I have run into the decision of sticking with my 10 bolt that has Eaton 3:42 posi in it, and going with a 12 bolt rearend. I suppose what I am looking for is some folks opinions on here on what would be the way to go with the rearend setup. I have had some people tell me that the 10 bolt is just fine for my car, and once I stick my 455 in there with the M-22 I have been told it should hold up fine. I am looking into taking my car into the 11's hopefully, but don't want to blow this thing up in the process either. I want a durable lasting rearend, I have had nothing but good luck with the Eaton 3:42 in my car now, but then again I have not run a bigblock on it yet either. Hoping some folks on here can help me weigh my options out between the two on which one to stick with. Since I already have the posi 10 bolt it would be easier to stick with it and call it a day, but the 12 bolt always lingers around in my mind. What should I go with? And what gear ratio? Most likely it will not be driven on the highway only on the street.
I'm in the same boat as you are, but I decided to stick with my 10 bolt. There isn't that much strength difference between both. The way I'm going is with a 33 spline spool with the upgraded axles. With your situation I would upgrade the axles and posi unit and you should be fine. The cost to get a 12 bolt built, or to build one yourself isn't worth the little bit you'll gain with a 12 bolt. If I wanted the best of both worlds I would get a ford 9".
Well I do have a fully restored 28 spline Ford 9" with disc brakes on it, but really did not want to travel this road, trying to keep car visually as stock as possible, except for under the hood that is. Would I really need to change out the 3:42 posi? Will it not work well with the 455 traction wise or what?
The 3:42 will be perfect for your car. The one thing with the rear is that it's hard to see when sitting on the ground. Plus, unless you're going to a judged show no one will probably look at what rear the car has. The good thing with the 9" is it's easy to change ratio's by removing the center section and putting a different one in.
Good deal thanks Rob. :TU: Are there anymore folks out there that want to drop their .02 on this? Any opinions or experiences are appreciated.
I ran a 10-bolt for years in a mid-high 11 second GS. That was with a factory posi unit. The Eaton unit is very good. I highly recommend the Eaton units. I did switch to a 12-bolt a few years ago and put an Eaton unit in it. I finally started having problems with the 10-bolt at that time. I was running 1.52-1.54 60' with the 10-bolt. I would spend the money elsewhere for now and possibly think about that switch later down the road. Hope this helps. Tom Jenkins
I asked Alan at Alan's Gear Works here in Clearwater FL about the 10 vs 12 issue. For a street car or drag car, 11 sec+ is fine for a 10 bolt. Once you get into the 10 sec range, time for 12 bolt. Also, 12 bolt is about 15% stronger than a 10 bolt. For more info, a magazine tested many rears for efficiency (friction/power transfer) 12 bolt Chevy was most efficient.
10 bolt - I have run the 10 bolt rear in my Chevelle for 26 years with no problem. 3600 lbs; ETs started at 15.10 (in 1978) and are now down to 10.75 (last year). I do have a full spool and Mark Williams axles with C clip eliminators now (race only). Auto trans with no transbrake. K
I have no idea, I think it is the 8.5 10 bolt, but I am not sure. How would I be able to tell for sure?
If the rear u-joint is held in place by 2 straps and 4 screws you have an 8.5. If you have 2 U-bolts, you have an 8.2.
I went with a 12 bolt years ago. Truthfully, I kind of regret it now. Years ago, it was the rear end to have because the aftermarket pretty much ONLY had a good selection of gears and diffs for that rear end. Now, it is a different story. Most parts are available for the 8.5" reads as well.
So what do you guys think about how this 10 bolt will react and run with an M-22? Will the rearend be able to hold up to the built 455 and the M-22? Keeping in mind that I would still be using the Eaton 3:42 gears. I don't think I would be sidestepping the clutch at 4,000 rpm's or higher more than once in a great while. And no I would not be running slicks the majority of the time this car is running, but mostly on street radials, only slicks once or twice maybe to pull a few ET's. Just don't want to get down the street and have to watch the tow truck driver tow my car home, if you know what I mean.
Andrew, You're exactly in the same boat as me. I got an Autogear M-22 to handle the power (www.autogear.net) and I'm upgrading the driveshaft to one of Denny's units. I think alot of people don't realise the amount of upgrading needed to handle the power. I'll be putting a driveshaft loop in and I already have a lakewood bellhousing with a block saver. With the amount of money already in my car, overkill with putting the power to the ground and knowing it's going to stay in all one piece is my goal.
The hardest you can be on the rear is two things you said you probably wouldn't do: high rpm side-stepping of the clutch, and slicks. I don't think you're going to have trouble in your application. The 3:42 gear should be a good one for a 455.
