just found an 8.5 rear axle that i think i am going to be picking up today for 180!
i currently have a 7.5 with a working G80. what i want to know is if i have to change the rear drive shaft, or get it worked on, to change over to the larger rear end. i thought that i read it some where but now i cant find it. i just need to know if i need to go shorter or longer, or nothing at all. if anyone happens to know which is which and possibly have a measurement??? that would be great.
thanks
-Jake

 

Really nothing wrong the 7.5, its a good axle

 

i agree. mine works great. but i want to be able to put a locker in mine. i have the G80 which works good. but if i go with the 8.5, i gain the ability to put a better locker in. i am thinking about going selectable at some point so i figured that since i could get the whole rear axle at a good price, i might as well make sure i can get this done on my own.
from everything that i have been reading, i think that i have to shorten the drive shaft about an inch. which i cant do, but there seems to be some places around me that do. can anyone confirm this? the shorter drive shaft thing? i just dont really want any surprises.

 

its mucho cheaper to have one shortened then lengthened. Usually around 100 bucks. As for the end bolting up,Notta clue. gimmie a bit and il do some googling as i have nothing to do today lol

 

some good ones here for 7.5
GM 7.5in. 28 Spline - Locker, Spool And Limited Slip

 

For most applications I believe that the 8.5 ZR2 rear end is a direct bolt in. At least it was on mine. I took the whole axle from a 98 ZR2 and put it under my 96 Blazer 4x4. I used my factory drive shaft and didn't have to modify anything. okiedoak20 did the same thing on his, but the axle he found used a different sized u-joint so he had to get an adapter u-joint. Other than that it should be a direct swap. Now if you're wanting to put a ZR2 axle under a 2wd Blazer I don't have any information about that, other than to remember that the ZR2 axle will be about 6 inches wider than a 2wd s-series.

 

hmmm...i didnt realize how many options there actually were... for some reason i couldnt find all of those. i want to stay away from the LSD's because i dont want to have to worry about the clutches and discs and having to rebuild it. i know that wouldnt happen for a long time, but i wouldnt want it to go out if i were out on the trail when i needed it the most.
i did see some actual lockers on there, some are for the open rear ends, which i dont have, but, it has opened up some things for me to think about now.
thanks newguy for your quick response and findings.

 

this ZR2 axle i found is out of a 99 and i have a 98 4x4. with it being wider than the one that i currently have it will fix my rear wheel spacing issue being inset, which i cant stand, and give me all the options of a selectable. but now that newguy brought up more options that i didnt know that i had, i have to think about it. so we shall see. i have made my mind up that if i do get the axle, i will be taking pictures for comparison and such and do a step by step to change it out. just incase someone else wants to. thanks for the help El Beautor.

 

im running fullsize 8.5 10bolts on my s10 and used the stock driveshaft when i put that in there. it may have needed shortening, but hard to tell as this truck also got a bunch of lift with it and it still worked.

but yeah the ujoints were the same

 

well i went and picked up the 8.5 rear axle. i figured that i had already set up a meet with the guy selling it so i didnt want to make him feel like he was wasting his time. i jumped in my mighty little blazer and headed south...way south! when i was almost in Mexico, i turned right and went to the storage facility where said item was being housed.
the seller had one clean as f**k 4 door s10 ZR5!! i couldnt believe it. not a dent in and the paint was in good shape. completely stock. i was impressed. anyway, back to the axle.
i took a look at it as he was giving me the history of it since he picked it from the zr2. he had the whole thing gone through, with paper work to back it up, cleaned up and new seals, ect. ect. i was thinking, yeah yeah, everyone has all that done. once i saw paper work and started to look a little closer, i was a believer. the G80 works perfect from both sides, going in both directions. the bearings are like butter with no slop. still has all the original parts including some new backing plates because he bent the old ones by accident. i got one heck of a steal on this axle for $180!!

he ended up buying a set of dana 44's so he was getting rid of all the zr2 stuff. he said that he had an iron front diff too. but it was going to a buddy. i told him that if his buddy backed out or changed his mind, i would be coming back down with cash money. he said he would keep that in mind. then he told me that he would be getting rid of the rims on his ride, which i really like, and that he would be selling those too....i told him to call me and not bother with making a craigslist ad. i would take those too. i think a met a dude who knows he has good stuff, but isnt looking to get rich off of anything and wants to pay it forward. we were already talking about going wheeling sometime.
all in all, i had a great experience and met a great guy who knows how it should go.


just thought i would update everyone.