Yeah, a tire twirl test is the easiest way to tell without taking things apart. Tag or casting numbers can be outdated if someone already changed gears on you.
The driveshaft (pinion yoke) will spin multiple times to the tire's one turn. With both wheels off the ground, the one tire revolution way works if it's a posi. If an open diff, have only one tire off the ground, and rotate the free tire two revolutions, not one. The number of times the driveshaft spins is your gear ratio (about 3.25 turns = 3:23 gears, etc.)

 

I'm sure it's a posi. The cover is removed and I looked at everything before I bought it the other day. I was reading that you can count the teeth to determine gear ratio. I was out in the garage in the middle of the night inspecting and wire brushing trying to find the other #s on the axle tube and still have not found any #s. However, it certainly does look like it's been in another vehicle aside from the Chevelle. The welds on the current coil spring perches are pretty funky. When I was twisting the gears around I noticed a small peice of orange gasket maker on one of the teeth which was probably used to count them? I should have counted right then and there but didn't as I was not aware of this until a bit later when I read about it. I'll do that today and figure it out.

 

Turn the ring gear while looking at the end of it. Most likely you'll see numbers stamped on the edge corresponding to the number of teeth on the ring and the pinion gears. Then just divide the small number into the big one, or divide the big number by the small one (however you understand division). .

 

78 On My Plate - That's a great question. We've been asked that a lot so we have put information on this topic on our Frequently Asked Questions (FAQ) section on Hotchkis.net: http://www.hotchkis.net/faq.html#sway

Here's the some information from that page:

Q) Are solid sway bars stronger than hollow sway bars?
Answer:
No. Sway bars work off of torsional force (twisting motion). Therefore, the material in the center of a solid bar plays little role in the resistance of torsional force. With this in mind, we have eliminated some of the center material and also moved some to the outside of the tube, where it is most effective. In turn, this produces a sway bar that is lighter in weight and just as stiff, if not stiffer than solid. For example, a 1'3/8" hollow bar is equivalent to a 1'1/4" solid. But the 1'3/8" hollow bar is 6% stiffer and 43% lighter than the 1'1/4" solid.


We also have this great PDF document with more in depth tech about sway bar design philosophy and information regarding hollow and solid sway bars.

http://www.hotchkis.net/_uploaded_fi...ons162file.pdf

 

78 on my plate – Unless the rear differential in your Camaro has the upper control arm bushing rings cast into the top of the housing like the ones in this photo, you don’t have a 68-72 Chevelle rear differential…unless somebody cut them off. You will have to check the top of the housing for signs of them. It’s highly possible somebody cut them off and cut the coil spring mounts off and welded leaf spring perches on your housing, but there would probably be signs of the work.

 

Did you bother to look at the picture of his rearend sitting in the truck bed? You can clearly see the ears on the axle housing cast in for a Chevelle. Shown in post #120.


78, your rear has those control arm ears cast into the housing shown in your picture, so it's always been a Chevelle rearend. Maybe they're just crappy factory welds, or maybe someone tried to touch them up and didn't weld well.

 

As my prior post, the picture and the subsequent post state, yes, the rings are on the differential. Thanks for the follow up reply Hotchkis, I am one to do my homework before making a purchase, I beat you to the punch a bit on the pdf file, but thank you for providing it for review and consideration before making a purchase. I visited the website yesterday. Also, unless someone broke into my garage and welded leaf spring perches on there, it's still got the coil spring perches that need to be cut off for my new perches (see previous posts.) Now that would be a good problem to have! lol. Hotchkis, I do have a question however. When you provided some statistical numbers regarding weight and strength I was wondering what the weight actually is that yours is 43% lighter than? Was also wondering what the comparisons are actually to? You used the term "the solid", is this any solid? I would love to know this before I purchase a new sway bar, thank so much again for helping me out.

BB427, I'm not positive but pretty sure that there has been some work done on this thing. I'll get a couple more pics up for you to take a look at. Not any problems as they are going to get removed in a day or so but these have to be different perches for the coils than from the factory. I can see where the other ones used to be. With those casting #s are you sure that it still could be a factory Chevelle rear end? What I read is that particular casting # was the same for ALL 1970 Pontiacs.

Thanks '69 for the info, I didn't know that the numbers would be on the ring gear. That'll make it easier to figure out. Haven't had a chance to do that yet, but will soon and hopefuly I'll be able to sleep tonight.

 

Boy, you guys are beating up on Hotchkis. Go back and reread what he said...."Unless the rear differential in your Camaro has the upper control arm bushing rings...." He was referring to the rearend in your Camaro, if it had coil spring mounts or not, not the "new" one in the truck bed (which is clearly obvious). Although, I don't quite follow the point he was trying to make.

 

I really wouldn't loose sleep over what the rear came out of. You can find out what gears are in it the way described and your cutting it up to put perches on it. So, Iif the width is right and the gears are right... your golden.

 

I know I'm a bit late chiming in here, but, is there something wrong with the 10 bolt in the car now? I didn't see anything stating that the housing had any defects/damage. If it's good, why replace it with a diff that you have to spend cash on to make it fit? From what I've caught up on in the later half of this thread, I'm getting that you hate the 2.41"s, want 3.73's, but are settling on 4.11's that you will be changing to 3.73's later. I've done a couple of conversions at our shop, you're looking at a couple hundred to set and weld the perches, the cost of the perches+shipping, and somebodies (most likely yours) labor to swap it out. Added to the the cost of the Chevelle axle seems a bit of a waste, just so you can put 3.73's in it at a later date. To go from 3.73 to 4.11, you're buying gears and a carrier anyway. The cheapest way out is to swap the 4.11's from the Chevelle axle into the diff that's in the car now, the bearing master kit is less than $200 and you're done. Then save up and get the 3.73's and carrier later. If you're worried about it being 28 or 30 spline, don't. Unless you're making good torque or racing a lot, it shouldn't be an issue. It's surprising what a 10 bolt can endure. I'm just sayin' think it over before you end up spending good money after bad.