Post by crabmaster on Oct 29, 2013 21:26:03 GMT
Some years ago when I obtained my MKII auto, I had particular trouble with the main double-row bearing in the automatic transmission – the brass cage had disappeared from one side and left the balls there in to wander about of their own accord. This in turn slightly bent the output shaft which caused the governor to wear a nice track in the housing. While my repair at the time made the car roadworthy again, I always had that nagging feeling about the output shaft being now forced to run true instead of on the eccentric to which it had become accustomed. Matters came to a head when it became clear that more transmission fluid was being deposited on the garage floor than was acceptable – most of which was coming from the torque converter after the car had been parked overnight. Obviously the front pump had worn, and the return valve not functioning at 100%, and so oil just filled up in the transmission case and came out the park cable – the outer covering of which had long since cracked away. The situation was made worse by the fact that knowing that I would have to replace this gearbox one day, I had obtained a second spare gearbox and had last year rebuilt it with new bands and clutches. There it was, sitting under a bench, while oil poured out of my existing one inconveniently installed in the car.
After many months of imagining what life would be like without any oil leaks, I finally gave in and decided to swap things over. Now, ordinarily, this would mean removing the power unit (from above or below as your preference may be), but this time, I decided to test the idea that the auto box could be disengaged from the drive plate and dropped down leaving the block and all attached to it up in the car.
I had to remove the battery, dip stick, and starter motor from above. The bell housing nuts and bolts also had to come off. From below, the sump guard had to go and also the gusset plate on the driver’s side was removed. The gear casing to block bolts were surprisingly easy to remove using a long extension socket and universal joint. Dealing with the universal joint nuts (metal Hardy Spicer type on an automatic) is painful since the spring in the sliding joint wants to keep things together so one has to disengage an upper or lower ball joint and angle the hub out to provide clearance at the inner universals. With the transmission support by a jack and a piece of wood (see later note), I estimated I had about 10 mm to move the thing to the left (viewed from the front) so disengage the spigot and then it would all just drop down.
The picture below shows the transmission ready to drop.
Of course things are not so easy. Although I got the spigot out of the bush in the crankshaft, it wouldn’t clear the bolt heads that hold the drive plate on.
The picture above shows the situation looking up from below. The torque converter is on the right, and the crankshaft is on the left. The hex bolt head that holds the drive plate on to the crank is only half-height, but that few mm is enough to stop the torque converter spigot from coming down freely. However, one may rotate the crank a little so that the spigot comes through the gaps between the bolts - with a little bit of cooperation from the engine mounts.
It is important to have your block of wood arranged so that the gearbox remains level. Any tipping over will result in the corner of the casing where the valve body is to go upwards and so get caught on the body work after which it is very difficult to get it to come back again. Of course the whole thing is extremely heavy, and when one is sliding around on the floor with jack, wood, levers and so on, there is not much room for making any mistakes. In fact, I would not recommend using a jack and piece of wood as shown in the picture here – it is dangerous. You will see later that I did indeed make a nice metal frame to hold the gearbox but this was already fitted to the replacement transmission which was waiting to be installed. With much struggling, cursing and appeals to certain deities, I finally got the old gearbox out from underneath and put is aside for later examination and disposal.
Then came the task of installing the newly restored gearbox. Of course it’s easier to take things off than put things on, and the main difficulty to begin with was to position the sump gasket so that it wouldn’t slide out while everything was being manhandled into position. I overcome this difficulty by coating both sides of the gasket with petroleum jelly, and tying the gasket into position at three corners with small pieces of string. I argued with myself that once things were almost right, I could snip the knots in the string and just pull them out. This worked surprisingly well.
Picture above shows the new transmission ready to be lifted up. Note how it is sitting in a metal cradle which will sit on the jack and everything will be level.
Getting up past the drive plate mounting bolts was difficult and I had to loosen the engine mounts more and lever things over again hoping that the radiator was still happy to be coming closer to the inner guard on the other side. However, the spigot finally went through the gap and all I had to do now was to get it to go inside the bush. With the torque converter pushed back as far as it would go, I got things into position and installed one drive plate-to-torque converter bolt and left it a little loose. Then I rotated the engine so that this bolt was at the top and the torque converter could swing a little bit. By using a screwdriver, I lined up another bolt hole (through the starter motor aperture) and then to my great satisfaction I heard a metalllic pop as the converter spigot snapped into the crankshaft bush. I refitted the torque converter bolts and made sure it all turned freely before tightening them up. By the time, the bell housing was very close to the adaptor plate, but then there’s a dilemma. Should one bring the bell housing to the adaptor plate first, or bring the sump up to the block first? I decided that I would get everything in both planes just touching, then I loosely did up the bell housing, and then tightened up the sump. Then I backed off the sump bolts just a little, loosened and retightened the bell housing, and then tightened up the sump again. Then for good measure, I loosened and retightened both sets of fasteners in the hope that by the time I was finished with this laborious procedure, the bell housing or the sump and gearbox casing was not being stressed unnecessarily. What they did in the factory for this I will probably never know, but I am sure they didn’t do it the way I did it.
It was then a matter of reinstalling all that was taken off and refilling with transmission fluid. Type F fluid is quite hard to purchase, the only supplier that I found with any quantity being Supercheap (a "discount" spare parts chain in Australia often referred to as "Supercr?p"). Of course when starting, there is a metallic gurgle from the transmission as oil and air comes out of the pump, but this soon passes, and time for a road test.
Setting the throttle cable is done a little bit by trial and error. It is easy to know if it is adjusted too much one way since a small adjustment makes such a large difference to the gear change points. So, after a fairly long drive, I arrived home and eagerly, or somewhat apprehensively, bent down with a torch to look for any leaks. Yes, you guessed it, several drops showing – from places the other gearbox did not leak.
One such leak was from the drive chain cover. Readers will be pleased to know that this cover can be removed with everything in situ. It entails removing the battery and tray, and the bottom gusset plate. It is then possible to undo all those little 7/16 screws and drop the plate off. Scraping the old gasket from the alloy housing is a challenge but can be done. I cut out a new gasket, and coated both sides with silastic, and refitted. I won’t tell you how long it took me to get some of those screws back in their holes and tightened up. Hint: bent wire looped around a screw is better than a magnet.
Another leak was from the speedo drive. Once you take off the cable and outer cover, you can withdraw the speedo drive shaft. If yours is like mine was, then there will be a nice little groove in the shaft made by the lip of the seal. Extraction of this seal is very difficult and obviously was not designed to be renewed in the ordinary course of ownership. Then, getting a new seal is also difficult and had to be specially ordered. I then proceeded to put a sleeve on the shaft by machining down the shaft a little, fitting an over-riding tube of mild steel, and then machining the tube to a nice finish the same diameter as the original shaft. Once back in place, this cleared up the leak very nicely.
So, after much ado, the transmission was dropped away from the engine and then lifted up and replaced. Was it worth it? What did I save? I didn’t have to take off the engine mounts, exhaust, carburetter, radiator. I didn’t have to lift the car other than to put on stands so that it was high enough for the transmission to slide out the front. If I had taken the whole thing out, I would have had to detach the transmission from the block anyway. On the minus side, it is difficult to disengage the torque converter from the drive plate because there is very little clearance to allow the spigot to clear the drive plate attachment bolts. One has to be very careful with the weight of the transmission to let it down and raise it up while keeping it level.
Would I do it this way again? Possibly – now that I know what things give trouble. By far the most frustrating attachment is the universal joints. Did I clear up all the leaks? No - one remained, and a very difficult one to solve - the details of which I will leave to another story.
Tony
