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Hi all, I'm putting a posi in my chev and am having trouble reading the gear mesh. It looks like it is either pinion too close or pinion too far away. Despite being a former chevy tech, I was never really into diffs. Therefore I know very little and am learning as I go.
Well my friend there really is no pattern there to see. What gears are you installing and what pinion shim did you start with and what's backlash set at? Remember to hold the ring gear tight while turning the pinion to get a good pattern.
Well my friend there really is no pattern there to see. What gears are you installing and what pinion shim did you start with and what's backlash set at? Remember to hold the ring gear tight while turning the pinion to get a good pattern.
3.73 yukon. 0.040 behind the pinion. Backlash is 0.010. I thought that you were supposed to move the ring gear and let the pinion drag.
Did you use the bearings that came on the limited slip differential? That is the upper spectrum of what the 12 bolt spec is, but isn't outrageous. I spin the pinion to better simulate it being driven...plus its easier with big axles.
Did you use the bearings that came on the limited slip differential? That is the upper spectrum of what the 12 bolt spec is, but isn't outrageous. I spin the pinion to better simulate it being driven...plus its easier with big axles.
I used timkens, it's an eaton posi and did not come with bearings. I figure run on the upper limit so when it gets warm and everything grows, it won't get too tight and gall up.
I might be confusing my 12-bolt setups with my 8.8's but it seems like that's a lot of pinion shim. 01ss would know better than me though, maybe he'll chime back in and recommend a starting point. As was mentioned, to get a good pattern image you need to hold the carrier with as much drag as possible while turning the pinion. That simulates a loaded gearset.
I might be confusing my 12-bolt setups with my 8.8's but it seems like that's a lot of pinion shim. 01ss would know better than me though, maybe he'll chime back in and recommend a starting point. As was mentioned, to get a good pattern image you need to hold the carrier with as much drag as possible while turning the pinion. That simulates a loaded gearset.
Oem is .030 i figured i'd start with a little more since. For no reason really.
get a good pattern first. put the marking compound on the gears heavily, cover the teeth read the pattern where it wears off the teeth. Don't try to read a pattern based on where the compound transfers onto the teeth.
Id go back with a stock shim and get a good pattern. Id also tighten backlash to 7ish. Once you do that I bet youll be pretty close and we could guide you the rest of the way. Hold the ring and turn the pinion
you need less pinion shim too. Go back to .030 and try again
I posted pictures of turning the pinion like you said, but it needs moderator approval for some reason... I'll try 0.030 worth of shim when i get home later today. what else is there after getting the pattern right other than setting bearing preload and using the crush sleeve?
Id go back with a stock shim and get a good pattern. Id also tighten backlash to 7ish. Once you do that I bet youll be pretty close and we could guide you the rest of the way. Hold the ring and turn the pinion
Here's what it looks like with 0.030 behind the pinion and 0.0065 of lash. http://imgur.com/a/WINOj
that's MUCH better, I would try a few thou. less and play with the backlash and you should be spot on. A lot of guys would run the pattern you have with .030 now but I don't like the hard line you have at the root of the tooth.
as long as you have a good pattern. setting up carrier preload and pinion bearing preload is all that's left really.
that's MUCH better, I would try a few thou. less and play with the backlash and you should be spot on. A lot of guys would run the pattern you have with .030 now but I don't like the hard line you have at the root of the tooth.
as long as you have a good pattern. setting up carrier preload and pinion bearing preload is all that's left really.
Okay so say 0.028 behind the pinion? I'll try it again later today. Shouldn't i have more lash than 0.0065?
Okay so say 0.028 behind the pinion? I'll try it again later today. Shouldn't i have more lash than 0.0065?
yes, way more. .0065 is almost zero lash. you may need to pull more than .002 out of the pinion to get the pattern and back lash you need. go down to .025 pinion shim and start there. it may be extreme but I bet it gets you pretty close with the correct backlash
yes, way more. .0065 is almost zero lash. you may need to pull more than .002 out of the pinion to get the pattern and back lash you need. go down to .025 pinion shim and start there. it may be extreme but I bet it gets you pretty close with the correct backlash
Okay, i will try that. I heard from mark williams 0.010- 0.012 is a good backlash to run.
You adjust backlash with carrier shims. You can make it whatever you want any time you want.
Yeah, i've got the carrier shims and setting backlash down. I'm a numbers guy so its pretty easy and straightforward for me. Reading abstract art on the other hand is greek to me.
01-03-2016, 05:03 PM
12 Bolt Setup. Trouble Reading Gears. 
