a friend of mine has a rear end out of an 89 350tpi for $200, its rear disc w/ 2.77 posi gears. before i buy it i want to know what size the ring gear is so i can upgrade to 3.42 or 3.73. any idea what size the ring gear is? he said he doesnt think its a 7.5 inch.

 

You could probably find a ton of info in the Transmission/Drivetrain forum, but, is the axle a 9-bolt? If so, there's not too many gear ratios available for it, although it's stronger then the 10-bolt axle. All 10-bolt 82-92 f-body axles will have 7.5 or 7 5/8 inch ring gears, and will take either size (7.5 or 7 5/8).

So you might want to skip on it if it's a 9-bolt... unless he takes $150 off the price

 

If it's a 9 bolt then it has a 7.75" ring gear. Another thing that may influence your decision is the fact that the posi in the BW has 4 pinions compared to the 2 in a 10 bolt making the 9 stronger. Check out www.9bolt.com , a pretty good source of parts and info on the Borg Warner rear. I'm putting the final touches on a 9 bolt for my 90 Formula. I've swapped the Saginaw brakes (junk) for the PBRs and bigger rotors. I personally wanted the 2.77 ratio for taking the car out on long trips since I've been using a 3.73 in the OE 10 bolt and am sick of it.

 

thanks guys, and im really not sure the reason why i posted in here. guess i wasnt paying attention, lol.

 

It's from a 350TPI and it's 2.77 gear so it has to be a 9 bolt. The only other ratios available are 3.27-3.45-3.70 and the only place I know of to get the gears are on here: www.9bolt.com (as posted above by Mongoose)

 

Randy's Ring and Pinion carry a gear for the 9 bolt. Notice I say a gear... hehe 3.73 going price of 190 bucks, Then another 117 or so for the overhaul kit... new seals and bearings.

Randy's Ring and Pinion

It will be noisey from what I heard.