Expected W123 RPM at 70mph

[gizzardio]

Hi

I'm a new owner of a W123 230CE Auto and just wanted to know what the normal or expected rpm is at 70mph? It feels pretty loud like it's working really hard at this speed but maybe that's the 4 speed auto box for you.

I did think maybe it wasn't changing into 4th as I only noticed 2 gear changes from stationary, unless 1st gear is not used unless manually selected?

Thanks

[r129sl]

It'll start in second unless you move the lever to the lowest setting.

They run quite fast at motorway speeds so that the engine is operating around the torque peak; good for efficiency and acceleration. I'd expect about 3,500rpm at 70, maybe more.

[Venisonpie]

Yeah they make a racket at motorway speeds, can't remember what my 280 used to rev at in top but by modern standards it was high. Fuel consumption was not great as a result.

[eccles]

Mine runs about 4000rpm at 70 with the auto box. Mine is a coupe, but a local chap has a very nice saloon and reckons his runs a fair bit lower at 70. I wonder if the saloon has a different diff ratio.

[maddernj]

I have a 230CE (1984) and mine will sit at 80mph @ 3500 rpm.

I tend to watch the revs more than the speedo on the motorway as it'll happily sit at 4000rpm but the fuel economy is rubbish over 4000rpm.

[eccles]

maddernj said:

I have a 230CE (1984) and mine will sit at 80mph @ 3500 rpm.

I tend to watch the revs more than the speedo on the motorway as it'll happily sit at 4000rpm but the fuel economy is rubbish over 4000rpm.

I thought mine was doing similar speeds/rpm but I've since found out my speedo is over reading by 8 or 9 mph! I wonder if my diff has been changed

[maddernj]

I can have a look to see if mine has had anything changed. I have all of the paperwork for its life, so know that the gearbox and engine had been re-built by the original owner. I'll have a look to see if any diff work was done, I'll also have a look at the original build sheet to see what that says.

[gizzardio]

Thanks for replies. It's reassuring to know I'm not missing a gear!

My speed also reads about 10-12ish% over. So indicated 80mph on motorway is just over 70mph according to my nav device.

[W124Bob]

You might be interested in this, yes it's a manual diesel but the diff is the same. In one of his earlier postings he talks about vacume, as well as operating the central locking it's used on the autobox to control shifting and throttle. So might be worth getting someone who knows older Mercs to do some leak testing.
https://youtu.be/_wBMwdG07ZM

[eccles]

gizzardio said:

Thanks for replies. It's reassuring to know I'm not missing a gear!

My speed also reads about 10-12ish% over. So indicated 80mph on motorway is just over 70mph according to my nav device.

I've checked more accurately now and it's more like 3700 @70mph, but like you my speedo is like your and a good 10mph out at 70.