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?

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

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.

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

Re: 8.5" GM Ten Bolt
 

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.

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

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

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!

Re: 8.5" GM Ten Bolt
 

Good axles and spool?

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

Re: 8.5" GM Ten Bolt
 

For comprable size (width) rears, the axles are interchangeable.

The axles in my 8.5" '73 Nova came out of a '68 Camaro 12 bolt.

Re: 8.5" GM Ten Bolt
 

I run a 10 bolt out of a GN in my Malibu wagon. 11.80@114...1.50 60ft. 35 spline mosier axels, mark williams spool and 4.88's from richmond. I got the housing for free but if I had to buy one I would definitly buy a 12 bolt for a g-body. The GM 8.5 10 bolts for a g-body are like hens teeth and super expensive to buy compaired to a 12 bolts from strange for 6-700 bucks (housing only). For a Camaro-Nova...if you have a 8.5...dont be scared. They will last under extreme abuse...and GM 12 bolts for these cars are way expensive...i think some people think there made out of platnum and gold. In factory form there garbage...my 2 cents.


PS...LPW girdle is a must for a 10 or 12 bolt. Plus they look cool. Not as cool as a Gold Moroso tin cover though:cool:

Re: 8.5" GM Ten Bolt
 

10.50's in a 68 Firebird. 1.44 60' time. Just finished my 12th year with it and had only cracked 7 of 10 teeth on the Richmond pinion gear.

Moser axles and spool 30 spline. 3300 lbs.


As far as price goes. A 10 bolt and 12 bolt are close only on the guts, it's the housing that cost more $.


Don't be scared of a 10 bolt

Re: 8.5" GM Ten Bolt
 

Who carries this girdle? "LPW girdle is a must for a 10"

I like the idea of the 35 spline axles and spool. Advantage is the cost of the housing. Disadvantage is the selection of gears. I've seen up to 5:57's, this would be more than you'd need in a stocker motor that likely will never exceed 7000 rpm.

What kind of times you turn with your H/CM car? You running the 330 HP crate motor?

Re: 8.5" GM Ten Bolt
 

This would be a second gen F body crate motor car. I would love to score a deal like I did back in the 70's, that 67 in my avatar had a Dana 60 out of a Cuda.... Practically fell in the car, the parking brake cables even hooked up, 1 1/2 narrower than the 8.2 ten bolt that I blew up in it. I couldn't find a twelve bolt back then for the love of money, stumbled on the Dana for 200.00!

Re: 8.5" GM Ten Bolt
 

LPW, Mosier or Strange make the cover. Gear selection is alright I guess. I turn my crate motor 7100 on a good day with 4.88's and 30-9 Radials. Its the 330hp motor. I run H and the index is 12.00. I have run 11.35 with no tricks. I have a 12 bolt in the Camaro and an 8.5 10 bolt in my station wagon. I drive the wagon on the street but its legal for I/CM.Its my backup...haha. It will run 11.80's...still under the index and will still qualify in street trim. Vortec motors are great!!!:D

Re: 8.5" GM Ten Bolt
 

Wonder what that dana is worth now...id bet its worth what 5 twelve bolts are worth now. Don't hesitate...run the 10 bolt with confidence. Newer chev pickups (88-98) had a 1350 yoke on the rear ends...get a yoke and seal for a newer pickup and it will work with your camaro 8.5. If its legal I would have 9in ford ends welded onto your 8.5 and use ford axels to get away from leaky c-clip eliminators. I can't stop them from leaking on my Wagon. Gasket paper/silicone and they still leak. :mad:

Re: 8.5" GM Ten Bolt
 

I have a 8.5 out of a 73 Cutlass that I cut down to fit my 68 Firebird. These have factory press on bearings. No c-clips. I think that most 73-77 cutlasses and regals had this type of rear end. So if you are cutting, go with one of these and eliminate the c-clip eliminators and bastardizing (new word of the day) the rearend.

Re: 8.5" GM Ten Bolt
 

U sure thats the same diff as the GM 8.5? The only rear that I know of that had pressed on bearings was a BOP 8.2. I know theres a difference for sure and parts availability is nill.

Re: 8.5" GM Ten Bolt
 

the 8.2 died in 71...a 71 nova could have either an 82. or 8.5. Tod where you located? I have an 8.5 housing out of a 73 nova that will fit. if ya live close to Ohio I'll take $20 bucks for it...I think I have the axles too.

Re: 8.5" GM Ten Bolt
 

You never mentioned what kind of car ?

Re: 8.5" GM Ten Bolt
 

"This would be a second gen F body crate motor car" quote from a previous thread by Tod Lane

Jigs up. Bud, it's the same car I brought up in "Starting a new stocker thread". 1979 Firebird T/A for a possible crate motor stocker combination. Tod and I are partners in this venture and a bracket car.


