C4 expert

[Nicks501]

Does anyone happen to have a bronco C4 transmission manual or detailed parts diagram they can share?

I got a 1971 U14 that the PO converted to automatic (I believe the transmission was from a 75 bronco) and the infamous "don't worry it was professionally rebuilt" promise from the PO. Driving it would shift way too soon and basically skip 2nd. It has been leaking from the shifter selector shaft and so dropped the pan last night to at least replace the shifter rod seals when I found the transmission filter has this cool storage compartment feature that can keep an extra spring in case you don't need it..... So trying to figure out where this spring might go, and if I should go ahead and pull the transmission and rebuild this fresh "rebuild"....

 

[pcf_mark]

The best person w/o a doubt is ViperWolf user on here. There should not be any extra springs anywhere! The spring you found is almost certainly the pressure valve spring that is installed with the filter.

https://classicbroncos.com/forums/threads/c4-transmission-filter-change.278045/

The stock transmission shifts very fast and gets into 3rd gear by 20 mph if I remember correctly. You can adjust the vacuum modulator / make sure it has vacuum first to alter the 1-2 shift. Try shifting manually to be sure all the gears are present and functional. A stock c4 shift smooth and at low rpm making the shift not very obvious.

 

[Nicks501]

The best person w/o a doubt is ViperWolf user on here. There should not be any extra springs anywhere! The spring you found is almost certainly the pressure valve spring that is installed with the filter.

https://classicbroncos.com/forums/threads/c4-transmission-filter-change.278045/

The stock transmission shifts very fast and gets into 3rd gear by 20 mph if I remember correctly. You can adjust the vacuum modulator / make sure it has vacuum first to alter the 1-2 shift. Try shifting manually to be sure all the gears are present and functional. A stock c4 shift smooth and at low rpm making the shift not very obvious.

Thanks @pcf_mark! That is kind of what I was thinking/hoping that it is the pressure valve spring. I haven't had a chance yet to see if the small spool piece that goes on the end of the spring is/was anywhere in the transmission. I should have taken a picture of where this spring was, it was clearly not in position and sandwiched between the filter and valve body when the filter was bolted back on...

And that is good to know that most C4's shift so quickly, but this is probably in 3rd by 10 mph, it quickly shifts through 2nd gear. Manually shifting the transmission all gears do what they are supposed to. I had tried to adjust the modulator before tearing into the transmission with no differences noticed at shifting points and made sure I was getting vacuum to it (didn't measure with a gauge, the ole finger over the hose end technique). I have a new modulator to try also in case the other was bad/wrong style.

 

[pcf_mark]

The little pushrod behind the modulator is important too - I believe you can change the length of one to change shift points. It has been at least 5 years my memory is not fresh on that. If you have all gears and just the timing is not to your liking you can put a shift kit in from transgo to give it some more spread and firm up the shifts w/o making it rough.