Posted By: turbobitt
TF 727 Valve body check ball questions - 03/21/09 02:46 AM
OK , this may be a stupid question and/or beaten to death, but I can't find anything in the tech archives. Why do some shiftkits remove some of the checkballs and others do not ? I am interested in making this shift as hard as possible for that "Hot rod" feel. This is a manual shift VB that I'm working on. I was comparing an old set of Fairbanks instructions to a set of Transgo instructions and noticed that one of the small checkballs is omitted for "Competition use" in the Fairbanks kit.
Allan G.
Posted By: John_Kunkel
Re: TF 727 Valve body check ball questions - 03/21/09 05:34 PM
Removing the #6 check ball (the one in the "D" shaped pocket) allows the maximum amount of fluid flow to the kickdown servo and the firmest 1-2 shift. There are two schools of thought on this, one school says that's good and another says it's not so good; thus the difference in kit makers instructions.
When using a VB with rear band apply the maximum fluid flow often causes severe overlap on a manual 1-2 upshift since the rear band just can't release as quickly as the kickdown band applies. Leaving the ball in place and adjusting the size of the servo feed orifice makes for a good firm shift without the overlap. Also removing the ball and/or blocking the accumulator makes the trans shift so hard that it can shear the splines in the aluminum front pinion carrier.
Depending on the year there can also be check balls in the transfer plate, one slows the application of the rear clutch and the other slows the application of the rear servo, this is intended to prevent parts breakage and has no adverse effect on performance. I've never understood why some kit makers have you remove them, no advantage that I can see unless you're trying to rock a stuck car by rapidly shifting from "R" to "D".
Posted By: BradD
Re: TF 727 Valve body check ball questions - 03/21/09 09:53 PM
John, are you saying the old trick of the accumulator blocking rod is a bad idea?? I definitely like a firm shift without tearing up parts!
Posted By: John_Kunkel
Re: TF 727 Valve body check ball questions - 03/22/09 06:57 PM
Actually, the accumulator SPRING is my favorite topic, while I don't advocate using the blocker rod I do recognize that it does firm the shift.
Since the rear servo releases through spring pressure only it can't release at the same rate as a hydraulic servo of near the same size can apply. Even if the buttmeter doesn't feel it, there is overlap if the servo feed is unrestricted. If you jack the rear wheels clear of the ground and manually shift from 1-2 at around 1500 rpm you will most likely see the rear wheels come to momentary stop due to the overlap.
