Extension Housing Surface Rough See Pic
 

Need some help here with a 4R70W.
http://www.photodump.com/direct/Rommel/XTNhousing.jpg
While replacing the extension housing gasket (bad leak), I noticed that there are surface areas where the gasket is placed that are very rough.

These areas are also where the gasket had failed, pieces of gasket were actually missing.

My concern now is that if I install the new gasket, it will once again leak.
Are these legitimate concerns?
I used a scotch-brite pad to clean up the mating surface but it didn't help the rougher areas. I'm afraid to block sand it, I do have some bodywork sandpaper 2000 grit but I doubt that would even smooth out the rough spots.

Should I block sand it with something(?), just bolt it up with new gasket and move-on, or get a replacement housing?

Thanks guys!

A good machine shop could fix that. You can't improve it with a Scotchbrite, the surface is probably not flat and that's why the original machining didn't clean up that area.

It might be cheaper to replace than to fix, your call.

Can you tell if it is an unfinish surface or Fretting from vibration and metal transfer. If it is Fretting did you notice a loose bolt or two during disassembly? If clearance isn't a problem i'd have it decked by a machine shop or you could use some RTV on both sides of the gasket and torque the bolts down well and run it. But who knows how long it would last.

I would put some silicone on that rough part before installing the gasket. Looks like corrosion got the best of it.
Alan

thanks for the feedback guys.


5 out of the 6 bolts were loose, one of the top 2 was very tight.
I had tightened the bottom 4 bolts about 2 weeks ago hoping to stop the leak, but it seemed to have made it worse.

I don't know if the rough surface is that way because of the original casting or due to damage from leak/loose mount.

Anyone know if a new factory replacement ext. housing from Ford has the bearing and seal already built-in to the tail housing or will I have to purchase those also and then rent a tool for the install?

If I install it with the gasket as is, which RTV or Silicone is recommended?
Would it be Black RTV sealant?
On both sides or just the fubar'd side?

Thanks again for all your input.

Just get some good quality RTV put some on both sides and i think you'll be ok if you knock down the high spots. It sound like it is fretting from being loose. make sure to tighten them down in a criss cross pattern.