Throwing Manual Transmission into Reverse While Traveling Forward at High Speeds

What happens? A couple people have claimed to me that your whole transmission will fall onto the roadway.

(Of course I don’t have the guts to try this!)

I love how often this get’s asked…

People who don’t know much about cars seem to find automatic transmissions almost magical. Like you’ll go back in time or something, if you did this… :rolleyes:

But they’re just a mechanical device like everything else in your car. And if you did this, basically something would get overstressed and either excessively wear or break or both. Most likely the torque converter (which acts as the clutch) or the ‘clutch packings’ (which hold & release gears from turning and make it shift automatically). When an auto tranny wears out from normal use these things are usually what’s worn out.

However, suffice it to say that an internal component of the tranny would break long before any of the mounting bolts did. So no, it would never ‘fall out onto the road’. :smiley:

With a manual transmission I suspect the weak link would be the clutch which you could easily burn out doing this type of thing.

I accidently slid an automatic transmission into park while moving at about 5mph. The truck (Chevy Suburban) barely slowed down, I just heard clicking noises and coasted until I hit the brake. No damage was done.

Hail Ants: In some custom or older muscle cars the torque converter plates can fracture, or the shaft connecting to the driveshaft can sanp which will/may cause the whole mess to shake off the chassis. I note that I have only seen this once in a hot rod Buic Sattelite with a 490 motor and a ratchet shifter (geared back to front for drag racing). The event was as follows, 90mph down Barbur blvd (a long boulvard in Portland) and the driver who had just installed the reverse gearbox slapped in the wrong direction from D to 3L, “kablam” followed by tears.

In a new car there is next to no way a properly functioning gearbox would let you make this shift and certainly no way to go from drive to reverse.

You can’t get a manual transmission into reverse gear while moving forward at any reasonable speed, say above 2 or 3 mph. However if you insist on pulling hard to try to do it while traveling forward at high speed you can scatter parts all over the inside of the transmission case. This site tells you about manual transmissions.

The link is to page 3 of the transmission description. To start at the beginning, after clicking of the link go to the bottom of the page and click previous page until you get to the start of the manual transmission explanation.

My mother actually did this once, quite accidentally. It was an auto, not a manual as in the OP, but we were on a driving holiday and our car was playing up. It was slipping out of gear about every 50km or so. So we (meaning my mother and father, as I was about 10) would have to shift into neutral, then back into drive. She accidentally hit the button that released the gate, and shoved the car into reverse going about 60km/h.

We stopped really fast, let me assure you. But apart from that, there were no serious side effects. Or none that were readily evident anyway. We completed the trip, and had the car another few years before my brother and I outgrew the back seat (we’re both kinda large), and we never had to replace the transmission on it.

I don’t suggest doing it on purpose, but it should not destroy your car or anything.

I was driving my car home from work one night down a hill, and in an effort to ease the burden from the brakes shifted into second while coasting down the hill. Well, this one night, as I pressed the button to release the gate to shift into second, I hit a pothole or something and accidentally jerked it up to reverse.

My life flashed before my eyes.

The car’s wheels seemed to seize up and the car started to fishtail. I came very close to hitting a tree before it stopped. By some miracle, the people behind me were able to get out of the way/stop in time. I put the car back into drive and drove home without incident.

OK, the OP asked about a manual trans.
In most manual transmissions the shafts would be turning (no syncromesh) and it would be diffcult if not almost impossible to move the lever into R gate. If you did suceed I would expect teeth to sheared off of one or more gears inside the trans. While this is not as specaular as having a trans fall on the ground it would be just as terminal.
Some modern manual transmissions have syncromesh manual boxes and you might get the trans into gear damage could still occur.

On an automatic, if no power is being applies, most likely rear wheels will lock. Probably won’t destroy a good trans the first time. With power applied, something will break, what ever is the weakest part. Trans driveshaft, depends.
Again on more modern autos, there are things that prevent the engagement of R when moving forward.

There was a General Motors transmission many years ago that would throw itself into reverse; ended up in a $17 million lawsuit because GM refused to repair on warranty, claiming that the car owners were doing this on purpose. (!)

