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Discussion Starter #1
I've been on this forum for a long time now, and have never heard anyone praise the hill-hold feature of the 722.3 transmission. Most people may not even realize they have this. For those who don't know, its where when you are in Drive on a hill, you can take your foot off the gas and the car won't roll back. I can't think of any other cars that have this. Just another little great piece of engineering in our 123s.

Jamie
 

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1981 300D
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oh, hmm. Honestly I thought is was like that in automatic transmissions. If it wasnt like that at the time not thats pretty neat.

Doesn't the w126 transmission have something to prevent it from gaining too much speed downhill?
 

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W-1-2-3 Go!
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In fact when I first experienced this, I was amazed that my car was even moving slowly forward (uphill) despite the lack of throttle input!
 

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I'm a left foot brake/right foot throttle type so I find the feature of no use. But my wife who is a right foot only type, loves it. By the way, Studebaker had this feature back in the '50s on all of its models including stick shifts.
 

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I thought the MB version was cool, partly because my other car (1997 Buick Riviera, Supercharged) has listed in the manual *specifically* that adding power to keep the car in position on an incline, and not using brakes, is not recommended due to excess transmission wear.

The MBs must have some other sort of valve body that handles this without requiring more torque input.

FB
 

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Was that feature actually put into the factory catalogs?
 

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FratBoy said:
I thought the MB version was cool, partly because my other car (1997 Buick Riviera, Supercharged) has listed in the manual *specifically* that adding power to keep the car in position on an incline, and not using brakes, is not recommended due to excess transmission wear.
The W123 owner's manual on my W123 Service Disc states the same thing as the Buick's manual.
It says
When stopping the car on a slope, do not hold it with the accelerator, use the service brake. This avoids unnecessary transmission heat-up.
 

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hmmm, I honestly never noticed it until you mentioned it. Actually it does quite well come to think about it!
 

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H-TownBenzoboy said:
The W123 owner's manual on my W123 Service Disc states the same thing as the Buick's manual.
It says
So with that we can safely say that ANY auto trans will partially hold a car on a hill and that it's just the design of an AT that causes some hill assist?

I too was told from day 1 to never hold the car on a hill using the throttle only becuase of transmission wear.

Heck why not replace using the brakes by throwing the transmission into P :D
 

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If it's not too steep, the car will actually roll uphill when I leave it in D (no throttle input using the pedal!) pretty surprising actually...
 

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karugs said:
If it's not too steep, the car will actually roll uphill when I leave it in D (no throttle input using the pedal!) pretty surprising actually...
One of my HS friend's 1985 F150 pickup would register 20mph without pressing on the gas pedal. ;)
 

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80`s Subaru standards had a hill hold feature, using the front brakes and locking them on until you moved.
 

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Discussion Starter #14
The Mercedes hill hold is all internal in the transmission, possibly with a one-way clutch or the valve body. When in drive stopped on a hill and no throttle input, the car will hold. Any slight throttle input will kick the hill hold off, and the car will roll backwards. I was playing with this and had someone else in the car while I moved the linkage. Any slight pull on the Bowden cable would release the car. I've never seen this feature mentioned in the manuals.

BTW, on other cars, holding the car on a hill with the accelerator will cause the fluid to overheat and breakdown, leading to internal trans damage.

Jamie
 

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i noticed this a while back and i thought maybe my brakes were acting up or something by not letting the car roll backwards. cool. i remember subaru used to advertise a car that did this back in the 80's.
 

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I assumed it was second gear kicking in because I know these trannies start in 2nd
 

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The "Hill Start Assist System" has nothing to do with the transmission, according to the 2006 ML-350 Operating Manual. "On uphill grades, the hill start assist system maintains the pressure in the brake system for approximately one second after you have released the brake pedal. Therefore, you can start off smoothly without the vehicle moving immediately after releasing the brake pedal."
:thumbsup:
 

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JamieK said:
The Mercedes hill hold is all internal in the transmission, possibly with a one-way clutch or the valve body. When in drive stopped on a hill and no throttle input, the car will hold. Any slight throttle input will kick the hill hold off, and the car will roll backwards. I was playing with this and had someone else in the car while I moved the linkage. Any slight pull on the Bowden cable would release the car. I've never seen this feature mentioned in the manuals.

BTW, on other cars, holding the car on a hill with the accelerator will cause the fluid to overheat and breakdown, leading to internal trans damage.

Jamie
When you apply slight throttle to the point where it shifts into first gear but no engine throttle is applied, thats when it starts rolling backwards because it is in first gear now.
 
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