Mis-shifting a manual gearbox...Can it cause any damage?
 

Hi guys,

I recently bought a 190E 2.3-16. Lovely little car. It has the manual dogleg gearbox which is brand new by the way. New clutch and flywheel too.
Anyway its been a while since i drove a manual, and my first time driving a gearbox with this pattern.
My question is...it may sound trivial but i will ask anyway!
I was in second gear and turning into a corner, speed was about 20mph. I tried to shift into 1st but i must have somehow shifted in between 1st and 3rd gear because i heard a kind of groaning noise.
I depressed the clutch and shifted firmly into 1st.
Will this have caused any damage? Can this kind of mis-shifting do any harm.
I will be more firm with my shifts in the future as this gearbox can be a bit stiff.
Any input appreciated!

Sounds like you didn't get it into gear all the way, let the clutch out, and ground the syncros a bit. What you heard is basically the syncronizer teeth grinding together because they had not been given enough time or force from the gear lever to mesh completely before the clutch was released.
This is certainly not the recipe for longevity of a tranny, but they can take a few gear crunches at low speeds with no real permanent damage.
Don't worry about it, just don't do it very often.
The classic symptom of worn/damaged syncros is notchy shift feel, kickback on the lever, difficulty going into gear, or more grinding, even with a good shift motion. if it still shifts fine, forget it.

Oh, one of the toughest things on the syncros is a downshift to 1st while just coasting down at, say 20MPH. The low engine speed and lower gear ratio of 1st gear makes the syncros work hard to match the gear and the engine speed.

DG

Thats exactly what happened S class guru.
On another note...My friend tonight revved the car whilst it was in neutral and idling to around 7,500rpm for about a second then let go of the accelerator. The red line starts at 7,000rpm.
Will this have caused any damage at all?

Anyone who rev's their engine to 7,500 rpm's in neutral should be thrown out of the car on their head. And yes it could have been catastrophic, but you surely would have known if damage was done.

Well it seems to be fine.
I dont know what he was trying to prove. But i saw it go over 7,000rpm for a split second, then he let go of the gas.
Drove it afterwards and it drove fine. Just a bit concerned about any lasting ill effects of his over zealousness.

The sound you heard was the synchros working extra hard to keep the gears from crunching. You were making it work harder than you really should. Just let the car slow down a bit before slipping it into gear and it will snick in with no whining.

Sounds like a nice car.

Tom W

Thanks Tom.
Would revving the engine like this have done any damage?

It is never good to rev up a motor beyond the red line. The danger is that the valves will go beyond the limit of control by the springs and "float" away from the cam shaft. When that happens the valve can impact the piston when it comes to the top of its travel, bending or breaking the valve. If the valve gets bent it will not seal correctly (or worse). improper sealing will lead to a burnt valve eventually. If the bend is severe you will have a heavy miss right away. If it happens to be slight you might not have much of a miss at first but soon it would get worse.

Is the car missing at all? If the idle is completely smooth you may have gotten away with a foolish act by your friend.

If the valve had broken there would be piston damage too. A bent valve could also cause piston damage as well.

If the car develops a miss in the next month or so you will have to do more investigation.

Good luck.

Tom W

Would damage occur even if it was in the red line for less than a second?
Its not missing or anything.
The idle is smooth.

One of my rules about downshifting in normal, everyday driving is to never put it in 1st gear if I'm moving more than about 10 MPH. Of course, this is dependent on the gearing of the particular vehicle. Another way to look at it is to watch the tach when you're slowing and downshift each gear when it indicates about 700 RPM above idle.

If you're driving in competition, this goes out the door as the speeds will be much higher and will require a fairly agressive double clutch to save the synchros from undue wear. In any case, you shouldn't feel an apreciable thump in the gear lever as it goes into gear.

Here's a question for your question - why do you think somebody bothered to put a 'red line' on your tach? Why did they put a red line on your temperature gauge? If there was no risk to your vehicle running it over those limitations, why do you think they would bother?

First gear is just there to get you going from a stop - imho you should only select 1st if you are planning to do that, otherwise 2nd will do and the damage to the gearbox is minimised. Shoving it into 1st at 20 m/h will kill the box, sooner or later.

Maybe you should sell your car to your friend?

Tough crowd!

hey go easy on the new guy!

If he knew these answers he wouldn't ask. Sometimes we all ask questions hoping that the answer is different from what we already think we know in our gut.

Tom W

Thanks Tom for speaking out what I also thought. Most of the times I am reluctant to post, being not knowledgeable in the (in others' eyes) most trivial issues.

I learn a lot from this forum and find many skillful and helpful people.

Thanks Tom.
We all have to start somewhere :)

But back on topic. I was doing some research on other forums and it turns out that some guy did this to his car and it cooked the flywheel. Hmm.
The car is behaving fine, but worst case scenario is damaged valves?

I cannot imagine how he would cook his flywheel doing what your buddy did.

This forum is a fantastic resource. When I was coming up I was lucky to have a father that could do about anything with his hands from plumbing to carpentry and fixing about anything on a car. So I learned a lot from him. The rest came from books or just tearing things apart and figuring out what needed done.

Having this place is like having twenty doting uncles just waiting for you to call and ask for help.

I have done a lot on cars but there are plenty of things I have never done and I can ask here and almost always find a good answer.

Sources for parts and expertise are another excellent thing to get here.

Keeping an older car on the road is easier now than ever before.

Thanks, Al Gore! (couldn't resist)

Tom W