Manual Trans. Clutch system hydraulics?

When I engage the clutch in 1st gear, it seems like the clutch is font fully separating from the transmission. For instance when im in 1st, clutch down, and rolling down a hill, I can hear the transmission turning. This seems to happen in 1st and 2nd... also sometimes the shifting in 1st and 2nd are rough or out of sync.

Could this be due to low hydraulic pressure in the master and slave cylinders? Sometimes my master cylinder makes a creaking noise that sounds like metal to metal...it does not sound like the normal pedal creak. so im guessing it may need replacing.

Any advice appreciated.

 

I think our manuals aren't completely manual for some reason. You can hear the transmission adjusting when you just hold the stick up to the gear, it's just more pronounced in 1st. It's like a sync gear needs a bit of time so it starts automatically adjusting before you're in the gear, or if the clutch is fully depressed and you're already in the gear it doesn't fully let it go. That's why it's rough if you try to shift too fast. Just a strange observation.

My wife's manual 5 series is nothing like this 6 speed. My observations about the tacoma are in relation to that BMW transmission. The clutch points are so far off between the two it's confusing to hop out of one and get into the other.

 

Hrmm that is strange. Also ive noticed that when I am in first or second....and the clutch is down, and im rolling over a bumpy surface, I hear feedback from the road in the tranny. I was wondering if this is common too. I havent really driven any other 2nd gen 5 or 6 speeds

 

What you're describing (and hearing) is the cone clutch (usually brass, not sure about the current 6 speed) matching the speed of the dog gear to the speed of the gear you want and the shaft it's on (mainshaft or layshaft). The initial difference in speed between the dog gear, the locking rings on the shaft and desired drive gear results in a torque difference between the two parts, preventing the dog gear from engaging the selected gear.


One the speeds of the parts have matched (synchronized) there is no torque differential between the parts, and the dog gear can engage and you're "in gear".


It is a manual transmission - the gearbox won't select, disengage or engage a particular drive gear for you. What it will (try) to do is keep you from forcing the lugs of a dog gear into the corresponding locking rings of a gear and shaft before the speeds of all the parts have matched up. Why it's louder in low gears, I'm not sure. I would imagine it has to do with the shaft those gears ride on and their relative size vs. speed inside the gearbox. You're really not "changing" gears (except for reverse) - all the gears are always meshed together (helical cut gears). You're more or less changing which part of the shaft is engaging with a particular gear, or like with 4th gear (usually it's 4th) (1:1) changing the interconnection between shafts (main and lay).


This crap is hard to visualize (for me). Whenever I've wanted to understand junk like this, I either go buy a part at a yard, take my own crap apart, or help someone fix their broken junk so I can get my hands on it.

 

if i am in first gear and push the clutch in, i can still hear the trans whining like it is in gear if im rolling down a hill...my 6sp civic si did this too...i'd say it's normal

 

Really? Our E60's 6 speed absolutely disengages with the clutch and if you dump it the car will let you know. Nothing engages before the clutch release.

I don't remember how my last manual (Celica) handled it.

I'm 50/50 if it's normal.

 

The transmission should still be spinning if its in gear since the wheels are spinning the transmission

 

ok, all the clutch does is separate the engine and transmission. if you are in first gear, the trans is in first gear. rolling down a hill in first, clutch in, means the transmission is still in first, it just doesn't turn the motor.

now, to make it interesting, imagine that you had a crawl-box and were in low/low and first gear, going down a hill. with the crawlbox, say 10:1 reduction. go down a hill, clutch in, and you could turn your input shaft fast enough to destroy a clutch. (centrifugal force)

with that in mind, coasting clutch in down hills in low gears is not the best idea

 

Thanks for the input gentlemen. Makes sense. I do visualize (for the most part) what you are saying obscurotron. In my old truck (ranger) I never heard it in the first 2 gears, but it has a different design too. ( a crappier one). Ive never rolled my trucks at any dangerous speed in low gear with clutch depressed, but maybe its just a lower speed = more noise by design in the taco. Its like 5mph in 1st here.

Although I do need to troubleshoot that clutch system. Im still getting a creak, and I dunno if its the slave cylinder or the bearing lever. Seems to be on the outside of the cab. I just need to get someone to actuate it whilst I look at the slave.