US-Gear 12-bolt pro gear issues ???

Kevin Panzino · 09-21-2024, 02:54 PM

Looking for some feedback from others on US gear 12 bolt pro gear sets. I honestly am completely lost right now on why this set is to damm loud on shutdown, and why the coast pattern looks so terrible when the drive pattern is good and all the other parameters are dead nuts.
Its, not only loud, but I can actually feel the pulsation of vibrations in my seat as the car coasts to a stop.

And with axles out, car on lift, driveshaft disconnected, just spinning spool with my hand it sounds horrendous....

I have pinion depth dead nuts, backlash at .008" and drive paste pattern looking good.

But, coast pattern is almost non existent. A thin line that is way, way too far down into the root to make any sense.

There is literally nothing else I could change to alter this situation..

Perhaps my housing warped/tweaked ???

Looking for some feedback, or maybe if anyone else has had similar issues with US gear Pro sets???

I'm about to put my old Richmond 5.57 back in with prob 200+ passes on em...

Kp

Adger Smith · 09-21-2024, 05:05 PM

Have you tried it at any other settings on BL ?

Jeff Stout · 09-21-2024, 08:31 PM

Curious on what shim you have on pinion.
My very first rear end I did when I was 18. New gear and bearings and I learned how to get the pattern needed. I fought this the whole weekend and couldn't get it right. I was so frustrated thinking it was me missing something. Called Monday and they sent another set out. Sent mine back and found out the gear was boxed before it was finish. It was the coast side that wouldn't come in. That first time gear change had me learn that new may not be right.

Mark Ugrich · 09-21-2024, 09:16 PM

I agree with Jeff. If you can get a decent load side pattern but the coast is deep in the gear, it would make sense the gear was manufactured wrong.

Gary Evans · 09-21-2024, 10:39 PM

Quote:

Originally Posted by Mark Ugrich

I agree with Jeff. If you can get a decent load side pattern but the coast is deep in the gear, it would make sense the gear was manufactured wrong.

I would agree that the ring gear was not manufactured correctly. Wouldn?t be afraid to put the Richmond gears back in. I just changed the gears in my A/SA Camaro after 29 years and over 2300 passes

Kevin Panzino · 09-22-2024, 08:07 AM

Thanks for the replies gents. I have tried .008 backlash and also tried .010?. To me the .008 sounds worse.
I am at .032? pinion shim and are spot on the 2.854? checking distance.
I?m really thinking I got a bad set.

Kp

Adger Smith · 09-22-2024, 08:46 AM

Kevin, I know this is Elementary, but you do know the caps and housing are not split on center? A pinion shim that thick could be putting the pinion deep. I would have thought around a .026 was thick enough. How much pinion shim was in it to begin with??? I agree the gear could be mismanfactured.

Kevin Panzino · 09-22-2024, 09:38 AM

Wait. What? I am I guess ashamed to say I never guessed the cap/housing split line wasn?t on center. It can?t be much, right? As you wouldn?t be able to get the races in or the caps on? I suppose the ends are relieved?

Yes I have been measuring checking distance for years from the cap face!!

I had .032? also in my old Richmond set. While it was always a tad loud on coastdown, it wasn?t this loud.

Now you really have me thinking.

One thing I can?t reconcile though is how I was able to get a good drive pattern, but terrible coast pattern?..

Old Richmond set had prob 500 passes fwiw. And teeth looked great.

Kp

Mark Ugrich · 09-22-2024, 10:45 AM

Quote:

Originally Posted by Adger Smith

Kevin, I know this is Elementary, but you do know the caps and housing are not split on center? A pinion shim that thick could be putting the pinion deep. I would have thought around a .026 was thick enough. How much pinion shim was in it to begin with??? I agree the gear could be mismanfactured.

Adger, I remember from my days as a heavy line tech at Buick using the kent moore tools to set pinion depth.The service manual said it was a ? nominal? measurement. Which I understood to mean, it is , but it isn?t , but it could be ,what you just measured.The caps not split on center might be the reason for a nominal measurement.

Greg Reimer 7376 · 09-22-2024, 02:20 PM

Seemed to me back in the days when 12 bolts were the newest things,a .030"-.032" pinion shim was correct about 90%of the time.It was far more common to be able to reuse the original pinion shim than not.It didn't matter too often if the gears were 2.73's or 5.86's. With a drag race ratio or anything in the 4.56-6.14 ratios, there would be variation in whatever carrier bearing shim you needed far more often than the pinion bearing shim.It was also common to take out an open carrier and install a correct series positraction carrier reusing the gear set without having to start from scratch to determine the proper shim thicknesses. The vendor that GM used to supply the gears must have been very accurate as to quality control.When everything that rotates gets replaced as in a new rear axle assembly being built, it usually is pretty consistent as well. The 8.50" 10 bolt that came out in 1973 to replace the 12 bolt was fairly close as well. Sounds to me that what you describe was a problem with the new gears.

