8 3/4 rear

[Dennis Gunter]

have a 66 Belvedere with a 440….the rear is 8 3/4,489 and 3:55 gears and has to be changed because of a constant whine and banging: sound like someone hitting a pipe with a hammer
want to change to a 3:23 ratio for better gas mileage and lower RPM….
tires are 27540R17 on the rear

sound about right? Anything else needs to be changed?
Thanks

 

[icetech]

have a 66 Belvedere with a 440….the rear is 8 3/4,489 and 3:55 gears and has to be changed because of a constant whine and banging: sound like someone hitting a pipe with a hammer
want to change to a 3:23 ratio for better gas mileage and lower RPM….
tires are 27540R17 on the rear

sound about right? Anything else needs to be changed?
Thanks

speedo cable gear on the cable...

 

[thegarage]

have a 66 Belvedere with a 440….the rear is 8 3/4,489 and 3:55 gears and has to be changed because of a constant whine and banging: sound like someone hitting a pipe with a hammer
want to change to a 3:23 ratio for better gas mileage and lower RPM….
tires are 27540R17 on the rear

sound about right? Anything else needs to be changed?
Thanks

I just came across this post and I'm wondering what you did with the 3:55 "489" center section after the swap. I'm in desperate need of a unit with a 3:55 gear ratio. I know anything can be purchased, but I'm extremely tight on funds and searching for something cheap. Thanks.

 

[toolmanmike]

I just came across this post and I'm wondering what you did with the 3:55 "489" center section after the swap. I'm in desperate need of a unit with a 3:55 gear ratio. I know anything can be purchased, but I'm extremely tight on funds and searching for something cheap. Thanks.

We don't buy and sell on information posts. It doesn't sound like the original poster has an extra rear end but was going to change gears because of a noise. Start a wanted ad in the Marketplace forums if you are needing parts. FYI, rear end cases with gears are not cheap.

 

[71Beeper]

Dennis, the 489 case will require a crush sleeve kit if you are having the 3:23 ring and pinion put in that case.

 

[thegarage]

We don't buy and sell on information posts. It doesn't sound like the original poster has an extra rear end but was going to change gears because of a noise. Start a wanted ad in the Marketplace forums if you are needing parts. FYI, rear end cases with gears are not cheap.

OK, thanks for the guidance, and I Know they're not cheap, but it doesn't hurt to ask.

 

[john-9]

have a 66 Belvedere with a 440….the rear is 8 3/4,489 and 3:55 gears and has to be changed because of a constant whine and banging: sound like someone hitting a pipe with a hammer
want to change to a 3:23 ratio for better gas mileage and lower RPM….
tires are 27540R17 on the rear

sound about right? Anything else needs to be changed?
Thanks

Dennis you may have broken teeth on the ring or pinion gear or maybe the carrier spider gears have welded themselves to the cross pin and wore out the case which might explain the banging noise. there is an ad on kijiji for 8-3/4 differentials. except for the speedo gear change it is a straight swap out for another diff. if your unit is trashed you want to clean your axle housing very well to get rid of any metal junk.