[nukezero]

okay i have a 6mt 335i and today this is what i did.

I was coming to a complete stop almost but slowed to around 5mph about to make a left turn quickly before the other oncoming car comes.

While the car was technically still rolling foward at 5 mph in neutral, i accidentally put to reverse instead of first gear. I slowly released the clutch and the car began to decellerate real fast but I never engaged the gear. i then realized i wasnt in first but was in reverse. it jusr felt like the clutch got slightly burned from trying to engage but couldnt.

There was no grinding, knocking, or shock from anything. did i damage the transmission?


The car drove fine. The besr way to describe it is like I am on a hill and rolling backwards and in first gear trying to take off going foward. But now reverse the scenario, instead of rolling backwards and in first gear, I am rolling forwards and trying to take off in reverse. Does this damage the transmission in any way?

I was really surprised I was allowed to shift to reverse when the car was still moving forward.

Thanks

[AndreyT]

You didn't damage anything, besides putting a bit more wear on your clutch than usual. But again, this amount of wear is probably smaller than a panicked uphill start does.

The fact that you managed to actually put it in reverse says that the forward speed was completely unremarkable.

[Red_Bean_Bun]

Did that once but the car was going forward at 15mph. After which the dash threw a sign with a clog.

Restarted the car and the error went away.

[nukezero]

Maybe I don't understand how transmissions work in general. But I want to ask a few questions and hopefully someone can answer this:

This is ONLY for 6 MT manual transmission, not automatics.

1. The flywheel and clutch both move the same direction regardless of going forward or reverse. True or false?

2. So if you are going in reverse, the clutch is still moving the same direction as when you are going forward?

3. The wheels are connected to the driveshafts which are connected to the tranny gears, which are connected to the clutch disc. So in that sense, when the wheels are moving, many of the transmission gears are moving with it? regardless of whether or not the clutch/flywheel is engaged?

4. So is it technically possible, if you roll a car downhill at 80MPH... but just before you started to roll, you put the gear into Reverse, and someone push the car downhill, all while you are holding the clutch pedal down.... Is this still okay? Now, what happens when they tried to slowly let the clutch out? Would the clutch just not engage ever, until the car reversed direction or would the clutch burn up? or would the transmission blow up?

5. I thought that the wheels are hard connected to the motion of the clutch?? So that if you immediately try to reverse direction, the transmission would blow up?

6. I'm still not understanding exactly how when I was moving forward while in reverse, letting the clutch out, the car was decellerating fast yet there was no transmission shock? Is it because the clutch and flywheel were not engaged? If so, I thought these two devices were spinning in the same direction? Unless, they are not spinning the same direction when the car is in reverse? If that is the case, then, someone else inside the transmission must be "slipping" to allow this to occur.

Just exactly what else would be "slipping" within the tranmission to allow someone to feather out a reverse gear, while the car is moving forward with no damage?

[Ethanderall]

2: No, the clutch moves in the same direction in forward or reverse GEAR, but the WHEELS change direction. Thus, if you manage to engage reverse gear while moving the WHEELS forward, the clutch plate will spin in the opposite direction of the flywheel and pressure plate.

If you disengage the clutch while moving forward in reverse gear, there is nothing to slip in the drivetrain besides the clutch itself, which is why a previous poster said you will have increased the wear on the clutch plate.

[Three_thirty_I]

At this low-ish speed nothing really to worry about, and the fact that there was no real crunch sound from the gearbox means that the syncros were able to cope as such. Clutch from such a brief moment should really not have taken too much of a pounding, as said, not more than a hasty pull off on a steep hill. At least reverse is situated on that side of the gate instead on where you could potentially being hauling along in 6'th!

[pimp4cheddar]

Thought this was a very X-Rated thread due to the title.

Because if there's one thing I know...its Trannies!

[DFW_M]

Originally Posted by nukezero

okay i have a 6mt 335i and today this is what i did.

I was coming to a complete stop almost but slowed to around 5mph about to make a left turn quickly before the other oncoming car comes.

While the car was technically still rolling foward at 5 mph in neutral, i accidentally put to reverse instead of first gear. I slowly released the clutch and the car began to decellerate real fast but I never engaged the gear. i then realized i wasnt in first but was in reverse. it jusr felt like the clutch got slightly burned from trying to engage but couldnt.

There was no grinding, knocking, or shock from anything. did i damage the transmission?


The car drove fine. The besr way to describe it is like I am on a hill and rolling backwards and in first gear trying to take off going foward. But now reverse the scenario, instead of rolling backwards and in first gear, I am rolling forwards and trying to take off in reverse. Does this damage the transmission in any way?

I was really surprised I was allowed to shift to reverse when the car was still moving forward.

Thanks

I am surprised that you can put it in a reverse "just like that"...especially if not fully stopped.
I am thinking that you actually did put it into the first and it was the engine braking effect you felt...

[Otruba_843]

Originally Posted by pimp4cheddar

Thought this was a very X-Rated thread due to the title.

Because if there's one thing I know...its Trannies!

When I was 5, I always wondered what happened if you shifted a car in reverse at 70 mph

[driverman]

No damage, no worries.

[SubzeroVR4]

I managed to do that on my 30000GT VR-4 6spd. I meant to go into 6th but instead hit reverse very very briefly and I decent feedback from the shifter like it was going to grind and I realized it was about to shift to reverse at 70mph.

I'd say you're fine. I'm not sure about BMW MTXs, but I didn't think there was any synchronizer for reverse so it would be nearly impossible to actually engage it at any speed above 3-5 mph.

