Easter weekend and I have lots of days on the car, well that’s what I was hoping anyway. I had promised to help to wife around the garden over Easter and the day we were hoping to have away in London didn’t happen for various reasons. But, I was still allowed a day pass to go work on my car so I was happy. I arrived at Mustang Maniac tools and food at the ready to last me the day. I managed to grab some time with Terry who kindly showed me how to change the main seals in the C4 transmission with me.
The first part was to remove the kick-down and gear lever on the side of the gearbox. This was a case of undoing the gear selector pressure plate on top of the valve body and removing the brains of the gearbox. The brains of the gearbox is a series of pipes and valves that operate in certain pressure conditions and should not be played with unless you know exactly what you are doing. A single thread from a cloth will be enough to damage the valves inside.
The bolts being removed from the valve body or brain.
Lifting the brain out and exposing the intricate pathways of the transmission fluid.
With the valve body lifted carefully out-of-the-way, it allowed access to the gear lever and kick-down mechanism. Remove the bolt from the outside and the two halves of the lever will separate the smaller part inside the outer sleeve.
The two rubber seals need to be replaced at this point, one on the main gearbox housing where the larger outer sleeve fits through on the outside casing, the other is on the end of the lever bar itself and will need to be pressed in with help of a vice as it’s a tight fit.
A rare glimpse at the inner workings of a C4 transmission.
To fit the lever back into place was simple enough, but locating the position of the gear selection lever to the valve body kick-down mechanism is tricky. The lever has to sit inside a cam and the kick-down connection sits just behind that. The horizontal bar at the top of the picture below shows where the lever cam must be located.
With the valve body in place it’s time to tighten the valve body back down in place, make sure the body does not lift of or move from the gear arm.
The next part would be to fit the filter back on, then the transmission sump. This is where my problem started. When the filter was first removed we also removed the spring but there was no steel ball bearing or valve plate sitting in the pressure relief channel. We were going to check if this model need it. It does.
The spring locates just where you can see two half-moon parts of casing just below the end of the spring. This is in fact a pressure regulator for the two half’s of the gearbox. So not only was it put back together with a pressure valve part missing, but there was also a bolt missing from the gear selector arm sprung plate as well. John hunted high and low all over the place for a ball bearing that size, he even opened up some scrap parts that may of had a bearing in them. Do you think we found one? No. We even split open a couple of old used spray cans to get the ball bearing(s) out. In today’s world that bearing has been replaced with a glass marble so it seems. Now it’s at this point I need to apologise again to John who punctured a can I gave him to get the (potential) bearing out. The tin of black spray paint gushed out, (even though no gas was coming out of the nozzle after I emptied it), and proceeded to spray satin black paint over his overalls and neck. Sorry John. John to his credit managed to remain calm, but the air did go a little blue if you get me. So I was going to have to try and buy one as the search was not proving to be successful at all. I was not a happy Easter Bunny at this point because some herbert didn’t put the gearbox back together properly, and it makes me wonder even more now about the health of the gearbox in general. The only good thing is that the fluid is clean, which can be a good sign of health for an auto transmission gearbox. But, these setbacks do happen in restoring old classic cars and I dare say there will be more. The guys at MM see it all the time where things are put back together with bits missing or not even secured where they should be, such as brake pipe valves, fuel lines, engine parts etc. Anyway in the mean time I cleaned up the back of the gearbox, fitted the seal gasket and re-attached the rear of gearbox and tightened the bolts up.
With the two halves back together again I fitted the new rear seal that protects the prop shaft from leaking when located in the gearbox. This particular seal is an upgraded version as these new seals have a collar rather than just the ring on the inside. I found a very large socket to fit over the end of the collar and tap it back into place.
The governor valve was next up to be fitted to the side of the gearbox, this is held in place by a sprung loaded clip and a bolt. Make sure the thin rod that fits into the end of the governor is in place or the gearbox will not change gear!
With the parts in place it was time to prep the sump and gasket ready to be fitted to the gearbox.
Now there wasn’t a great deal I could do so I just tinkered around. I said my farewells to the chaps at the end of the day and thought all the way home where I could get a single ball bearing from. Once I arrived home I went to my man cave and looked through my odds and ends tin. As a creature of habit when I finish a can of spray I cut it open to get the ball bearing out.
Note: Please be very careful if you are mad enough to attempt this at home as it could explode if any air pressure remains in the tin, if in doubt don’t do it.
In previous posts I have used the bearings to seal up fittings when spraying or to stop the area being contaminated. They do come in handy. So I opened the lid and tipped it out onto my bench, I found the perfect size!
I have now packed the spring and bearing away very carefully ready for next week. Not only did a find a bearing, but I found two balls, now I was a happy bunny again. It’s amazing how a single tiny part can stop an entire days plans. I was hoping to get the box fitted back on the car last week, but it will have to be next week now. Something to look forward to now.