D to R shifting while driving, possible? - PeachParts Mercedes-Benz Forum

Guenter · #1 02-02-2006, 08:55 PM

Hi All,

as the title says.... I'm not about to try it, but when I do it at low speeds there does not appear to be any sort of savety gate to prevent shifting into reverse while driving.

cheers, guenter

420 SE · #2 02-02-2006, 09:38 PM

Except you have to pass through neutral to do it, so I guess it is possible.

SatRoc · #3 02-02-2006, 10:07 PM

Reminds me of a very old story about a guy who has his car towed into the transmission repair shop. When the manager asked what happened he said, "I was sitting at the light and this hot car pulls up next to me. I dropped the transmission into "L" for "Leave". As we pulled away, I moved it into "D" for "Drag". He was pulling ahead, so I put it into "R" for "Race". I think I need to see the transmission man!"

t walgamuth · #4 02-02-2006, 11:04 PM

go into reverse while moving very fast.

of course i am not about to try it out. my luck the interlock or whatever does it would be out!

now a 1950 pontiac with hydromatic will do it! one of my high school buddies tried it and didnt wreck his tranny. those hydromatics were TOUGH! and when mercedes built their first automatic they looked very closely at it and built a very similar but more compact tranny.

tom w

MS Fowler · #5 02-03-2006, 05:25 AM

Going waaaay back, the Model T Ford's transmission used planetary gear sets just like just about every automatic ever built--except, of copurse it was manually controlled. In all but the first 4,000 of the 15million T's built, the tranny was controlled by three foot pedals. One of them engaged the transission brake, but one of the pedals engaged reverse. Model T drivers will tell you that jabbing the reverse pedal was more effective than the brake in slowing the vehicle.
Since planetary gears sets are always in constant mesh, and gear changes are effected by applying clutches and brakes ( or bands) to various drum combinations, it is possible to engage reverse at any time, unlike sliding gear transmissions. However, it does place major stress on the components. Most modern auto trannys are equipped with electrical interlocks to prevent reverse from engaging while driving forward.

mbdoc · #6 02-03-2006, 08:11 AM

Mercedes AUTOMATIC transmissions are designed to have reverse "lock-out" above 5KPH. Designed to block the shifter from moving from N to R.

stevebfl · #7 02-03-2006, 08:46 AM

As Doc points out there is a lock-out. It is internal and is activated (at least on non electronic transmissions) by the governor.

Guenter · #8 02-03-2006, 10:28 AM

Quote:

Originally Posted by M.B.DOC

Mercedes AUTOMATIC transmissions are designed to have reverse "lock-out" above 5KPH. Designed to block the shifter from moving from N to R.

Hey, thanks! well that explains it since I probably wasn't going more than a couple of kph when trying this on purpose .... and to my astonishment

found that it shifted. My wife does drive it and, well you know....

Jim Anderson · #9 02-03-2006, 12:00 PM

When I was driving taxi (somebody else's car) and was on ice I tried it, the transmission does go into reverse. Putting it into park didn't happen, I guess the gears were turning too fast. I did hear something rattling until I dropped down to about 5 mph, then it dropped in and locked the back wheels, which was a non-event, being on ice.

Putting it in reverse and punching it on ice turned out to be a much better way of stopping than using the brakes

Hatterasguy · #10 02-03-2006, 01:05 PM

When I first started to drive the trans on my Camry was put into reverse at about 40mph(long story

) Anyway the car acted like someone had slamed on the brakes and the engine stalled, causing a CE light. I restared it and everything seemed fine, the fluid did too. That was several years ago and that trans is still on the road probably with another 25k on it.