Chevyss Posted October 7, 2009 Share Posted October 7, 2009 Just curious about the rear end. I have way to much time on my hands and need projects for this winter. I've wanted to make sure that my rearend is strong and less chance of breaking something. Some say that the 12 bolt is as strong as you need for a street/some strip car. Then I've heard different axles, posi, gears, c-clip eliminator and so on. Has there been a thread that covers all this?? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Heckeng Posted October 7, 2009 Share Posted October 7, 2009 I don't think there is a single thread for this, but it is fun stuff to talk about, so let's make one! 1. Axles. . . Stock axles are not the best units. They are good for street, but if you have serious power, some $200 Moser or Strange axles would be nice insurance and are made with stronger material than original, as well as being thicker the whole length of the axles. My Moser axles were nearly 1/4" thicker in the worst part of the stock axles. Here is a pic of my stock axle compared to a Moser. 2. Posi. . . The GM posi's are actually very nice units. There were supposedly 2 or 3 manufacturers that supplied them to GM originally, most of which were made by Eaton from my understanding. If your posi is original and has been around the block, you might consider rebuilding it with new clutches, but it is likely a pretty strong unit. 3. Gears. . . 12 bolt gears are usually more than adequate for street/strip. The larger the diameter of the ring gear, the stronger the ring gear teeth which if abused will shear off. Another weak area for some rear end gears is the pinion shaft diameter. 12 bolt pinions are thicker there than the 9" ford and hold up pretty well. Some people will "upgrade" their gears to racing units which are actually a tougher material which actually means it is softer. They make it softer so that it absorbs the impact of launches better and are less prone to shattering from being too brittle. The downside of these gears is that they wear significantly faster than street gears and don't hold up to driving that well. 4. C-Clip Eliminators. . . The c-clip axles have one MAJOR weak point. The axles have a "nub" machined into the inside end of them and a c-clip keeps them from falling out. where the nub is machined down, the diameter is pretty small and if you put a bind on those axles through lots of torque, or even through normal driving, sometimes the nub breaks off and your wheel and axle go flying past you while your quarter panel creates a 4th of july show for people behind you! This is a major reason to remove the c-clip from the equation. People will install c-clip eliminators which basically are a bolt on axle housing end that changes the GM style end to a ford style end but they are only bolted on instead of being welded on. These have flanges and bolts that keep the axles in the car instead of the c-clips now. So, if your axle breaks inside the diff, the c-clip eliminator flange keeps the axle attached to the car instead of letting it fall out. The negatives about the c-clips are that since they are bolt-on items, they are prone to leaking. Also, for normal driving, some people don't like that all of your axle force can be put to the ground through the 4 3/8" bolts on each axle. 5. Differential Cover. . . Lots of torque on a diff will put lots of stress on the diff casing, especially on the main caps as the pinion gear will try to push the ring gear away from it and out the rear of the diff. To counter this, they have aluminum differential covers with built in bearing supports. These covers have bolts that apply a slight pressure (5-10 lbft on the bolt) on the back side of the bearing main cap. This helps to counter act any give the caps may have in them which could otherwise lead to a catastrophic failure. Ok, some other people need to tell me what I forgot now! Quote Link to comment Share on other sites More sharing options...
Chevyss Posted October 7, 2009 Author Share Posted October 7, 2009 Thanks Scott. I replace the open rearend with a Auburn posi and richmond gears. Installed the c-clip eliminators. It hasn't had any serious stress put on it since I rebuilt it, but next year I want to make a full season of racing. I've spent a lot of cash putting this car together over the past three years and I want to put it to use. I have that bug again after 40 years. Thanks for your help. I'm kind of, if I'm going to do something, I want to do it right. I know that Currie makes a 9" ford axle that is made just to bolt right in what the GM came out. There is also the Dana 60 as an option. Quote Link to comment Share on other sites More sharing options...
Heckeng Posted October 7, 2009 Share Posted October 7, 2009 You are probably good to go with what you have done. My only comment would be on your particular posi. Those are cone style clutches and you need to be careful about one wheel spinning while the other doesn't because the cone can wear out and not be replaced from my understanding of it. I know lots of people say they run them with no issues at all though! I think that you are probably good to 600-700 hp with your setup as it sits! Quote Link to comment Share on other sites More sharing options...
USMCBLB125 Posted October 7, 2009 Share Posted October 7, 2009 I had an auburn posi and richmond gears, and what Scott mentioned happened to my unit. The car was gone before I had a chance to rebuild it, so I never got to see what happend. I just know I was doing a burnout at the track and only one wheel was spinning. Pretty embarassing on car with 500+ HP and everything thinks you're running without a posi lol. Quote Link to comment Share on other sites More sharing options...
Chevyss Posted October 8, 2009 Author Share Posted October 8, 2009 I think to be safe I'll get a 9" ford to fit the Monte and then I won't have any issues for next year. Save up my change and get it just before the season starts. Now I'll have a nice 12 bolt for sale. 3.73 Quote Link to comment Share on other sites More sharing options...
