08-2008, 02:38 PM
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Default RE: trouble getting 5sp into first

oh, ya... any idea how the rev limiter works?
 
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Old 02-08-2008, 02:52 PM
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Default RE: trouble getting 5sp into first

The rev limiter can't prevent you from over-revving if you downshift.

It's programmed into the fuel injection so itshuts off fuel when the revs go too high. But if you manage to shift into 1st at 50mph, then engage your clutch, the rev limiter is powerless to prevent it from over-revving.
 
  #6  
Old 02-08-2008, 03:10 PM
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Default RE: trouble getting 5sp into first

read synchronizers for a general idea...

http://auto.howstuffworks.com/transmission3.htm
 
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Old 02-08-2008, 03:50 PM
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Default RE: trouble getting 5sp into first

thanks!!
 
  #8  
Old 02-08-2008, 04:27 PM
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Default RE: trouble getting 5sp into first

ORIGINAL: 98accordlx most of the time only when im down shifting and rolling at a good speed tho. i had the master cylinder checked out when i got my last oil change and dude said it was fine...
is the some kind of safety feature so you dont over ref the motor?
wuts going on?
Are you inexperienced with manual transmissions? It's nothing to do with any 'safety feature' or rev limiter.

If you try to change into a lower gear when the road speed is significantly too high for that gear ratio and the lower rpm the engine is currently at, then thesynchromesh will resist you doing so. The synchromesh is designed to automatically synchronise (match) the rotational speeds of the actual gears (of the two gears you're attempting to mesh into each other), but if the rotational gear speeds are very different it won't be able to do so (nor should it).

If you actually managed to get it into the lower gear with the engine rpm much too low for that gear then when you let the clutch out the car would 'lurch' badly when you let the clutch out (unless you did so very progressively and allowed the clutch to slip a lot, which isn't good for the clutch). This is not good as it creates an uncontrolled effective braking force to the front wheels (low rpm engine trying to 'brake' the front wheels, wheels attempting to 'force' an increase in engine rpm), that could cause loss of traction (especially in slippery conditions), and is generally just not smooth or kind to the drivetrain.

In order to engage a lower gear smoothly when the engine speed and road speed don't match reasonably closely you need to 'double clutch' (which is a confusing term because with a synchro box you don't actually need to depress the clutch twice as you would have to with a non synchro box) in order to match engine rpm to road speed for a smooth gear shift, or even any shift at all.

The difficulty is usually greater with a downshift from 2nd to 1st because this is likely to be the largest gap between the ratios in the box (a low first gear to assist easy take off, especially hill starts with a heavy load in the car), but if you can rev match well it becomes possible to downshift into 1st (or any lower gear) from any other gear, so long as road speed won't cause the engine to be at ridiculous rpm when 1st (or other lower gear) is selected.







 
  #9  
Old 02-08-2008, 05:59 PM
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Default RE: trouble getting 5sp into first

ORIGINAL: JohnL

ORIGINAL: 98accordlx most of the time only when im down shifting and rolling at a good speed tho. i had the master cylinder checked out when i got my last oil change and dude said it was fine...
is the some kind of safety feature so you dont over ref the motor?
wuts going on?
Are you inexperienced with manual transmissions? It's nothing to do with any 'safety feature' or rev limiter.

If you try to change into a lower gear when the road speed is significantly too high for that gear ratio and the lower rpm the engine is currently at, then thesynchromesh will resist you doing so. The synchromesh is designed to automatically synchronise (match) the rotational speeds of the actual gears (of the two gears you're attempting to mesh into each other), but if the rotational gear speeds are very different it won't be able to do so (nor should it).

If you actually managed to get it into the lower gear with the engine rpm much too low for that gear then when you let the clutch out the car would 'lurch' badly when you let the clutch out (unless you did so very progressively and allowed the clutch to slip a lot, which isn't good for the clutch). This is not good as it creates an uncontrolled effective braking force to the front wheels (low rpm engine trying to 'brake' the front wheels, wheels attempting to 'force' an increase in engine rpm), that could cause loss of traction (especially in slippery conditions), and is generally just not smooth or kind to the drivetrain.

In order to engage a lower gear smoothly when the engine speed and road speed don't match reasonably closely you need to 'double clutch' (which is a confusing term because with a synchro box you don't actually need to depress the clutch twice as you would have to with a non synchro box) in order to match engine rpm to road speed for a smooth gear shift, or even any shift at all.

The difficulty is usually greater with a downshift from 2nd to 1st because this is likely to be the largest gap between the ratios in the box (a low first gear to assist easy take off, especially hill starts with a heavy load in the car), but if you can rev match well it becomes possible to downshift into 1st (or any lower gear) from any other gear, so long as road speed won't cause the engine to be at ridiculous rpm when 1st (or other lower gear) is selected.








thats exactly what i was looking for

i learned how to drive on a stick, took a brake for a year when i lost my lisence but id say i have a good amount of expirence with a stick, 5 yrs+, but not particurlaly alot of expirence with this car.

so I think basically what im feeling is the synchromesh resistance, because itwont go in (even if it would i wont push it hard enough to get it in), when i feel that i slow down and then put it in. most of the time i dont even downshift into first, i was just curious about what was going on?

that was awsome... ur the man...thanks a bunch
 
  #10  
Old 02-08-2008, 07:36 PM
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Default RE: trouble getting 5sp into first

ok so on the ride home i put some more thought into this....

please correct me if im wrong

and please bear with me, im not savy on all the terminology :P

when you push the cluch in it essentially disconnects the main motor shaft (thats connected to the pistons) from the transmission.

but the engine rpm doesnt have anything to do with getting into gear, it has to do with the transmission rpm.

the tire rpm = axle rpm = rpm of the lower shaft (from the illustration provided by sir nasy... thanks man

each gear has an allowable range of lower shaft rpm that it will synchronize with, and my tires/lower shaft are rotating too fast to synchronize into first gear.

??is that about the jist of it??
 

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