In this video Jay Robarge of Broader Performance will go over some common intermediate servo designs, modifications as well as safety concerns when making modifications to the servo on Ford C4 transmissions.
Back in the early 90's I did the modification with using an A servo piston, without the O-ring on the outer piston, with an H servo cover. Then plugging the vent hole. I was using it with a valve body that I used the old B&M Manual-Pak kit to convert to a full manual, but still forward pattern, valve body. Never ran into problems with it locking up on me, but I was pretty particular on my maintenance and usually pulled the transmission out in 100 runs to freshen everything up, so there was not time for the seals to harden up. Where I DID have problems is that thin portion of the gasket, near the now plugged vent hole blowing out. Cost me $800 in a final round back in the late 90's. Made a girdle to surround the entire servo cover, with a set screw right over the weak spot of the gasket. That cured the problem, but never trusted the setup again, so I purchased an aftermarket servo. Quite honestly, I never noticed any difference between the H servo, my modification and the aftermarket one and was probably just as well off continuing to use the H servo. Where I DID have problems with it locking up in high gear was when I started to make a little more power, about 1986 with my '68 Mustang. I was still using the factory shifter with the solid shifter rod. The valve body at that time had just a standard B&M shift kit of that time period that had 3 different stages of modifications. The car was probably starting to flex and was pulling on the high gear detent. My memory from almost 40 years ago is not very good, but I think at that time I studied the hydraulic diagram and determined it was possible to leak pressure to start to lock up the low/reverse band if that happened. I DO know that I ended up skidding in the grass and was probably lucky that the car wasn't faster than it was. Bought an aftermarket shifter with a cable and also bought that B&M Manual-Pak at the same time and never had another problem.
Yes I used a B and M Manual -Pak back in 1976 in a 65 Mustang. But I did it for mountain driving so I could control the down shifts for engine braking going down grade. Kind of a hard shift but worked fine. I just followed the instructions.
@@GaryH-pw9cm They worked great for drag racing. Good firm shifts and no flare. Came with all the jigs to make the modifications and very complete instructions. I used that valve body for a lot of years and it is still in my shed somewhere.
Sonnax and Superior R Code servos for the C6 both have the o-ring. I will be running your C6 auto shift VB and just want to make sure I should be removing the o-ring in my Supeior R Code servo? Thanks again for putting your experience and knowledge out here for those of us wanting to learn the art of these antique transmissions.
Just looked at my Sonnax C4 "C" servo, and it doesn't have the o-ring, rather the body has a slight step on the od, and a notch in the side just like your mod. Love the videos, keep them coming! Btw I'll be in touch to order a stall converter for my c4 to go with your transbrake i just bought 👍