Read “How to Avoid Getting Mugged by Mr. Badwrench,” if it’s still in print.

:rolleyes: indeed.

But thanks for all your comments everyone.

It’s MANUAL transmission, not automatic, that lucwarm was asking about.

The answer is: the stick doesn’t go into gear, but the gearbox says “ggggccccccccccchhhhhhhhhhhhhhhhhhrrrrrrrrr”, followed by a quick “doh” from the driver.

Yep. Just wanted to reiterate what the previous posters have said. Basically, it’s almost impossible to do. You’ll get various sorts of feedback indicating that you are about to do a stupid thing. Namely, like jjiimm said, the stick will not go into gear; you’ll feel the stick shudder and you’ll hear a lovely gear-grinding noise. Occassionally when I park, I try to stick the car into reverse before coming to a full stop and even at 1 km/h or less, you get the horrible grinding noise, and the gear won’t go in.
Also, there’s generally no synchromesh on the reverse gear, which makes it pretty much impossible to shift from anything but standstill to reverse.

With automatics (though not in the OP, they have been mentioned), I have once accidentally went straight from 5-10 mph in drive to reverse. On a 1992 Chevy Cavalier, this is what happens: The car shuts itself off. All the “Check Engine” and warning lights came on, but the engine turned off. There was no great whistle or the sounds of little itty bits fusing together. It had exactly the same effect as turning the car off with the key.
I restarted it with no problem, and resumed parking.

Alright… I know this is a old message. But I hope somebody will reply. I am(at least was) a automatic transmission fan for about 10 years and couple of days back I went for a brand new Toyota corolla with a stick. Since I am not familiar with the stick, I was driving here and there in my neighborhood(about 40mph), and unfortunately I confused with 5th gear and reverse. I tried to put 4th to reverse and I heard the gear grinding noise. At that instance I realized the stupid thing that I did. My question is will that one mistake can severely affect the gearbox?
Please let me know.

Severely? If it was only for a few seconds, no. Probably put several years of wear on the affected gears, though.

It’s something you clearly noticed immediately and immediately corrected. Unless you are experiencing some other issues I would assume it’s fine. My dad’s old car held up fine after the hell I put it through learning to drive stick back in the day.

I assume you just got a grinding sound and couldn’t actually get it in reverse, right? Should be fine, I’d think. I experienced that several times (although not going into reverse by accident–I was just trying to practice clutchless shifting through rev-matching–I know, not the best thing to do to your car) with my Mazda 3, and I’ve gotten nearly 100,000 miles on it so far with the original clutch and tranny, and it shows no sign of slowing down.

probably not, like GaryT said it puts additional wear on some of the parts, but no transmission I know of has such slim margins that one missed shift or grind would trash it. My Neon is a stick shift, and when the release fork was worn out the clutch would frequently not disengage completely. I pulled a “D’oh!” every so often and ground a few 1-2 and 2-3 upshifts. Car has 145,000 miles on it now and still shifts fine (with a new release fork.)

if you see the howstuffworks link near the top of this thread, you can see that the actual “gears” of the transmission are always engaged. What you’re grinding when you bungle a shift is the collar as it tries to engage the face of the gear.

this link even has a nice interactive animation:

Nope… It didn’t go in to reverse at all. Once I heard the sound, I realized the thing that I did and I released the clutch. It was in 4th and travelling about 35mph(That means for sure, it was not in reverse).

So again… based on your comment, I hope I didn’t kill my gearbox. I was about to cry…I don’t want to kill my brand new car with 89miles on it.

Thanks for your words…again… you saved my rest of the day. My wife will not kill me, hopefully, after I tell this… because this whole manual car idea is mine. :rolleyes:

I seem to recall the Mythbusters tested this out a while back. Maybe somebody can refresh my memory as to what ended up happening.

The car used, a mid 90’s Ford LTD, coasted to a stop without causing much damage. They found out later that the transmission worked as designed. Ford engineers had idiot proofed their transmissions a few years earlier.

Years ago I drove in some demo derbies and slammed the transmission from drive to reverse and reverse to drive and never broke the transmission. It was damage to other parts that stopped the car, generally from getting clobbered by other cars.