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USA Standard Gear

USA Standard Gear (ZG GM8.5-373) Ring & Pinion Gear Set for GM 8.5 Differential

    • Based on 858 reviews
Condition: New
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Availability: In Stock.
Fulfilled by Amazon
Arrives Saturday, Dec 28
Order within 11 hours and 21 minutes
Available payment plans shown during checkout

Style: GM 8.5" 3.73 Ratio


Features

  • USA Standard ring and pinion sets are the right choice to add confidence to your install
  • USA Standard Gear offers a full line of ring and pinion sets for a variety of common and hard to find applications
  • USA standard gear offers a standard one year against defects on their ring and pinion sets
  • This product is used in a 3. 73 axle ratio
  • 12 Ring Gear Bolts

Manufacturer: ‎Yukon Gear


Brand: ‎USA Standard Gear


Model: ‎USA Standard Gear (ZG GM8.5-373) Ring & Pinion Gear Set for GM 8.5 Differential


Item Weight: ‎17.67 pounds


Product Dimensions: ‎16 x 12 x 6 inches


Country of Origin: ‎Korea, Republic of


Item model number: ‎ZG GM8.5-373


Exterior: ‎Machined


Manufacturer Part Number: ‎ZG GM8.5-373


OEM Part Number: ‎FDHDZG GM8.5-373


Date First Available: February 13, 2012


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Saturday, Dec 28

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

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Top Amazon Reviews

    • Very loud gears but performs well
Style: GM 8.5" 3.73 Ratio
The price was right. This is not a daily driver for me. Good strength under lots of load, pulls well. However, these gears are loud. Didn’t come with any numbers for the pinion depth install as other pinions would. Gets the job done for little money. Pick your poison is all I can say!
Reviewed in the United States 🇺🇸 on March 10, 2023 by Abner Flores-Salyers
    • I have before was great. The last one was damaged I think from shipping.
Style: Dana 80 3.73 Ratio
The internal foam was damaged. The product had pinion chips from shifting around. It is only one had problem.
Reviewed in the United States 🇺🇸 on March 25, 2023 by Robert Crabtree
    • Notice for GM 12 bolt C10 diff install
Style: GM 12-Bolt Truck 3.73 Ratio
Review Image by Rascal The Rat Rascal The Rat
Review Image by Rascal The Rat Rascal The Rat
Review Image by Rascal The Rat Rascal The Rat
Review Image by Rascal The Rat Rascal The Rat
Review Image by Rascal The Rat Rascal The Rat
Review Image by Rascal The Rat Rascal The Rat
Review Image by Rascal The Rat Rascal The Rat
These gears appear to be good quality and the wear pattern looks the best I've ever seen after adjustment. I have a 12 bolt 8.875 GM truck rear in my '67 C10. All 3 of my C10's, '67, '68, '69 2wd trucks had 3.08 factory installed gears. I guess because of only a 3 speed auto trans in my '67 and '68, it was better on the highway. My '69 is a 3 speed manual. I decided that since I built a 383 stroker small block and installed a 3000 rpm stall converter in the TH400, due to the cam profile, I would replace the 3.08 geared, one wheel peel with a 3.73 gear and a Spartan "lunch box" locker. I'm just about to fire this thing up in a week or two. Just waiting on the machine shop to do the final piston fit honing and it ready to assemble, stab it in, hook everything up, start it up, and hold onto my hat. But I digress. Sorry, lost track. Anyhow, changing the gears from 3.08 to 3.73 I obviously had to re-shim my carrier to move it to the left. The factory shims were just about equal from one side to the other. Left being a .230 and right being a .243 thickness. I had to bring my left side to .445 and the right only has .024 gap in order to get my .006-.010 backlash needed for a good pattern. I even had to shim my pinion an additional .030 just to get it right. It's not quite a tight fit as factory, but I don't have a housing spreader and the 3 very thin .008 shims were giving a fit without trying to fold over on me. I don't think .004" is going to give me any trouble. Especially with the Moser girdled diff cover I'm using. Okay, here's the issue I ran into. Being that I needed to shift the carrier over almost a quarter inch, the right side of the carrier was hitting the area just outside and to the front of the bore for the carrier bearing. So, I removed the carrier and used a dremel tool to slightly grind the carrier housing on the four 'corners' where the bearing is pressed on. I took off about .100" on each edge and it then fit like a glove. I got my backlash to .008". Installed the yoke with a new crush sleeve and torqued the pinion nut to 11 in.lbs. Re-installed my carrier and torqued the caps to 60 ft.lbs. and installed the diff girdle cover. Hint to the next guy