<font face="Comic Sans MS">First try to get the fill plug out of your rear differential. Nail it with penetrating fluid, wait a while, smack it with a hammer a bit (the plug itself not the housing, you can get an extension for a ratchet, put it in the square hole on the fill plug and whack the extension with the hammer if need be). When you get that out, put it back in snugly (not too tight). Now run to the parts store for either some RTV (my choice) or a gasket for the 7.5" ring gear Corporate 10 bolt rear end. While you're there, grab some gear lube (I would say at least 3 containers of GL 5 (a few spares couldn't hurt just in case), 80w90 or realistically anything in that general range is ok). Pull the rear cover off the diff (by removing 10 bolts, also treating them the same way you did with the drain plug, penetrating fluid and some whacks with a hammer) but when you do, be sure to have a decent sized drain pan centered under the cover, and pull (carefully) the bottom of it out first. It drains better with the fill plug out. It helps to have the rear end raised up and supported by jack stands, so you can rotate the tires easily. Rotate them until you can see the numbers stamped into the ring gear. The ones you're interested in are written like a ratio. Example: 41:10 which equals a 4.10 ratio. Just divide the first number by the second and you get your ratio.
The reason I'm recommending this procedure to procure your gear ratio is actually two reasons. The first reason is that your axle will thank you for it, considering this is an 86 and I'd doubt it's been changed in forever(although it's just an assumption). The second reason is that someone might have swapped gears in it to a different ratio and the glovebox would be lying to you...
Just a thought...
Oh, about the tire size thing, you can fit whatever tires you want... With a sawzall and a willingness to drop in a 350cid V8 or larger... [img]/wwwthreads_images/icons/laugh.gif[/img]
With my 3.73 diff ratio, 235/75 15's are about the tallest I'd go... [img]/wwwthreads_images/icons/crazy.gif[/img] That's with a carbuerated 2.8L and the Borg Warner Non world class T5 manual transmission...</font>
ORC Land Use columnist:
My May Column