C4 Shifting problem - trans experts help.....

[Broncofan76]

i just bought 1973 EB with a 302 and a C4. It was not shifting at all when I got it (stuck in 3) and I had to manually shift it to get it home. Have since hooked up the kickdown and it now shifts BUT - it revs up really high between gears prior to shifting. I also replaced the modulator and still has these symptoms. Any ideas? I'm not very experienced with trans issues but would like to get my new toy on the road and mechanically sound so can start the endless list of upgrades and repairs I have in mind!
thanks

 

[Viperwolf1]

Sticky valves in the valve body and governor. You could try to adjust the front band to minimize the flare between gears but it really sounds like it needs a refresh to me.

 

[Broncofan76]

Sticky valves in the valve body and governor. You could try to adjust the front band to minimize the flare between gears but it really sounds like it needs a refresh to me.

okay, dont think it needs a torque converter? just doing some research and hoped this would do it. Is $700 a good price for a rebuild? I have a quote for $400 and one for $700. seems like a big difference. Anything I should look at having done to it while it's out and being rebuilt? Or is it straightforward just build it back the way it is supposed to be built?
thanks!

 

[Greg_B]

You can just about buy a brand new tranmission for that much money. I spent 600 a few years ago and wish I had just bought a new one from Jegs, Summit or one of the many transmission shops on the net and installed it myself.

The guy who did mine was a joke... I have battled that thing for years with little problems like leaky seals, hard shift, soft shifts, missing bolts, loose bolts... all sorts of crazy things.

Now that I think about it... maybe I should have just switched to the AOD or the NV3550 so I could have the overdrive.

Greg

 

[Viperwolf1]

Always a good idea to replace the converter when doing a rebuild. The converter can hold a lot of debris inside. Rebuilt converters are cheap, less than $100.

$400 is on the cheap end for parts and labor. It costs me about $250-$300 for parts for a completely stock rebuild. That includes converter and shift kit. Find a place that guaranties it's work and will fix problems if they happen.

A shift kit will help the trans live longer and so will a large external cooler. Flush out the existing cooler lines before installing a rebuilt trans. A stock rebuild will last a long time behind a mild 302. If you plan to push out over 300 hp then you should look at some clutch upgrades and other mods but that gets expensive quickly.

 

[Broncofan76]

my mechanic seems to think it's a clogged up governor? does that sound like it could be the problem?
he said to run it for a few hundred miles and do a few trans fluid changes to see if it breaks the debris loose before we pull the whole thing and go form there.
sound accurate? or at least a good guess.
thanks

 

[77BRONKOTN]

Modulators are adjustable, is the little rod inside the modulator ? Whats the vacuum source.

 

[oldiron]

my mechanic seems to think it's a clogged up governor? does that sound like it could be the problem?
he said to run it for a few hundred miles and do a few trans fluid changes to see if it breaks the debris loose before we pull the whole thing and go form there.
sound accurate? or at least a good guess.
thanks

Depending on how long it has been sitting, I'd try this first.
Greg

 

[Broncofan76]

Modulators are adjustable, is the little rod inside the modulator ? Whats the vacuum source.

will check for the little rod and I guess it will be obvious how to adjust it?
the vacuum is coming from the carb. there are 2 vacuum nipples on the modulator and I have about 4 choices on a vacuum connector to the carb. I think i have tried all combinations.
I'll mess with it more today or tomorrow and report back.
thanks

 

[Broncofan76]

Depending on how long it has been sitting, I'd try this first.
Greg

It has been sitting up for a while. The PO said he never drove it for like a year.
thanks

 

[Broncofan76]

okay. THAT problem seems to have "worked itself out" after driving a bit today. It no longer revs high (spins free) just before shifting. Now it has the following symptoms:

* Often starts out in 2nd but if I give it tons of gas will shift into 1st and feels much better
* Sometimes starts out in 1st
* Almost always runs REALLY high RMPs before shifting from 2nd to 3rd

Generally it feels very inconsistent and crappy - wrong gear, high RPM etc. Any ideas? Vacuum lines to modulator?
BTW - it is a C5, nit a C4 as I first posted.

Ideas? thanks!

 

[Viperwolf1]

okay. THAT problem seems to have "worked itself out" after driving a bit today. It no longer revs high (spins free) just before shifting. Now it has the following symptoms:

* Often starts out in 2nd but if I give it tons of gas will shift into 1st and feels much better
* Sometimes starts out in 1st
* Almost always runs REALLY high RMPs before shifting from 2nd to 3rd

Generally it feels very inconsistent and crappy - wrong gear, high RPM etc. Any ideas? Vacuum lines to modulator?
BTW - it is a C5, nit a C4 as I first posted.

Ideas? thanks!

Still sticky valves in the valve body and/or governor.

C4 and C5 are basically the same trans.

 

[Broncofan76]

Still sticky valves in the valve body and/or governor.

C4 and C5 are basically the same trans.

so just ride it out and see if it fixes itself? Is there an additive that might free up some parts in there? Really like to avoid dropping the trans $$!

thanks

 

[Viperwolf1]

Look in the tech articles. There's one on cleaning up the valve body. I'd try that first.

 

[Broncofan76]

Look in the tech articles. There's one on cleaning up the valve body. I'd try that first.

Dude, am I being dense or what? I can not seem to locate the tech article on this subject. Would you be so kind as to provide a link?
thanks and sorry....

 

[Viperwolf1]

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