[Kernel Kurtz]

My understanding is that reverse is synchronized in BMW transmissions.

The additional wear from doing this one time would be negligible.

[AndreyT]

Originally Posted by nukezero

1. The flywheel and clutch both move the same direction regardless of going forward or reverse.

That's correct. Well, depending on what you mean. Engine flywheel always spins in the same direction. So, when the clutch is engaged, the clutch will also spin in the same direction. But when the clutch is disengaged, it can spin in any direction, depending on which way (forward or backward) the car is rolling and which gear (forward or reverse) is selected.

Originally Posted by nukezero

2. So if you are going in reverse, the clutch is still moving the same direction as when you are going forward?

If you are going in reverse with reverse gear selected, the clutch is spinning in the same direction as when you are going forward with forward gear selected.

Originally Posted by nukezero

3. The wheels are connected to the driveshafts which are connected to the tranny gears, which are connected to the clutch disc. So in that sense, when the wheels are moving, many of the transmission gears are moving with it? regardless of whether or not the clutch/flywheel is engaged?

That's correct.

Originally Posted by nukezero

4. So is it technically possible, if you roll a car downhill at 80MPH... but just before you started to roll, you put the gear into Reverse, and someone push the car downhill, all while you are holding the clutch pedal down.... Is this still okay?

Well, yes, it is OK, as long as you are holding the clutch pedal down. However, reverse gear is a low gear. If you make the car roll at 80 MPH is such a low gear, the disengaged clutch will achieve such high RPMs that I'd say all bets are off. Something might just get torn apart by "centrifugal" forces. The same concern would apply in 1st forward gear, for example.

Originally Posted by nukezero

Now, what happens when they tried to slowly let the clutch out? Would the clutch just not engage ever, until the car reversed direction or would the clutch burn up? or would the transmission blow up?

The clutch will slip, wear and burn up, simultaneously forcing the engine to spin faster and, possibly, making the wheels to skid. What exactly will happen depends on how aggressively you release it and how strong the parts are. A very aggressive release might damage the transmission and/or the engine. Or it might simply lock up the drive wheels and make them lose traction.

Originally Posted by nukezero

5. I thought that the wheels are hard connected to the motion of the clutch??

That's correct, as long as the transmission is in gear (not in neutral).

Originally Posted by nukezero

So that if you immediately try to reverse direction, the transmission would blow up?

The transmission will receive tremendous loads. It might blow up, yes. Or the clutch might overheat and start slipping. Or the wheels might lock up and start slipping. I.e. something has got to give, but it is hard to predict which part will do it first. Several variables are involved.

Originally Posted by nukezero

6. I'm still not understanding exactly how when I was moving forward while in reverse, letting the clutch out, the car was decellerating fast yet there was no transmission shock?

Well, you clutch engagement was probably not as aggressive as you thought it was. On top of that the CDV (clutch delay valve) could've made the engagement more gentle for you, i.e. even if you released your clutch pedal quickly, the plate itself was engaging relatively slowly.

Originally Posted by nukezero

Is it because the clutch and flywheel were not engaged? If so, I thought these two devices were spinning in the same direction? Unless, they are not spinning the same direction when the car is in reverse?

The car was rolling backward with reverse gear engaged? No, they were spinning in opposite directions.

Originally Posted by nukezero

If that is the case, then, someone else inside the transmission must be "slipping" to allow this to occur.

Manual transmission has only two points of slippage: the clutch-flywheel contact and the tires-road contact. There's noting else.

Originally Posted by nukezero

Just exactly what else would be "slipping" within the tranmission to allow someone to feather out a reverse gear, while the car is moving forward with no damage?

Clutch. At your speed the tires probably didn't slip. That leaves the clutch.

[iconfat]

Correct me if im wrong but i understand you shouldn't ever be downshifting into first. It's a take-off gear only.

[nukezero]

Thanks guys, I think from what I'm hearing now, in my scenario, both the flywheel and clutch disc were spinning at opposite directions at that moment in time. Since I had the reverse gear engaged, but car was moving forward, the clutch now wants to spin the opposite direction of the flywheel.

I am pretty positive, I went into reverse based on when I removed the gear out and because like I said, I was able to get into gear (which I thought was 1st), slide out the clutch and gave it some gas, but the car wouldn't move, just decellerated even more and felt like I was trying to take off on a steep hill.

BTW, I still have CDV - guess I'll keep it in there for mistakes like this!

So I take it that in the following situations, the clutch and flywheel spin the opposite direction for a brief moment in time, which increases wear:

1. Rolling backwards on hill, in first gear, trying to take off going forward

2. Rolling forwards on hill, in reverse gear, trying to take off going backwards

Originally Posted by iconfat

Correct me if im wrong but i understand you shouldn't ever be downshifting into first. It's a take-off gear only.

Really? I don't think so, there are some cases where I'm in such a low speed in the parking lot that if I use 2nd, the RPM would be so low I'd nearly stall. Even though the car is still rolling.

[Three_thirty_I]

Technically not suppose to gear down to 1st while driving, for instance if you are about to take a sharp low speed turn going from 3rd to 2nd - not suppose to drop down to 1st in the same manner. But in the case of driving in a parking area for instance and you find that the speed is a bit too low (especially if on an incline), then slow down and gently change to 1st, and then stay in 1st until you know that your car's speed is going to be higher enough for a higher gear. Basically anything faster than walking pace is not ideal speeds for dropping to 1st gear...