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Discussion Starter · #1 ·
So I’m getting ready to put an HD valve body in when I do my filter and fluid service on my 68
I’ll be using an OE replacement pan from Dorman with integrated drain plug (I don’t tow so don’t need deep pan heating up 4 more quarts of fluid)

my factory bolts are already pretty rusted out so I was going to source new ones - they are marked 8.8 on the bolt head

my choices are zinc plated 10.9 bolts,or stainless bolts marked A2-70, which I’m told is less strong overall

in an application like this with 7-9 ft lbs max torque per bolt does it matter if they are “not as strong” as original? Obviously stainless is the best corrosion resistant - but if it would cause an issue to use them I’ll get the zinc plated 10.9
 

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So I’m getting ready to put an HD valve body in when I do my filter and fluid service on my 68
I’ll be using an OE replacement pan from Dorman with integrated drain plug (I don’t tow so don’t need deep pan heating up 4 more quarts of fluid)

my factory bolts are already pretty rusted out so I was going to source new ones - they are marked 8.8 on the bolt head

my choices are zinc plated 10.9 bolts,or stainless bolts marked A2-70, which I’m told is less strong overall

in an application like this with 7-9 ft lbs max torque per bolt does it matter if they are “not as strong” as original? Obviously stainless is the best corrosion resistant - but if it would cause an issue to use them I’ll get the zinc plated 10.9
There are a couple things to know about fasteners. The torque is the preload/deadlog which pre-stresses teh bolt and stretches it like a spring. Then you have live loads ontop of that. You do not want to torque a bolt to its yield strength and then have significant loads ontop of that because it will yield the bolt and permanantly deform.

If a grade 8.8 is specified then it is OK to use a grade 8.8 bolt and more than likely use a stronger one. ]

A2-70 if manufactured to ISO 3506 has a minimum tensile strength of 700 MPA, 8.8 is 800 MPA. More than likely the A2-70 would be OK. If you do use it, use a thread lubricant and thread slowly by hand, so that the threads do not gall.

You could use the Grade 8.8 zinc plated so long as the drain pan you are bolting it to isn't aluminum. Zinc + Aluminum do not play nicely together. I'd probably go with the zinc coated (galvanized) fasteners or find some non-galvanized ones.
 

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Discussion Starter · #3 ·
These are the sort of things I wanted to know - I was more concerned with 'well over time if the stainless is a weaker bolt it may lose torque/loosen, the vibrations of the transmission etc'

The stainless A2-70 I would use a drop of anti seize on it for galling like you mentioned, thread by hand to snug it and start with 6-7 ft lbs of torque (105 in-lbs is the max spec for the transmission drain pan) - they are small M6 bolts so really not much is needed to secure.

The transmission case is aluminum I believe? So would there be an issue of zinc plated bolts being used on the case (the threaded portions?) - the pan I am using is an OEM replacement so it is stamped powdercoated steel
 

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These are the sort of things I wanted to know - I was more concerned with 'well over time if the stainless is a weaker bolt it may lose torque/loosen, the vibrations of the transmission etc'

The stainless A2-70 I would use a drop of anti seize on it for galling like you mentioned, thread by hand to snug it and start with 6-7 ft lbs of torque (105 in-lbs is the max spec for the transmission drain pan) - they are small M6 bolts so really not much is needed to secure.

The transmission case is aluminum I believe? So would there be an issue of zinc plated bolts being used on the case (the threaded portions?) - the pan I am using is an OEM replacement so it is stamped powdercoated steel
Well if zinc doesn't play well with aluminum ,then does it make sense to be threading a zinc coated bolt into aluminum ? I sure wouldn't do it .
 

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These are the sort of things I wanted to know - I was more concerned with 'well over time if the stainless is a weaker bolt it may lose torque/loosen, the vibrations of the transmission etc'

The stainless A2-70 I would use a drop of anti seize on it for galling like you mentioned, thread by hand to snug it and start with 6-7 ft lbs of torque (105 in-lbs is the max spec for the transmission drain pan) - they are small M6 bolts so really not much is needed to secure.