that decides to rebuild a differential. Purchase some cheap new pinion bearings in addition to the bearings that you are going to install. Grind the inner race of the cheap bearings so they slide over the pinion without being pressed on. This will save a bunch of time and frustration when adjusting or shimming the pinion depth. When it's all clocked in, just remove the dummy bearings and press the final good bearings onto the pinion. Oh, btw, the spartan locker is a pain in the butt to install with the diff housing in the vehicle. If possible, remove it and set it on a bench or jack stands with the yoke facing the floor. It's much easier to articulate the c-clips this way as long as you hold your tongue right. Good luck ... show more
Reviewed in the United States 🇺🇸 on August 3, 2019 by Rascal The Rat Rascal The Rat
    • Running gear
Style: GM 8.5" 3.42 Ratio
I had 373’s in before, these give me better normal driving conditions without the RPM’s
Reviewed in the United States 🇺🇸 on March 15, 2023 by Stub Nichols
    • Awesome product!
Style: Dana 30 Reverse Rotation 4.56 Ratio
Great quality and durability! I ordered this ring & pinion set and it saved the weekend. It arrived quickly and just as described. It fit my 1999 Jeep Cherokee with stock front axle perfectly. Just like OEM!
Reviewed in the United States 🇺🇸 on February 18, 2023 by Jaime N Montalvo
    • got a sticker in it !
Style: GM 8.5" 4.11 Ratio
great brand , they are in a daily driver no complaints
Reviewed in the United States 🇺🇸 on February 10, 2023 by Mother
    • Lots of noise
Style: GM 8.5" 3.73 Ratio
Well. Where do I start. I installed these on my 2009 Chevy Silverado. Had pinion depth set correctly and had a perfect wear pattern. Back lash and preload also correct. Filled with oil and went on a drive. Didn't even make it a mile and turned around due to loud gear noise. I can deal with a little noise but these were loud. Took everything back apart thinking I have pinion bearing load incorrect. Everything looked good. Knocked out races and purchased new pinion bearings thinking this could be my issue. Crushed the sleeve and set everything up. Checked my wear pattern again after setting back lash and it was set good. Went for a drive and still just as loud. At this point I think I installed it wrong. Called my buddy (GM certified tech) and he helped me take it back apart. He looked at all bearings and wear pattern and confirmed it looked good. He took pinion back off and measured old shims to new shims I installed to confirm preload. He then came to recommendation that I use a OE pinion bearing vs the Toyo I just installed. We picked up a bearing and had to change pinion shim to accommodate different bearing (thank goodness for cheap harbor freight press). Set everything up and took for a drive. Still loud!! I drove truck for "break in" and pulled over to let cool down thinking this will eliminate the noise. When I pulled over I checked my temparure of differential and it was at 128 F on a 100 degree day. Once it cooled off I drove and still noisy. Got home and checked diff temp. Reading 125 F. Not bad at all. Called Yukon Gear who makes USA standard gear and told them my problem. He transferred me to their technical person and he told me the USA gears have a known problem for being noisy on 07 - 13 Silverados??? He said the 2009 and up was worse due to difference in pinion bearing size? He told me to get with supplier for return. I ordered a set of GM 3.73 gears (expensive!!!!) And called Amazon. Amazon was super helpful and accepted the return request. Once I got my GM gears, I installed them and boxed these back up to Amazon. The new GM gears make zero noise. Same sound my factory 3.23 gears made. Nothing! Funny thing to I was so tired of working on the rear end I wasn't exactly thrilled on my back lash setting on the GM gears (still within spec) and they made no noise compared to "right on the money" I had for USA gears. I will say this though. If I had a car I didn't drive often at all or an off-road rig, I'd use USA standard gears. Although they were super loud they didn't run hot. For a daily driver like my case. I wouldn't recommend these. I don't know. Maybe I didn't do enough homework and these gears aren't meant for my application. Don't know and don't care lol. It's done now. Figured I'd share my experience. ... show more
Reviewed in the United States 🇺🇸 on July 25, 2018 by Amazon Customer
    • Worth it.
Style: AMC Model 35 3.55 Ratio
What's to review? Set them up and break them in properly and you shouldn't have a problem. This is going on a stock daily driver. It will be fine.
Reviewed in the United States 🇺🇸 on November 9, 2022 by Installer

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