Steam Clean

The task for the weekend was to sort out the C4 Automatic Transmission gearbox. The guys at Mustang Maniac had already pulled the box out from storage and set it by the stand. The gearbox is lifted onto the stand and bolted into place just like the engine was so you can rotate it in any direction to work on.

Once we started to roll the C4 around the transmission fluids came running out and made a nice mess of Adam’s yard, it almost looked like the gear box was bleeding with the red transmission fluid. Sorry Mate! The gearbox was soaked in a strong cleaner and degreaser while we pulled out the steam pressure washer. The gearbox was pretty heavily caked in what ever from the road and was going to need a couple of going overs. Adam kicked of the first few jets of cleaning and the difference was amazing to even start with.

Adam handed over the lance to me and said with a smile, “I hope you have a change of clothes?” I laughed and said “I will be careful don’t worry”. I always carry a spare pair with me down to MM just in case as you never know so I wasn’t worried. I started and then I got covered within about two minutes flat. I was careful but still got sprayed. The weird angles and crevices on the casting made the water jet back out at strange angles, I was convinced that I was a water magnet. The only up side was the water was hot so it wasn’t to bad until I stood around. Needless to say I got changed after the soaking pretty quickly. Now it could be my paranoia, but I swear I could hear laughing as endless warm clouds of water came my way. But still the gearbox was looking great after the first clean up, more soaking for the second session and another blasting of steam. I did clean up the yard and swept the oil away after I finished with it all.

We allowed the gearbox to dry out and moved it over to where the car is stored in Yogi’s garage. On the stand Adam had a good look over the gearbox and discovered that the casing was from anywhere from 1970 to early eighties casing cast, but the rear section was from a 1964. This may not sound like an issue but the number of splines on the drive shaft could be twenty-four or twenty-six or a combination either end. So it looks as though the C4 case and insides; or the just the casing were swapped over in a previous ownership. Now this doesn’t worry me in the slightest, as potentially there is fifteen years less wear and tear on the mechanicals inside. The car stood for twelve years before I purchased her so that’s almost thirty years less wear and tear.


We rolled the C4 upside down and Adam started to undo the sump bolts to expose the insides and the filter which he was eager to look at.

Removing the filter which looked OK if not a little dirty, I was relived to see no gearing teeth wedged in their or a filthy sludge. surrounded by bits of metal swarf.

It turns out that some of the insides were from a 1974, which leads us to believe that a rebuild or swap out was performed at some point using the original parts from the previous gearbox that were not under stress or worn, such as the filter holder etc. The back section of the gearbox was unbolted and the housing removed for me to clean up at home. So far the gearbox looks OK with no bits of metal lying around. How it performs when it gets going we will have to wait and see.

Sunday was a case of clean up prep ready to put back on the main gear housing. This was a more degreasing and a light rub with some nylon scouring pads to clean the outside. The old gasket had to be removed and leave a clean surface ready for the new one.

The casing was dried and allowed to dry in the sun for while before the self etch primer was applied, two thin coats as recommended.

I sprayed a non visible area with wheel silver to see what it would look like, it came out looking like new aluminium not to far away from the original colour.

The reaming hardware for the nuts and bolts were cleaned up and sprayed with self etch again then with Tough Black which is a chip resistant paint. To hold all the bolts head up I used my useless malting wire brush to hold them while spraying. The bigger bolts were pressed into an old small box and sprayed the same.

The last part for now was the pipe work. There was the transmission dipstick pipe, a vacuum pipe and the selector arm to the gearbox. These were all rusty and in a bad way.

Same old story with these was to wire wheel them of with the rotary attachment to my drill. They came up quite well considering.


Obviously to leave them as bare metal would cause rust issues in no time at all, so again treated with a self etch primer then sprayed with a chrome spray. This was a new manufacturer I tried and the results were so much better than the Halfrauds version. The sprayed parts almost had a mirror like finish to them. The selector lever I coated in Tough Black again as this was likely to get more exposure to wear than the pipes would.

All in all a good amount of work. But, in the back of the mind I still worry about the health of the gearbox as it’s an unknown entity so far on the car.

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8 thoughts on “Steam Clean

  1. Nice work! That later ’74 C4 is stronger and better than what would have originally come in your ’66. It looks like it’s in good shape!

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