C-4 will not downshift after being on the highway

Put a used C-4 in the sunliner and it will not downshift at all after being on the highway a few miles but will start downshifting after manually shifting on the side streets,I presume its the governor sticking so can anything be done while still in the car.

Have you pulled the vacuum hose off of the vacuum modulator to see if it's wet with tranny fluid? That's my only guess for a relatively easy fix.

It sounds to me like the governor might be stuck, Depending on the year - I believe it is located under the tailshaft housing. Drop the driveshaft, remove the mount fasteners and then remove the bolts from the tailshaft housing, You will need to remove the speedo drive connection cable, but you may or may not need to remove the speedo drive from the housing. slide the housing off and inspect the governor for movement, it works on centrifugal force, so you can pull the weights out ( carefully) and feel if it does move or is stuck hard. Roger Just had his trans worked on as it had some "stuck" components from sitting. The C-4 is a pretty simple unit, the shifts happen when the governor moves, the vaccum modulator can modify the shift points but the governor is the main operator. Hopefully the gasket doesn't break when removing the housing, and be careful to not overtighten the bolts when re-installing. Don't be a gorilla, you can damage the case! HTH...

Just a thought......many years ago I had a C4 that started acting strange. Turns out the valve body bolts had worked themselves loose. Of course I didn't find out what the problem was until I did a postmortem after I had burned up the clutches and bands.

Likely not your problem but might be worth a look just for peace of mind.



.

i was going to say governor as well but he stated it will not down shift but then it will downshift in the same sentence .. stuck governors wont unstick themselves ..

Will not down shift automaticly after the highway drive but will manually and after a few miles with start to down shift when its supposed to until taken on the highway then back to having to manually do it again..

One other though. Try this;

Put the transmission in drive and when you take off does it up shift one or 2 times?

If it only up shifts once, come to a complete stop put it in 2 (or on the green dot if that is how the quadrant is marked). Does it now up shift twice and operate normally?

If so you have a dual range (green dot) transmission and it's operating as it should. On these transmission the "drive" position only uses 2nd and 3rd gear while the "2nd" gear shift position uses all 3 gears and is the position the used for normal driving.


.

This is a later trans and shifts 2 times when in drive,most likely will have the trans I took out rebuilt again.

It now will not downshift at all,as soon as its put in D its in third so its manual shift only right now,after taking it on a couple hundred mile trip it started working better but today it did a delayed shift into second them full on manual so I am going to get the trans I took out gone through again.

Sucks. Thanks for the update.

I am now thinking of never using automatic trans again,since I am planning on putting a Y block in it again I do not want to have that trans rebuilt since its a pan filled where the C-4 to Y block adapter is for a case filled. A friend has a case filled I can use and is good enough to just put in so that might be where I go. I am seriously thinking about going to a manual trans when the Y block goes in.

A manually operated trans in a hot rod will always rule. Especially with the plethora of overdrive combinations available now. A C-4 is a good unit. Light, simple, easily rebuilt. But like many things in our cars.. it has some "quirks", when I was working in a tranny shop here we would have one kick our butts every once in a while. Like this one, some wouldn't shift up or down or shift once and never even move after that. Most of the time we'd drop the valve body and double check everything, including the gaskets. The re-install, double checking the torque setting / sequence / re-assembly. We'd rarely find anything visually, but sometimes things would just click and the unit would work after. We always blamed the problem that the case and valve body were so "light" they would bend just enough to cause an issue. I did the same steps when re-doing my A.O.D. just to make sure it works after install. It did / does. 8-)

I think I am going to check the governor on any used trans I get from now on.