230s won't shift into 4th gear - PeachParts Mercedes-Benz Forum

Scutch · #1 09-22-2008, 12:48 AM

Hello,
]I was driving on the highway tonight and at first it seemed like I was losing power intermittently for a few seconds, but then my RPMs went really high. I pulled over and drove a little more and realized that the automatic transmission will no longer shift into 4th. It had shifted me to 3rd. Otherwise, from a start it seems to shift like it used to from 2nd to 3rd, but never makes it to 4th. I tried shifting the lever around a bit, but could not get anything to change. It seems like I am clicking into the 4th position, but the car just won't go into 4th at any speed.

I know my shift linkage has been feeling pretty loose. (Sometimes even when it is in PARK I have to push the shifter all the way back so I can start the car.) Also, I have been noticing that the car will often shift straight from 2nd to 4th unless I have plenty of pressure on the pedal. If the pedal is almost to the floor it used to shift through the gears fine. Before the happened I could shift fine manually if I needed to, but it was definitely loose.

I am hoping this is only a linkage problem and nothing worse.

In the manual under diagnosis: "Transmission with not change to 4th gear in selector lever position 4."

It says
1. Stepped pressure too low
2. Sleeve 16 stuck
3. Ball valve between regulating pump and secondary pump leaks.

I'm not sure what this is. Does anyone have any ideas? What is "Sleeve 16?" My guess is that is the 3-4 valve. I'm not sure what to check for the 1-3 above.

Is there any hope? Could this be an adjustment? Is there anything I can check? Could my double-acting solenoid that hasn't ever been "acting" have some effect on this?

Help. Thanks

Eddie

todds · #2 09-22-2008, 02:29 PM

Could definitely be your linkage being off, but mine was loose and I didn't have any of those problems. Repairing it simply made the shifter tighter and more exact. It could also be your vaccum to the modulator, that would be an easy thing to check, do you have a vac guage/mityvac handy?

Scutch · #3 09-22-2008, 02:51 PM

If it was the vacuum modulator wouldn't all the gears be off? Wouldn't I have trouble getting into the other gears?

What are modulator symptoms.

Thanks for the reply by the way. In my town, finding a mechanic who knows these cars is one thing. Transmission problems leave me totally on my own.

todds · #4 09-22-2008, 02:55 PM

Well if your vacuum was way the heck off, your car would act like it was floored all the time and never shift into high. Similar to the kickdown being stuck on, which could also be the problem. You should check the inspection hole on the tunnel to look at the solenoid on top of the tranny to make sure it clicks into it's three positions properly: Idle, Floored, and Everything in between.

Scutch · #5 09-22-2008, 03:12 PM

I'll do that next. I don't think that solenoid has been working since I got the car.

Thanks

Scutch · #6 09-22-2008, 08:26 PM

I checked the double-acting solenoid. It was not working, but was in the center position. I changed the position a drove it a little and the shifting only got worse. It went back to normal when I put it back into the center position. Still not shifting into 4th.

I guess I am looking at getting another transmission.

wbain5280 · #7 09-23-2008, 03:29 AM

Start with new bushings. Check the play in the column, it also has bushings, in the little transfer box on the steering column firewall section and finally the shift rod itself. These things do wear out.

todds · #8 09-23-2008, 01:12 PM

Were you able to check the vac line to the modulator? I'm not sure if it could effect it that dramatically, but maybe it got unplugged or torn and so the modulator thinks the throttle is wide open.

It should be seeing a decent amount of vacuum at idle and during gentle driving. Beyond that, yeah, you may need a new one. Mine experienced similar symptoms when the rear pump died, which can be replaced.

Scutch · #9 09-23-2008, 03:07 PM

I took the car to auto trans shop. The guy was insistent that with my symptoms, it could neither be the linkage or the vacuum because both would effect all shifting. This seems to make sense. Am I wrong? Only 4th gear is effected.