The transmission case is aluminum I believe? So would there be an issue of zinc plated bolts being used on the case (the threaded portions?) - the pan I am using is an OEM replacement so it is stamped powdercoated steel
Any salt on the roads where you are?
Well if zinc doesn't play well with aluminum ,then does it make sense to be threading a zinc coated bolt into aluminum ? I sure wouldn't do it .
You'll get varying opinions on that one. 'Mileage may vary'. If you look at the Galvanic series you'll find out that zinc and aluminum are pretty close to each other. Stainless and Aluminum are further away. Most aluminum boat builders(modifiers) will specify stainless fasteners, that's the only reason why I say they don't play nicely. In theory they work well together.

Fastenal actually recommends galvanic bolts and aluminum together. In practice you'll find most people will install stainless to aluminum without incident all the time. I know I have. I have stainless hardware all over my tin boat, but it's usually in fresh water.
 

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You'll get varying opinions on that one. 'Mileage may vary'. If you look at the Galvanic series you'll find out that zinc and aluminum are pretty close to each other. Stainless and Aluminum are further away. Most aluminum boat builders will specify stainless fasteners, that's the only reason why I say they don't play nicely. In theory they work well together.

Fastenal actually recommends galvanic bolts and aluminum together. In practice you'll find most people will install stainless to aluminum without incident.
I think I would just get some new OE bolts .
 

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I think I would just get some new OE bolts .
Don't need to go to the OEM. The type/material is stamped right on the head. You can just buy Grade 8.8 steel bolts and that is what OE used. Stainless steel and Steel are pretty close to each other as well so there wouldn't be much change corrosion wise on the aluminum between the two.
 

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Discussion Starter · #8 ·
Wow I like to start intelligent conversation here for sure -

Spoke to Dave @ Mag Hytec and he includes zinc plated bolts and stainless washers with this aluminum pan because of the dissimilar metals theory (stainless threads on an aluminum threaded case) if that says something - No salt on the roads by me, I do spend a fair amount of weekends at the beach (salt air) during the summer but my truck does not see the hell of winters you all do -

OE bolts are 8.8 steel that is black oxide (manganese phosphate) and the only reason I'd like to get stainless or zinc coated, is because I barely have any corrosion anywhere on the truck but my transmission pan bolts oddly enough are showing some corrosion although the rest of the fasteners on the vehicle aren't

If I wasn't being a cheapskate and just bought a deep pan for the transmission I wouldn't even be making this thread or asking these questions I'd just have the zinc plated hardware Mag Hytec includes :)
 

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You can go with OEM grade 8.8, zinc coated, 316 stainless, 304 stainless, doesn’t really matter. Zinc or copper coat. Strength of all of these are about 3 to 4 times more tensile strength than the aluminum casting they are going into. That’s why the torque value is so low. Just go to local hardware store and get stainless steel and move on to the next project.
 

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Discussion Starter · #10 ·
Thank you Gurus! I will report back if I end up with the Dorman pan on my trans (and a drop of anti seize on the stainless bolts to prevent galling)
 

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Discussion Starter · #12 ·
That is what I plan on- the 19-up trucks use the same pan etc - but Mopar now fits with a reusable gasket instead of RTV

My trans builder who built my heavy duty valve body says he uses the Mopar reusable 19-up gasket on every 68RFE he builds whether it’s a deep aluminum aftermarket pan, or stock pan, hasn’t had a leak yet - I trust him so that’s what I’m doing. Going to surgically clean the RTV up and I’ll be much happier with a drain plug and a gasket going forward
 

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That is what I plan on- the 19-up trucks use the same pan etc - but Mopar now fits with a reusable gasket instead of RTV

My trans builder who built my heavy duty valve body says he uses the Mopar reusable 19-up gasket on every 68RFE he builds whether it’s a deep aluminum aftermarket pan, or stock pan, hasn’t had a leak yet - I trust him so that’s what I’m doing. Going to surgically clean the RTV up and I’ll be much happier with a drain plug and a gasket going forward
Thanks for that info. I kick myself I didn't put a drain plug in from Genos on my first change . I will for sure on the second along with that reusable gasket .
 

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I serviced mine in the driveway alone and also installed the Mag-Hytec pan with the gasket. What a pain. But got it done and no leaks. That pan is a heavy beast. My brain keeps writing checks my body can't cash.
 
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