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C4 Question..... I need Help!

Stutsmo

Contributor
Bronco Guru
Joined
Jan 24, 2009
Messages
2,547
Any C4 Gurus able to help me out? I have just finished converting my 69 DD to the C4.Everything is in and bolted up properly. The only thing that is not on is the kickdown rod because I have a holly 2 barrel carb and it looks like I am going to have to do some modification to it to get it to work properly. So I have the lever on the tranny in the up position.( I have actually tried both positions and down will not allow it to shift to 3rd.)
The problem I am having is 3rd gear is not working properly it seems week. The tires will spin on the jack stands but very slow and with very little power. So I took it down the street and it will not shift by its self into any gear I had to manually shift it. When I got to 3rd gear it felt like it coasted for a few seconds and then when it grabbed it went to 1st gear and the tires barked. 1st and 2nd gear worked good when shifting manually.

I have gone back over the simple things to make sure it is nothing I did when I put it in.
1. Made sure the shift linkage was right.
2. I am getting good vacuum to the shift module.
3. The transmission fluid looks good… still clean with no foaming.

I’ll tell you that honestly I know nothing about the inside workings of transmissions. Mine was rebuilt with a Transtar overhaul kit and a B&M Transpack shift kit when it was rebuilt. The pump was bad and had to be rebuilt. Other than that I am clueless. Does this problem sound like it is something in the shift kit was not installed properly? If so I still have the directions and could probably figure it out, or does it sound like something went wrong with the rebuild kit?
 
Last edited:

av bronco

Bronco Guru
Joined
Mar 3, 2008
Messages
1,742
Loc.
Palmdale CA
if it's a fresh rebuild you probably got a stuck valve in your V/B, assuming the oil level is correct and your shifter is adjusted correctly, might want to run a pressure check to confirm the rebuild is ok. there are two pressure cheks you can run, by the shift linkage there is a 1/8 pipe plug- that will tell you running pressure- then when you drop the valve body there are certan ports you can hit with air to make sure the clutch drums and band are not bypassing. these trannys are easy to get a speck of dirt in a valve and screw everything up, they have to be hospital clean.
 
OP
OP
Stutsmo

Stutsmo

Contributor
Bronco Guru
Joined
Jan 24, 2009
Messages
2,547
Thanks for the response. I checked the valve behind the vacuum shift modulator and compared it to a spare C4 that I have and discovered that valve was in backwards! I Put it in correctly and now the transmission works just fine! I am so relieved that an hour later I still have a smile on my face! Now all I need to do is get the top and doors back on and I can start driving it again. Hopefully sometime this week!
 
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