Good morning. The 901 on my project has already been removed from the car. I need to open it up to replace the 2nd gear synchro and it obviously needs to be clear clean clean before I do that.

Is it safe to pressure wash the exterior case so long as I don’t spray where the input shaft is?

And been there / cleaned that tips to share?

Thanks!

Oven cleaner

If you are careful around the seals, and tape the breather well, pressure washer will work. I did this a little over a year ago (pressure washer), with no ill effect. I was VERY careful.

Start out with a small putty knife and clean all that you can that way. It will make the overall cleaning go better

+ brake cleaner and a piece of 6mil plastic to work over. Multiple cans. Stinks to high heaven and puts you on the moon.

First drain all the gear oil. I got a wood movers dolly and screwed some 2 x 4s across it narrower than the bellhousing (using long wood screws through the bolt holes to secure) so the transmission could stand vertically and be easily rotated to get at all the nooks and crannies.

Remove the speedo drive and block the hole. Tape up the vent well and put a tarp under the dolly/transmission as you work. it's a greasy mess. Like 914sixer said, use a putty knife to get all the thick junk. Then I used 4 cans of brake cleaner to loosen it all up. More expensive than oven cleaner, but it seems to work quicker. Then I removed the stub axles to get at the tight spots and used a steam cleaner to do the final cleaning (HF has em for under a hundred bucks and it's my new favorite tool).

Finally I painted with Alumi-blast and it turned out great. There's some disagreement as to how much paint (especially silver) contains heat, but I figure it isn't significant and protecting the box from the elements is probably better net-net.

If breaking the whole tranny down, I might consider having it dipped to save myself the greasy mess and my wife complaining about stains on the driveway;)

Click to view attachment

I use mineral spirits or naphtha and a small tray. I use a small bristle brush with the bristles cut short. Putty knife and small scrapers to get into cracks. I don't use brake cleaner in spray cans as much because I hate the spray coming back in my face. It also drys a little too fast. It works good as a last cleaner

Thanks for the discussion.

Did you use brake cleaner or brake fluid? i have tons of brake fluid but never thought of using it as a cleaner. Thanks

good catch. I used cleaner. F'in auto correct! Will edit.

Steam pressure washer. 5 minutes and done.

Steam cleaner. 210* hot water melts a lot of gunk off. Alternately you can use a pressure washer or take it to a DIY spray car wash. As others have said, tape up the seals and breather, I use aluminum duct tape.

After that foaming engine cleaner with an assortment of scrapers, then brake cleaner.

Then re-tape and media blast with walnut shells.

For a coating I use Dupli-Color spray hi-temp clear

Pressure washing is a mixed bag. I have seen corrosion from that technique. If you are pulling the stack anyway, just take the case and have it cleaned at a machine shop in a hot tank. If you are pulling the shafts from the intermediate plate, take that and the tail cone, too. Oven cleaner works best with pressure washer. Pre soak. I have someone else do it, I hate cleaning these things. I have found that acetone works wonders for cleaning up the old varnishy, baked on gunk inside and out.

This is what I did...

Sure looks nice!

Pressure wash, remove internals and then media blast in a tumbler.

No paint or spray coatings of any kind will be required on the finished product. The magnesium pores will close and the case will darken again over time as when it was new.


Click to view attachment

FWIW Ian's case looks great, but I'm into originality so its all a matter of preference.

I used this stuff:

https://www.lowes.com/pd/Crown-128-fl-oz-Se...Remover/3024382

I brushed it on, let it soak and then pressure-washed the outside. It took me 6 times before I got everything off.

I also chipped off the heavy deposits with a chisel, used a wire brush (hand and on a drill) and got in the nooks and crannies with a pick.

I did mine in a dirt area in my backyard. Then I scooped up the dirty dirt and put it in the trash.

Don't do what I did and soak it in a big metal farm tank sealed up with butyl using kerosene as a cleaning agent.

Oh, the case got clean. But the Kero ate the butyl sealing up the tank and stripped a layer of asphalt down my driveway. It was bad. It was also the day before I was supposed to fly to Cancun for a week. My driveway looked like ass for a few months till the sun bleached the asphalt all the same color again.

Zach

Never tried oven cleaner, but Gunk Engine Cleaner stuff works pretty good, especially if you do it on a hot day in the sun. Spray it on and let it sit for 15 minutes then use a stiff plastic brush and a tub of really hot water to loosen and much grime as possible, and hose it off.

Wish there was a good way to catch the oil and grime. Can't be good for the environment rinsing that stuff into the lawn or storm drain. Going to a professional steam rack is probably the most environmentally friendly plan.

While your choice of clearer/solvent is up to the individual, as others have noted heat works wonders.

I set my trans in front of just a standard electric heater for several hours prior to soaking with a non-toxic citrus based clearer. Let soak about 20-min and used a nylon brush to work it in.

After it is clean, use a fine brass wire wheel brush to do a final clean

The results are astounding.

it’s the heat part of the steam pressure washer that makes it work. Takes it down to bare metal without any chemicals. We did 30 trans and 20 engine cases in a day. Then did 50 - 356 engine cases and heads the next. Impossible without the right tool.

If you want it to darken a bit quicker.

Eagle One Mag Etch Wheel cleaner. Spray it on good and even, let it sit a few minutes, and spray off with water, dry it in an oven if you can for an hour. If not let them sit in the sun if you can and dry for 24 hours.

After this you can coat with Gibbs, which will darken it a bit more, or shot it with a graphite spray , wipe it down, and it will be nice and dark. And then seal with Gibbs to protect it.

The true way to paint Mag takes a lot of steps.

Clean
Oven Heat - outgas
Steam clean
(optional Weld pitting - then clean again, outgas again)
Prep with Alodine
Use an Acid primer, to get your bite, let cure
2K Prime cure (optional is to fill imperfections, then re 2K prime let cure a long time - 72 hours to a week, unless you can bake them)
Paint cure
Clear cure
Done

Old guy in Cincinnati that did Ferrari and Alpha magnesium wheel restorations taught me this method. Works very well very durable. He is gone now, but not forgotten. And no his name was not Johnny Rotten. One of his counterparts wrote a really nice article about the process. This guy mounts the tires before he does the top and clear coats. Oh course he is dealing with the Alpha and Ferrari crowd, so

Rattle caning VHT on it works, but it will start flacking off over time. I have one in my shop right now that looks like a snake shedding it skin.

Thanks, good discussion

Good idea on the non-toxic citrus cleaner, thats gotta be safer to spill on the ground than Gunk cleaner, which is probably kerosene plus who knows what else in a spray can.