Should I paint the inside of a bell housing?

[robroy]

Good day!!!

I'm going to be painting the exterior of my bell housing. The inside of the bell housing looks very clean (no rust or anything) but is bare metal.

Is it a good idea to paint the inside of the bell housing in addition to the outside? Or is there any special reason I should avoid this, like paint coming off and getting on the clutch or anything?

Or is there just no point in painting the inside since it never gets rusty and it's invisible once put together?

Thanks very much for the excellent advice! I'm going out in the yard to sand blast the exterior now.

-Robroy

[averagef250]

Might as well paint the inside as well.

[robroy]

Hey Dustin! Thanks for replying. Okay doke, I'll go ahead and paint both sides.

Thanks again,
-Robroy

[robroy]

One more question: Would you recommend painting the machined, flat surfaces on the bell housing or avoiding them?

As I understand it, the machined surfaces on the bell housing don't have to actually seal--they just have to discourage dirt/water from splashing up around the clutch. Is that true?

So is it fine to go ahead and paint all the machined surfaces as well, or would it be more ideal to mask them off and leave them bare metal?

Thanks very much!!!
-Robroy

[fireguywtc]

I would Robroy, you are not going to hurt anything. You may scratch up the machined part on installation but no big deal. Paint it all!

[robroy]

Excellent; that makes it a whole lot easier!

Thanks Bill!
-Robroy

[robroy]

Degreased it, blasted it with aluminum oxide, cleaned it up, and gave it a coat of Rust Bullet. It looks like a whole new animal! I'll post some photos when I get them.

Thanks for the advice!
-Robroy

[mmerlinn]

Paint basically serves two purposes.

1) Alleviate possible corrosion problems
2) Make it look pretty

Bell housing corrosion is not an issue. You can leave a cast iron bell outside in the weeds for DECADES and not be able to measure the corrosion. Aluminum bells, even when painted, seldom last more than a few years in the weather before they are corroded beyond hope.

Installed in a vehicle both last for DECADES without corrosion problems except in extreme conditions. Therefore I see no reason to paint the bell at all for corrosion resistance.

Since no one will be seeing the inside of the bell, painting the entire bell to make it look pretty seems like a waste of paint on the inside. Outside is an entirely different matter.

Me? I would only paint the outside.

[fmartin_gila1]

I would not paint any of the machined surfaces. If you got extra heavy coating of paint, could possibly contribute to problems with misalighnment and clutch malfunction.

Fred

[mmerlinn]

I would not paint any of the machined surfaces. If you got extra heavy coating of paint, could possibly contribute to problems with misalighnment and clutch malfunction.

Fred

Fred is correct.

NEVER paint ANY machined surface on the bell. Your tolerances will be screwed up. And screwed up tolerances cause problems.

[robroy]

Hey Fred and Mmerlinn,

Oh well too late! But I still have a chance to get rid of the paint from the machined surfaces if I think I need to. I can use a wire wheel to scratch it off. The only trouble is that unless I'm extremely careful there, I could wind up removing a tiny yet significant amount of metal from those surfaces (and make them not as flat anymore also).

Any more opinions on this?

Thanks very much!
-Robroy

[robroy]

Also, I'd be wondering how close the tolerances really are with a bell housing. A layer of paint will add maybe 1/32" (for thick paint) to the space between the bell and the engine, and another 1/32" to the space between the bell and the transmission.

My numbers are based on my imagination, not upon actually measuring the thickness of paint. But with these numbers, would 1/32" difference really do anything there? I thought the tolerances weren't that tight in that area.

My decision at this point is whether or not to try to remove the paint from those surfaces. I'd do it in a second if there were some way to guarantee not harming the machined surfaces with my efforts. The paint I used (unfortunately at this point) contains isocyanates so it should be very hard by around now. It has had twenty hours to cure.

Thanks!!!
-Robroy

[mmerlinn]

It is more of a question of whether the paint is EVENLY thick on the surfaces. If it is not, then you run the risk of cocking the bell to one side or the other misaligning the transmission and input shaft. If the thickness is relatively uniform, you are probably ok as the difference in length really does not matter.

If it is a cast iron bell it is darn near impossible to remove enough metal to make any difference. With an aluminum bell as long as you don't go overboard you probably won't hurt it.

[robroy]

Hey Mmerlinn thanks for your reply!

Yeah it's a cast iron bell. The paint looked super even on there, but naturally that's not really possible to gauge with the naked eye (unless it's extremely wrong, which it ain't).

Maybe I'll take a scraper to the paint on the machined surface and see how easily it comes off. If I'm lucky I got a bad scald on the paint job and it'll scrape off easily!

Thanks again,
-Robroy

[mmerlinn]

Try removing the paint from inside the round hole where the bearing retainer fits. You MUST remove any paint there, so that will tell you how hard it comes off. The big round hole fits the retainer relatively tightly so as to index the bell to the case.

Using a power WIRE wheel to remove paint won't hurt your bell. Don't use a power SANDING wheel.