8.5" GM Ten Bolt

Tod Lane · 11-15-2008, 04:47 PM

Can this rear end be built to survive 450 HP in a 3300 lb automatic car, or should I just junk it and spend the extra for a 12 bolt?

Any other advantages to a 12 bolt besides strength?

Chipper Chapman · 11-15-2008, 06:55 PM

If you're planning on spool and axles anyway, don't be scared of the ten 8.5 Once the spool and axles are in they don't know what housing is around them! A girdle cover wouldn't be a bad idea for 10 or 12 bolt. The only big downside to the 8.5 is that there isn't as big of a gear selection as the 12 bolt has.

My 2 cents

j gardiner · 11-15-2008, 07:15 PM

I have just finished my eleventh season with my 8.5 rear and i have never had a problem. My car weighs 3350 lbs. and has about 500 hp or so. There are alot of people smarter than me who say a 8.5 is stronger than a 12 bolt. A 8.5 has a thicker ring gear and even though it has less ring gear bolts they are larger 7/16 compared to 3/8. There are alot of Buick gn's running in the 8s with this rear. So by all means you should be able to use this rear with no problems.

Chad E532 · 11-16-2008, 11:37 AM

I recently had a 10 bolt and 12 bolt sitting next to one another in the garage. It was interesting to see that the castings were the same overall size. The pinion bearings were very close to the same size. The carrier bearings however on the 12 bolt were larger. One other interesting note, my 10 bolt used 7/16 fasteners where the 12 bolt uses 3/8 bolts to attach the ring gear to the spool.
Which ever option you choose, make sure to have the tubes welded to the casting. I had one twist this year and it was a pain to repair.

Chad

Robert Swartz · 11-16-2008, 02:24 PM

Quote:

Originally Posted by Chipper Chapman

If you're planning on spool and axles anyway, don't be scared of the ten 8.5 Once the spool and axles are in they don't know what housing is around them! A girdle cover wouldn't be a bad idea for 10 or 12 bolt. The only big downside to the 8.5 is that there isn't as big of a gear selection as the 12 bolt has.

My 2 cents

Interesting stuff here. Looking at the Summit catalogue, they offer a Moser 33 spline spool, no doubt Moser would have the axles as well. They have Richmond 4:88, 5:13, 5:38 and 5:57 gear sets. That's not a terrible selection, work fine for motors running in the 7000 rpm range. If you were running a stick car or a trans brake, might be a different story?

Just running the cost figures, could probably assemble one of these for half what you'd have in a comparable 12 bolt. The 12 bolt would have a better value as a resale point. Sounds like a few of you guys are running these rear ends, be worth looking into.

5448 · 11-16-2008, 06:04 PM

I have been running an 8.5" in my '71 Nova for the past 12 seasons with no problems. Car is 3240 lb with me in it, 500 hp small block, auto, footbrake car. My quickest 60' is 1.39, for reference. I haven't fully welded the tubes to the housing(yet), and I run a stock cover.
I agree with Chad that you should fully weld the tubes to the housing for piece of mind. The girdle cover may be cheap insurance as well. I may even take my own advice and add these upgrades to my 8.5"!

Eric

greg fulk · 11-16-2008, 11:56 PM

My cutlass has an 8.5 stock axles with a best 60' of 1.63 & E.T 12.51 in a 3600 lbs carhttps://www.autoimagery.com/store/cgi-bin/imageFolio.cgi?action=view&link=NHRA_Division_3/2008_Division_3_events/Columbus_-_NHRA_Divisional_-_Jul_2008/Stock&image=0830-09029.jpg&img=12&tt=&tfile=tn_0830-09029.jpg

Tod Lane · 11-17-2008, 12:05 AM

Thanks for the info guys, it looks like a usable alternative for what I have in mind, the extra $$ for a 12 bolt could be used elsewhere!

Tod Lane · 11-17-2008, 12:06 AM

Quote:

Originally Posted by 5448

I have been running an 8.5" in my '71 Nova for the past 12 seasons with no problems. Car is 3240 lb with me in it, 500 hp small block, auto, footbrake car. My quickest 60' is 1.39, for reference. I haven't fully welded the tubes to the housing(yet), and I run a stock cover.
I agree with Chad that you should fully weld the tubes to the housing for piece of mind. The girdle cover may be cheap insurance as well. I may even take my own advice and add these upgrades to my 8.5"!

Eric

Good axles and spool?

5448 · 11-17-2008, 10:11 AM

Tod,
I just run 28 spline Moser axles with C-clip eliminators and a standard Strange steel spool.

