I'm having transmission shifting problems (which I'll be diagnosing this weekend with a MityVac). But for the time being I'd like to know what the typical rpm is at 40mph for a w123. Right now I'm at about 2k.

I guess the better question is, what's a good cruising rpm? Since my tranny isn't functioning properly, the car drives at a higher rpm than it should (due to late shifts) and I'm concerned about wear and tear on the motor. If I'm on the freeway going 50mph I'm at 3k rpm... in third gear because it wont shift to fourth.

When did the shifting problem begin?

It is very easy to put the selector is S instead of D, but it can look like it's in D, at least that is how it is on my car. I know I'm due for shifter bushings.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

It's been like that every since I got the car (I bought it not running and swapped a working motor into it). It's in 'D' while driving. The shifts are very rough as well... which is why I think it's due to lack of vacuum.

At 60, I'm currently pulling about 2700 rpm. This number has changed since I got the car. At first it was about 3100 at 60, then it dropped to about 2900 after a bunch of TLC. Recently I gave it a blow-out run, at one point taking her to 90-95 mph and keeping it there a few miles. Rpms at 60 have dropped again to 2700. Think I have stuck rings on #5 that seem to be improving with a quart of MMO and bottle of PowerService in each fill-up over the last few tanks.

Cruising at 40 you should be in fourth and well below 2000 (1800 on the way to work just now, not really 'well below'). In third it sounds about right from what I can recall.

With a healthy motor these cars can run all day at 3500+ rpm on the highway, so I wouldn't worry about breaking anything for a good while yet.

And I second the checking the shifter and bushings before getting too far into the more complex and expensive possibilities.

Heh - you posted while I was typing. Yeah, sounds like vacuum/linkage if it's all rough.

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1984 300D Light Blue/Blue
2006 C280 Silver/Black

Check the kickdown switch. It could be stuck down, keeping it engaged. It's under the carpet, by the accelerator. You can unplug it and then test drive and see if the tranny shifts in to 4th.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Rrgrassi is right do this first. I do not care if his handle indicates he is deep into grass. That is your first thing to check. The transmission cannot get into fourth gear at all and shifts will be very high rpm wise.

I have not mowed my lawn yet...

Actually, my handle is my two initials and my last name...yep. it's Italian!

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

I unplugged the Kickdown switch and still the same. I messed with the Bowden cable however and had some success. The car now shifts earlier and into 4th (thank god!). However, the shifts are still rough... so looks like I'll have to diagnose the vacuum system to make sure its receiving the proper amount.

From what I have researched on this forum and remember I am a extreme novice.......the bowden cable on top of the valve cover will adjust (be easy I just broke mine) WHEN the tranny shifts and on the transmission itself there is a modulator covered by a plastic cap that will adjust how HARD the tranny shifts, but most members will tell you to trace all of your vacuum leaks first.which is what I am trying to do also
peterschmidt.com has all the vacuum diagrams, there are also lines that can be eliminated..egr and some other things
By just adjusting the bowden cable on mine....my 85 300D went from being a slug to actually feeling like a real car!! Good luck!
There is tons of info here just have to do some digging...

62 mph=3280 rpm in 4th gear.