Gear Ratio

If I change my curremt rear end to one of a different ratio will my 4 wheel drive still work right?

First, you will have to change the ratio up front to match the ratio in back. I have heard--but not confirmed--that about 3% difference in wheel speed is about all the 4wd stuff can take.

Second, you'll have to screw with the computer to get it to accept the new ratio so that it knows what speed you're going. Otherwise, I suspect you'll have no end of trans shifting problems, drivability problems, etc.

about 3% difference in wheel speed is about all the 4wd stuff can take.

I wonder if that is why my 4WD locks up easily... I don't use 4WD unless it snows.

Whem I bought my trailblazer I needed to swap in a whole new rear axle ass. because the previous one was broken. I think the one I put in is a different ratio than the front one. My 4wd locks up also on dry pavement if i go over maybe 5 mph. I also also have the speedometer problem , it is off by about 5 mph. Car drives fine otherwise. I have been looking for a rear to match the front but cant find one. Any one know where I can find one?

Look inside your glovebox for the RPO codes. There are 3 options for TBs, 3.42, 3.73, 4.10. If it says GU6 you have a 3.42 ratio, GT4=3.73, or GT5=4.10 ratio. Also, if you see a G80, it previously had a locking differential. Hopefully you can figure out which rear axle your TB originally had and get a new one with the proper ratio! Good luck!

Can I find out the ratio from the vin number also?

Dont think so, unless you want to hassle with going to a GM dealership and asking them to run a specs sheet on your TB. It is much easier to just open the glovebox up and look at the first or second row of letters/numbers. They will be in groups. It took me only about 30 sec to find the GT4 and G80 codes on my TB.

The reason I ask is I dont have the trailblazer I swaped the rear out of anymore but I know the vin. Ill just have to ask the dealer, I doubt they will be excited to help.

Ohhh, thats the reason for the vin question. Sorry, cant help there.

Ok I found out what I gearing I need. Do I need to order anything else other than the ring and pinon?

Ok I found out what I gearing I need. Do I need to order anything else other than the ring and pinon?

if you are doing this yourself.... and your asking this... you may need to get someone to do it for you...

usually just a ring and pinion is needed... if there are alot of miles... get the installer kit too.. usually replaces bearings, races, and shims...

randys ring and pinion is a good source.... google it... for their site