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haybayhill0 07-11-2010 05:40 PM

Transmission housing crack
Restoring a 1969 912-On cleaning the alum. transmission housing, I spot a 4" fore and aft hairline crack in the upper mid L side. It crosses one outer rib.I'm inclined to forget I saw it. What think? Thanks, Bob P.

Matt Monson 07-11-2010 05:45 PM

Crack or casting mark? Post a picture. It wouldn't be the first time someone mistook a casting mark...

cgarr 07-11-2010 05:45 PM

Can you post a pic? A lot of these are just casting marks.

dsmyth 07-11-2010 06:18 PM

Bet its a casting mark. I got fooled by my tranny last year. Almost shot myself. Glad I posted a picture here first. It looked so much like a crack.

haybayhill0 07-11-2010 06:18 PM

Definitly a crack. Bob P

Flieger 07-11-2010 06:36 PM

If your are so sure, why did you ask? Post a photo.

Quicksilver 07-11-2010 06:53 PM

There have been a number of "OMG I have a crack" threads that are actually casting marks on the transmission.

Really... Post a picture.

Matt Monson 07-11-2010 07:12 PM


Originally Posted by haybayhill0 (Post 5449621)
.I'm inclined to forget I saw it. What think? Thanks, Bob P.

In the absence of a picture, this sounds like a good idea to me...;)

haybayhill0 07-12-2010 07:46 AM
This is the CRACK-not a cast mark. My question is can I live with it? Thanks, Bob

Peter Zimmermann 07-12-2010 09:02 AM

Can you pull back a little with the camera so we can get a better reference of where the crack is?

Jim_Brown 07-12-2010 09:23 AM


I had a similar crack on my '69T mag case 901. Is your case Al or magnesium? looks like mag to me from the pic.

I replaced my housing with a 914 housing. The swap required relocating the vent and swapping internals/nose cone. I had everything out and apart already and needed the 914 for some pieces to do the simplified differential fix so it didn't cost much extra. The most difficult part was getting the pinion depth correct without the elusive pinion depth setting tool.

After I did all that I saw the thread below with a post by Grady Clay. Apparently these cracks are fairly common. If Grady is living with them on his 914/6 race car I wouldn't worry if I was you.

You may want to do some searching on the simplified differential issue/fix to see if it applies to your transmission.

Good Luck,

Matt Monson 07-12-2010 09:29 AM

It looks to me like a mag-case box and it looks like the crack is down towards the fill plug in the body of the case. If it were mine I would replace the case.

And yes, that's clearly a crack. Please don't take offense at our doubts. It's not personal. We've had people equally adamant about a crack in their case show up pictures of casting marks. We just want to be sure.

Peter Zimmermann 07-12-2010 09:38 AM


Originally Posted by Matt Monson (Post 5450515)
It looks to me like a mag-case box and it looks like the crack is down towards the fill plug in the body of the case. If it were mine I would replace the case.

Agree. At the very least I would disassemble the unit and try to learn why the crack is there, and how deep it is.

NoLift911 07-12-2010 12:30 PM

I guess it would depend on if it is leaking - from that crack in terms of an issue.

You mentioned that you cleaned this area up - was that area leaking, continues to leak?

On a 69 912 - I have not heard of too many grenading tranny cases....due to cracks or otherwise.

haybayhill0 07-12-2010 07:03 PM

Thank you all. The crack is high in the case- would only leak from splash. My son, who worked as a race school mechanic sme years past told of formula ford trans cases having to be crack welded regularly. This and Grady Clay's comments incline me to keep my head in the sand and at most stop drill the crack, V-grind it and epoxy fill. I'm not ordinarily this optimistic, only when the alternative is so daunting! Thanks again, Bob Prentice

GeorgeK 07-12-2010 10:33 PM

Is it your only car?
If not, drive it and check it after a week. If it is oily and dirty, it leaks. If not, space out the checks.
Don't start to drill/weld/epoxy as long as the leak is not determined.

haybayhill0 07-13-2010 06:08 PM

The crack is exactly where Grady Clay said his were. I drilled the ends(not quite through), Vee'd the crack with a Dremel tool and filled it with JB Weld. An expert aluminum welder friend thought this was a good idea. I feel much better now.Won't know denouement 'til I finish the restoation. Could be dead by then. By the way , JBWeld is the same colour as the casting- you'll never spot it! Thanks again for all your advice. Bob Prentice

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