jk828

When driving and I floor the pedal, the transmission down shifts but only holds 2nd for 2 or 3 seconds before shifting back to 3rd. Would this be controlled by the governor? The trans was just rebuilt and the shop did install a new governor. I will call them tomorrow but was hoping to educate myself a little before talking to them.

Fun71

Make sure the kickdown cable is connected. I had a similar issue on my car, and it was caused by the cable coming out of the plastic bushing on the gas pedal arm. The cable could also be disconnected at the transmission end since someone was working with the governor recently.

Vintage Chief

Kenneth - Couldn't the ATM (Automatic Transmission Modulator) also effect this?

Vintage Chief

I'd also check the state of your ATM valve the purpose of which is to shift gears. Be certain the ATM valve metal line is well connected to the rubber lines & the rubber (vacuum) line is on manifold intake and the other end of the line is connected correctly/securely into the ATM valve at the transmission & not leaking.

Fun71

Loss of vacuum to the modulator will result in the trans remaining in low gear, with no full throttle upshift until the engine is screaming at redline. At light throttle, it will upshift as soon as you let off the throttle, and downshift as soon as you apply any amount of throttle.

That's the only failure mode I know of, there may be other things that can happen but the loss of vacuum is the only one I have experienced.

jk828

OK, I just verified that the kick down cable is functioning. While checking things out, I did notice one thing. When I switched from the jetaway to the th350, I made a new 3/16 hard line to the modulator with short sections of rubber at each end. The hose at each end seems like they may be a little loose fitting. I did not flare the hard line at all, just slid the vacuum lines on. Would that loose fit be enough to cause a problem? If so, should I switch to a 1/4" line or just put a small flare on the 3/16" line?

Vintage Chief

The short answer to your question is yes - a loose fit can cause a problem. You obviously want to maintain the capability to consistently pull a vacuum through the ATM valve vacuum line. What one person considers loose may not be so loose to another person. The connections need to be tight. You don't need to flare the metal ends, why not use clamps around the rubber where it joins metal?

Vintage Chief

I just re-read your post. You fabricated a new 3/16" hard line? Isn't the original 1/4" hard line? I honestly don't know. But, if you did in fact go from 1/4" to 3/16" hard line, since 3/16" is narrower than 1/4" you effectively lost vacuum by restricting that ATM vacuum line. You want to maintain optimal vacuum so whatever you did, do not change the size of the ATM valve vacuum line since going narrower is more restrictive.

EDIT: And, of course, make certain you're using vacuum hose and not another hose not suited for vacuum (which may collapse).

jk828

The jetaway used a 3/16 line so that is what I made the line out of for the 350. I just did a search and most are saying to use 1/4". I will change it out and see if it makes a difference.

matt69olds

The vacuum modulator only controls part throttle shifts based on engine vacuum. Light throttle, high manifold vacuum=early smooth shifts. Give it more throttle, vacuum dross, shifts get later and firmer.

Assuming the modulator is adjustable, you can move the shift points up or down around 2-4 mph at most. If you need bigger changes, the governor will need modifications.

Vintage Chief

Oh I see, that makes sense. Thanks!

matt69olds

The vacuum modulator doesn’t care what size the line is, as long as the connection is tight with no leaks. Most replacement vacuum modulators include a 90* rubber hose elbow, a 3/16 steel line fits well.

jk828

Ok, whether it was necessary or not, I installed a 1/4" hard line and made sure the vacuum lines were secure at both ends. It still shifts the same. At lower speeds, it will run 2nd out for quite a while before shifting to 3rd. At higher speeds, around 60-65, when you want to pass somebody (or keep a buddy from passing you), it still only holds 2nd for probably 2 seconds tops before shifting in to 3rd. I have the original governor from the transmission and I am considering putting it back in. I am not sure why it was replaced because it was a low mileage trans and it measures .801. Which from my research, they should be between .790 and .80. Any thoughts?

Koda

Your kickdown is not working right. You're getting the tail end of the low vacuum shift, but it will dump you back into high at 65 or so. You won't be able to downshift at all via anything other than the shifter at 70. How did you verify the kickdown is functioning? Do you mean it mechanically works? It hits a switch for a solenoid in there.

jk828

My verification was that the cable is fully pulled at WOT and that the transmission does in fact down shift at WOT. Other than initiating the down shift, what other purpose does the cable have?

Vintage Chief

Did you call the shop today that rebuilt your transmission and installed a new governor?

Sugar Bear

Has the kickdown cable been adjusted? There is a tab that is lifted up, the pedal is pushed to the floor, released and the tab is pushed back in.

Good luck!!!

jk828

Waiting on a return call from the shop. The cable was adjusted like stated above.

Vintage Chief

I believe everyone is doing their best to try to assist you in your understanding and diagnostics of the issue. You said you were going to call them today albeit my question to you. If you had a shop recently rebuild the transmission and install a new governor you'd certainly be well within your expectations of posing some additional questions to them as you describe to them your issue. Hopefully they'll return your call and get you back on the road - they may know something or suspect something which will greatly assist.

jk828

The shop got back to me and his first thought is like several of yours, adjust the kick down cable. He told me to try and get a little more tension on it. I will try and readjust this evening and see if it changes anything. I was under the impression that the cable was properly adjusted simply by the fact that it would make the trans kickdown at WOT.

jk828

The cable was adjusted properly, as I thought, so there was no more adjustment. I did watch the tach and it shifts back to third around 4100 rpm.