Okay in my 96 blazer the back tires locked up while i was doing 70 on highway to work. When they put it on the tow bed the back tires wouldn't even roll when he was putting it up on the bed. I believe the rear differential went out, how hard is it to replace the whole rear differential assembly. The blazer has almost 300 hundred thousand miles on it. So in your opinion is it even worth trying to replace it, and how hard is it to replace the whole assembly. Thanks

 

It's easier with 2 people, but manageable with 1. Just make sure the gears and brakes are the same.

 

As long as you're replacing the whole assembly with an identical assembly, it can be done in a few hours by anybody with decent mechanical ability. The worst part will probably be trying to get the bolts out of the leaf spring shackles. Like DonL said, make sure the gear ratio and the brakes are the same. Also 2WD or 4WD.

 

How do i find out the gear ratio? I know i need the 4wd one for a 4 door but i cant seem to find what gear ratio i need.

 

The most reliable way is to take the covers off and read the ratios off the gears. The easiest way is to check the option code in your glovebox and make sure the replacement comes from one with the same code.

 

Glove box RPO codes:
GU4=3.08
GU5=3.23
GU6=3.42
GT4=3.73
GT5=4.10
HC4=4.56
G80 - locking differential
Be aware that that all 2WDs are narrower than you need, and that ZR2 4WDs are wider than you need. I wouldn't switch springs unless I had to. I believe the u-bolts will be much easier to get off than the spring bolts.
I'm thinking the 96's did not have disc brakes - but maybe they did. If you have drum brakes get one of them. If you have disc brakes, get one of those.
Don't start this job without a good 1/2 inch drive socket set and a breaker bar. You will need a floor jack or a strong friend to help get the rear in place.

Most importantly!! Good jack stands! Don't get squashed.

 

I wouldn't change the springs, either, but I had to drop the back of mine down to slide the axle out. It would be a piece of cake if it were spring over axle.

 

When I pulled the housing out in my S10, I just pushed the housing to one side until the other side cleared the inside of the spring and dropped down - then the other way to get the second side out. Reverse to get it back in. But I did have the vehicle on jack stands and the housing balanced on a floor jack. I'm sure either way will work fine.

 

Yeah, I didn't even take the wheels off mine, much less the brakes, lol. And I was going to replace the rear springs anyway, so it didn't add any labor.

Thanks for posting those option codes, BTW. I knew they had been posted at one time, but I didn't know where to find them. I'm sure they'll help the OP out.

 

I'll second LesMyer's method for swapping the rear axle. That's how I did it on my Blazer, and I did it by myself in my driveway with hand tools. It only took me a couple hours to get everything done.