The silicone is the factory seal on those (extension housing and top) it was cheaper to manufacture that way. It being gobbed on and smeared like that doesn't speak of much care being taken during the 'overhaul'. As for being cleaner, it's kind of hard to see in the picture, is that grit inside the shifter housing, or casting bumps? The dents in the seal look like a hack install, however the seal doesn't look new.
If you want to pull the top to check inside, you have to pull the extension housing off. To do that put it in Neutral, then you have to pull the shift block off, drive the roll pin towards the case with a suitable tool, the block is relieved on the bottom side, so after you drive it far enough it will more or less fall out. You then have to wiggle the block off the back of the shift rail, be careful there is a ball bearing and spring in a hole in the bottom of the shift block that ride in the detent plate (the part in the picture with the blue grease on it) don't loose them (or the roll pin). After that you take ALL the bolts out of the extension housing and it should pull off (a rap or two with a plastic hammer helps, but be carefull not to crack the top casting as it sticks into the shifter box). There is a bearing on the back of the countershaft (the bottom one) in the back of the extension housing, I have never had one fall off while doing this, but it's something to be aware of
There should be an o ring around the stub on the top casting where it mates with the shifter box portion of the extension housing. Take all the bolts out of the top and it should lift off of the main case, you will liely have to wiggle/ finagel the shift forks out of the gears (as they come with the top). The sender with the wires on the top is the reverse lockout switch (if it has one) and can stay there (the one on the side is the backup light switch).
You should have a good look at the inside of the box now, you decide how it looks (post pics too, please).
Just out of curiosity, is this supposed to be a World Class or a Non World Class box? The WC boxes have fiber synchros and needle bearings between the gears and the main shaft, the NWC box has brass synchros and bushings between the gears and main shaft.
Not trying to come off as a know it all here, I have had a few of these that far appart and no further (WC & NWC are the same for this). The biggest pain is getting the shift forks out and back into the collars (as long as you find ALL the bolts, on the first one I did I missed ONE bolt on the extension housing for about 15 minutes
).
If you get as far as puting the extension housing back on and it comes up about 1/4" or so from seating on the main case it's probably the bearing on the back of the countershaft. Some of them have a small relief notch in the collar of the bearing (it doesn't look like a 'manufactured' notch on the ones I have seen) that lines up with a tab or tang cast into the extension housing (kind of a PITA if it turns on you while you are putting it back together).
FWIW I prefer the 'Right Stuff' brand of "Tube 'O Gasket". Evil nasty looking stuff while you're putting it on, but I haven't had a leak on anything I have used it on.
Hope that helps.
