tranny painting????

[oldmule]

I've noticed a few people on here have some really nice paint on their trannys. IE, Donsrods T

I was taught in school that the tranny breathed through the aluminum. But, looking at the painted trannys - TH350 in this case - I don't see any paint peeling or bubbling.

Can someone chime in on this? What prep did you use, is there a special paint? Or is it just my noggin over thinking this?

 

[Gastrick]

I've painted aluminum transmissions numerous times and have never had any kind of problem. On the transmissions that I want to look nice, I prime them with PPG DP epoxy primer and then paint them with PPG Deltron. I would guess that the brand of paint wouldn't really matter though as long as the case is oil/grease free. I've also spray bombed them with good results. Many aftermarket aluminum automatic transmissions such as TCI and others come painted also.

 

[Gastrick]

I reckon that since the case is aluminum, you should actually use zinc chromate as a surfacer, but I don't.

 

[oldmule]

The epoxy primer makes good sense. I haven't been around a body shop since HS days - um, back in 84-85, but have tried to watch what people are doing.
I want to do my 18 Dodge tranny, but wanted to check this out. I've always seen the TCI trannies and wondered how they did it.

Do you do any kind of surface prep other than cleaning?
Thanks,

 

[Gastrick]

Do you do any kind of surface prep other than cleaning?
Thanks,

It depends on the reult I'm after. Sometimes I completely smooth the tranny with disks and sandpaper if I want a show finish. If it doesn't matter, I clean the case with a solvent, go over it with a Scotch sanding pad, blow it real good, clean it with a solvent again, and shoot it.

 

[440shorty]

say what??

I'm not bashing here, just throwing in a fact. Transmissions "breathe" through a vent, located somewhere on the transmission. Not through aluminum, which if it were porous enough to serve as a vent, would also leak like a sieve.

On most GM rear-drive transmissions, the vent is either a thin metal or plastic pipe or a larger plastic tube with a "hat" that in any case is located on top of the transmission at the base of the bellhousing area.

Ford vent locations vary. Cast-iron case transmissions had a vent tube that exited the back of the case near the top, then turned downwards. Some C4's had the vent in the extension housing, at the front. C6 transmissions have the vent at the base of the bellhousing, up top, with a little metal "hat."

Chryslers are tricky. The vent is located at the top of the pump body, inside the bellhousing area. That is why a Chrysler can appear to be leaking out the front when over filled - the fluid is merely running out of the vent.
Painting the transmission is no problem, as has already been covered.

440shorty

 

[oldmule]

I'm not bashing here, just throwing in a fact. Transmissions "breathe" through a vent, located somewhere on the transmission. Not through aluminum, which if it were porous enough to serve as a vent, would also leak like a sieve.

On most GM rear-drive transmissions, the vent is either a thin metal or plastic pipe or a larger plastic tube with a "hat" that in any case is located on top of the transmission at the base of the bellhousing area.

Ford vent locations vary. Cast-iron case transmissions had a vent tube that exited the back of the case near the top, then turned downwards. Some C4's had the vent in the extension housing, at the front. C6 transmissions have the vent at the base of the bellhousing, up top, with a little metal "hat."

Chryslers are tricky. The vent is located at the top of the pump body, inside the bellhousing area. That is why a Chrysler can appear to be leaking out the front when over filled - the fluid is merely running out of the vent.
Painting the transmission is no problem, as has already been covered.

440shorty

Um yeah, the famous tube.
What I was getting at was the aluminum the tranny was cast from is a more porous metal that does allow a minor amount of gas passage. That gas I thought would cause issues with peeling. I'm not saying there is holes big enough for ANY fluid to pass through. It's a membrane affect. Kind of like the plastic on an ATV or motorcycle gas tank. It breathes as well and over time a painted tank will develop bubbles. At least on the older plastic tanks used post 84 model years in some rigs.

Have you ever broken a tranny in half and looked at the metal closely? It's quite porous.

 

[buckeyedon]

Oldmule, My 2 cents if you can bare it. When you were in school they said don’t paint because the transmission breaths. I believe breathing as they put it had more to do with heat dispersion than gases or venting. Remember the old automatics fluid pump efficiency is not that of a modern transmissions. They did not cool as good. And remember paint used to contain heavy metals lead for one. Painting in days gone by was also insulating and blocking heat release. And they would run hot. We don’t have this problem with modern paints. So no problem.

 

[LoneWolfStreetRods]

You can paint trannys, but boy, do they get ****ed.

 

[oldmule]

Oldmule, My 2 cents if you can bare it. When you were in school they said don’t paint because the transmission breaths. I believe breathing as they put it had more to do with heat dispersion than gases or venting. Remember the old automatics fluid pump efficiency is not that of a modern transmissions. They did not cool as good. And remember paint used to contain heavy metals lead for one. Painting in days gone by was also insulating and blocking heat release. And they would run hot. We don’t have this problem with modern paints. So no problem.

Makes good sense to me. Thanks!
Part of what I was referring to was from tranny classes and part was from college physics...... I did both so that if I couldn't get a decent Geology job, I could fall back on mechanics..... But, when you put yourself through school, the extra money from turning wrenches helps.

Lonewolf, I imagine they would get a little ticked (you might change their color scheme for the evening), now change that to Grannys and boy, we got a heck of an issue...