Gu6 Rear Gears

The Detroit Truetrac is becoming the differential of choice. You can get it for a good price on ebay: GM 8.5" CHEVY 10 BOLT 8.6 DETROIT TRUETRAC POSI 913A481:eBay Motors (item 330335502533 end time Jun-14-09 09:19:01 PDT)
If you get it, make sure you run regular gear oil not synthetic. The synthetic has given a few people lock up problems.

I think the friction modifiers would be more of the issue and cause problems than it being synthetic. I've been running straight Mobile 1 sythetic gear oil in the factory weight since the gear and True Trac swap with no issues, about 5K miles.

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Originally Posted by 99LS1

I have 17" denali wheels with 275/60/17 on her now. I don't know how much off of stock that is..... When I get the trans rebuilt I will put in a converter, I am just not sure how much stall to get. Does anyone knowe what the best posi is for a 2wd rcsb????

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275 is width in mm which is equal to 10.82 in
60 is the aspect ratio which is the distance from the lip of the rim to the edge of the tire.
60% of 275 is 6.5 in
6.5x2+17(rim diameter)= 30in which is like zebra said, half inch shorter than 245/75R16