09-21-2024, 02:54 PM	#1
Kevin Panzino Senior Member Join Date: Oct 2002 Location: Pittsburgh Posts: 547 Likes: 271 Liked 620 Times in 120 Posts	US-Gear 12-bolt pro gear issues ??? Looking for some feedback from others on US gear 12 bolt pro gear sets. I honestly am completely lost right now on why this set is to damm loud on shutdown, and why the coast pattern looks so terrible when the drive pattern is good and all the other parameters are dead nuts. Its, not only loud, but I can actually feel the pulsation of vibrations in my seat as the car coasts to a stop. And with axles out, car on lift, driveshaft disconnected, just spinning spool with my hand it sounds horrendous.... I have pinion depth dead nuts, backlash at .008" and drive paste pattern looking good. But, coast pattern is almost non existent. A thin line that is way, way too far down into the root to make any sense. There is literally nothing else I could change to alter this situation.. Perhaps my housing warped/tweaked ??? Looking for some feedback, or maybe if anyone else has had similar issues with US gear Pro sets??? I'm about to put my old Richmond 5.57 back in with prob 200+ passes on em... Kp

09-21-2024, 05:05 PM	#2
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,416 Likes: 517 Liked 760 Times in 291 Posts	Re: US-Gear 12-bolt pro gear issues ??? Have you tried it at any other settings on BL ? __________________ Adger Smith (Former SS)

09-21-2024, 08:31 PM	#3
Jeff Stout VIP Member Join Date: Dec 2001 Location: phoenix Posts: 1,464 Likes: 59 Liked 701 Times in 278 Posts	Re: US-Gear 12-bolt pro gear issues ??? Curious on what shim you have on pinion. My very first rear end I did when I was 18. New gear and bearings and I learned how to get the pattern needed. I fought this the whole weekend and couldn't get it right. I was so frustrated thinking it was me missing something. Called Monday and they sent another set out. Sent mine back and found out the gear was boxed before it was finish. It was the coast side that wouldn't come in. That first time gear change had me learn that new may not be right.

09-21-2024, 09:16 PM	#4
Mark Ugrich Member Join Date: May 2011 Location: Auburndale,Florida Posts: 211 Likes: 22 Liked 60 Times in 34 Posts	Re: US-Gear 12-bolt pro gear issues ??? I agree with Jeff. If you can get a decent load side pattern but the coast is deep in the gear, it would make sense the gear was manufactured wrong.

09-22-2024, 08:07 AM	#6
Kevin Panzino Senior Member Join Date: Oct 2002 Location: Pittsburgh Posts: 547 Likes: 271 Liked 620 Times in 120 Posts	Re: US-Gear 12-bolt pro gear issues ??? Thanks for the replies gents. I have tried .008 backlash and also tried .010?. To me the .008 sounds worse. I am at .032? pinion shim and are spot on the 2.854? checking distance. I?m really thinking I got a bad set. Kp

09-22-2024, 08:46 AM	#7
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,416 Likes: 517 Liked 760 Times in 291 Posts	Re: US-Gear 12-bolt pro gear issues ??? Kevin, I know this is Elementary, but you do know the caps and housing are not split on center? A pinion shim that thick could be putting the pinion deep. I would have thought around a .026 was thick enough. How much pinion shim was in it to begin with??? I agree the gear could be mismanfactured. __________________ Adger Smith (Former SS)

09-22-2024, 09:38 AM	#8
Kevin Panzino Senior Member Join Date: Oct 2002 Location: Pittsburgh Posts: 547 Likes: 271 Liked 620 Times in 120 Posts	Re: US-Gear 12-bolt pro gear issues ??? Wait. What? I am I guess ashamed to say I never guessed the cap/housing split line wasn?t on center. It can?t be much, right? As you wouldn?t be able to get the races in or the caps on? I suppose the ends are relieved? Yes I have been measuring checking distance for years from the cap face!! I had .032? also in my old Richmond set. While it was always a tad loud on coastdown, it wasn?t this loud. Now you really have me thinking. One thing I can?t reconcile though is how I was able to get a good drive pattern, but terrible coast pattern?.. Old Richmond set had prob 500 passes fwiw. And teeth looked great. Kp

09-22-2024, 02:20 PM	#10
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,125 Likes: 172 Liked 687 Times in 214 Posts	Re: US-Gear 12-bolt pro gear issues ??? Seemed to me back in the days when 12 bolts were the newest things,a .030"-.032" pinion shim was correct about 90%of the time.It was far more common to be able to reuse the original pinion shim than not.It didn't matter too often if the gears were 2.73's or 5.86's. With a drag race ratio or anything in the 4.56-6.14 ratios, there would be variation in whatever carrier bearing shim you needed far more often than the pinion bearing shim.It was also common to take out an open carrier and install a correct series positraction carrier reusing the gear set without having to start from scratch to determine the proper shim thicknesses. The vendor that GM used to supply the gears must have been very accurate as to quality control.When everything that rotates gets replaced as in a new rear axle assembly being built, it usually is pretty consistent as well. The 8.50" 10 bolt that came out in 1973 to replace the 12 bolt was fairly close as well. Sounds to me that what you describe was a problem with the new gears.