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slownugly 01-17-2013 11:54 AM

First time setting up rear end.
2 Attachment(s)
Hey guys! Im trying to get my rear end squared away so I can get it bolted back under the truck (47 Dodge). The rear end in question is a 8.5 10 bolt with Detroit True Trac and Richmond 3.73s.

I have been messing around with pinion shims and backlash for about 5 hours now and got a pattern that looks me!? I want to get some professionals opinions on it to make sure Im on the right track since this is my first time messing with this.

The drive side pattern is the first photo below and the coast is the second:

any help is greatly appreciated! Im going at this semi-blind so I could use some help. Thanks! 01-17-2013 01:00 PM

Try this Precision Gear - PG Tech - Contact Patterns

big gear head 01-17-2013 01:33 PM

Looks like the pinion needs to go a little deeper. Try adding about .003 to the pinion shim.

Use an axle to turn everything when checking the pattern. Be sure that you have the pinion bearing preload set correctly each time you check it. If you are not consistant with the bearing preload then the pattern changes will be confusing. Add a drop of oil to the marking compound to thin it slightly and make several revolutions with the ring gear in both directions to wipe away the compound enough to make the pattern clear and easy to read.

slownugly 01-18-2013 12:37 PM

2 Attachment(s)
Thanks guys!

Gear head I went with your suggestions and Im now running a .035" shim under my pinion with .010" backlash (on the first pattern I posted I had a .032" shim and .012 backlash)

This is the pattern I have now (pictured below: 1st pic-drive pattern, 2nd pic-coast)

Thanks again!

big gear head 01-18-2013 01:16 PM

Yes, that is better. Look at the drive pattern in the first post. Notice that it favors the face of the tooth and the root is curved and not as long as the face. In the second set the pattern is about equal at the face and root of the tooth, which is what you are looking for. Many people get hung up on heel to toe, when root to face is what is most important. You probably will not be able to move this pattern off of the toe, so I wouldn't worry about that. Notice that your coast pattern is still favoring the face a little. You might try adding about .002 to .003 more to the pinion shim and see if it moves the coast side closer to the root without messing up the drive side.

slownugly 01-18-2013 03:44 PM

2 Attachment(s)
Thanks again gear head!! :thumbup:

Here is the set up with .038" shim under pinion, .008" backlash and between 15-20 in/lbs of preload on the pinion nut. Let me know what you think.

drive pattern-1st pic, coast-2nd pic

big gear head 01-18-2013 04:07 PM

The coast side looks much better, but the drive side looked a little better before. Try increasing the backlash by about .002 and see what happens to the drive side.

slownugly 01-18-2013 05:38 PM


Originally Posted by big gear head (Post 1636319)
The coast side looks much better, but the drive side looked a little better before. Try increasing the backlash by about .002 and see what happens to the drive side.

Ok will do! Im gonna take .005 off of one side and add it to the other to increase the backlash and see what that looks like. Ill post the pictures when I get the pattern. Thanks for all your help! Ive heard that reading a pattern correctly is more of an art than a science, so it has helped having someone who knows what to look for. Thanks bud!

slownugly 01-18-2013 06:59 PM

Gear head,
I was only able to adjust the backlash in .005" increments since thats what shims came with my richmond kit. I adjusted the pinion shim to .038" and adjusted the carrier by .005" and the backlash ended up at .012".

Personally, Id like to stay at .010" or lower, but not sure if the allowance works both ways. Ive found through research that .008"-.010" (.010 is stamped on my gears) is where you want to run it, so not sure if .012" would fly?

If I went up to .040" would this tighten up the backlash if I left the carrier shims the way they are? Or should I just run with the .035" pinion shim and take everything back to the way I had it in my second pattern I posted?

big gear head 01-18-2013 07:51 PM

The pattern is probably better with the .038 shim. If you can get the backlash to .010 it would move the drive pattern a little more to the heel and possibly make it look right. Increasing the backlash moves the pattern toward the heel. Closing the backlash moves the pattern toward the toe. Increasing the pinion shim moves the pattern toward the root and taking shim out of the pinion moves the pattern toward the face. Don't try to make up for backlash by changing the pinion depth.

If you can add some shim to the right side without taking anything out of the left side it might move the backlash .002. Do you have the shims tight enough that youc an not pull the differential out by hand? If you can't get the backlash to .010 then stay with .008 and .038 pinion shim.

slownugly 01-18-2013 08:18 PM

Ok sounds good! I will mess with it and see what I can come up with. Ill post back and let you know what I find out. Thanks for the quick response!:thumbup:

Right now my carrier is pretty snug and with just the carrier in place it has drag and can spin almost one full turn. To get it out I have to use a pry bar and cant get it out by hand alone, so I believe my shims are good? At least for set up, I may add .005" to each side to preload them on final assembly?

big gear head 01-19-2013 05:51 AM

I wouldn't try adding .005 to each side if it's already that tight. You will probably damage your shims if you try that. Maybe just try adding .005 to the right side to open up the backlash just a little.

I know that this is a little late, but if you decide to do another gear sometime don't get a Richmond installation kit, or a Ratech kit or anything else that Jeg's or Summit sell. The kits that DTS, Tom's Differentials and Randy's Ring & Pinion sell have the super shim sets in them. You can make much more accurate backlash adjustments with these, and they are much easier to use. The shims in the other kits are just not good enough.

slownugly 01-19-2013 07:40 AM

Yea, I thought that this kit would come with the adjustable shim stacks that adjust by smaller increments but it didnt and another lesson is learned!

I will still try to add a little to the right side to open the .008 to .010 and see what it reads.

So do you think the .038 pinion shim is the more ideal pattern if i can get the backlash squared away?

Thanks gear head!

big gear head 01-19-2013 08:27 AM

If you can get the backlash to .010 we will see what the pattern looks like. You may need to go back a little on the pinion shim if the drive pattern doesn't look better. If you could take the pinion shim to .037 it might help. I've got a few thousand shims, so making small adjustments is no problem for me. For the guy who only has about 10 shims from one installation kit it's a little harder.

slownugly 01-19-2013 09:18 AM

2 Attachment(s)
I was able to get the backlash to .009" by adding a .005" shim to the right side carrier. My pinion shim measures .038" and this is the pattern I was able to obtain. Let me know what you think?

This looks way better than my very first pattern that I started with and its been awesome adjusting it and being able to see how the pattern changes. Im glad I didnt call it good enough with the original!?

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