C4 under mild driving slips or revs before finding 3rd

[Faster Eddie]

First to second, normal, second to third, like a 1 second wind up as if it's not in any gear, then finds third.

If I'm accelerating, no problems at all, but just rolling in the neighborhood or a parking lot or taking off from a light slowly; that's when it does it.

Do I have a big problem or can something be adjusted?

Thanks in advance!!

 

[Show Links]

Same problem solved

I had the same problem. Tried adjusting vacuum modulator (I run the red striped modulator with two vacuum lines), but that had no effect. I then found a post from, I believe, Bronco Howie that recommended plugging the second, small line from the modulator with a BB. I gave it a try and it worked!

If you have the dual modulator, block the vacuum from the smaller of the two lines and see if it works for you.

Good luck

 

[half cab]

That's Ford's version of a natural shift kit

 

[Faster Eddie]

Thanks, I just found the similar posts, I'll get on it.

 

[Faster Eddie]

Installed a return spring on the kickdown linkage. Snooped around with carb cleaner searching for leaks, nothing. Bought a vacuum tester/ brake bleeder kit, plugged it into the transmission vac line an the needle just bounced from zero to 15 the whole time. My modulator only has one spout for the vacuum line. So...what's next? Change the fluid and filter, check it, then try a modulator if still wonky?

 

[Broncmeister]

I had the same problem. Tried adjusting vacuum modulator (I run the red striped modulator with two vacuum lines), but that had no effect. I then found a post from, I believe, Bronco Howie that recommended plugging the second, small line from the modulator with a BB. I gave it a try and it worked!

If you have the dual modulator, block the vacuum from the smaller of the two lines and see if it works for you.

Good luck

I am having the exact same problem, shift flare from second to third. I will try this advice as well.... but one question, to be clear when we talk about a BB do we mean the little pellet from a bb gun?

 

[Show Links]

Bb

I can't claim credit for this solution, but, to answer your question, the BB is bigger than a standard BB gun. Perhaps twice as big. If you do not have a BB large enough, simply plug the SMALLER of the two modulator vacuum lines with a golf tee, appropriate size bolt or whatever works to permanently plug the line where it connects to the vacuum tree. The vacuum tree is located on the manifold located behind the carburetor. Once you plug the modulator vacuum line, make certain you then plug the vacuum port on the tree, so you do not have a massive vacuum leak.

Let everyone know if it works.

Good luck,

Rob

 

[Show Links]

Beyond my paygrade

Hey Eddie,
I'm not qualified to answer your question if the BB didn't fix the problem. Do a search. There are many opinions and experience others have shared that will help you determine your next step.
Sorry I couldn't be of help.
Rob

 

[Faster Eddie]

Thanks Rob. Mine doesn't have 2 vacuum lines. Only one so the BB thing can't help.

 

[Show Links]

Oops

Sorry about that Eddie. Hopefully some other members will jump in and help you with next steps.
Rob

 

[Viperwolf1]

Two things happen when shifting from 2nd to 3rd. The 2nd gear band has to release and the 3rd gear clutch has to apply. The timing between those two things occurring is the root cause of this problem. Many things can affect this timing including valve body issues, clutch and servo seals and wear on friction materials.

I would start troubleshooting at the valve body. Look for sticking valves or a bad gasket.

 

[Faster Eddie]

Thanks VW1. I have no experience except for changing tranny fluid. Is this something I can learn on the interwebz? Or am I digging deeper into the hole to pay a shop?

 

[Viperwolf1]

http://classicbroncos.com/tech/c4-valve-body-service-and-modifications

 

[Faster Eddie]

Engine is a 347 stroker and has about 14# vacuum according to my gauge. Can't find leaks at all. I swapped out the modulator and no change. (as some predicted)

Gonna take it and get it serviced. What do I ask them to do? Drive it and troubleshoot, or service the valve body, or rebuild the transmission?

 

[Viperwolf1]

Engine is a 347 stroker and has about 14# vacuum according to my gauge. Can't find leaks at all. I swapped out the modulator and no change. (as some predicted)

Gonna take it and get it serviced. What do I ask them to do? Drive it and troubleshoot, or service the valve body, or rebuild the transmission?

Start here.

I would start troubleshooting at the valve body. Look for sticking valves or a bad gasket.

The servo can also be checked out and resealed without pulling the trans. If fact the valve body has to be out to install the servo so might as well do them both at the same time. If it still has problems after all this it's going to be an internal clutch issue.