87 300SDL won't go into 4th?
 

I recently cleaned some vacuum lines on my 300sdl om603 turbo, most of them are ok except for the one connected to the nipple on the intake manifold which was plugged with oily stuff. I felt the increase in power after cleaning up that line.

Now that it seems like a different car. I'm not sure what the cruising RPM should be. At the moment, my engine revs at around 3200 at 60MPH on the highway. I can feel the engine breaking when I let off the pedal at this speed. Is this normal? or am I missing my 4th gear?

TIA

How many times does it shift if you take off from a stop and get up to highway speed?

Make sure the kick down switch is not depressed. It is under the throttle pedal.

I have to drive out and count to be sure. I'm aware that these cars start from 2nd if I don't select 2 then D while stopped - or am I wrong? (edit)

For example, when the selector is on D and I'm doing 50mph at around 3000rpm. If I let the pedal off and manually select 3, it should shift down and I should get a higher rpm right?

Also, I checked the fluid level earlier after driving around the neighborhood for 10mins., it's about .3" below the bottom line.

I unplugged the kick down switch yesterday, I tested it with a meter and it seems to be working fine. Although I haven't put it back yet.

Are you sure you have second gear start? I know in my 87 300d w/ om603 it is first gear start. But I won't say yours (w126) definitely is first start either cause I don't know.

How fast can you get the car up to? If you're in fourth you should be able to easily hit 75+ and even up to 100 don't think you could do that in 3rd.

Cruising at over 40 on flat ground my car is usually in fourth already, so yes shifting into 3rd at around 50 or so should cause it to downshift noticeably and rev up.

You could try disconnected vacuum completely w/ the kickdown disconnected as well the transmission should shift through all the gears but with very hard shifts.

Maybe it's low fluid, hope so think I read somewhere that fourth is the first gear to go on worn out transmissions. Good luck, what fun these 28 yr old automatics are huh :cool:

I took it out for a spin, I think it starts in 1st too. I only noticed 2 shifts, so I think I'm missing the 4th. My revs are 2900 at 50mph and around 3200 at 60mph.

My kickdown is disconnected at the moment. Which vacuum lines should I disconnect? Is it the single line that went to the transmission?

I will have to check the fluid again, it's quite tricky with this car. The tranny was rebuilt about 1 1/2 years ago before I got it from the PO so it's quite young.

Yes the single line going to the transmission, be sure to cap it somehow so it's not open to the air. Also you won't want to drive too long without any vacuum, the shifts will be very uncomfortable.

And by cap I mean on the vacuum supply side, so it's not leaking vacuum out.

Or sucking air in haha you get the picture

Thanks for the info.

I disconnected the vacuum but I still don't get the 4th gear.

There is a kick down solenoid located on the transmission itself, if this is stuck, will it allow me to move up to 3rd gear but not 4th?

Does anyone have the numbers with regard to the speed vs. rpm on their 87 300SDL?

For my 300SDL at 70 MPH, the engine is at 3000 RPM. Sure sounds like you aren't getting 4th gear.

Agree with MI300SDL

2850 rpms @ 70mph

Thanks for the input. I now know that I'm not getting 4th gear for sure. Any more insights are appreciated.

What I've done so far: fluid level ok, disconnected the kick down switch, disconnected the transmission vac line - still no 4th

Time for fresh ATF fluid and filter change...

Any possibility that your shifter lever / linkage is messed up, and when you think you have selected "D" you are really in "3"? That would be a nice simple and probably cheap fix...

Vacuum is used to control the soft/hard nature of the shifting.

There is a cable from the transmission to the throttle linkage (aka Bowden cable) which controls the shift timing (how early/late the transmission will up-shift depending on throttle position). It is under the intake manifold close to the oil filter canister, real pain in the but to reach on an OM603.

I don't think that either of these is the issue in your case.

I'll change the ATF and filter to rule it out. My shift lever is firm, I will have to check the linkage though.

I didn't get any positive result when I messed with the vacuum and bowden cable, I don't think it's the issue neither.


Do you have any info regarding the kick down solenoid (the one attached to the transmission)? I have read some threads about it but the TS doesn't report back in each of the posts I read, so they're inconclusive.

I haven't updated this in a while. I did an atf/filter change and I got my 4th gear back.

However, I'm still having issues. When accelerating with about 1/3 pedal, I have to let go for a second or two before it shifts to 4th. And when in 4th @ 50mph, the rev would go up (flaring?) if I give it more than 1/4 pedal. It doesn't happen when I speed up very gradually with a very light touch on the accelerator.

Sounds like the clutches are slipping???

This won't help with the flaring, and I'm probably wrong anyway, but:

When I got my '84 W123, it wouldn't shift in 4th either. The only way to make it shift into 4th was either accelerating very slowly, or letting go of the throttle and resuming once I was above 40mph or so, to make it shift up.

Reason? Bowden cable too tight. Loosened it up to where it has a tiny little bit of slack, and it shifts at much better points now and gave me 4th gear back without a problem.

I'm not a mechanic and I don't know much, but you could give it a try. The bowden cable is easily adjusted by hand. If it doesn't work, you can adjust it back to where it was, no harm done, but at the very least you can rule it out.

It feels like it, but I'm not very sure. Do you think changing the K2 spring will help?

Thanks, I'll try to adjust the bowden cable again and see if I'll have better shifting.

Trying to diagnose my new 82 300d - since search brought me here, thought I'd ask. I'm not familiar with what to listen/feel for with the tranny and I've already fixed some clunking in the downshift to 1st by finding a cracked vacuum line.

When I'm on highway doing 65-70 my tach reads somewhere around 30, maybe tad under. Does this mean I'm getting 4th? I can't tell if I'm feeling all the shifts that I should.

That car was geared for the 55mph NMSL, 3000rpm at 70mph sounds right.

X2

70 MPH at 3000rpm....that's what my SDL turns.

ok, thanks!