1998 XJ....... what material is the transmission case made of ??? Aluminum? Iron? Mild steel?

 

336 cast aluminum

 

Thank you. I'm in process of replacing lines with AN fittings.

I'm going to use aluminum fitting as I'm assuming it's best to use aluminum to aluminum.

 

It doesn't really matter as long as you get the right thread and get it sealed

 

Actually, the opposite is true. Aluminum to aluminum is not recommended in most cases, as the aluminum can weld to itself. If you do use aluminum fittings, use some copper anti-seize.

Better yet, use steel fittings.

 

See that's what I don't understand. I know that galvanic corrosion exists with any dissimilar metals, ie aluminum and steel. I would think that would make it worse.

I know that aluminum to aluminum can 'gall' but that's usually with a lot of friction and/or load, ie small threads, high load/repetitive strains.

And as pointed out important to use anti-sieze (I use nickel based).

So which is more important......galling versus corrosion??

The corrosion is not such a big issue if it is 'sealed' as someone suggested earlier. But I live in a very corrosive winter state.......just eats everything up. And that area is very exposed.

 

There's no galvanic corrosion unless there is water, as in a coolant system or a boat sitting in water. But from road spray, I'd be a lot more worried about the aluminum fittings. Either way, remember that your lines are steel, so you arelady have steel in the mix. Fluid Film is your friend!


In addition to galling (which can happen with threaded fittings, no repeated friction required), there is the problem of like metals simply becoming welded together. It's called, "cold welding".

https://www.practicalmachinist.com/v...threads-76880/

Nickel and copper are right next to each other on the galvanic table, so no real difference.


https://bearhawkforums.com/forum/bea...el-an-fittings

 

I'm not sure what alloy stainless fasteners come with parabolic radio dishes for long distance data links, but they are single use permanent if you don't use antiseize on them. They weld right when you tighten them.

Only slightly related to this discussion, but take it for what it is.

I think we just about finished the topic when water (polar liquids) vs oil (non-polar) came up. But I know for sure I don't like being the solver that has to cut those stainless bolts, and I doubt you want to be the one to solve aluminum ANs welded into aluminum holes.

 

Yeah, I found on motorcycles that stainless fasteners into aluminum threads would seize pretty bad without antiseize. Careful getting the old adapters out and screwing in the new ones. A few people here have managed to break off the aluminum boss on the transmission.