I have an 83 300CD.... the question is.... If the transmission modulator does not get vacuum (either unplugged or unable to hold the vacuum) can it do anything? or is it useless with no vacuum.....

My transmission downshifts at low and high speeds at random....

When it's cold it operates normally....

I'm almost ready for a Trans-X treatment....

Any thoughts?....

Much appreciated......

If unplug you will have hard shifts, since the modulator is the load input for the transmission, if it can not hold any vacuum as in leaking, the car can slip on hard acceleration. It can also cause erratic shifting. What do you mean by down shifting at random?

once the engine warms up and I presume the transmission also....I'll be cruising around (whether at 30mph or 65mph) and at random it will suddenly downshift.... at high speeds of course it gets dangerous with tires screeching... I have to shift into neutral... then ease it back into drive and it catches high gear for a while until the next random downshift.....

sometimes it won't shift out of 2nd until i put it in neutral and drop it back down to drive....

it's very strange.....

Sounds like you are loosing governor pressure. Disconnect the kick-down solenoid to be sure it isn't happening electrically.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

I tried that... nothing changed.....

Any other ideas?

I used Trans X on a 300E and it works fine. Every car is different, but for me it worked and I got a $5 rebate.

I've got the trans x in it now.... now I have to drive dangerously for a hundred miles!!! and see what happens....

what is it that tells the transmission when to shift?

if the modulator is unplugged ... how does it know when to up or down shift?

Does anybody have an idea?