How bad is this corrosion on my 915 Mag Trans?

[tocobill]

So I pulled the 915 trans I bought for the rsr out today to degrease it take a close look at it. It was pretty dirty .. typical oil/sludge grime and a few wasps mad a home in the casting fins. Got it all cleaned and noticed it had alot of corrosion in the bell area and where the studs thread into. My last 915 mag trans was in my 73 and it was in fairly good condition until I got rid out it. I never remember seeing this kinda of corrosion before. Looks like electrolysis from dissimilar metals steel and magnesium. Posted a few pics. Going to break it open in the next few days to see how bad the inside looks. What do the 915 Gurus have to say? Normal and useable or am I looking for another case? Thanks!

[moneymanager]

I'm going to guess it's just fine unless in pulling it apart you discover major thin spots or find all the external nuts and bolts "welded" in place.

[theiceman]

Bet that cleans up real nice with some carefull media blasting ..

[tocobill]

Thanks guys. Im not to worried about the case but these spots specifically ....

[gamin]

It should be fine. Clean it up maybe some gentle wire brush action. Then you want to preserve. Go to your local marine (boat) supply store and get a marine corrosion prevention product. Apply said product liberally to the clean tranny case. I did this to the mag case 911 tranny in my 70 with very good results. No visible corrosion for about 5 years now. I don't remember the name of the product but it was in an aerosol can and was bluish in color. Applied it to the mag parts of the engine case as well and all is good to this point.

[Porsche84]

Mag cases corrode worse where steel meets Mag. My guess is that your trans will be OK, but the two detent screws look kind of marginal. I think all of the Mag cases have thread inserts for the detents so that should be good just might be an issue sealing it. Be careful if you touch up (grind) the bosses there as the height is important. If you take off too much the detent will lock the shift rod. If there is nothing wrong with shifting, I wouldn't take it apart. Unless it had water inside there should be no corrosion in there. The side cover is easy to replace and cheap so you might want to go with a better one.

If you get to a point where you decide you need parts. I have a bunch of mag and aluminum cases.

[tocobill]

Thanks Gary and Jerry! I am going to open and rebuilt the box since its going in front of a 3.6 for my rsr build. The side plate will also get replaced. The "detents" were the corrosion that I was worried about the most. I will see what I have when I open it up and will most likely be in touch.

[Porsche84]

I have the late Aluminum side covers which are much stronger and way cheaper than billet. The later ones have an extra circumferential rib which adds much mor strength. I would not use a Mag side cover with the 3.6

[tocobill]

Thanks Jerry. Yep no mag side cover. Was going to go wevo side cover, gate shift, and bearing retainer. Is the later alum side cover really stronger then a wevo or cms billet piece? I went mag based trans for the steel bearing housings and the weight advantage over the later aluminum. I seen some really gnarly cars running these boxes with the additional aftermarket pieces no problem ... some have said they are stronger when built right. We shall see, lol.

[Porsche84]

I would not say the later cover is stronger than the WEVO billet but I have not seen one fail, but I'd probably do billet if I was building a high HP engine, ie over 400 hp. I have the 930 type retainer and the WEVO gate in my 915 trans and the later side cover. I am getting just over 300 hp with my 3.6 and the trans has held up well for 10 years of track use

[tobluforu]

Clean the hell out of it, then spray the crap out of it with gibs.

[Porsche84]

tocobill

Send me your address again. My computer crashed and all old e-mails are gone.....
jandsaustin1 at verizon.net

Thanks