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Using stainless steel tunnel and diff brace bolts?
Anyone have experience using stainless steel tunnel bolts? Long story short several of my bolts broke due to corrosion. I did drive the car for 13+ years and 200+k year round, including snow the salt did a number on those areas, with some of those bolts broken and corroded. Car is still taken apart after parking it 2 years ago
I used regular gray Permatex anti seize before but it washed out. These days I use a more expensive marine anti seize but don't have long term experience with it. I'll note I have the aftermarket aluminum stiffener.
I likely won't drive the car in snow as much as I used to, as now I have an AWD CUV with snow tires, but taking the vette out for a spin in the snow is still fun
My thinking is- use the stainless bolts but use rubber/plastic washers to isolate the aluminum tunnel plate. Looks like these are suitable, from Amazon but slow boat from China.
Next- my DTE diff/trans brace has also seen better days. The aftermarket metric bolts looks like it didn't have much zinc on them. Some were so rusted I had to pound on the socket to get them to fit. However, none were stuck in the diffy case. I'm also considering replacing these with stainless metric ones. I plan to strip the peeling powdercoat and POR15 the brace. Any thoughts on the stainless into the aluminum diffy case? Big concern with the dissimilar metal. I'd use as much marine anti seize as possible.
Also these are A2 flange bolts, as the size and length in stainless was difficult to find, where the DTE bolts were 8.8 grade. Given that these don't directly support the diffy/trans, thought they'd be sufficiently strong. Thoughts/experience?
I’ve had stainless steel bolts on my tunnel plate for the last 10 years with no issues. Not sure about the trans brace though. Does your car ever see winter salt?
On structural parts like the brace the right grade stainless bolt could be used. But, generally speaking the average stainless bolt isn't really suitable for structural use. Generally speaking, I'd also be looking for rolled threads, not cut threads. You can see and feel the roughness of cut threads.
Do be careful because stainless can gall and then the bolt or hole threads get damaged and the bolt ends up stuck in the hole. It can happen easily without doing anything wrong. Even happens when just spinning a bolt into a hole if it catches a little and you use a wrench to keep turning it. Steel bolts can have tight spots like that and you just turn the bolt past them. A similar tight spot with stainless can end up binding so badly the bolt never comes out again.
This is really good stuff guys- glad I posted. Yes the car was exposed to winter salt, every year. The salt is really damaging- from causing the snow tire beads to leak, to eating away the PCM, lots of salt got caught up above the exhaust pipes and on the tunnel cover. I tried my hardest too to clean it with a pressure washer but the water may not have reached everywhere. I've salt proofed the car as much as I can- painting the ECU, using bead sealer, POR 15 the frame etc, now the stainless consideration.
The DTE brace bolts threads weren't bad at all, it was just the damn heads got real deformed cause of rust. Might reconsider there. However I poked around and sounds like there's some anti seize greases specifically meant for anti galling with dissimmilar metals in salt water for boats- like Tef-Gel. At $24 for 2 oz, it ain't cheap, but might be the ticket...
12-05-2017, 09:34 PM
Using stainless steel tunnel and diff brace bolts?
the salt did a number on those areas, with some of those bolts broken and corroded. Car is still taken apart after parking it 2 years ago 