Heckeng Posted October 8, 2009 Share Posted October 8, 2009 Before you do that, check into what diffs you can get for the 9". They are a little limited as far as the actual differential goes. I believe you can get a Detroit TruTrack which is a gear reduction style posi--no clutches to wear out and they have been getting good reviews so far. You can also get a detroit locker which is very strong but a little different and "notchy". It takes a little bit to get used to but they are extremely reliable and everybody I know who has used one likes it. Do NOT get the OEM style Ford Traction-Lok differentials, they are weak and you will DEFINITELY blow it up! While you are at it, you might upgrade to some 33 or 35 spline axles as well! Quote Link to comment Share on other sites More sharing options...
Chevyss Posted October 8, 2009 Author Share Posted October 8, 2009 I think Currie will make one to your specs. You tell them what you are looking to do and they will make a complete in the crate, made to fit application and from that point you will have no worries about the diff. Then comes the driveshaft and joints. Dennis' Driveshafts will make one so strong you can never break it. Then come driveshift loop. And on goes the process of a never done Monte. Oh well, I could be into horses, boats, golf, gambling and other vises. Keeps me out of trouble. Thanks Scott Quote Link to comment Share on other sites More sharing options...
Ian Posted October 8, 2009 Share Posted October 8, 2009 Royce have you looked a Moser? http://www.moserengineering.com/Pages/Housings/hous-ford9.html I had one of their 9" bolt in rears in a G-Body and was happy with it. It fit real nice. They will also build it for what you are going to be doing. They also do a Dana 60 for our cars... Quote Link to comment Share on other sites More sharing options...
CrazyDavey Posted October 8, 2009 Share Posted October 8, 2009 Royce, I'd blow up what you have first, you've got a winch right? 3 grand is a lot for it might break, if it does then.... Seriously, 12 bolts are pretty strong, put a little pre-load on it before you launch and it should hold up. I would upgrade the u-joints and maybe some hardened axles though if you haven't already...Davey Quote Link to comment Share on other sites More sharing options...
kc8oye Posted October 8, 2009 Share Posted October 8, 2009 a stock 10bolt is plenty strong enough for street use. You do not need to worry until you get into slicks. so far I've been putting 300hp thru my stock 10bolt into 26x10 MT E/T Drag (full on bias ply slicks) with no issues.... granted, I wasted my posi with a burnout and one my brakes hanging up. .but that's another story Quote Link to comment Share on other sites More sharing options...
Heckeng Posted October 8, 2009 Share Posted October 8, 2009 Royce, I'd blow up what you have first, you've got a winch right? 3 grand is a lot for it might break, if it does then.... Seriously, 12 bolts are pretty strong, put a little pre-load on it before you launch and it should hold up. I would upgrade the u-joints and maybe some hardened axles though if you haven't already...Davey I agree Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted October 9, 2009 Share Posted October 9, 2009 I haven't broke mine yet and you all know what I throw at it, keep your money 'til it breaks Quote Link to comment Share on other sites More sharing options...
Guest slacker Posted October 11, 2009 Share Posted October 11, 2009 I think to be safe I'll get a 9" ford to fit the Monte and then I won't have any issues for next year. Save up my change and get it just before the season starts. Now I'll have a nice 12 bolt for sale. 3.73 I agree!! Buy a 9" and sell me your 12-Bolt.. You know it better to be safe than sorry! Quote Link to comment Share on other sites More sharing options...
monzaz Posted October 23, 2009 Share Posted October 23, 2009 I'll take the 12 bolt every time. And keep the money in my pocket. The stock 12 bolt is way stronger than any stock 9" Look how much money you need to stick into a Ford 9" to make it strong. All the aftermarket 12 bolt chevy rears do not even have any mods done to strengthen it...Same as it ever was. OH and your 9" is a 10 bolt that is what people KEEP FORGETTING...Dana 60 is 12 bolt , 8 3/4 mopar is 12 bolt As far as ring gear size ...does not mean a thing for drag racing as your going a 1/4 mile ...back in the day larger ring gears were made to bleed off the heat of towing and the rpms of the 2 speed trannies heat on the freeway etc. larger gears dissipate heat. ford has the smallest 1.313 pinion front pinion support blows off from the small bolts and thin casting. cases shatter... But I will say this they sure made alot of them and they are CHEAP... price and built wise (stock form). They only became popular because they are a drop out...and CHEAP to buy cause Henry flooded the market under every Ford, Lincoln, Mercury and Truck... MASS PRODUCTION If you look at any aftermarket 9" it does not have ONE stock part left...lol. because it was plain not strong enough. The aftermarket had to redesign the whole rear to make it truly strong. besides assembly is your biggest concern in just about any drive line parts Engine, trans, rear end... you can have all the biggest baddest parts and if you install them wrong you have big bad JUNK parts... Keep your car GM and be proud... It is your car and you can buy what you want...We are still free with choosing here in our wonderful country... I still have some freedom of speech too. Take care and have a great time on the drag race seen what ever you do choose to use... Jim Quote Link to comment Share on other sites More sharing options...
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