Rear differential efficiency

Kenny Wigington · 08-15-2009, 06:32 PM

As far as GM's go, has anyone done any A-B-A testing, or a real good A-B of which is more efficient, the 10 bolt (8.5) or the 12 bolt. Looking in another area, for some gains for future.

Thanks !
Kenny

.

Dragsinger · 08-16-2009, 05:53 AM

Kenny, I have no test results but offer these thoughts. The 8.5 will be at least a few pounds lighter and has proven to be completely acceptable in even very high powered cars.

From the view point of mechanical losses, I do not think the difference will be enough to measure, I think either choice will give good results.

Is this for your stocker? If so, what are your running now?

Kenny Wigington · 08-16-2009, 06:25 AM

Yes, thanks Larry. I was thinking of trying to make it as effiecient as it could be. I have the 10 bolt in mine now, and was wondering if the 12 bolt was worth a swap, as far as reducing the losses wherever they are.

Dragsinger · 08-16-2009, 07:04 AM

I think you have the best choice. Going to a 12 bolt would not gain anything, in fact, I think you would loose ground because if nothing else, the added weight.

Greg Reimer 7376 · 08-16-2009, 08:57 AM

Once you put a spool,good axles, wheel studs, the proper bearing kit and steel web caps in the 8.5" 10 bolt,(which you do to any race car rear end,anyway),it probably has 90-95% the strength of a 12 bolt. I don't think the weight is more than 5 pounds difference, but cost and availability is a real factor here. I wouldn't pull out a 12 bolt in any of my cars for a 10 bolt because they are there already,but if I had the 8.5" 10 bolt, I would go no further in my search. One advantage to the 12 bolt is the availability of gear ratios is larger.

ron mattson · 08-18-2009, 01:53 PM

i just switched from a 8.5 ten bolt to a 12 bolt and with similar
components and same gear ratio i think the
10 bolt was .03-.05 quicker, both are set up the same way.

08-15-2009, 06:32 PM	#1
Kenny Wigington Senior Member Join Date: Sep 2004 Location: Cumming,Ga. USA Posts: 967 Likes: 36 Liked 60 Times in 12 Posts	Rear differential efficiency As far as GM's go, has anyone done any A-B-A testing, or a real good A-B of which is more efficient, the 10 bolt (8.5) or the 12 bolt. Looking in another area, for some gains for future. Thanks ! Kenny . __________________ 2894 STK

08-16-2009, 05:53 AM	#2
Dragsinger VIP Member Join Date: Jul 2008 Location: Liberty City [East Texas] Posts: 1,760 Likes: 5 Liked 99 Times in 60 Posts	Re: Rear differential efficiency Kenny, I have no test results but offer these thoughts. The 8.5 will be at least a few pounds lighter and has proven to be completely acceptable in even very high powered cars. From the view point of mechanical losses, I do not think the difference will be enough to measure, I think either choice will give good results. Is this for your stocker? If so, what are your running now? __________________ Larry Woodfin 471W

08-16-2009, 06:25 AM	#3
Kenny Wigington Senior Member Join Date: Sep 2004 Location: Cumming,Ga. USA Posts: 967 Likes: 36 Liked 60 Times in 12 Posts	Re: Rear differential efficiency Yes, thanks Larry. I was thinking of trying to make it as effiecient as it could be. I have the 10 bolt in mine now, and was wondering if the 12 bolt was worth a swap, as far as reducing the losses wherever they are. __________________ 2894 STK

08-16-2009, 07:04 AM	#4
Dragsinger VIP Member Join Date: Jul 2008 Location: Liberty City [East Texas] Posts: 1,760 Likes: 5 Liked 99 Times in 60 Posts	Re: Rear differential efficiency I think you have the best choice. Going to a 12 bolt would not gain anything, in fact, I think you would loose ground because if nothing else, the added weight. __________________ Larry Woodfin 471W

08-16-2009, 08:57 AM	#5
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,136 Likes: 172 Liked 705 Times in 219 Posts	Re: Rear differential efficiency Once you put a spool,good axles, wheel studs, the proper bearing kit and steel web caps in the 8.5" 10 bolt,(which you do to any race car rear end,anyway),it probably has 90-95% the strength of a 12 bolt. I don't think the weight is more than 5 pounds difference, but cost and availability is a real factor here. I wouldn't pull out a 12 bolt in any of my cars for a 10 bolt because they are there already,but if I had the 8.5" 10 bolt, I would go no further in my search. One advantage to the 12 bolt is the availability of gear ratios is larger.

08-18-2009, 01:53 PM	#6
ron mattson Member Join Date: Nov 2005 Location: cloquet mn Posts: 466 Likes: 17 Liked 67 Times in 30 Posts	Re: Rear differential efficiency i just switched from a 8.5 ten bolt to a 12 bolt and with similar components and same gear ratio i think the 10 bolt was .03-.05 quicker, both are set up the same way.