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Old 05-28-2018, 05:05 PM   #335
1971_c10
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Join Date: Nov 2012
Location: Broomfield, CO
Posts: 242
Re: C10CJ: A Pro-touring '71 Stepside on a No Limit Pro-C10 Chassis

Oh, and another follow up... leaky 3rd member.

So I tore the rear end apart (this time I decided to go way down and pulled the brakes off to re-align the calipers a little better) and went to town. I decided while I had the 3rd member out I'd throw some paint on, so I did that first.

On to the leak. Turns out is was leaking from the gasket for sure and I wasn't quite sure if it was also leaking from the stud. So on re-assembly, I decided to just do RTV on the gasket first. So I applied some black RTV in a very thin layer to both sides of the gasket. Installed the 3rd member, but did not reseat the axles and left the driveshaft disconnected and just hand tightened all the nuts to where they were snug. I then let the housing sit one hour before torquing everything to the 35 ft-lb spec. After torquing, I let the housing sit for a good 14 hours before I filled with fluid.

Once I filled it with fluid I figured it would be about 2 hours before a leak started if one where to start (based on the last time I did this). Sure enough, it was leaking. Although this time I got lucky and as I crawled under the truck I got to witness a drop of fluid seeping out through the threads at the end of the nut. Not even through the split in the lock washer, but through the threads. Grrr.

So mod to this round, I pulled the nut, lock washer and copper washer on just that stud. I then put black RTV on both sides of the copper washer. Since this isn't inside the housing, I was very liberal with the RTV. I put the copper washer back on then put a gob of ARP thread sealant on the stud and put the lock washer/nut back on and re-torqued. I did this whole procedure very fast as the drip was at a rate of about one every 5 min, so I had limited time before more oil started to mix with my uncured RTV.

Well, so far so good. No leaks and I've gotten 2 thermal cycles on the rear end (get it hot by driving then let it cool). I'm still not 100% on this solution but it's working for now. If it start leaking again I'm going to need to take a real close look at the interface between the stud head and axle housing to see why it is leaking. We run metal to metal joints all over the jet engines I design and we don't have leaks on joints with upwards of 800 psi on them. Hmmm.

Ok, now rant, there are 4 studs below the fluid line, why this one leaks and the other 3 do not is beyond me. Frustrating for sure as it is a PIA to be pulling the 3rd member every couple weeks. But it's just ammo against my Ford buddies. Only leak I have on the entire truck is from the dang Ford part (of course none of it is Ford parts, but it's still a good jab).
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Chris

Build Thread for my '71 Pro-Touring: http://67-72chevytrucks.com/vboard/s...d.php?t=722029
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