7.5" or 8.5" Diff in '99 Bravada??
 

Did a forum search but didn't find this info.....

For some reason, I'd been under the impression Bravadas all got the 8.5" rear differential. My SPID sticker does say G80 and GC1 but no code stating the ring gear diameter. Then I noticed the housing has the two sharp "ears" dangling from it indicating a 7.5" ring gear instead of the square tangs of the 8.5"..... so I guess I've got the 7.5" instead of 8.5"?? I haven't serviced mine yet but at 132K, that time is coming. Only having a 7.5" makes me a little nervous as I've blown a couple of 7.5" in 229-powered Elkies and Malibus..... granted, they had over 200K on them but still...

BTW, I found servicing the fluid in the front diff case to be simplicity itself, only took me maybe 20 minutes and most of that was waiting for the fluid to stop dripping. It's actually easier than changing engine oil and filter (damb GM for mounting that remote oil filter on its side.... since they hung a remote filter, why couldn't they have hung it vertically so it doesn't drip all over everything when you remove it?? :mad:), IMHO. The transfer case is just a tiny bit more difficult, you have to reach higher to get to the fill port but it, too, is really a snap.

Then I see there was apparently a ZR2 optional rear diff and another posting by Swartlkk seems to indicate even the ZR2 was only 8.2" or something? So the majority of Blazers and Bravadas only got the 7.5" differential? I take it the ZR2 was only available in Blazers? Thanks!

The ZR2's came with the 8.5 diff. As far as I have ever found all other S-series came with the 7.5 diff, including the Bravada. The G80 locking diff was an option on most trucks (maybe standard on the Bravada?) and could be ordered in either axle and any gear ratio. For normal driving the 7.5 axle should be fine. If you want an 8.5 diff in your truck it's a straight across swap that can be done quite easily. Just find a ZR2 donor and go to town.

Some 5 speed blazers also came with the 8.5/8.6.

Thanks, guys. I don't know whether Bravadas came standard with the G80 but my window sticker says nothing about the G80 locker, just AWD. So maybe AWD automatically meant G80.

Isn't ZR2 wider than 4x4 wider than 2wd? Isnt ZR2 spring pad wider than non ZR2?
edit: All spring pads are 38.5 in apart

The Regular production options (RPO) codes. There should be a sticker label inside your glove box. Look for the code G80. 8.5 - 3.73