I've searched high and low but cannot find any info on the problem. I've replaced the bushings, no change. occasionally the shifter will move as it should but most of the time you have to hold it forward to get reverse to engage and it will seldom go into park. The linkage looks fine. HELP!

1984 300TD 231,000

If you disconnect the linkage from the shifter rod on the tranny, can you engage all of the gears by pulling on the rod itself?

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Dave
1983 300D Daily Driver

Yes, it seems to work fine once you get it to go in park once, but if you start the engine, it reverts back to the same problem. When I had the linkage off to replace the bushings, it would move just fine. I pulled the shifter and everything is good. The previous owner says he had no problem. Could it be something with the nuetral saftey switch?

1984 300TD 231,000

There is a hydraulic valve which, when activated, mechanically prevents reverse, and hence park being engaged when you're going more than about 10 mph.

It's possible that there's a problem with this valve, or with the governor valve which provides the oil pressure which activates the valve. This would explain how you can obtain reverse when the engine is off, and there's no hydraulic pressure anywhere in the gearbox.

I *think* it's possible to gain access to the governor via a cap in the side of the gearbox tailpiece, and I *think* there's also a port which allows you to check governor pressure - governor pressure should be pretty much zero until the car is rolling along.

If the shifting problem only occurs when the motor is turned on, you know it is not in the tranny or linkage. It would seem to me to be torque related. What kind of shape are your motor mounts and shocks in? Check the tranny mount as well. Your motor/tranny may be moving under torque just enough to bind the shift linkage. Just a guess, but that is where I would look next.

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Dave
1983 300D Daily Driver

>>... you know it is not in the tranny...

As there is a hydraulically activated mechanical lock which can prevent reverse and park being selected, which I described above, I can't agree with that logic - the lock is a safety device to protect the gearbox from the type of dullard who might select reverse [or even park!!] while travelling forward at high speed

It's possible that the fault is external to the gearbox as described, but, it's still possible that the fault is internal. In fact, if the refusal to select reverse when the engine starts is repeatable is much more likely to indicate a systematic internal problem.

I changed the left side motor mount. It was completely shot from fuel leaking on it from the primer( changed that too). Is there supposed to be two shocks? There is only one on the left side.
The other side is a little lower and needs to be changed but that looks like a real challenge. Advice anybody?
As far as the transmission and other mounts they are original but look intact. The problem is inconsistent, but troubling. It feels like it is mechanical but I can find no external obstruction . How difficult is it to remove the transmisson? I replaced the axles and I think changing the motor mount was more difficult than that.
I am new to MB and welcome any help. Thanks

It seems to me that NumberCruncher has the best hypothesis so far as to the cause of the problem. If he's right, I don't see any need to remove the transmission.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

>>How difficult is it to remove the transmisson?

You're a long way away from being in a position to *know* that you need to remove the gearbox.

Even if you find that you need to work on the valve body, or governor, you can do this without removing the gearbox from the car.

OK. I will try to locate what you describe (NumberCruncher). Do I have to drain the fluid before I open this "cap"? You mentioned a port to check, at the risk of sounding stupid, would a regular PSI gauge work? Is the threading BPT?

Thanks

Before you start tests and dismantling, can I just double check the symptoms?

Is this *all* true to say;

- That with the engine off, but with the ignition on, you can move the selector through all positions?

- When in the park position, the park is being engaged - i.e., you can't roll the car along.

- When you start the engine, the selector becomes blocked and you can no longer engage reverse, and definitely not park?

All true, but...

As it sits right now on jack stands, motor off, she'll not move into reverse much less park. You can shift from N, D, and S but not L.

>>All true, but...

And without disturbing anything else, with the car still on the stands, if you now disconnect the linkage, can you obtain all positions?

Yes. It seems to move through all positions.

>> Yes. It seems to move through all positions.

When you say it seems to move through all positions, what, exactly do you mean?

Do you mean the lever inside the car moves through all positions?

or,

Do you mean that the linkage on the side of the gearbox (which you'll need to be under the car to pull on) moves through all positions, i.e., you can count the detents for P, R, B, D, etc...