Speedway Motors C3 Diff. Cover

[Ralphy]

I received my C3 differential cover last week. I removed some of the heavy cast lines and bead blasted. If you ever buy one of these, there is a little bit of work that I feel has to be done. The surface around the gasket area mount holes are not flat, especialy the side holes. The holes go right into the radius of the first fin. Mainly due to the thickness of the aluminum cast, so spot facing needs to be done. Very stout piece however. The flange thickness is app. 9/16" thick. This cover has a good area for mounting toe rods like the C4 design. Changing out your crossmember would be a must. I also will probably add a drain plug. The flange match to the housing is a little off at the bottom 45's, just a looks thing though. The pocket for the bearing cap looked real fugly, took some work getting in and cleaning up!





Ralphy

 

[69427]

What's your plans for the mounting configuration?

 

[Ralphy]

Great question, I have a 4" diameter round tube frame. My thinking is to weld a 1 3/4" crossmember tube forward, right over the halfshafts. This would be app. 1" to 1 1/2" forward of the mounting surface on the cover. I'm thinking of using a 1/2" thick aluminum plate. Going the inner width 26" with half shell aluminum clamps. Then maybe to insure it's rigid enough, two more half shell clamps just outside the cover mount. Sort of a home made bat wing.

The reason I want to put the cross tube over the halfshafts? I'm thinking maybe down the road adding an upper link and going to splined halfshafts. This would give me a good mounting point.

 

[68/70Vette]

Don't you think that after going to the trouble to make this unit, they would have had all the proper machine work done, so I'd be a straight install?

It's a casting? Wouldn't computer controlled machined billet be the way to go?
Isn't their a strenght concern with a casting? I suppose it's the way it is now, because they had limited financial resources.

I've always wondered why someone didn't make this part in aluminum, years ago. Also, a finned aluminum cover will help with diff heating. Tom, supposedly, will offer for sale and aluminum diff case and cover. I wonder if his, to be, cover will bolt to a stock C3 iron case? I'm thinking it won't since I'd suppose he'd have the cover ready for production and sale, before production of the case was ready for sale.

 

[Ralphy]

The thought never crossed my mind having to use a billet cover. $$$$$, Do you really see the necessity? Hell, how much strength is in a C4 aluminum cover? However it would be nice looking. Saw recently, Kirkham building billet Ford oil pans, WOW!

Also my first feelings about the limited machine work was surprised. But then again if your the type to go through all the fab work removing the leaf spring and changing the mounting. I would think you better already have an access to more than a set of Craftsman Tools. I wonder if you bought the polished version that they offer, would it still be lacking flat surfaces at the mount holes.

I really wanted the fake quick change cover, ............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ NOT! LOL