The Colorado has drums in the rear too.

 

i want to change my rear to disc also does the front have to be adjust or some for the disc to work? if you have the the same radito in the as the back will it work i got all stock 95 blazer 4wd 4dr.

 

Ratio has nothing to do with the brakes working... it's the gearing in the differential. If your truck is 3.42:1, meaning everytime the driveshaft turns 3.42 times, the hubs turn once... then both front and rear have to match... if you engage 4wd with different gearing front and rear you'll break something because the wheels will want to be turning at different speeds while not being able too. Make sense?

As far as discs instead of drums? You may need to modify the lines, and may even need a different booster (but that's unlikely IMO)

 

I think he's talking about the ratio on the proportioning ratio, not the differential.

I've heard of people doing this swap before, and never heard about need to change anything with the proportioning system. I can't be sure though...