shift weirdness

Had some shifting difficulties with an '83 300D. Replaced the plastic shift arms. Now, shifting is erratic - sometimes perfect - sometimes rough. If I keep it floored, it's much, much smoother than if if I go easy.

If I take it easy, shift points vary with the throttle position. In this case. the tranny usually will only stay in second gear for a few seconds before shifting into 3rd -- much too early. I realize this description isn' much to go on.

Any thoughts??

Reply to
Ron Tellus
Loading thread data ...

Excellent. Any ideas where I can buy or find a step by step troubleshooting guide for this subsystem?

Reply to
Ron Tellus

I believe there are two issues to be investigated.

The transmission's shifts are coordinated with the throttle position. The older models have a "pressure" rod or cable from the (top rear of the engine) throttle linkage down to the right side of the transmission. At some point after '82, I believe, this was changed to a vacuum system. Your car is up shifting prematurely because its transmission isn't getting the correct throttle position message.

The transmission's shifts are modulated by a vacuum powered modulator whose vacuum supply is controlled by a throttle linked vacuum valve on the injection pump. The principle is: the greater the vacuum the softer the shift, conversely at full throttle there's no vacuum to the modulator because M-B wants a fast, hard shift.

Reply to
T.G. Lambach

Thanks for the good info. I've had the same problem on my wife's 300D. When I drive it is simply hold the tranny in the gear I want until I reach the shift rpm that feels good.

Reply to
Ernie Sparks

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.