Re: 8.5" 2wd in a 4wd
Not to open an old topic but thought i would post what i know in this area since i've handled a bunch of these rear ends for projects and selling them.
there should be 3 widths of 8.5's
54" 2WD blazer OR S10 3.42
59" 4WD NON ZR2
62" ZR2 4WD 3.73 Rumored 4.10
I've handled mostly 2WD 54" axles because thats where the demand is however these days its getting harder and harder to find low enough mile units to be worth swapping instead of just getting and 8.5 and cutting them down when your regearing.
The 5 Speed 4.3L S10's and blazer after 96 ( i keep hearing pre 96 also however i've had at least 4 5sp 4.3L S10's that still had a 7.625 when i showed up.. swaps? ehh who knows but can't confirm or deny) The best years are 99+ because most of there were larger bearing axles which some people only use the late model ones however they should all be 30 spline.
2wd 5spd blazers came with the factory vented disc on a aluminum caliper these axles are the most highly searched for usually going for 600-1200 from Ebay, Forums and junk yards who know what they have. I've bought 6 of these axles and never paid over 400 but on the S10 side sometimes people fight to pay 600-800 for a low mile 20-60k loaded 2wd disc posi rear. 99% of these 2wd 8.5's will be 3.42 rear end gear ratio and almost all will have posi's.
2wd 5spd 4.3 S10's came with this axle however the posi isn't always in it and they usually don't have the disc option. I've seen one late model 4.3L extreem 5spd that had a disc setup in the rear but it was a high mile modded trucks so my hopes are low that it was factory. These can be converted do disc and you can use all the parts from the Dime a dozen Zr2 or(so i'm told blazer 7.625) rears that include these disc. These rears normally sell for 250-1000 depending on market place, miles etc. 95% of these 2wd 8.5's will be 3.42 rear end gear ratio and MOST will have posi's.
JUST A NOTE: Zq8 and extreem doesn't mean they got a 8.5 actually, I've yet to buy one that came from an extreem. Junk yards almost ALWAYS have these axles listed wrong which usually works in your favor buying 8.5's for 7.625 prices but you have to be able to pick them out of a lineup. Not only look for the round cover and square casting marks on the bottom instead of the fang looking marks on the bottom of the 7.625 (8.5 will have those fang looking casting marks on the TOP!) but also the 8.5 the axle tube are larger so where they go into the pumpkin they they larger to match the casting size while keeping the ride height tappering them down before the perches this is the quickest way to tell.
the 4wd 59" is a rough one to find, your basically looking for stock height 4wd 5spd trucks. I've only seen one of these and it was one that someone else found bought and was selling it all appeared to be correct. I'm not sure what gear options or posi was in these though.
The zr2 breaks the mold.. It should be on all Zr2 equiped trucks auto or manual and should include the same nice vented disc setup. These trucks almost always have the G80 posi, and allot of them are 3.73.. I've been told ALL are however i'm not trusting my source on that just yet. These normally go for 200-700 depending on miles and how big of a rip off etc. AGAIN 62" WIDE!!!!
