my 83SD, car rolls back on hills at idle... - PeachParts Mercedes-Benz Forum

vstech · #1 09-03-2009, 09:03 AM

on the 82, on a hill, in D, at idle, the car would not roll back. but on this 83, it does... are there different transmissions in these two cars? is this normal, or should I plan on having the transmission looked at?
otherwise it shifts great (waaaay better than the 82's transmission) whatdoyouthink?
the 82 had leather seats, while the 83 has mbtex. perhaps there is a cheaper transmission option too? Phil said there were two different transmissions available for the car, is that one of the differences?

alfa 75 · #2 09-03-2009, 10:06 AM

How steep of a hill are we talking?

vstech · #3 09-03-2009, 10:08 AM

average hill. nothing major

oldsinner111 · #4 09-03-2009, 10:19 AM

There is no hill holder.Your foot holds the brake.

Oracle12345 · #5 09-03-2009, 10:23 AM

Quote:

Originally Posted by oldsinner111

There is no hill holder.Your foot holds the brake.

lol

oldsinner111 · #6 09-03-2009, 10:56 AM

I believe its better on these trannies,no hill holder.I have not seen one American transmission go as many miles,as these Mercedes.Now there was one car my Dad had,he never changed filters,or fluid.A 1962 Mercury S 55,with the 390 4 barrell. He traded with 340,000 miles.Cylinders were all even.
Thats the only U.S. trans I saw that lasted,Maybe the new fangled hill holders,burnt the fluid,and created heat.Also the shift from type F fluid,to the newer stuff.

pawoSD · #7 09-03-2009, 01:08 PM

Quote:

Originally Posted by vstech

on the 82, on a hill, in D, at idle, the car would not roll back. but on this 83, it does... are there different transmissions in these two cars? is this normal, or should I plan on having the transmission looked at?
otherwise it shifts great (waaaay better than the 82's transmission) whatdoyouthink?
the 82 had leather seats, while the 83 has mbtex. perhaps there is a cheaper transmission option too? Phil said there were two different transmissions available for the car, is that one of the differences?

Rolling back on a hill depends on the engine idle speed and bowden cable adjustment. It has to do with the torque converter. At lower idle speeds, there is less coupling resistance pressure in the torque converter, thus, it can roll backwards on a hill. With a higher idle this is not an issue. Also, the adjustment of the bowden cable can affect how much the trans is "engaged and ready to push" while at idle. I have all of mine tuned to sit perfectly on even fairly steep hills without rolling back.

There are no "other" or "cheaper" transmissions for these cars....they all have the same one, including the 300D's...the only difference between them is the speedo cable vs. electronic speedo.

The '85s did have a different transmission in California Models....but in '83 there were no differences.

vstech · #8 09-04-2009, 09:03 AM

well that makes sense. the idle was nearly 900RPM on that car... on this one it sits around 500. I do need to adjust it up a hair, as it rattles a bit... still tinkering with this baby.
Thanks!

vstech · #9 09-22-2010, 10:48 PM

Hmmm I'm back driving the 82, and on steep hills, the car definitely has a lock that keeps the car from rolling back much.
I can climb the hill, come to a stop, let off the brake, and the car will roll back about 6" AND stop. a solid clunk as it stops.
my transmission was rebuilt, perhaps an option was installed that has a roll back stop added...

mach0415 · #10 09-23-2010, 05:43 PM

My 85 SD will not roll either. Put in in neutral, and it will roll. I would imagine the line pressure would have something to do with torque converter clutch engagement if this is part of MB's strategy. mine idles at 700-750 and holds. Do you think the calipers are sticking slightly?

Alastair · #11 09-23-2010, 05:58 PM

My '85 wagon will hold on hills...

There seems to be almost a switch action, just a very slight pressure on the accelerator--not actually increasing engine speed, affects it....

Seems to be Vacuum operated, the valve on the cam-box is about the only thing that changes state at such low accel positions, before it takes up the play and alters the IP.

I have a 722.405 trans in 1985 W123 and N/A OM.617

pawoSD · #12 09-23-2010, 06:51 PM

Quote:

Originally Posted by Alastair

My '85 wagon will hold on hills...

There seems to be almost a switch action, just a very slight pressure on the accelerator--not actually increasing engine speed, affects it....

Seems to be Vacuum operated, the valve on the cam-box is about the only thing that changes state at such low accel positions, before it takes up the play and alters the IP.

I have a 722.405 trans in 1985 W123 and N/A OM.617

It is not vacuum activated. I removed the cam-box vacuum unit from all of our cars and they will still hold on a moderate hill. Depends on the idle speed and pressure in the torque converter. On a REAL steep hill they will all roll back. There is no "anti-rollback" feature in these transmissions.

dude99 · #13 09-23-2010, 07:04 PM

I was under the impression that w126's had a sensor that when on a hill would downshift into 1st to hold it...

-=DeanstuD=- · #14 09-23-2010, 07:44 PM

Quote:

Originally Posted by dude99

I was under the impression that w126's had a sensor that when on a hill would downshift into 1st to hold it...

I am pretty new to it all, but I think that is a petrol car function.

pawoSD · #15 09-23-2010, 09:05 PM

Quote:

Originally Posted by -=DeanstuD=-

I am pretty new to it all, but I think that is a petrol car function.

It is a function of neither. My 300E takes off in 2nd always, it only drops to 1st if the takeoff is difficult (aka steep hill) or if you mash the throttle 75% or more.

Or, if you manually put it in 1st with the shifter. Which I do pretty often.