450slc automatic transmission

[joeltracey]

Hi All,

I own a '79 450 slc which I bought as a restoration project a while back. As such haven't had the opportunity to drive it on the open road (can`t wait for that day!!!). I have moved the car around the yard a few times and noticed something about the automatic transmission when I engage it. When D or R are selected the car jolts forward or backward after a seconds delay. The revs also drop significantly. The engine is in need of a bit of tuning as it idles a bit fast when in neutral. I realise this could be the cause of the problem but I just wanted to ask in case it's actually a problem with the transmission.

I'd appreciate any advice on the matter. Myros and Television you guys have been helpful to me already, what do you think?? Thanks,

Joel

 

[television]

If the Idle revs are too high, it will make a jolt, and slow the engine down.
I cant remember the correct idle speed for your car 600 in P, somewhere around that.

Malcolm

 

[joeltracey]

Hi Malcolm,

Thanks again for your advice. So if I sort the engine out and get it idling at 600rpm in P (which I think you are right about actually) then should that stop the jolt when D or R is engaged?? Or does it always jolt a little anyway??

Joel

 

[Myros]

Idle speed should be

between 500 and 750rpm in D, when the engine is at operating temp. That usually equates to about 1000rpm-1100 in P or N. The art is setting the idle low enough not to jolt the box too much, but high enough so you don't stall with a full auxiliary load on.
Warm the engine, (friend, helper or press-ganged spouse required), select D, hand brake on, full pressure on the foorbrake, switch on all the electrics and then set the idle to where it will ahppiliy sustain itself. I suggest working down from 800rpm, rather than up from 500.

The box will always jolt a bit when shifting. Not worth a rebuild to fix a minor niggle.

Good luck

 

[joeltracey]

Thanks M,

Happy to hear that the transmission is ok after all!! I will have to work with the electrics a bit before I can set the idle speed as some things such as the blower don`t work. Would it be important to turn the steering to full lock also when setting the idle speed? Cheers,

Joel

 

[Myros]

good thinking

but you'll ruin your tyres and strain the gear if you saw away at the wheel while setting up. Go for a comfortable idle with all the other gear on and then add 50rpm.That should do it ok. I ran around with the setting tool in the glove box for a few weeks after replacing the idle control valve, making a few tweeks every now and then.

 

[rickstergirls]

450 SLC chrome wheel arches

My gear box take a second or so to get into reverse, i think that is about right and idles high in P as it is usually from a cold start. should be nothing to worry about.

Hi all I purchased a set of four chrome wheel arches (fenders) yes I know people said in past threads they look tacky but on an old classic like the 1979 SLC it gives it extra class.

Only issue is I do not know how to fit them do I need to drill wholes into the arch to fit?

Any one please advise. The car has been garaged and i am not trying to hide rust and rarely comes out in the rain.

thanks
Ricky:???:

 

[joeltracey]

Myros,

Thanks for that, advice taken.

Out of interest, where is the idle control valve?! And could you explain about the 'setting tool'. What is it exactly?

Sorry to pester but I'm thristy for knowledge when it comes to this car!!

Cheers,

Joel

 

[Myros]

on our 85 500SL

the idle control valve was faulty/sticking when we bought it, so the engine didn't idle down as it warmed up, but stayed rich and fast, idling at about 1500 in P. It sits under the air filter at the front half of the engine, is about 10cm long, 3cm in dia and has rubber/vacuum hose and electrical connections. My mechie temporarily leaned the engine right off at the CO adjustment( thorugh the hole and seal in the air filter) so that I could control the car until I got a new valve. I got one from Mercman, (£100, next day, brilliant service) and fitted it. I then richened the mixture back to where it should have been once the engine was warmed up. I had it a bit too high at first, then a bit too low (stalled when in transition from cold to warm) and now I have it just about right. She burbles nicely at 750 in D when warm, and the car throbs like a big cat purring. I could goose it up to 800 and get rid of the throb, but I actually like it.
The idle speed itself is electonically set by the idle relay. The mixture is set so that at 750-800 the CO emissions are acceptable.
I don't know if its exactly the same set up on yours. Mine has the mechanical fule injection, but some of the earlier models had electrical, and they might differ considerably in setting up.

 

[joeltracey]

No my slc is mechanical fuel injection also. Actually it idles a bit fast in P or N even when warmed up. When cold it revs at 2000rpm ,or possibly more I think (never actually checked carefully). When warmed up which takes a couple of minutes the revs are about 1500rpm in P or N. However, the revs in D or R (when warm) are too low because it wants to stall. Probably somewhere around 500-600rpm. Summary - It needs less in P/N and more in D/R! Strewth!

Must take a look at the idle control valve, could be suffering from the same problem! Needs a tune up too me thinks! Thanks again,

Joel