ML270 2002 tiptronic gearbox

[zac]

I have noticed that when my ML changes gear the reves increase sightly between gears, it does not happen when you accellerate quickly and does not appear to be slipping when it engages any gear, is this normal ? would a oil change help as it appeares to do it when it,s hot.:? :?

 

[television]

I have noticed that when my ML changes gear the reves increase sightly between gears, it does not happen when you accellerate quickly and does not appear to be slipping when it engages any gear, is this normal ? would a oil change help as it appeares to do it when it,s hot.:? :?

If the car is over 50k miles then change the oil and filter as it does sound as though there is a little bit of slipping between the gears, that let the revs rise

 

[greenfingers]

Mine was recently changed at 75k.
The old fluid was fairly blackish, which gave me some concern.

I would be very interested to hear how your gearbox works, as I am still convinced that I have 'slipping clutch' syndrome.

Other autos I've owned seem to 'lock' into each gear as they progress through the different ratios; my ML is very different - if I accelerate at half throttle, the changes are stepped as you would expect, but if I increase throttle in any gear, the engine revs immediately increase as if the clutch is slipping.

A pundit on here previously mentioned that the torque convertor should never actually lock up, but I can't help feeling something is wrong when I hit 3/4 throttle and the engine revs straight up to 3000rpm. It is as if I cannot use the torque that is already available.

 

[zac]

Thanks, It's as if it's taking too long to change gear and the reves rise but it does not appear to be slipping when in gear, if you push it it does not do it, is there a clutch for each gear as it appeares to be the change between 3-4 gear,

I appeares to have got rid of one problem (vibration) and got another.

 

[eric242340]

Thanks, It's as if it's taking too long to change gear and the reves rise but it does not appear to be slipping when in gear, if you push it it does not do it, is there a clutch for each gear as it appeares to be the change between 3-4 gear,

I appeares to have got rid of one problem (vibration) and got another.

If it shifts gear between 2500 and 2800 at normal driving then there is no big problem. A simple oil change and filter may help solve your worries. I will give you one test for slipping clutches and this may prove or eleviate your fears. Put the car in drive and park/handbrake on, foot on the brake, raise the engine revs and if they start to die at 2000/2500 rpm then all is normal. If, on the other hand, the revs go beyond 3000 rpm, then the clutches are slipping. A serious word of caution here as this is a test normally performed by skilled mechanics, raise the revs gently and only try this once, too many times and you can actually cause damage.

 

[zac]

Just come back from a drive around the gower (wales) it's more evident when the engine has warmed up, could the oil be the problem when hot?, the gear changes are where you said, you only really notice it when you watch the rev counter as the gear changes are smooth, just wondering if its normal ? It does not do it all the time??

Bit of a strange one these mercs?.

 

[oigle]

You are worrying needlessly. Situation normal. Light throttle always produces a kind of "step" in the gearchange, like it is just having a little rest before selecting the next gear. The engine revs will fluctuate a bit during the "step" - Normal!! Heavier throttle settings makes for a quicker change.
Eric's idea of revving against the brake won't work if you use the footbrake. It cancels the throttle input and returns the motor to idle, unless you flatten the throttle, which I wouldn't advise. This is a very harsh test on the box and should be done with caution. I wouldn't go down that track as I am quite sure your box is working normally.

 

[television]

You are worrying needlessly. Situation normal. Light throttle always produces a kind of "step" in the gearchange, like it is just having a little rest before selecting the next gear. The engine revs will fluctuate a bit during the "step" - Normal!! Heavier throttle settings makes for a quicker change.
Eric's idea of revving against the brake won't work if you use the footbrake. It cancels the throttle input and returns the motor to idle, unless you flatten the throttle, which I wouldn't advise. This is a very harsh test on the box and should be done with caution. I wouldn't go down that track as I am quite sure your box is working normally.

The stall test as it is called is something that went out in the late 70s. there is nothing in the MB serve programs for doing this test, the 123 car was the last that I can recall where this as a check, and as you say should not be done.

 

[zac]

Many Thanks!! this puts my mind at rest, will be changing the oil as a matter of coarse.

PS Did not do the stall test!.

 

[kebo57]

Many Thanks!! this puts my mind at rest, will be changing the oil as a matter of coarse.

PS Did not do the stall test!.

Hi Zac

My ML does the same thing as your's does
sort of increases rev's instead of kicking down every time you light accelerate
anyway I had the trailer with the offroader on the back this weekend 2.5 tons in total, went up some very steep hills, also a three mile hill climb 3000 rev's all the way no slipping apart from what you mension about

Kevin

PS just gone over 161,000 miles

 

[greenfingers]

Oigle had at first persuaded me that my gearbox was behaving normally. My concerns were initiated when towing a caravan, but after hearing about his marathon problem free towing trips in Oz, my autobox seemed to behave the same as his.

It is a relief to hear of other ML owners sharing the same experience.
Oigle, Kebo, Zac, myself, and (from memory) Psmart and Panasonic have all commented on this.

I did try the stall test today, and immediately realised that the revs were not going to exceed 2400. I have experienced slipping manual clutches before, and this did not feel the same.

At last I am now able to stop worrying about it, so thanks to everyone for their comments, and I will now shut up about it until something really does go wrong. :grin:

 

[zac]

I think if it was not for this forum there may be a few very rich garages out there!!.

Thanks!!

 

[eric242340]

The stall test is ancient, as Malcolm says, but its a very fast way of checking for clutch slip and its still used today by mechanics. However I must point out that its not a test to be tried without experience as it may actually cause clutch damage. But you tried it and it proved its worth

 

[psmart]

Ive looked at this a little since last commenting, and basically, if you dont want the revs to be higher than the speed/gear ratio dictates, accelerate slow and smoothly. Demand acceleration or power and the revs rise considerably higher than your motion dictates.

Pretend you dont like feathering Mr Browns cap, ie. drive economically, and you will see very little rev rise/fall in relation to your speed.

Ive done over 12K since fitting a new Turbo/replacing all the oil,seals etc on the trannie,transfer case, axle housings and its still going smooth.

ps) Eric... now I know why I ruined my SD1 auto-box..... used to hold on the brakes, max out on power, then rocket off to win the `boy wonder`off the mark race :Oops: .... and the donuts wont have helped!!!

 

[eric242340]

Ive looked at this a little since last commenting, and basically, if you dont want the revs to be higher than the speed/gear ratio dictates, accelerate slow and smoothly. Demand acceleration or power and the revs rise considerably higher than your motion dictates.

Pretend you dont like feathering Mr Browns cap, ie. drive economically, and you will see very little rev rise/fall in relation to your speed.

Ive done over 12K since fitting a new Turbo/replacing all the oil,seals etc on the trannie,transfer case, axle housings and its still going smooth.

ps) Eric... now I know why I ruined my SD1 auto-box..... used to hold on the brakes, max out on power, then rocket off to win the `boy wonder`off the mark race :Oops: .... and the donuts wont have helped!!!

Donuts? on an auto

 

[zac]

The rev don't rise when it's changed gear they rise in between gears when you drive lightly, if you push it the gear change is quick so it does not happen.

 

[greenfingers]

Zac, you need to change the fluid.
About £50 for the bits, and around £50 for the work.
Then you will have a dilution of 1/2 old and 1/2 new (4 litres), plus a clean filter, and evidence of anything to worry about.

Misbehaving autoboxes are well documented on here, and the top recommended cure is a fluid change.

 

[zac]

Thanks will give it a go!, let you now the results.