mpowell

I am throwing this out there before testing anything out regarding my 67 442 Switch Pitch TH400 suddenly not shifting into 3rd gear until i get over 3k RPM's. It was shifting at what i considered normal, under normal driving conditions, at a much lower RPM but now i have this condition. The trans has a fresh rebuild but i expect the vacuum modulator was not replaced. 2 questions, first, does the 3k shift point in 3rd sound like it could be a vacuum modulator issue and second, does the stock switch pitch TH400 use a different modulator than a standard stock TH400?
I plan to test the diaphragm in the modulator but wanted to go ahead and order a new modulator as it is likely very old anyway. I do have all the service manuals and PIM's but am jumping the gun here before i dig in this weekend. Any info would be appreciated. Thanks.

oldcutlass

The modulator is the same. Either it's a bad modulator or loss of vacuum.

Sugar Bear

Check the vacuum source to the modulator really well...X2 oldcutlass . Could also be a sticky governor.

Hairy Olds

Pull the governor out and clean the shaft with brake clean if it's stuck.

mpowell

Thanks, guys for the reply. Glad to hear it the same modulator as i was concerned if specific to switch pitch it would be unobtanium. I will take your advice and check it out this weekend. Cheers!

oldcutlass

Also make sure the kickdown switch is not activated.

mpowell

Will do sir. Thanks

mpowell

So i changed the vacuum modulator this weekend and finally got around to a test drive. Drives like a dream! Much smoother than before. Not only did the 2nd to 3rd gear change go to a normal rpm range but all shifts are smooth under normal driving. Before the 2 to 3 problems, it was hitting hard in each gear always. Now if i get on it, the hard shift is there, but so happy with the smooth shifts driving normal. One more observation, before when shifting manually, 2 to 3 would NOT shift on command at low speed. Now it shifts when i do. Thanks for the advice gents.

jklmmorr

One other question, can the governor be removed without draining the fluid from the transmission? Looking at pictures in the manuals, that appears to be the case. However, in the manuals, the transmissions are out of the car.

Sugar Bear

Yes the governor can be R & R'd without draining the transmission although it may lose a small amount of fluid. Fluid loss can be lessened by raising the rear of the car higher than the front or the left side higher than the right . Be absolutely certain that the car is safely and fully supported and chocked when it is on an angle.

jklmmorr

Thank you and great tips for doing the work.