Posted by David Blodgett on December 06, 1998 at 23:14:16:
In Reply to: Re: C4 tranny improvement...harder shifts for pocket change! posted by T.L. on December 06, 1998 at 14:46:48:
Well, I'm not sure if this is the problem, but it could just be a mildly clogged filter. The way I understand it the valve body in an automatic tranny acts kind of like a computer. It takes input like engine speeds, etc. and decides where to send the fluid. I could be that at a low rpm while the fluid isn't being forced through the converter as hard, the valve body starts sending the fluid through the second gear circuit, then after that circuit fills up if the fluid is being slowed down by a clogged filter it may be taking long enough for second gear to kick in that the rpms are still high enough to make the valve body to shift into third gear. Then when it does shift into third gear the engine rps'm drop because you're not traveling fast enough causing the valvebody to shift back into second. I'm not sure if this is correct, it's just a guess. But a filter only costs a few dollars, and it never hurts to change it. (even if you don't use the cotter pin.) :) I was having similar problems with mine, and Iput in a new filter and new fluid. Things improved a lot. Good luck.
: That's interesting; my C-4 always shifted really hard in completely stock form and I've always loved that. But I realize that not all C-4s shift as hard as mine. My tranny has a problem with "free-wheeling" between 2nd & 3rd when going from 5-10 MPH (such as in a parking lot). That's the only time it does it and otherwise it works great. Any thoughts??...
: : Going through some books in the local library, I found an article on modifying a C4 for harder, firmer shifts that will cost only a few dollars. It is done by increasing fluid pressure from 65-70psi to in excess of 100psi. All you need is a new gasket, filter, and a small cotter pin. The modifications can be done WITHOUT removing the trans from the car ( a huge plus ). I'm going to scan the article as soon as I can check out the book again. If you would like a copy of the article, send me an email.