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Discussion Starter #1
I am about to set up my 12-bolt with a new set of gears. It is my first time doing it, and have got all the tools necessary for the job. How much pinion shims should I start with. The gear ration is 4.10-1. The Richmond installation guide says that .035 will be the right thickness to start with if you don’t have any old shims, which I don’t. I if you compare the default pinion shims info that Richmond says to article I found on Hotrod magazine http://hotrod.com/techarticles/84118/ I don’t get the numbers right if you look at the chart in the middle of the page. If 4.10 should be in the middle of 4.56 and 3.73 .035 must be to much. .030 makes more sense if you look at the Hotrod chart. The best thing must be to have some sort of chance to get it right the first time I pressing the bearing to the pinion. Does anyone has idea what pinion shims to start with? Maybe a more complete chart. Does anyone have some links to other pages/articles on the net?

Kalle
 

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.035 would be a good place to start. But to get it right the first time get a pinion depth gauge and it will give you the exact masurments.


there is no exact measurement a chart will give you because every housing is different.

hope this help
 

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I removed and pressed my pinion bearing on four times getting the shim stack right and I started with my original shims. To get it right on the first try is just plain lucky. By the fourth time I was getting pretty fast at removing and reinstalling the pinion gear though.
 

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use a old lower pinion bearing, take a die grinder to the inside of it so it will slip on and off the pinion, use as a test bearing tell you get the right shim thickness


dont install the crush sleeve until you have the right shim thickness
 

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.035 is a good place to start since it is in the middle of the shim range and you are starting from scratch, I used a hone on my bearing to ease the press fit since I didnt have an old bearing when I did my 12 bolt, still has to be pressed on and off, but it goes much easier.
Also I dont like crush sleves at all, I use a solid spacer with shims to preload my pinion bearings, much easier to deal with later on if a seal leaks or something, you dont have to worry about losing tension on your nut, just replace the seal and tighten it back up. Most places sell these kits for about 25 bucks, which is way more than a crush sleve, but they can be reused forever.
Most imprtant thing is to be patient and stay at it till you get a good pattern, I build diffs all the time at work and sometimes you get a fighter that takes a few tries to get it right, but if you dont it will be noisy.

Mike
 
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Aftermarket pinions usually have a dimension etched into the butt end of the gear, such as 3.459 or whatever. Thiks dimension is the depth that butt facing sits in relation to the centerline of the carrier.

Now, there are a lot of depth methods available, but...the correct way to get it done is to use centers in the carrier bearing bore holes that hold a shaft and dial indicator or depth micrometer to do the measuring.

The reason the centers are the way to go is, not all carrier bearing bores are dead center in their cap separations. In other words, the carrier bearing holes sometimes aren't centered half in the housing, half in the cap. This means the centers are the most accurate method of setting the pinion depth.

Do start with the .035 shim, but be ready to change it if need be. You really do need a pinion bearing puller, it makes life with pinion setting much easier.

All aftermarket gear sets are run in on a setup/test machine at the factory, and that is where the pinion depth dimension is derived, stick with it and the whole process will be as easy as it can be.
 

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Most 12 bolt richmond gears like .033 under the pinion from my experience. Just thought I would throw iit out there for you.

Miles:D
 

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Discussion Starter #8
Hi everybody thanks for sharing your knowledge with me!

So in other words, there are no shortcuts. I have few more questions for you.
When I am setting the preload on the pinion bearings (crush sleeve), should the carrier be mounted in the housing, or is it only the pinion? How is it with the bearings, should there be pre lubed with oil must they be “dry” when setting the pinion preload?


Take care


Kalle
 

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Discussion Starter #10
“total shim thickness”

Thanks everybody for your posts so far! What should I be doing without you!

“Backlash is adjusted with shims on either side of the case. The total thickness of the shims depends on what case you have. Most 12-bolts need a total shim thickness (both sides) of .484 inch, but our earlier case only takes .170 inch. Correct backlash for a 12-bolt is .005 to .010 inch. Adding shims to the ring-gear side moves the ring gear closer to the pinion, which decreases backlash. Conversely, removing shims from this side increases backlash. As shim thickness is removed from one side, it should be added to the other side to maintain the proper preload on the case. We ended up with .080 inch total on the left side and .090 inch on the right.” (http://hotrod.com/techarticles/84118/)

Is this the right way to go, I mean with total amount of shims? So if I have that total amount of shims, the carrier bearing preload will be ok? The reason I am asking: I haven’t seen this “total shim thickness” some were else.



Kalle
 

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JBimmolate said:
Most 12 bolt richmond gears like .033 under the pinion from my experience. Just thought I would throw iit out there for you.

Miles:D
Yes, I start with .030

Speedway Motors sells a real nice pinion-depth set. Expensive for a one time set up (about 350.00$) but is a good bargain for what you get.
 

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The carrier shims overall thickness wil vary due to how carriers are machined. So that will not always give you the correct preload.

Miles:D
 

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Discussion Starter #13
Thanks for your inputs JBimmolate !


So how do I know if I have the right preload?


Kalle
 

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What ever happenned to "Watson guide to happy rearends?

Does that still exist any where?

Mark (di I still exiast?)
 

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Just remember to follow the break-in for new gears and you'll be fine. Oh yeah and don't forget the OIL!

Miles:D
 
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