'75 240D missing 4th gear
 

I searched, but havent found what I am looking for. My car sounds like it is doing 4k rpm at 65mph. supposedly it should be shifting to 4th at about 61mph. What things can cause this? Is there a mannefold that could be leaking vaccume? Linkage that I can adjust?
Thanks!

The diesels of that era have a 4-something rear-end ratio, so I think you are in 4th. Have you tried counting the shifts?

The transmission should shift far before 61mph in 3rd gear. My manual redlines at 56mph (at the supposed governed 4250rpm). Anywhere beyond 65mph sounds like a Oster Blender anyhow.

Did this problem happen all of the sudden or did you recently acquire the car this way?

ctaylor738,
I try to count the shifts, but from either it is not shifting into fourth, or the shift from second to third is very quick and hard to notice.

diametricalbenz,
I just bought this car and it does sound like a blender at freeway speeds.


The numbers that I am going off of are the ones stated in the owners manual. Supposedly, my top speed is 90mph (not realistic). If so, then the car would be so high pitched that only dogs could hear me coming.

I aske about vaccume leaks because my door actuators all have busted hoses, etc. I also can not find any info on the trannys for my w115 model. I can barely find info on the engines. (I'm sure this is nothing new to the members)

I had reacently found a wire on the tranny that was disconnected and reconnected it. I don't believe that there was a change, though.

Have you tried shifting the transmission in each gear to see if you can get it to rev to each shift point? That may or may not be helpful since S holds it in 2 right? or is S 3rd gear? Can the car go beyond 61mph? If it can go beyond that, it should definitely be in 4th otherwise the valvetrain could be damaged. I once took mine up to 86-87 mph once on a slight downhill slope and the fury of the engine at that noise made it quite scary :D The noise is much of the character of that engine in my opinion :)

I am not sure what gears S and L are, either. I tried shifting them, however, and was not able to be certain of what I was doing. My guess was that L is 1, and S is 2 :confused:

I wish I had a tach so I could be sure, but with no distributor/coil I do not have anything to use easily. You are right, I love the sound of the engine :) I have an affinity for cars like these. Lots of personality. I'll be driving it today and will do some further diagnostics. I can get it up to 75-80 mph if I want, but I am scared that I may destroy my engine. Let me do some mathe with the ratios provided in the manual. That will tell me also if I am in third. (I just had this thought).

Thanks for all of your ideas, insight, responses!

If you're touching 75-80 you're definitely in 4th. You couldn't run it at that speed 3rd gear. The car has to make do with 62hp so you really have to wind it up to bring it up to freeway speeds.

There have been threads about the "tiny tach" which is an electronic pickup tachometer and or the dial type VDO tach also with an electronic pickup which I have been considering for some time which should solve the 240d tachometerless situation. :)

Ok, here is the latest data. I can cruise at 70mph with the engine screaming (my other figures were wrong). It does not shift after around 45mph. What RPMs should I be running at 70mph in 4th?

On the lighter side, I just changed the shocks :) Brakes are next.