Differential Questions

[ITSANSS]

1985 Chevrolet Silverado
355c.i. engine (just a stock crate engine)
700R4 transmission

Differential cover has been wet around the bottom edge for years.  For the past year, there has actually been a couple drops of gear oil on the garage floor.

Got the cover off this morning and just got done extracting one of the bolts that snapped off inside the housing.  Those fricking bolts were so fricking tight, I'm surprised only one broke off.  The hole is all chewed up, but very surprisingly enough, a run through with a tap and the bolt still threads in all the way and gets tight.  One thing I noticed before I even started taking the bolts out is that there is NO FRICKING FILL PLUG on the cover.  If engineering had a face, I'd hit it with a hammer.  What should I do?  Run to Advance Auto and get an oil pan drain plug and drill the cover and install it up on the top somewhere?  

Also, another surprise is that there ain't any sludge inside the differential and there was still plenty of, good looking, fluid in there.  lol

Also, since I got the thing apart, how do I figure what the gear ratio is?  Ain't it stamped inside there somewhere?  I see a few numbers here and there (but don't appear to be ratio numbers) and several spots stamped with "GM".

Thanks, ya'll.

[84c20]

The fill plug should be on the side of the diff, not generally on the cover. Did you ever get the broken bolt out?

[Irish_Alley]

The plug will be beside the pinion. The ratio you need the numbers on the ring divide the last two sets of numbers like 45/11 =4.9

[ITSANSS]

Ha!  Just found the plug.  It's on the passenger side on the front (towards front of pick-up) of the differential.  Got it out, barely.  It was buried under a bunch of muck.

Yeah, the broken bolt was extracted successfully.  Still can' believe that the hole was salvaged.  Just knew I would have to drill it out bigger and tap and die it.

It's been a while since Automotive Service Technology at school.  The ring gear is the big gear in there, right?  lol  I vaguely remember doing this in class.  Mark one of the teeth with chalk or somethin' and then roll the vehicle back/forth while counting teeth.  What is the last two sets of numbers that I divide by?

Thanks, ya'll

[Irish_Alley]

Your talking about measuring lash and what not lol. Find the numbers on you ring the big thing you see with teeth. Then divide those numbers

[bobcooter]

I think what Irish is trying to tell you is that you divied the number of teeth on the ring gear (the big one) by the number of teeth on the pinion (the small one). That will be your gear ratio.

[Irish_Alley]

kind of hard to see the pinion much easer to take the numbers off the ring just spin the tire till the numbers show up right in your face on the outside edge of the ring. Lets say the numbers are 55 11 there are some more numbers but it’s the last ones you look for but then you divide 55/11 it’s a 4.545 which is know as a 4.56 or 44/11 which is a 4.09 or known as 4.10

[VileZambonie]

The formula for calculating the ratio is real simple. Just remember driven over drive.

Driven gear ÷ Drive gear

On the side of the ring gear will be the number of teeth

[ITSANSS]

Got 'er done.  No leaks!

2.73:1 ratio.

Thanks, ya'll!