Rebuilding rear differential; gear pattern? - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #1 of 38 (permalink) Old Sep 22nd, 18, 12:47 PM Thread Starter
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Tom
 
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Rebuilding rear differential; gear pattern?

Hey guys, so I am completely rebuilding the rear end in my 1966 Chevelle with new ring and pinion, disc brakes and new upper and lower control arms. I'm working on setting up the brand new Richmond 3:73 rear differential gears now.

I have a good pinion pre-load. I have correctly set the backslash and the carrier bearing pre-load. All that I'm totally happy with. And so then I moved on to checking the gear pattern with some grease. I placed the axles in and held them tightly with my hands to add some load while I turned the pinion and carrier. And here are my results...

The depth of the pattern seems to be pretty well centered from face to root. The coast side (concave) is pretty well centered from toe to heel. The drive side (convex) also looks centered from face to root. It is a little towards the toe end of the gear though.

What do you think? It looks like moving the pattern towards the heel or toe isn't necessary and can't be accomplished due to machining details that are done at the factory. Some places I've read say you can change the toe-heel location by adjusting carrier backlash, but that will change the pattern on the two sides in opposite direction, and I only need to move one (I think). Its the depth that is important and can be changed by pinion shims. So how does my depth look? Is there anything you guys would recommend changing and re-testing?

Thanks,
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post #2 of 38 (permalink) Old Sep 22nd, 18, 1:24 PM Thread Starter
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Tom
 
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Re: Rebuilding rear differential; gear pattern?

Another shot, showing depth a little better of the coast side.
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post #3 of 38 (permalink) Old Sep 22nd, 18, 1:39 PM
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Re: Rebuilding rear differential; gear pattern?

Forward and backward ?


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post #4 of 38 (permalink) Old Sep 22nd, 18, 2:10 PM
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Re: Rebuilding rear differential; gear pattern?

The pinion is too deep. Notice the very sharp line at the root of the teeth and the curve on the face side. Take about .005 out of the pinion shim and give it another shot.
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post #5 of 38 (permalink) Old Sep 22nd, 18, 5:05 PM Thread Starter
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Re: Rebuilding rear differential; gear pattern?

Quote:
Originally Posted by Slick87gn View Post
Forward and backward ?


Quote:
Originally Posted by big gear head View Post
The pinion is too deep. Notice the very sharp line at the root of the teeth and the curve on the face side. Take about .005 out of the pinion shim and give it another shot.
Thanks for the reply. Interesting, I was thinking just the opposite, the pattern didn't look deep enough into the ring gear teeth. I currently have a 0.028" pinion shim. You think I should go to 0.023"? Also, when I tore this apart (previous owner) had a 0.031" shim in there. But I don't read too much into it, as I had a lot of whine and 3 broken ring gear teeth...

Thanks again,

Tom
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post #6 of 38 (permalink) Old Sep 22nd, 18, 6:06 PM
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Re: Rebuilding rear differential; gear pattern?

Freddie guided me through my setup, you've got the right man on the job.
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post #7 of 38 (permalink) Old Sep 22nd, 18, 6:11 PM Thread Starter
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Tom
 
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Quote:
Originally Posted by Dansk View Post
Freddie guided me through my setup, you've got the right man on the job.
Oh yea I know it! I've read a ton of Freddie's posts and have learned a ton. Just not enough obviously...

Tom

1966 Chevelle SS, 355 V-8, TH-350.
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post #8 of 38 (permalink) Old Sep 22nd, 18, 6:48 PM
 
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Re: Rebuilding rear differential; gear pattern?

+1, Move the pinion out a touch.
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post #9 of 38 (permalink) Old Oct 8th, 18, 8:14 PM Thread Starter
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Re: Rebuilding rear differential; gear pattern?

Quote:
Originally Posted by big gear head View Post
The pinion is too deep. Notice the very sharp line at the root of the teeth and the curve on the face side. Take about .005 out of the pinion shim and give it another shot.
Ok guys, sorry it has been a couple of weeks since I originally posted...I finally got back to working on the Chevelle and have run another pattern. I took out 0.005" of pinion shim from the last run and set everything up again. This time, I have these specs:

0.023" pinion shim (-0.005" from last time)
18 in-lb pinion pre-load
0.220" left shims (+0.005" than last time to get proper carrier bearing pre-load)
0.263" right shims (+0.005" than last time to get proper carrier bearing pre-load)
0.008" backlash
29 in-lb pinion pre-load with carrier in place.

So what do you think with this go around?! I inserted an axle and turned it in both directions repeatedly to get the pattern. In order to see the depth of the teeth properly, I have scribed a thin line at the root of the gear teeth.

Thanks!

Tom
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post #10 of 38 (permalink) Old Oct 8th, 18, 9:40 PM
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Re: Rebuilding rear differential; gear pattern?

Disregard!

Dave
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post #11 of 38 (permalink) Old Oct 8th, 18, 10:49 PM
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Re: Rebuilding rear differential; gear pattern?

the pattern doesnt really look like youve changed anything. its still to deep. .023 is usually not enough shim. are you sure the bearing is seated on the pinion and the races seated in the housing? take a brass drift and good sized hammer and give the pinion a pop on the nut end and the gear end and see if it doesnt turn a lot easier. if it gets looser retorgue the nut and do it again untill theres no change. dont hit it hard just a good pop. see what freddie says but thats my opinion
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post #12 of 38 (permalink) Old Oct 9th, 18, 7:41 AM
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Re: Rebuilding rear differential; gear pattern?

I agree, the pinion is still too deep. As Gary said, check the bearing races and be sure that they are completely seated in the housing. I use a .001 feeler gauge to check behind the races to see if they are seated. If everything checks out well then take another .005 out of the pinion shim and try again.


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post #13 of 38 (permalink) Old Oct 9th, 18, 6:41 PM Thread Starter
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Thanks guys, I thought the same thing that the pattern didn't look much different...and I was getting worried about heading so far away from the average shim thickness.

I'll check the new races with the feeler gauge and will use a brass drift to seat the pinion. I do know I loaded up the press pretty good when installing the pinion bearing, to make sure it was seated firmly. I'll check the rest.

Thanks!

Tom

1966 Chevelle SS, 355 V-8, TH-350.
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post #14 of 38 (permalink) Old Oct 9th, 18, 11:42 PM
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Re: Rebuilding rear differential; gear pattern?

Sometimes you can raise a burr on the housing when driving the old races out. I had that issue on an 8.2 and it stumped me for a while. Now I've learned to always check for burrs or raised metal before driving in new races. I should thank Freddie again, as he was the guy that suggested that this was my issue - he was right!
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post #15 of 38 (permalink) Old Oct 11th, 18, 9:16 PM Thread Starter
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Well...you guys were right again. I removed the carrier and gave both sides of the pinion a whack with a brass punch. Sure enough, the preload on the pinion loosened. So I removed the pinion and used the old races to better seat the new ones. I thought I did a pretty good job, but the feeler gauge tip was money. I checked with my smallest .0015 and sure enough a could slip it in between the race and the housing on the larger race on one half side. So I gave it a few more whacks and got it tight. Great tip!

I'm now in the process of setting it up again. I just decided to leave the .023 pinion shim and see where I go from there. There is already a noticeable difference in how much shim I'm needing to get the right backlash, more than before, a sure sign the pinion moved in the right direction. Gave up for the night.

Thanks guys, making progress...
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