"mew", hmm, teach me to write at 5:00am, good thing I majored in English.

Re: 8.5" GM Ten Bolt
 

YES, it is. the only difference is that they have press on axle bearings. I have put 77 Camaro guts inside of one, if that says anything.

Re: 8.5" GM Ten Bolt
 

Does this particular diff have provisions for a torque arm ?? And do you still have it ?

Re: 8.5" GM Ten Bolt
 

I'm running a 8.5 10 Bolt in my 1971 Caprice. It weighs 3950lbs, and I've been 1.45 60ft. 10.74@125 with a small block. Footbraking.


I run it with a Moser spool, 33 spline axles, LPW girdle, and C-clip eliminators.

They'll hold up if you set them up right. I've ran it with that combo since 2005.

Re: 8.5" GM Ten Bolt
 

When I purchased my 1996 S10 brand new in March of the same year I had no idea that I had a 8.5 10 bolt in it. Now being a stocker I consider that my lottery being that every other S10 I new up to that point was a 7.5. All I did was C-clip elims, spool and Richmond 5.38/5.57 gears with stock axles with high 1.5s and low 1.6s short times at 2950 lbs up to 3300. Now if your looking for a S10 8.5 here is what you must look for. They only came with the 96-03 L35 4.3(W on 8th digit of vin) mated to a 5 speed. They did come in more than one width however being the S10 ZR2's RE was about 7 inches wider. It sure does feel nice to give some input on something on here that I don't feel like everyone knows already.

Re: 8.5" GM Ten Bolt
 

George, What is the width of the narrow (drum brake) version (drum to drum, outside)?
Thanks

Re: 8.5" GM Ten Bolt
 

55 inches for the regular S10 65 inches for the ZR2. Just crawled under each to make sure. The ZR2 footprint isn't 10 inches wider however due to the amount of backspacing like a FWD car.

P.S. The ZR2 also has disk brakes.

Re: 8.5" GM Ten Bolt
 

I wish I could get a hold of a 8.5 10 bolt for a fourth-gen f-body. Would beat the hell out of having to carry the extra weight of a 12 bolt, and still have more gear selection than the 7.5 10 bolt.

Re: 8.5" GM Ten Bolt
 

What is the width of your rearend bolt face to bolt face?

Re: 8.5" GM Ten Bolt
 

I'll have to lay underneath it and measure it one day. The problem is that you cant get an 8.5 with a torque arm provision.

Re: 8.5" GM Ten Bolt
 

Lee Before 12bolts where available with mounting brackets for torque arms ,i made a mount to install one in a 3 rd gen Camaro. Had a 350 crate motor in it that ran 10..80s and it never came off but had to tighten the bolts often . Get a good welder and brace it with a U bolt around the snout. Mike

Re: 8.5" GM Ten Bolt
 

Mike, Do you have any pictures of this mount?

If so, leernorton@gmail.com

Thanks!

Re: 8.5" GM Ten Bolt
 

Lee sorry no pictures but i know Gary Russell had a mount like mine on his fourth gen Camaro when he first built it . I sold my car to Cantucci, if i see him i will take a picture.... MIke

Re: 8.5" GM Ten Bolt
 

I have a 71 Nova with a 10 bolt. What do I look for to know if I have the large or small one? Is it maybe ring gear diameter? I knew this a long time ago but can't remember now. My thoughts were to just buy a complete 12 bolt from Strange, but it sounds like the big 10 bolt is plenty stout. Car came with a 307 and a glide. Still has the glide in it. I'm betting it's the small one.

Re: 8.5" GM Ten Bolt
 

I have a horrible memory! I just this morning remember something about the ring gear bolts are larger on the 8.5. Is this how one tells and, if so, what is the size comparison?

Re: 8.5" GM Ten Bolt
 

Re: 8.5" GM Ten Bolt
 

Not sure about the 8.2, but the 8.5 has 7/16 bolts. The 12 bolt has 3/8 bolts.

Dont' worry about the memory, you probably forgot more than most people will ever know.

Re: 8.5" GM Ten Bolt
 

I am almost sure the ring gear bolts are larger on the 8.5. Thanks for posting the website address.

Re: 8.5" GM Ten Bolt
 

I am using the 8.5 in my Grand National . I put Axles with C-clip ele. and a spool in it and using the stock 3.42 gears the car has run 9.64 at 140.11. Leaving off the trans brake at 20 lbs of boost on 28X10.5 Mickey Thompson slicks. It been hanging in there... The picture in my avatar photo is a pretty tipical launch for the car..
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