Ring and pinion set up question
 

I'm setting up a new set of Motive pro gears in my 12 bolt,the pattern is out towards the heal of the gear. Do I need a thicker pinion shim or thinner to move in towards the toe? Right now it has a .016. Thank you.

Re: Ring and pinion set up question
 

Try a .030-.035. That was where the Richmond pro gears usually were.

Re: Ring and pinion set up question
 

Dana,

What ratio are you installing?

As posted above, a pinion shim of .032 - .033 will almost always be good with a 12 bolt.

Re: Ring and pinion set up question
 

They are 4.56's. It's a Strange housing,could that make a difference?
Looking at an old Richmond gear instruction book I have, the pattern looks like one they show as having "low tooth contact,heavy in the root of the drive gear.Move the pinion out of the gear mesh,i.e. increase the pinion cone setting.Translation, please, Lol.
My present pattern doesn't look quite as low on the toe side as their drawing,though.

Re: Ring and pinion set up question
 

Moving the pinion in or out will not change the contact pattern from heel to toe, it will only move the pattern deeper into the root of the teeth or out toward the top edge of the tooth. Heel to toe is mostly affected by the cut of the gear and the alignment of the pinion bore machining to the carrier bearing bore. What you are looking for is the pattern to be centered between the root of the tooth and the edge of the tooth with a rounded edge on the pattern and not a pointed edge on the pattern.

Re: Ring and pinion set up question
 

The pattern does come to a point at the root side of the tooth. Not at all bullet shaped. I did increase the pinion shim to .022. It was .018, not .016. How do I get rid of the sharp point? Back lash is set at .008-.010. The ring gear is marked .008 from Motive.

Re: Ring and pinion set up question
 

Dana, The Strange housing could indeed require a different shim. The above posted suggestions were for a factory GM housing.

You can search the web, even Youtube, for "rear gear setup patterns" might find some help.

Also, consider talking with Strange about a suggested shim thickness.

Did the housing have a gear set? If so, the original shim would be a good starting point.

Re: Ring and pinion set up question
 

Gear sets typically come with an instruction sheet, with pictures of example patterns, and what is required to correct them. I would never do one without my old Zoom "gear setter", for measuring pinion depth. Puts them dead nuts. Good investment imho.

Re: Ring and pinion set up question
 

Looking at the Richmond instructions, it looks as though I have low tooth contact.According to the instructions, this is solved by increasing the pinion cone setting. Does this sound like I need to decrease the pinion shim thickness?

Re: Ring and pinion set up question
 

You mean Pinion Depth? i've never heard the term Pinion Cone. More shim puts it deeper. I have never seen one require a shim as thin as you mentioned. I can't remember ever using a shim thinner than .028". As has been mentioned, .030" to .033" is very common.

Re: Ring and pinion set up question
 

Try a 0.035" shim between the pinion gear and the pinion, and 0.008" to 0.010" back lash, as measured at the outside end of the ring gear teeth, measured 4-8 places around the ring gear. Make sure you're measuring the back lash with the dial indicator as close to perpendicular to the rotation of the gear as possible.

Re: Ring and pinion set up question
 

Back in the bad old days,I was a line mechanic at a few Chevy dealers. There were still quite a few 12 bolt equipped cars running around out there then, and it seemed that the lower the gear, the thicker the pinion shim needed to be for a good set up. OEM stock gear ratios, 2.73-3.73's seemed to like a .030"-.031" shim, 4.10-4.88's all seemed to like an .032" shim,5.38's and 5.57's seemed to need an.032-.033", and insane ratios like 6.14's might want an .034-.035. .008-.011 on the backlash seemed to be optimal,as well.You are right in the center of the infield with the dimensions you mentioned, but you didn't state what gear ratio you are using. This info should get you started.

Re: Ring and pinion set up question
 

If the pattern comes to a point on the root side, you need to pull the pinion farther away from the ring gear, which in this case would mean removing some pinion shim. That being said, removing shim would move you outside the normal range on shim. I would make sure that the inner pinion race is fully seated in the housing bore as this would give you a false reading.

Re: Ring and pinion set up question
 

Thank you for all of your replies. I will be in the garage working on it tonight,I'll let you know how it comes out. Thanks again.

Re: Ring and pinion set up question
 

Once again,thank you all for the help. I finished with the pattern set-up and ended up with a .028 pinion shim and .009-.010 back lash. The pattern still looked good with a .030 shim,.032 was too deep.I talked with a tech at Strange,he checked with an assembler,who said he normally ends up with a .020-.028 pinion shim with the Strange 12 bolts.On a side note,I had to wrap a shop rag around the pinion between the yoke and the housing to get a good preload on the gears. Then I turned the ring gear with a wrench on the ring gear bolts.Once I did that,I got a very clear pattern. Thanks to Johnny at Motive/Richmond for the tip.