R129 SL hill hold?

[94mattda]

Hello all, I have recently changed car to a 1999 SL320. All previous W124 and even an R129 albeit older that I’ve owned had hill hold so that when you took your foot off of the pedals on an incline it would stay still if it was in D and not roll backwards. This one does roll backwards!! I also noticed when it changed down into 1st when turning into our drive way it makes a clunk. All gears work well, are very smooth and transmission oil was changed approx 2 years ago. It hasn’t done much mileage in that time. Could it be this do you think ?

 

[flowrider]

10 years since a transmission oil change is a very long time. I would change it and see if the problem goes. Transmission oil should be changed every 4 years.

 

[Deletedmember130310]

An automatic that rolls backwards when in drive uphill???

 

[94mattda]

Will do, I thought I’d ask as our auto Evoque doesn’t have hill hold like I’m used to but a temporary parking brake when you tap the pedal. I wandered after reading a thread about hill hold that manufactures stopped doing it as it causes higher emissions but can’t see how.

 

[94mattda]

An automatic that rolls backwards when in drive uphill???

Yes it rolls backwards slowly when in D on a hill. Usually I’d expect it to hold itself at a junction or lights etc. I’ve not experienced before on a Mercedes Auto this lack of hill hold. I know smart cars and some Vauxhall’s I’ve driven don’t have any type of hill hold but I’d have expected this to have it

 

[BTB 500]

Some MB models would often hold position on a slope in D with the engine running, but this was just a function of the weight/rpm/gearing etc. and AFAIK not a specific feature until much later (Hill Start Assist and/or Brake Hold - introduced from about 10 years ago IIRC). I just checked my 1997 R129 handbook and that certainly says you must use the foot or parking brake to stop it rolling backwards on a slope. Neither of our 2007 MBs have any type of hill hold feature either.

 

[94mattda]

Thanks. Makes sense, our w124 coupe and 190e have all held and my old R129 did but that was a different engine and 10 years olde again. I just expected it to have it as it was a very handy/lazy feature to have

 

[ray_hennig]

And my 300CE holds and did so even before the 'box rebuild.

RayH

 

[CaptainChaos]

Surely any conventional autobox should not roll back in D?
It's nothing to go with having hill hold, it should be a simple function of the transmission!

As a basic check I would check the fluid level if it's easy to do. If not, get a garage to look at it.

 

[BTB 500]

Surely any conventional autobox should not roll back in D?
It's nothing to go with having hill hold, it should be a simple function of the transmission!

A torque converter supplies a fixed amount of torque with the engine idling. This is just fluid pressure ... of course there's no lock-up in 1st gear. So depending on the slope angle, idle rpm, weight of the vehicle and drive ratios it may or may not hold on a hill. Too steep and it will roll back, too shallow and it will still creep forward. We have two MBs with the 5-speed box and one 7-speed, and they all seem to work this way. Brake Hold and Hill Start Assist were specific functions that MB added later on.

 

[CaptainChaos]

Yes, agreed. Wouldn't it have to be a very steep hill to roll back though? I had an old Range Rover (two tons, 4 speed box) and even living in an area renowned for the steepness of its hills it never rolled back. I would have thought an SL320 would be fine.

 

[BTB 500]

I think it varies a lot ... our Vito (3.0 V6, 5-speed) holds on medium slopes but will definitely roll back slowly on steeper ones.

 

[Doodle]

Depending on what boxes the OP had in their 124s etc, it could be that the "creep" on the 722.3 is simply a bit more substantial?

 

[Bellow]

Doodle is correct to identify the transmission's contribution as 'creep' - and the torque converter's characteristics (stall ratio) influence the degree of it.
HSA a feature that uses the brakes - is usually disabled if the handbrake lever is raised - even slightly - via its switch. Foot operated parking brakes may be different in this regard, but it's usually one or the other - HSA or parking brake - at any given time.
HSA (on my car at least) isn't a hold function for when stationary. It only applies between brake release and throttle application and for a preset period of circa 0.75s and, as per before, not if the handbrake was used - foot brake is its cue.

 

[renault12ts]

Don't forget the sprag clutch. My old W210s would hold on a hill (if not too steep) so long as the box was in S not D (or the other way round). But this era of MB did not have hill hold...but a sprag clutch.

 

[renault12ts]

Surely any conventional autobox should not roll back in D?
It's nothing to go with having hill hold, it should be a simple function of the transmission!

As a basic check I would check the fluid level if it's easy to do. If not, get a garage to look at it.

If the engine is just idling then it would not be moving much fluid in the box to prevent roll back...and even on a very steep hill your RR would likely roll back unless there is a sprag clutch or you have a few revs on the engine.

 

[ray_hennig]

If the engine is just idling then it would not be moving much fluid in the box to prevent roll back...and even on a very steep hill your RR would likely roll back unless there is a sprag clutch or you have a few revs on the engine.

I'm always surprised by how steep a hill my 300CE will hold on. It's always been that way. If I remember, I'll try on the way out of the car park (very steep) tomorrow morning and report back.

RayH

 

[BTB 500]

There's a humpback bridge just before a set of traffic lights near us, and the Vito will hold or not depending on how many cars are in front of us (which part of the slope we stop on).