My 88 Club Wagon is back from surgery and we are just getting reacquainted now that it has much taller gears . The C 6 was shifting between second and third at 25 - 30 mph with the old gears , so I was never really too concerned , just assumed it was a city driving phenomenon . Tonight it almost seemed like it wouldn't hold 3rd gear , downshifting at the slightest change in pedal pressure and reluctant to upshift . I'm heading out on a long trip , towing a trailer load of snowmobiles for 150 miles and then continuing with just the family and gear into southern Minnesota , roughly 600 miles round trip . Second gear now is pretty close to what third was when I had a 4.56 rear end so I'm confident that I can get down the road but I certainly don't want to end up broken down somewhere ! Can anybody give me any advise about this situation ?

 

I did a second search after posting and believe that I found a similar situation , the suggestion was a possible vacuum leak in the modulator line or faulty modulator . Dumb question I know , but this is my first auto trans . Where the heck is the modulator ? Any tricks to replacing it ?

 

Someone far more knowledgable about Ford auto trans will come along soon BUT if the C6 is similar to a GM Turbo Hydramatic the vacuum modulator will be the only external device with a vacuum line running to it, typically mounted on the side of the transmission.

IIRC there tends to be a single bolt holding it to the trans case where it fits into a grommeted inlet, the engine vacuum line running into it from the opposite end.

Not sure this helps but maybe moving this back to the top will get better attention. Maybe a general online Google search for images would work too?

 

The modulator is on the passenger's side of the transmission. It has a vacuum line connected to it. The other end of the line connects to the engine intake manifold.

If the line is still connected take it off and see if there is oil in it. If it is wet inside the vacuum modulator must be replaced. If it is dry the line probably has a crack and is leaking vacuum. If so, replace the entire line.

 

there is a short rubber hose that seems good and the steel line it connects to looks ohay also . No oil , so I may try to pull vacuum lines on the distribution rail to locate the actuator line , then run ribber all the way .