Technical Anyone have experience peening porous holes shut in aluminum?

That’s a failed casting. Send it back.

 

I would say casting flaw. The aluminum or the mold was to cool at the time that case was pored.
Sad to say , that is a warranty issue.
Vic

 

If good old GM tells you "to-pack-sand"(pun intended) on a replacement.......I would clean with acetone/lacquer thinner and smear in the JB Weld.
Being on a seam I would worry peening would/could make matters worse.
The 'leak' you described would NOT be hard to live with if all else fails. IMO
6sally6

 

Yes.....despite the major setback in assembling the project a replacement is still my top choice. Like I said earlier though....took 2 months to find this one....not sure they'll fine another is a warehouse somewhere.

 

Thanks, a most helpful Thread subject.

 

Push the issue, defective new part and no other replacement inventory, go for a warranty payout and keep the trans. They don't really want to take it back and fix or scrap it. Make it so it's easier for you to go away than find a new trans in their system. Don't release the one you have until a replacement is physically in front of you at a dealer or distribution warehouse.

Those stating impregnation, the trans would have to be disassembled to outer casting only, single setups on impregnation are pricey. Had to deal with it thru work.

 

You might have gotten a seconds tranny. Or a product not quite good enough. But ship it anyway. Better than nothing. Try a can of stop leak.

 

If GM doesn't want to warranty it. you might think of using one of the windshield carck repair kits. It forces a type of plastic into some pretty small cracks and is should handle whatever heat the trans will generate. Just a thought.

 

OP, just curious, why a new NV3500...You mentioned it's a truck so you need the low first gear?

 

When I was fabbing the truck 8 years ago I picked one up cheap....like 200 bucks. Was going to just freshen it up and go...built my trans tunnel around it. When I tried to freshen it up it turned out to be the older HM290 style and wouldn't come apart easily. It was more cost effective to buy a new one rather than potentially break the HM290 case and pay for a rebuild. The newer version also has a single shift rail versus multiple. In retrospect another trans would have been a better choice but not redoing my trans tunnel and driveshaft now that it's all painted.

 

I've called all over the country this morning and this seems to have been the last transmission available from GM anywhere in the US.

 

That sucks!
Not a good place to be.
My concern would be that because the pinhole in on a seem, that it might just be the tip of the iceberg.
You could seal it with epoxy and never have another problem, or the vibration it may face may split the bottom of the case in half.

Are they talking about any kind of discount for you to keep it?
What are the chances of finding a new, or a good used case and swapping the new guts into it?

 

I used GMPartsGiant.com for the trans and they are deciding if I could do a return but they are trying to state that it's an electrical part since it has sensors for the speedo output and reverse lights which we all know is BS. If they do authorize a return that still leaves me with no trans.
I'm hoping GM will discount me in some way. But not sure how to go about actually talking to someone about it. After that if I epoxy it I may try to eventually pick up a good core for cheap and just hold it in case this case let's go.

 

I had a trans case in my drag racer with nearly the same problem. Drained the oil, cleaned it really good with brake clean, let it sit for a few days, cleaned it again, then jammed JB weld into the area, forcing into the area the best I could. Ran it for several years, until the case was replaced. And, it was not replaced because of the leak, but because the bearing bores had become loose.
Good luck with it.

 

WOW ... talk about trying their absolute hardest to weasel out of accepting the apparent fact that they sold a flawed product. That is both disgusting and pathetic.

 

Just a thought if GM blows you off completely.and it dips enough that you cant live with it......Pull the trans,and roll it over. Degrease the leak area then drill over lapping 1/8 inch holes about 3/16 inch deep being careful not to go through.Now you have a groove say 1 inch long. Clean again with brake clean then fill with JB weld.

 

Yes, kind of sucks. You probably don't have much to loose trying the peen and JB Weld. However, I personally would get a good fix on it sooner rather than later. Both an epoxy repair and a welding repair require pretty much oil free material to work. Aluminium is porous enough that oil impregnation is the biggest issue in both repairs. And the longer you run it the bigger the issue. And as others have mentioned, you may just be seeing the tip of the ice burg. So I personally I would want the peace of mind and would pull the tail housing off, clean it up, and maybe do some minor exploration surgery with a small die grinder. At that point you will know if the flaw is an epoxy or welding repair and just make it go away. Good luck.

 

Unfortunately there is no tail piece on the trans....it's the whole back of the case. I plan to pull the trans next week and flip it so I know there's no more fluid trying to seep out. Then I'll attempt epoxy. Not what I was hoping for with a brand new trans.

 

I've fixed porous Knucklehead cases with epoxy. Easy peasy, done.

 

Anyone ever tried this stuff? Buddy who used to be a GM tech suggested it.

ACDelco GM Original Equipment 10-2010 RTV Engine Sealant - 5.3 oz Cartridge https://www.amazon.com/dp/B007Q0ZOHQ/ref=cm_sw_r_awdo_navT_g_ZCXKTCENHR4ZBMW9ZWEC

 

First thing I would try is draining it, pull the drive shaft, put a shop vac on the tail shaft, suck some brake clean up there followed by wicking loctite.

 

If GM flakes out on you: Drill a tiny hole, tap it for a short 6-32 screw, smear some sealer on it and screw it in. Or better yet, I'd be real tempted to spend a couple hours disassembling it enough to where I could drill a hole directly into that pore and all the way through the case. Inspect the hole to see if there is indeed a larger flaw. Tap for an 1/8" or 1/4" magnetic pipe plug, screw it in and run it. Extra drain hole, and a magnet to collect steel "dust" that always shows up in a transmission.

 

I have had success with both epoxy & low temp aluminum " weld" in non stress situations like this . A little exploring with a small rotary file might shed some light on the problem .

 

Just a quick update on the GM side of things....got the runaround all day yesterday and was basically told because GM Parts Giant isn't a direct distributor for them the factory warranty on the trans doesn't apply...which sounds like BS.
Still sounds like I may be able to ship the trans back to the supplier for a refund but again that leaves me without a replacement trans. I'm fairly confident I can seal this up but still don't think I should be paying full price for a leaky transmission.

 

Before you ship it back, draw a big black sharpie circle around that pinhole so the next guy that gets the trans might look it over closely to see why that circle is there.

 

I have fixed similar issues with epoxy (JB Weld) as well. Like you know it has to be really clean to bond. One thing I also figured out is if you heat up the case area slightly with a heat gun, the epoxy flows and fills in better.

 

If nothing else did you use a credit card? You can always dispute the charge.Sounds like GM deserves it.

 

I did but the vendor isn't a direct GM affiliate

 

Ebbspeeds idea is the best. I have drilled and tapped many leaks to stop them. It will be permanent and you won't have to remove the trans.

 

I`d just return it and change transmissions. If you have trouble down the road. You are back to square one again. What was the cost of the tranny? Just because you have a part, doesn`t mean you should use it. Think long term.