Eric

11-15-2008, 04:47 PM	#1
Tod Lane Member Join Date: Jul 2008 Posts: 152 Likes: 0 Liked 2 Times in 2 Posts	8.5" GM Ten Bolt Can this rear end be built to survive 450 HP in a 3300 lb automatic car, or should I just junk it and spend the extra for a 12 bolt? Any other advantages to a 12 bolt besides strength?

11-15-2008, 06:55 PM	#2
Chipper Chapman Member Join Date: Jan 2004 Location: Belmont N.S. Canada Posts: 454 Likes: 215 Liked 142 Times in 64 Posts	Re: 8.5" GM Ten Bolt If you're planning on spool and axles anyway, don't be scared of the ten 8.5 Once the spool and axles are in they don't know what housing is around them! A girdle cover wouldn't be a bad idea for 10 or 12 bolt. The only big downside to the 8.5 is that there isn't as big of a gear selection as the 12 bolt has. My 2 cents

11-15-2008, 07:15 PM	#3
j gardiner Member Join Date: Jul 2006 Location: waldorf Posts: 196 Likes: 11 Liked 12 Times in 8 Posts	Re: 8.5" GM Ten Bolt I have just finished my eleventh season with my 8.5 rear and i have never had a problem. My car weighs 3350 lbs. and has about 500 hp or so. There are alot of people smarter than me who say a 8.5 is stronger than a 12 bolt. A 8.5 has a thicker ring gear and even though it has less ring gear bolts they are larger 7/16 compared to 3/8. There are alot of Buick gn's running in the 8s with this rear. So by all means you should be able to use this rear with no problems.

11-16-2008, 11:37 AM	#4
Chad E532 Member Join Date: Jul 2008 Location: Lindstrom MN Posts: 156 Likes: 5 Liked 54 Times in 7 Posts	Re: 8.5" GM Ten Bolt I recently had a 10 bolt and 12 bolt sitting next to one another in the garage. It was interesting to see that the castings were the same overall size. The pinion bearings were very close to the same size. The carrier bearings however on the 12 bolt were larger. One other interesting note, my 10 bolt used 7/16 fasteners where the 12 bolt uses 3/8 bolts to attach the ring gear to the spool. Which ever option you choose, make sure to have the tubes welded to the casting. I had one twist this year and it was a pain to repair. Chad

11-16-2008, 06:04 PM	#6
5448 Junior Member Join Date: Nov 2008 Posts: 4 Likes: 0 Liked 0 Times in 0 Posts	Re: 8.5" GM Ten Bolt I have been running an 8.5" in my '71 Nova for the past 12 seasons with no problems. Car is 3240 lb with me in it, 500 hp small block, auto, footbrake car. My quickest 60' is 1.39, for reference. I haven't fully welded the tubes to the housing(yet), and I run a stock cover. I agree with Chad that you should fully weld the tubes to the housing for piece of mind. The girdle cover may be cheap insurance as well. I may even take my own advice and add these upgrades to my 8.5"! Eric

11-16-2008, 11:56 PM	#7
greg fulk VIP Member Join Date: Jan 2003 Location: jackson Posts: 1,165 Likes: 0 Liked 5 Times in 3 Posts	Re: 8.5" GM Ten Bolt My cutlass has an 8.5 stock axles with a best 60' of 1.63 & E.T 12.51 in a 3600 lbs carhttps://www.autoimagery.com/store/cgi-bin/imageFolio.cgi?action=view&link=NHRA_Division_3/2008_Division_3_events/Columbus_-_NHRA_Divisional_-_Jul_2008/Stock&image=0830-09029.jpg&img=12&tt=&tfile=tn_0830-09029.jpg __________________ Greg Fulk 308 308X P/SA "ALL AMERICAN"

11-17-2008, 12:05 AM	#8
Tod Lane Member Join Date: Jul 2008 Posts: 152 Likes: 0 Liked 2 Times in 2 Posts	Re: 8.5" GM Ten Bolt Thanks for the info guys, it looks like a usable alternative for what I have in mind, the extra $$ for a 12 bolt could be used elsewhere!

11-17-2008, 10:11 AM	#10
5448 Junior Member Join Date: Nov 2008 Posts: 4 Likes: 0 Liked 0 Times in 0 Posts	Re: 8.5" GM Ten Bolt Tod, I just run 28 spline Moser axles with C-clip eliminators and a standard Strange steel spool. Eric