Hi

I try to buy rear brake discs and I found two different Delco part numbers for it depending on rear differential aspect ratio. How could I determine what aspect ratio is in my car and what is the difference between rotors?

Cheers, Marcin

 

there are identification and manufacture codes stamped on the right rear axle tube on the front side of the tube. they contain info on rear axle ratio, differential type, manufactor and build info

 

Hi

I found on AC Delco web site that for 2000 year 4WD Blazer they have 2 different rear brake discs but which one to use depend on rear axle ring and not on rear axle ratio.
I have found RPO GU6 in my glove box so I have had axle ratio 3,42. To read anything on my axle tube was impossible .
AC Delco web says to use differet rotors when axle is saginaw. I can see some RPO codes for saginaw but no one is used in my car so I hope I have no saginaw rear axle. The conclusion is to use standard rear brake rotors for 4WD, am I right? Or maybe I made a mistake?

Marcin

 

Could you link to this site???

I don't know what the rear end ratio would have to do with the rear drum brakes, but a quick search on the Advanced Auto website for a 2000 Blazer shows quite a few choices when looking at Raybestos, but Bendix only shows one. The Raybestos rear rotors show choices for the 3.42 axle ratio and for the 3.73 axle ratio... Shouldn't make a difference...

Only thing I can think that 'may' be different would be the ZR2 axles vs. all of the rest of the blazer axles... The ZR2 has a larger axle.

 

Hi

They told me at shop that difference is in axle ratio. But at AC Delco I find this http://tinyurl.com/y36jud which shows the difference not for axle ratio but for saginaw axles. For saginaw I can find RPO, etc...

I decided to buy rotors and check but I hoped AC Delco is right.

Marcin

 

Yup, now that's the difference I expected to see, not in the rear end ratio... Any non-ZR2 blazer has a 7.625" ring gear. But comparing part numbers, they are the same... LOL

 

Sorry I cant understand.

I can see two different rear brake discs:

177-843 for:
With RPO 7.625 R/GR SAGINAW-AMERICAN
and
With RPO 8.50/8.625 R/GR SAGINAW-AMERICAN AXLE

and also rotor 18A875 for:
ROTOR ONLY 4 WHEEL DRIVE

What Blazer is ZR2? In my understandig if there is no RPO for SAGINAW-AMERICAN the proper rotor should be 18A875? Is'n it true?


Marcin

 

Those different PNs are for different tier rotors (ie. one is more expensive and better quality). I would suspect the durastop (PN 18A875) rotors to be cheaper, but either will work equally as well.

 

So if they are the same size they could work in my car and no metter which one I buy? Great! It makes me happy becouse in Poland I can easily buy front brake rotors but only one seller has rear rotors. Thanks!


Marcin

 

The bigger ring gear (8.50) is the ZR2 rear axle size.

If you dont have a ZR2 get the 7. whatever, if you do get the 8. whatever.