The angular rotation associated with 0.007" backlash measured on the edge of the ring feels like more angular slop with hand on yoke (parking brake locking the axles). I noticed this when I was measuring for the drive shaft. I'm reasoning the 0.007" backlash measured on the edge of the ring cuts an angle.... that angle is being multiplied through the ratio.... not the tangential displacement, which is also multiplied by the ratio, but reduced again by smaller radius of the yoke. It was an interesting observation.... I know the backlash is seven thou but it feels exaggerated chattering the yoke back and forth with axels locked... maybe some part of that 'feels extra slop' is in the internals of the carrier... it's certainly not in the splines.
Anyway, with Holley LS mounts, 5.3/4L60, and the 8.5" rear, I need driveshaft with 47.94" u-joint to u-joint center. I'll drop it off for machining on Monday.
Did you just use MATH? STOP IT! Makes my brain hurt.
Regardless of the tooth shape, clearance is clearance and you're on spot realizing when you measure ring gear backlash to the pinion it's only going to be that particular clearance between those two gears because that's all you're setting up. Obviously, that's the important part. That clearance isn't going to change just because you grab the yoke or the ring gear.
But, as you suspect, there are clearances in spider gears and cross shafts (notice how easily it slipped in, which is the main reason those stupid retainer pins break off inside) and the rest of the setup that you basically are taking up ALL slop on both sides of that equation when you rock the yoke. Perfectly normal that it feels like there's more clearance than 0.007". I'm no expert, but mechanical clearance is mechanical clearance. It's all additive when you're changing directions of rotation with helical gear sets to which I believe
64nailhead was trying to allude to when he said it's not precise. Because he's right, yoke "slop" isn't. I don't know of any specification exists for yoke slop, anyway. So what's excessive?
If it's super-sloppy it may be of concern. I'm sure you inspected the wear on the other components. If there are grooves you can catch your fingernails in or chipped off teeth, that would be a concern. But normally, if you set that gear backlash up and other components are in good shape, you shouldn't have any worries.
You did a great job setting up that rear end and probably learned a few things or three you can pass on to the rest of the group with the experience you gained.
When in doubt when it comes to rear gear setups, I always try to ask an "expert" (although he can be a little grumpy sometimes). But he always does respond with good advice. His name is Jim, but goes by the screen name "Monzaz" most of the time and has setup 100s of GM rear ends in his lifetime. Even runs a forum on it and frequents other car forums under the user name "Monzaz". He's forgotten more than most people know about GM rears. Here's his website forum at jdrace.com :
http://www.jdrace.com/phpbb3/
