CA WTB - NOS 12 Bolt Truck 3.73 Rear Ring & Pinion Set

[pjmoreland]

I'm looking for a NOS 4 series differential gear set to put in my truck. The ring part number should be 3817778 and the tooth counts are 11:41 (3.73). Thank you.

[MDFarms]

Good luck! I went down that road all.last winter and found one NOS but it was the wrong gear for my carrier. NOS Ring and Pinion in 3.73. My carrier was a 3.07 - 3.73 and this ring was for the other carrier. I sold it to a guy in California.

[pjmoreland]

Yeah, it seems pretty unlikely. I saw your set, and I saw another set on eBay, but in both cases I was too slow.

[72again4x4]

I have a 12 bolt sitting in the backyard. Believe it's a 3.73, was out of my 72 k10. I can check it this weekend and let you know. Double checking, you only need the gears or carrier too?
Roger

[pjmoreland]

Originally Posted by 72again4x4

I have a 12 bolt sitting in the backyard. Believe it's a 3.73, was out of my 72 k10. I can check it this weekend and let you know. Double checking, you only need the gears or carrier too?
Roger

Hi, Roger. I am looking for just the ring and pinion without a carrier. From what I've read, it is extremely difficult to setup a used set of gears in a different housing due to the gears having worn in based on the setup and dimensions of the original housing. That's why I'm looking for GM New Old Stock.

[72again4x4]

Ok makes sense. Thought I would take a shot sense it's just sitting there not doing me any good. Good luck on the search.

[WETOWM]

if there are GM gears they will setup in a different housing with not problem or difficulty I do it all the time much easer than aftermarket gears

[pjmoreland]

Originally Posted by WETOWM

if there are GM gears they will setup in a different housing with not problem or difficulty I do it all the time much easer than aftermarket gears

That is good to know. Thanks!

[pjmoreland]

Originally Posted by 72again4x4

Ok makes sense. Thought I would take a shot sense it's just sitting there not doing me any good. Good luck on the search.

Hello again. Based on what WETOWM said, I'm interested in your gears. Would you be willing to crack open the rear end you have to see how they look? The set I have has rust pitting on the teeth. Thanks in advance.

[72again4x4]

Of course, should be home in a couple of hours. I'll crack her open and get some pics.

[Curtb1971]

If 72again4x4's gears are good it's easier to set the pattern in a different housing on used gears if he runs a paint pattern and measures the carrier/pinion shims. Just gives the installer a closer base line. If you weren't so far we just build a 3:73 with new Yukon gears and a duragrip posi that I'm thinking of selling in turn for a 9 inch.

[pjmoreland]

Originally Posted by Curtb1971

If 72again4x4's gears are good it's easier to set the pattern in a different housing on used gears if he runs a paint pattern and measures the carrier/pinion shims. Just gives the installer a closer base line. If you weren't so far we just build a 3:73 with new Yukon gears and a duragrip posi that I'm thinking of selling in turn for a 9 inch.

That's good to know. Thank you.

Roger, would you be able to include the carrier and pinion shims with the gears? Any chance you have some gear pattern paint?

[72again4x4]

Hi Patrick,
Sure I can do that. I can run a pattern first and take some pictures for you before I tear it down. I'll label everything too and keep the shims in the exact order I removed them from.

[pjmoreland]

Originally Posted by 72again4x4

Hi Patrick,
Sure I can do that. I can run a pattern first and take some pictures for you before I tear it down. I'll label everything too and keep the shims in the exact order I removed them from.

Thanks so much. Let me know if you'd like me to order you some pattern paint.

[pjmoreland]

Thank you so much, Roger, for helping me out. You really have gone above and beyond what most would be willing to do. I will use your gear patterns as a guide when setting the gears up in my truck.

[72again4x4]

Gears are on the way, let me know how they work out. Glad I could help.

[pjmoreland]

I installed the gears today. The pinion shim from the gearset I removed from my rear end was .028", and the pinion shim from my "new" gears is .027". I installed the .028. The "new" carrier shims are too thick to fit in my housing. The shims on the left side I ended up with that gave me .009" backlash were within
.001" of the left "new" carrier shim.

The paint pattern that Roger took before disassembling the "new" gears seems to me like the pinion was shimmed too far out from the factory, and there may have been too much backlash. Should I try to improve the pattern, or do I need to stick with duplicating the pattern since it is a used gear set?

Here are some photos that show where I'm at currently.

[Dave]

PJ,
Your right in thinking your too far out on the ring gear. I've run into this before and have referred to the GM service manual for specs. Once, I knew what the spec range was, then it's a matter of getting the right shim pack combo to get you where you need to be. It's a PIA because sometimes it takes multiple times to get it right, as in all day. You can do it, just keep trying buddy.

[pjmoreland]

Thanks, Dave. The thing I'm struggling with is the advice I have received to try and reproduce the original pattern of this used gearset. The original pattern was not great, so do I still try to reproduce it, or do i go for a more by-the-book pattern?

[72again4x4]

Pj,
I just wanted to chime in a little. Even with that pattern I made on those gears, there was never any gear noises or sloppy feeling when driving the truck. It always felt really solid even at highway speed.
Anyway, looking good and I’m following along to see how it turns out.
Roger

[pjmoreland]

Thank you, Roger. That's good to know. I may need to start a thread over in the Drivetrain forum to get some advice about whether or not I should stray from the original pattern to center it up.

[pjmoreland]

I started this thread in the Engine & Drivetrain forum.

http://67-72chevytrucks.com/vboard/s...13#post9087513