Curious transmission question 1991 350SDL
 

So this question stems from my recent road trips across Canada and different cities south of the border, I noticed as I'm driving in my 91 350SDL that the car seems to rev really high (I know this has been discussed), I do have a 2.47 rear end in my car that I swap out before I go on any road trips but it still seems to rev high for my liking. This got me thinking about the W140 transmission, my questions are do the W140 with the OM603 come with a 5 speed or were they all 4 speed? and how easy would it be to swap over if they are indeed 5 speed? What are the gear ratio's compared to the W126 350SDL?

Mercedes Benz EPC 140.134 Chassis Information | Everything Benz

Says no - the automatic transmission fitted is a 722.367 => that'll be a 4 speed auto

Anyway even if a 5 speed auto was fitted I think that top gear would be a 1:1

EDIT - this is wrong for the 722.5 transmission see

http://en.wikipedia.org/wiki/Mercedes-Benz_5G-Tronic_transmission


5 speed manuals or 6 speed manuals have a slight "overdrive" effect say 1:0.85 / 1:0.80 or so

See

S 280 | W140 Mercedes-Benz S Class

for example...

The rear axle ratio on a W140 is meant to be 1:2.82 according to the Russian EPC

350 SD
 

How high are the revs we're talking about? at what speed? My folks have a 350SD and its fantastic on the highway, never noticed anything like that. Are you sure its getting into 4th gear?

The 722.5 and 722.6 have overdrive 5th gears. The 722.5 (300SL/SL320 and 300SE/S320 through '96) needs a simple controller so it shifts properly through 4th. Without the controller it shifts from 3rd to 5th which might not be a problem for the way you drive. A 722.6 needs a full blown controller. No two ways about it but there are folks who dabble in standalone controllers. As of 2-3 years ago none were released products but I heard there are working models out there.

Consider the TC stall characteristics before you lower engine rpm. You might reduce engine rpms to the point that the TC slips at cruising speed.

Sixto
87 300D

That's a good point particularly for more modern TCs with a device that locks the drive - what's that called again? A lock out? I'm pretty sure the 722.3 and 722.4 TCs don't have them - but from say 722.5 they might...

PS I've altered the first post I made in this thread to give a link to the 722.5 information on wikipedia - it shows the final drive gear ratio

Don't get me wrong the car drives great but with the 2.47 rear end based on the GPS driving at approx. 120kph the RPM's sit around the 3000 mark.

That's the German way.

Sixto
87 300D

It means that you don't have to wait around for the transmission to shift on the highway. My 350 turns the same RPMs.

-J