Blasting and rear axle stuff

[71CHEVYSHORTBED402]

1971 SWB, rear leaf springs

I spent many hours cleaning this axle. Hit with a rust inhibitor cocktail for a stint, then rinsed it off. Less the rust inhibitor, it could work as is with the paints I'm using. But I'm not done (cough!). After all that work, I think I'm going to have it blasted anyway.

Won't come as a shock the entire housing shell is pitted (cast iron?). Sands nicely however. I've never had a piece blasted before, but my son says it will remove that pitting for a nice "finish". Is that true?

Apparently the manufacturer welds a protection "scab" on the axle for the lower leaf spring U-bolt plates. Some of that flaked off, so found another use for a welder.

Edit: My truck had a rubber fuel hose clamped onto a ventilation tube on the axle. I read that factory was a fitting instead? I also read a similar fitting was on the transmission vent tube? My transmission vent tube had nothing on it.



Other than that, for what it's worth the axle has many stamps. I can't make out a date stamp though, assuming there is one.

• The axle is stamped TRT W112, 3896839 N, GM 58, 12345, D141, 6T 90 (may be a character between T and 9), and I couldn't tell you, looks like CONG.
  
• The pinion is stamped 9210 GM

[B. W.]

It'll give it a nice finish. Sorry, don't have any closer. You can see a couple of spots I missed. I think I cleaned those up?

[71CHEVYSHORTBED402]

Originally Posted by B. W.

It'll give it a nice finish. Sorry, don't have any closer. You can see a couple of spots I missed. I think I cleaned those up?

Yeah, B.W., you cleaned those up. I blew it up. From what I see it looks nice. You know anything about the vent fitting, per the "edit" in the OP?

[Ironangel]

I use these vents on the Turbo 350, they just push in. On the axle housing I run a piece of 1/4" fuel line about 2' foot long from the barb on the axle to the vent and zip tie the vent and line to a cross member in the frame. https://www.ebay.com/itm/4-PACK-GM-T...!US!-1&vxp=mtr

[71CHEVYSHORTBED402]

Originally Posted by Ironangel

I use these vents on the Turbo 350, they just push in. On the axle housing I run a piece of 1/4" fuel line about 2' foot long from the barb on the axle to the vent and zip tie the vent and line to a cross member in the frame. https://www.ebay.com/itm/4-PACK-GM-T...!US!-1&vxp=mtr

Thanks Michael. My axle had the same set-up, only a P clamp for the frame.

[clay68c10]

The center of the axle is cast iron. Blasting may smooth it out some, but it won’t look quite as smooth like the tubes.

[volksworld]

the finish on blasting has everything to do with what grit is used...aggressive media used for fast rust removal can leave the surface rougher than it started out...finer grit leaves a better finish but takes a heck of a lot longer and therefore uses much more media....i use 180 grit aluminum oxide in my blast cabinet which leaves a finish i can prime and paint without sanding....but its still a casting which is pretty much molten iron poured into sand...blasting will knock off rust but the only way to get it really smooth is sanding or filler

[71CHEVYSHORTBED402]

Thanks for the info. I picked up an "NOS" vent tube for cheap like what Ironangle shows. They generally sell them as axle vents. I don't suppose it will fit on my axle port intended for a hose, but it will satisfy my curiosity. May fit on the transmission tube, but did those tubes have a vent from factory? Ironangle's link reads for transmissions, but not a 400TH. Seems to me the tube off the transmission would be the same TH350 and 400. Not exactly critical.

[B. W.]

Originally Posted by 71CHEVYSHORTBED402

Yeah, B.W., you cleaned those up. I blew it up. From what I see it looks nice. You know anything about the vent fitting, per the "edit" in the OP?

The factory vent on my D60 is in the left side tube. It vents right at the tube. (circled in red) I'm going to route it up to the frame (like Ironangel says)

[71CHEVYSHORTBED402]

Originally Posted by B. W.

The factory vent on my D60 is in the left side tube. It vents right at the tube. (circled in red) I'm going to route it up to the frame (like Ironangel says)

I agree, hose is a better option.

I should have mentioned, those vents seem to be standard for GM axles, for 1938 (all) through 72 (some). Skipped 1965 somehow, couldn't tell you.

The book shows the part is for 1966-72 service 10-30, G10-20 (van) and Blazer. What throws me off is it displays that info. under the header G-30. I'm missing the point.

The part # is 3820840..............Likely the same as what Ironangel shows only cheaper. According to some Ebay sellers, MUCH cheaper.