Thought I might gain insight here. I have a '79 116 chassis turbo diesel. It wont shift out of 1st gear until about 3500 rpms. I adjusted the modulator all the way out, but it hasnt helped. The modulator holds good vacuum. Can a modulator be faulty even if it holds vacuum, or am I dealing with a sticky valve in the valve body?I havent had the car very long , but I know that it sat for a period of time. Anyone have any insight/knowledge of these 4 bolt pan trannys? Any direction would be appreciated. Thanks Dave

Hello Dave,

As I understand, the modulator does not determine the rpm of the shift, just the pressure used.

I understand that there is a governor that sets a default shift for each gear, modified by the position of a Bowden Cable which transmits throttle position. More throttle = later shift, less throttle = sooner shift.

Check the cable, is should have NO tension at idle position, but no real slack, either. Slack will fool the transmission into thinking your throttle is less open than it is, delaying shifts.

Of course, there could be other reasons too.

Check the cable (use Search for Bowden Cable for a whole lot of posts on the subject) and others will add their knowledge.

Best Regards,
Jim

Thanks jim,I understand the cable concept, however this has a rod, and I've adjusted it a few times, but dosent seem to affect it other than if too much tension, it wont shift at all. Thanks dave