DD_545i

I was wondering how a dying clutch behaves just prior to it giving up. Does it fail to engage, thereby leaving you in gear when you'd rather have the drive being disengaged by the clutch? Or is it the other way around (which I suspect to be the case)? As in, you want to get drive but as you rev, the clutch will fight you and you don't get any drive engaged. It would seem like this is the safe way to go (in a train's dead-man's switch kind of way).

I ask because as I was reversing out of the garage today, which normally involves me putting it into "R" and taking my foot off the brake. The tickover revs is enough to get me going and out of the garage at an ideal speed. Today, I noticed that I was going slower than I wanted as I was coming out of the garage (might have all been in my head, but it seemed slow). So I gave the throttle pedal a quick blip. What would normally happen when I do that, it would get me going a bit faster. Today though, even though I was in "R" and moving, instead of having the effect I expected. It just raised the revs and made no difference at all.

So that made me contemplate what signs to look for. I've never had a clutch die on me in 20 years of dying. Maybe because I never keep the cars long enough, and most of them have been manual/stick. This one's automatic.

So if my clutch does start to fail, then I imagine that when I'm at a traffic light, I'll either be having to press the brake harder because a failing clutch doesn't suppress the drive as much as it should. Or, when I want to get going and floor it, the failing clutch will result in higher revs and less drive. Or could a clutch fail in either of those ways.

It's actually probably fine, but it'll be good to know.

craigm1841

I am confused. In what way does a clutch supress drive? Your braking should have nothing to do with your clutch. If the car is in gear and you hit the throttle and the revs jump but the car only slightly increases in speed, you are looking at a bad clutch on a stick, slipping transmission on an auto.

To be honest, when I saw this thread, I assumed you had a MT. when I read your last paragraph about braking and clutches supressing drive (which a clutch will never do), I thought you have an automatic, in which case it is a transmission problem or even your torque converter. If you have SMG, I am not to familiar with the workings of that.

This would probably do better outside of the lounge, but I never set foot in any forum other than the lounge around here. Is your car Auto, SMG, or MT? I can provide more insight if you let me know that.

DD_545i

It's regular auto (not even sport auto). If you're in drive and you're stopped with your foot on the brake, then the clutch is partially engaged, isn't it?. Or not? Now I rethink it, I guess it is just the engine (revs) v brake. The clutch probably doesn't get involved.

So you're saying that if I'm in gear and I rev and get less reaction than I expect, then it's more of a torque converter issue than the clutch.

craigm1841

Automatics dont have clutches, they use torque converters. An automatic transmission is always engaged when in gear. If you ar giving it gas, and not getting an equal response from both the engine and driveline, you may be looking at a slipping transmission or torque converter issue, more likely a slipping tranny.

Try this... Put your car in drive, turn off traction control, put your foot on the brake, and slowly give it gas. your car should rev a bit, but you should feel equal force pushing you forward. Your car will eventually move forward. If you are able to get a response of more than 2K RPMs or so without your car either pushing forward or spinning your back tires you have a slipping transmission. Your front brakes are much stronger than your back, so with a rear weel drive car, it is easy to determine if the tranny is slipping.

DD_545i

Thanks for the education.

I'll give that technique a try. I think I can remember how it felt the last time I tried doing that (for a spirited start that I did to film this animated gif below). So far I've only noticed that one blip in an otherwise faultless experience so far. It could easily have been an over-reaction to something that was nothing. Maybe my throttle blip was so short and that was why I got no reaction to it (while reversing out of the garage).

craigm1841

If you had just started the car seconds before, it may have just been a bit sluggish. I am well versed car drivetrains and understand them very well, I am not 100% sure why the transmission or torque converter is very sluggish the first few seconds a car is running. If I am in a rush and throw the car in drive and take off 3 seconds after starting it, it can feel like the driveline isnt matching the expected RPMs, but this subsides immediately. You may also not be entirely familiar with the gear ratio of "R", as it is geared MUCH higher than 1st gear. This is so you can get out of sticky situations with a powerful low-end, but it limits your top speed to a guestimated 20 MPH because driving in reverse is dangerous. You can also damage your rear-end in reverse, as the gears arent designed to work clockwise. reverse is more of a neccessary evil.

Id say it isnt anything at all. Try my test, just do it in a safe place with nothing around.

DD_545i

I hadn't known that about the first few seconds. It was definitely a start/throw/drive/3 seconds scenario like you described above. I won't get to try it until saturday, but will report back

DD_545i

Tried it today. TC off, foot on brake, 1st gear. Plenty of force trying to break free below 2K. Not sure when the rear wheels started spinning - must have been around 2K-2.5K. I definitely didn't get any kind of slipping transmission feeling.

Seems like it was the start/engage/go-too-quick scenario as you described.

Cheers

craigm1841