differential

y30786 · 10-30-2006, 07:36 PM

Hello, guys have a nother question for you guys. What would be the best rear end for my 86 cutlass supreme brougham? Building up my 307 with junk yard parts and figured I would look for a rear end while I was at it. If any ideas please tell me, what vehicle, what year, and what ever else I need to look for a decent build up.

thanks
y30786

Oldsmaniac · 10-31-2006, 04:38 PM

The 83/84 Hurst Olds came with a 373 rear gear.....that would be a good ratio or a 342 gear from a Buick Grand National. The heavier duty rears were an 8.5 posi verses the standard 7.5 that the Cutlass posi cars used. I believe you will find the 8.5 unit on all Grand Nationals and 442 posi cars from 85 up....G body. Bad news is the 8.5 units are getting scarce and quite pricy....600 or more for the whole rear unless ya get lucky in a junkyard.

Oldsmaniac · 10-31-2006, 05:16 PM

Oh.....I wouldnt waste my time trying to increase the HP with the 307....Most everyone goes with the 350 or 403 as they are both smallblocks and have the same external dimentions so nothing changes under the hood except HP......I doubt you will find anything in the junkyards to soup up the 307....the speed shop and machine shop would be more likely but the 403 and 350 builder core engines are still in some yards.

10-30-2006, 07:36 PM	#1 (permalink)
y30786 Junior Member Join Date: Oct 2006 Posts: 11	differential Hello, guys have a nother question for you guys. What would be the best rear end for my 86 cutlass supreme brougham? Building up my 307 with junk yard parts and figured I would look for a rear end while I was at it. If any ideas please tell me, what vehicle, what year, and what ever else I need to look for a decent build up. thanks y30786

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10-31-2006, 04:38 PM	#2 (permalink)
Oldsmaniac Senior Member Join Date: Oct 2005 Location: NJ Posts: 428	The 83/84 Hurst Olds came with a 373 rear gear.....that would be a good ratio or a 342 gear from a Buick Grand National. The heavier duty rears were an 8.5 posi verses the standard 7.5 that the Cutlass posi cars used. I believe you will find the 8.5 unit on all Grand Nationals and 442 posi cars from 85 up....G body. Bad news is the 8.5 units are getting scarce and quite pricy....600 or more for the whole rear unless ya get lucky in a junkyard.

10-31-2006, 05:16 PM	#3 (permalink)
Oldsmaniac Senior Member Join Date: Oct 2005 Location: NJ Posts: 428	Oh.....I wouldnt waste my time trying to increase the HP with the 307....Most everyone goes with the 350 or 403 as they are both smallblocks and have the same external dimentions so nothing changes under the hood except HP......I doubt you will find anything in the junkyards to soup up the 307....the speed shop and machine shop would be more likely but the 403 and 350 builder core engines are still in some yards.