C4 not shifting into 3rd

[WarEagle]

Hey all,

I'm having trouble with my C4 with only 50 rebuilt miles (hooked to a 300) shifting from 2 to 3rd. It is fine from 1st to 2nd. Also, when in 2nd and you let off the gas, it does not shift into neutral, it stays in 2nd. I have had this problem awhile, but have not addressed it as the truck was not street legal until recently. Last week though it did shift fine into 3rd, but is playing games again today.

Fluid level is fine, vacuum at modulator is 18" hg, modulator is tuned for the proper shift points. I did adjust it counter clockwise but the 1st to 2nd shift was too quick and still did not go into 3rd so I turned it back.

I've read several previous threads, but could not find a similar problem discussed. Any ideas???

Thanks

[WarEagle]

Well, some good news. I turned the screw in the vacuum modulator counter clockwise a quarter turn, then ran the truck. It shifted into 2nd quickly, about 10 mph, then finally hit 3rd around 40 mph. I ran the truck from a dead stop through the gears several times, then turned the screw back to where it was. Everything is shifting fine now. Something in there was stuck. Not sure if there is any damage internally, but so far so good. The kickdown linkage cable is hooked up also now and works.
Now just have to fix the 'bog' after it downshifts.

[Manny]

Sounds like you had a gummed up valve or sticky valve. Hopefully its freeing up get it warmed up real good a time or two let us know. Had a c4 in a bronco come thru a while back. I built it over a year ago now and the truck has not been run ye. Guy i built it for is doing total drivetrain overhaul. Scared we may have issues as you did...