Tranny won't shift

[WudreauxTWW]

I had the misfortune of having to replace my flexplate last weekend. After I got everything back together and topped off with tranny fluid I took her out for a test run.... bad news. It goes into reverse fine, goes into drive just fine, but stays in first regarless of how fast it goes. What gives? Any ideas? What tells the tranny it's time to shift? Transmisions are still a source of black magic to me... I wish I knew more about how they work.

I have a TH400 with Qtrac and low range.

Thanks for any help I can get with this.

[Rande]

Check your vacuum line from the engine to the tranny. It connects to the vacuum modulator on the tranny which controls shifting. The modulator sticks out from the tranny on the passenger side. Its a small metal cannister that threads into the tranny.

[J4GRAND]

I had a similar thing happen when I replaced the engine in my 73. About a 1000 miles after the engine replacement, it wouldn't shift unless I really wound it out- not good on a new engine. Turns out, the torque converter wasn't seated all the way onto the tranny and was causing the pump to bind leading to a loss of pressure in the trans. Hopefully, this is it. Bad news; you'll have to pull the trans again.

[WudreauxTWW]

Thanks for the advice. I'm going to try the vacuum modulator first... that is if I can find one. Separating the tranny from the engine again would be a royal PITA. Oh well, if you don't take the time to do it the first time, you can always take the time to do it again.

[Careful34]

Did you ever figure out the problem on this one?

[dcarroll38732]

J4GRAND, When you put the trans in was the convertor away from the flywheel about a half of an inch. The reason why I ask is I have the same promblem and want to be sure this is not what is wrong with mine. I had the tranny rebuilt and when I put it in it would not shift manually or else. In shop for a second rebuild now, manual valve body, extra clutches, the works.

[Careful34]

bump. Come on Wudreaux! Read your post!

[gsmikie]

Originally posted by dcarroll38732:
J4GRAND, When you put the trans in was the convertor away from the flywheel about a half of an inch. The reason why I ask is I have the same promblem and want to be sure this is not what is wrong with mine. I had the tranny rebuilt and when I put it in it would not shift manually or else. In shop for a second rebuild now, manual valve body, extra clutches, the works.what year truck do you have ????? and what trans do you have ?????

[Casey]

Originally posted by Wudreaux:I have a TH400 with Qtrac and low range.:rolleyes: Dude! I am keeping my eye on any questions you answer about the 400 gsmikie! You really know this s***!!

[gsmikie]

since it is the th400 could(can) you spin the converter by hand before you bolted it to the flexplate ????? you can use a old set of a/c gauges and get pressure readings from the trans ......is the modulator hooked to constent vacuum ????

[dcarroll38732]

Yes you could spin it freely. I have the modulator hooked straight to the intake, right behind the carb.. It is pulling 14" of vac. It still should shift manually, shouldn't it?

[gsmikie]

the next thing to check is the govoner pass side at the rear of the trans it is a square cover held on with 4 bolts get a pan to catch the fluid (1 qt) remove the cover and in a light twisting motion pull the govoner out of the case check the gear on the end for teeth it should not look like it was spun in a bench grinder hold the govoner up by the gear (gear up) and squeeze the fly weights of the govoner with your other hand (if you only have one hand you will need help)watch the shaft in the center of the govoner to make sure it slides up and down when you sqeeze the fly weights if it does not clean it with laqure thinner until it does lube it with a light (wd-40 ) and reinstall

[gsmikie]

make sure the vac modulator will hold vacuum

[Pman]

I bet Wudreaux sold his Jeep, dropped this forum, and is now driving a Neon.