I looked at the modulator today. It looked fine, there were no obvious breaks in trhe line.

Todd, are you saying that your rear pump going out (this is the pump that creates trans fluid pressure) caused only 4th gear to go out and you had no other symptoms?

Can a bad modulator only cause symptoms on certain gears and not all of them?

I have my manual tranny on my 67 that worked fine. I am leaning in the direction of using that tranny as a replacement in this car. I have not had a very good time with the automatic. Just replacing the double-acting solenoid will be $350 just for the part.

I don't want to make this switch in haste, but I get the feeling that fixing the automatic will be more money and time than paying a mechanic to switch the transmissions.

I'll probably be starting a new post about what the small print is on changing transmissions.

Thanks
Eddie

Mike D · #10 09-23-2008, 03:54 PM

Figure on a minimum of $1500.00 USD to have the existing transmission rebuilt and if you are having the shop do all the labor add another $400.00.

If you are not concerned with keeping the car "original" then definitely do the manual transmission swap. It will add a little more "zip" to the car. Figure on $700 to $1000 labor cost from the shop (apx. 12 hours of shop time).

Scutch · #11 09-23-2008, 06:01 PM

Thanks Mike, That's what I figured on costs. Mike, any tips on the conversion? I notice I'll need to replace the master cylinder reservoir so I can add the line that goes to the clutch cylinder.

It seems like I'll have to take the brake and clutch out of my manual as a pair and put them in the automatic.

Eddie

Mike D · #12 09-23-2008, 11:11 PM

Shouldn't need to replace the brake M.C.. Just add the clutch master. It's a closed system and shouldn't really be tied together anyway.

Do a "search" on the board. Lot's of people have done the change and they've documented the process. I've done three or four and it's a pretty straight foward deal.

ja17 · #13 09-23-2008, 11:39 PM

Hello,

Remove the tranmission pan and check to see if you have any parts or debris in it.

Sometimes the valve body bolts come loose and the gasket blows or begins to leak causing shift problems.

When you get it fixed work on the solenoid. Use plenty of penetrant to free its linkage up. It will upshift and downsift smoother and you will have an awsome passing gear.

Recently found a nice 250SE at the local "Pick and Pull" It had the same auto tranny as yours. It was half price day so I removed the virgin cylinder head, entire fuel injection system including the injection pump, the rare oil cooler system (optional on 230SLs), the early acrylic heater levers (don't fall apart like the black rubber ones), the "051" distributor and a few other items for about $100.00. I noticed that the automatic tranny was clean and had the Mercedes factory rebuilt tag on it. On half price week end the tranny would have cost me $40.00. Had to leave but intended on returning in the morning, but never made it till a few days later. Car was gone crushed! :=(

Scutch · #14 09-24-2008, 03:20 AM

Mike, I was only talking about the reservoir on the brake master cylinder. There is a line that runs off it back down through the firewall into the clutch master. It seems that the clutch system uses the brake fluid.

I am not sure what you mean by closed. The clutch hydrolics?

My pedal assembly in the manual car seems to have some welded pieces that make separating them not the way to go.

I have looked up other conversions on the board. They all seemed to be for different models. I never know what the similarities are between models.

todds · #15 09-24-2008, 10:56 AM

Quote:

Todd, are you saying that your rear pump going out (this is the pump that creates trans fluid pressure) caused only 4th gear to go out and you had no other symptoms?

Well, this is what the tranny shop claimed, and is definitely the behavior my car was exhibiting. In the end, I'll never know because the transmission is back in Germany as a core right now!

Incidentally, my new transmission has harsh downshifts when decellerating despite a working idle switch and solenoid. It downshifts under WOT just fine. I ended up giving my modulator a half turn and it seemed to abate the problem almost entirely, although now flooring it from a stop will chirp the tires on the shift from 1st to 2nd. My car feels the same, whether the idle switch is activated or not.

If I were you, I'd do the manual conversion!