So I had to replace the rear end in my Blazer tonight. I have a 96 LS 4x4 4 door with drum brakes. The rearend I pulled and put in is from a GMC Jimmy SLE 4x4 4 door with disc brakes. The only code I could find on either was 282 on the broken one and 174 on the one I installed. Does that help anyone to decide which gear ratio these are before I try engaging 4 wheel dig? I'm sure I may get flamed but I feel it is a good question.

 

You'll need to look in the glove box of each vehicle for the RPO codes. They'll probably both be GU6 or 3.43:1 ratio.

Later, Doug

 

I looked in the glove box but there are tons of these 3 digit codes and I don't know which one is for what. Any help with finding the right one?

Ok in my truck I see GT4 and G80. Where can I look these codes up to see what they are or do I just have to call a dealer?

Well I found this and its pretty helpful. Just scroll down the RPO codes. It looks like they have every RPO code and the description listed. Hopes this helps someone as much as it has helped me. I learn something everyday. I'm just ready to get my truck in the woods again.

 

Top of the Tech Article (DIY) section: RPO Decoder by VIN

Not to mention the multitude of other posts regarding "gear+ratio" or "RPO decoder".

 

Well sorry I didn't see all that and I did find myself looking through posts. I just needed some help, not scorning. But I posted the link with the RPO codes just in case someone happened to be on here and saw it maybe it would help. Sorry to repost a stupid question. Anyway I have it figured out now. The rear end I broke was a GT4 which is a 3.73:1 and the rear end I put in is a GU6 which like above mentioned is 3:42:1. So I guess I can just pull the ring and pinion from the front of the donor blazer and then I'll be in business again. Good is now I have disc brakes in the rear.

 

Check the attitude at the door man. No scorning involved, just posting of information that is at your finger tips.

And if you change your ratio, you'll have to get the gear ratio in the PCM changed so your speedo and transmission shift timings are correct. It would be best to get the proper 3.73 rear axle.

 

I'm not trying to give attitude, just felt I was being scorned for asking a legite question. I just don't have the time to scroll through every thread on here. Thanks for the info, I do appreciate it. My speedo is already off due to the 31's I have on there. Would my fuel milage not get better if I did the GU6 front gears too?

 

With 31's, your mileage would likely go the opposite direction if moving to 3.42 gears. Your motor will have to work a lot more to get you down the road due to less mechanical advantage. Typically, with larger tires, you would go to lower gears (numerically higher) to return the vehicle to *stock* performance characteristics.

 

With 31's, your mileage would likely go the opposite direction if moving to 3.42 gears. Your motor will have to work a lot more to get you down the road due to less mechanical advantage. Typically, with larger tires, you would go to lower gears (numerically higher) to return the vehicle to *stock* performance characteristics.

 

Thanks, I'm not to good with gearing and ratios and stuff. And yes it takes a while for it to finally shift into OD with this rear end in there. But hey it will get me to work and back for now.