refinishing 8-3/4 housing

[Burdar]

It's time to turn my attention to refinishing my 8-3/4 axle housing. 

I'm not sure what the original application was but it's an older unit with 4 nubs on the back side.(maybe late 50's, early 60's car or truck)  It's been shortened to fit my A-body.  I spent about a half hour last night cleaning it up with a paint/rust stripping wheel.  It's now pretty clean but there are a lot of small pits and some pretty big scrapes/gouges in the metal.(maybe it was out of an old farm truck)

So, my thought was to start sanding with 100 grit on a random orbital sander and see if I can get some of the more minor pits out.  The larger gouges and scrapes will need to be filled with something.  I HATE...I repeat, HATE sanding filler.  It instantly clogs the paper and turns into a big mess for me.  I've heard JB weld is acceptable for this.  Thoughts?  Once the deep imperfections are filled I was going to spray with a high build primer and give it a good once over.(what grit paper?)

I've got some Extreme Chassis Black paint left over that I was going to top coat it with.  Looking online the instructions say to wait 24 hours between coats.  That seems like a long time to wait.   

[JS29]

Cheep fillers clog  sand paper,  Incorrect amount of hardener and not letting it cure will do it as well.  320/400 grit will do the job you want, but bare metal needs etch or epoxy primer before high build is applied.   

[Burdar]

The Extreme Chassis Black states not to use it over self etch primer.  Does that mean it shouldn't come into direct contact with it?  It's ok to use it if there is a high built in between?  Dumb question but I'm dumb so...

If I spray a self etch and then the high build...if I break through to bare metal while sanding, what do I spray the bare spots with?  Just mist them with more self etch?  It's OK to get a little bit of it on top of the high build?

[JS29]

  + 

[gzig5]

I would weld up the larger pits and scratches.  TIG is easier to dress but MIG would be fine too.  Mind your heat input.

[Marty]

The Extreme Chassis Black states not to use it over self etch primer.  Does that mean it shouldn't come into direct contact with it?  It's ok to use it if there is a high built in between?  Dumb question but I'm dumb so...

If I spray a self etch and then the high build...if I break through to bare metal while sanding, what do I spray the bare spots with?  Just mist them with more self etch?  It's OK to get a little bit of it on top of the high build?

Acid Etch primer will not burn you. Although, you shouldn't come in contact with any of these chemicals. Acid Etch (Self Etch.) primer is old technology. On some finishes, the Acid Etch primer will attack and break down these newer primers and finishes over time. Could be months or even years before the paint lifts and separates. I would use DTM high-built primer. "Direct to Metal." It bonds to metal like Epoxy and fills imperfections at the same time. Drys quickly and sands very easily. 220 grit then finish with 320.

[jimynick]

Ever the contrarian, when I did mine, I used "Tiger hair" a short strand fibreglass product that's waterproof. As mentioned, mix it correctly and in this case, let it go rock hard, then I used some 40 grit to knock it down to metal and then I'd DTM high-build it, and cut the first application with 120 and re-coat, and you should then be able to go finer to the 320-400 noted. You can ask Alan what chalk colour is appropriate. LOL     

[Burdar]

I would weld up the larger pits and scratches.

I just welded up the larger divots and ground them back flush.  Will continue the process in the coming days.  Thanks