Harsh Kickdown.

[Jonathan Laws]

The kickdown on my '89 500 SEC is rather harsh at times. Rather than smoothly shifting down from 4th to 3rd it tends to slam the gear in, sometimes after what seems like a slight delay. This only seems to be happening on high speed kickdowns, 60mph and above. Anyone have any ideas as to what the problem may be and how to rectify it? It's just had a large service by the way.

Thanks in advance.

J.

 

[Andy]

Hi J,

You don't mention how many miles the vehicle has done. Which is always usfull at it gives a basic view on the wear and tear that may of taken place. I am firstly assuming there is no excessive free play in the rear axle. I am then assuming all other changes are ok and relatively smooth. If this is the case then the gear box pressures are probably ok. I would suspect excess clearence in K2 brake band. Due to excessive clearence between the brake band & drum. The only way to rectify this would be to remove the gear box &  strip. Check all release clearences in both brake bands & adjust accordingly. While the box is apart, check all clutch packs are ok.  I would watch who you take it to as most gear box repair specialists will not set the gear box clearences. If the release clearences are not reset to minimum clearence then the box changes will always be harsh. Never assume if you replace all the clutch plates that the gear box will be back to standard. The problem is that they could of left the factory incorrectly set.

Again I am assuming everything else is ok with the box. If I can be of further assistance contact me directly on the land line or via my web site.

Regards
Andy@ www.mercedesservicing.com

My land line number is on the website.

 

[Jonathan Laws]

Hi,

Thanks for the reply. The car has done 137,000 miles. Considering the work that you mention, do you have any idea how much all this is likely to cost? I'm assuming (not being of a mechanical nature) that all this won't cone cheap?

Thanks.

J.

 

[Andy]

Hi J,

It will cost in the region of £600.00. If we were to carry out the repairs, while the box was apart we replace all clutch packs & replace drum seals also. As well as the release clearences.

Although you could drive a little more sedately. But then whats 5.0litres for.

If you want any more info. Give me a ring on 0121 558-4848 or email me from my web page

Regards
Andy @www.mercedesservicing.com

 

[Rex Graveley]

I have a 1982 SEC500 with the same harsh kickdown. It also jerks into reverse about 2 seconds after selection. Does this have the same cause and will a gearbox rebuild cure this as well?

 

[Andy]

Hi Rex,

I think you have the same problem. Reverse is in the front part of the box. What usually happens is that the clutch packs for reverse (LB3) start to loose the lining. This causes excessive freeplay. Hence the time it takes to go into reverse.

For those who may be reading this. The problem with these boxes. Is there is very little you can do from the outside. Unless you are certain that the guts of the box is in A1 condition. Any slipping or problem with the gear changes you would then look at the valve chest. Which is the brains of the box. Trouble is. If the gear box has done a few miles & all the box pressures are ok. The gear box filter is in good condition. Then the box has to be removed to be inspected. Clearences adjusted. Then look at the valve chest.

Sorry there is no short cut.

Back to you Rex, if you done a similar millage then the box will require removal & strip.

Sorry for the bad news lads

Regards
Andy@www.mercedesservicing.com

 

[Jonathan Laws]

Thanks for the replies Andy. I will certainly bear your advice in mind although at £600 I think I can live with this problem for a little while longer yet; the problem seems to be not as bad after the recent service but this is obviously something that will need attention in the not to distant future.

I shall be in touch when I've decided I can't live with it any longer.

Thanks again

J.