489 gear pattern setup results

[AR67GTX]

I’ve posted a couple other threads leading up to this. Been through a couple sets of noisy Richmond gears by one shop and then bought a set of US Gear - gears (made in US instead of India) and had another shop set them up. Drove a very few miles, just enough to determine they howled on steady throttle and also a little on coast. Decided I probably can’t screw gears up any worse than these shops so pulled it for 5th time to tackle myself.

Here is the pattern on the US Gears set up by the shop with a .031 pinion depth shim and .007 backlash. The shims I have are all .0005” greater than nominal thickness so a .010 + .020 shim actually mic out at .031”. I‘ve zeroed my caliper, checked it on feeler gages and that just seems to be how they run.

The drive side looks fair but a little low towards the toe and the coast side appears to be too deep into the root. I did about 8 different pinion depth set ups from .045” pinion depth shims to .022” shims to bracket the shop set up at .031”. I also patterned each with backlash of .006“ and .008”. The outer limit pinion depth setups were obviously off and it appeared the range where both coast and drive patterns were shaping up was somewhere in the pinion depth shim range of .025” to .027“. I didn’t see a lot of difference with .006” and .008” backlash with the .0027” pinion depth shim but with a .0025” pinion depth shim it looks like the coast pattern starts to fall off the crown with .008” backlash.

Pinion depth shim .027“, backlash .006” below:

Pinion depth shim .025”, backlash .006” below:

To my unpracticed eye I think the .027 pattern looks as good as I’m going to get. I think the drive side of the .025” pinion depth shim set up is getting a little funky and possibly falling off the crown. I would like to try a .028” pinion depth shim set up but with the shims I have I can’t come up with that combination right now. I have some more shims coming but until I get them I’m not sure if I can get that combo.

Anyone experienced with this, I would appreciate your thoughts and observations.

 

[Fran Blacker]

PDS .027 BL.006 Looked best to me.

 

[Cranky]

Is .006 your tightest spot?? Keep in mind that noise on coast is a sign of the pinion being too deep......

 

[AR67GTX]

My backlash seems to vary about .001” around the ring gear. I was using pretty much the same spot to set backlash and run the various patterns for consistency. When I get into the final setup I’ll probably set the tightest point at .006” BL. I also learned the ring gear needs to be spun a few times also each time the backlash adjusters are moved, to center the carrier and bearings well before measuring. I talked to a guy who uses US Gears frequently on older Corvette rear ends and he said he usually sets them at .006” BL with good results. I know that seems a hair tighter than the FSM but then these aren’t OEM gears either so - well, I don’t know.

I had not heard that about coast noise and too-deep a pinion. Since I’m going shallower with pinion depth I hope that holds true and takes care of some of the noise. I’m hoping for the best but know my chances of a totally quiet gear set are pretty slim given the gears available today.

Thanks

 

[john-9]

i agree .027 shim shows the best drive and coast pattern looks to be a text book excellent pattern -- your backlash at .006 is fine -- i always set backlash at the minimum figure .006 - .008 because once you run the gear set the backlash will usually open up by about .003..

 

[Cranky]

My backlash seems to vary about .001” around the ring gear. I was using pretty much the same spot to set backlash and run the various patterns for consistency. When I get into the final setup I’ll probably set the tightest point at .006” BL. I also learned the ring gear needs to be spun a few times also each time the backlash adjusters are moved, to center the carrier and bearings well before measuring. I talked to a guy who uses US Gears frequently on older Corvette rear ends and he said he usually sets them at .006” BL with good results. I know that seems a hair tighter than the FSM but then these aren’t OEM gears either so - well, I don’t know.

I had not heard that about coast noise and too-deep a pinion. Since I’m going shallower with pinion depth I hope that holds true and takes care of some of the noise. I’m hoping for the best but know my chances of a totally quiet gear set are pretty slim given the gears available today.

Thanks

Only .001" difference is pretty good. Recommended to check in 3 places but I usually do 4 and have seen as much as .004" difference before. Imo, it's a good idea to check the runout of the gear flange of the carrier. I've found a couple that were running out pretty bad before. They can change due to excessive heat or when someone socks too much power to them and/or gear breakage.

 

[AR67GTX]

I’ll double check it. Fortunately it’s a new sure grip with only 1000 miles or so on it and I haven’t hammered it hard or anything.

 

[AR67GTX]

I ran a .029” pinion depth set up this morning just to see what it looked like. I also need to correct the driveline shop pinion depth shimming dimension I reported above as a starting point. The shims got mangled some from the bearing separator and I have to kind of hunt and peck to find an undamaged area on them to measure. But I measure .010 + .010 + .012 for a starting place of .032” shim Instead of .031”

The .029” shim pattern with .008 backlash looked a bit better than the .006 one, but I still think overall that the .027” pinion depth pattern set up still looks a bit better. Anyone see otherwise???

Also, I marked off 4 equal distant points around the carrier rim that the ring gear bolts against To check runout. I didn’t want to remove the ring gear unless there was an issue. Actually the runout was less than .001” all the way around, more like .0005”

The .029“ pinion depth shim pictues:

 

[33 IMP]

I wish you the very best with your setup.
But, fair warning, I was told by a good friend that owned his own rearend shop, that once any gear set howls, no matter how good the future setup is, or the tech , it will howl.

 

[AR67GTX]

Yes, I’m hoping otherwise as I only put about 15 easy miles on it with 90-140 oil. Just enough to determine if it was going to make noise. We’ll see.

 

[john-9]

for sure the .027 shim shows a better pattern , contact pattern on the drive and coast sides covers more of the tooth -- you can see with the .029 shim the drive side pattern is fading and the coast side as well -

 

[AR67GTX]

Someone I know who has a differential business back East asked me to put a drop of gear oil on the teeth and re-roll the patter with the .029” shim. He seems to think it’s a little better than the .027” shim. I still think the .027” shim pattern looks better but here are the later .029 pattern pictures he asked me to run. I think the oil does produce a little more distinct pattern.

 

[Fran Blacker]

Drive side doesn't look as good. MO but not an expert.

 

[AR67GTX]

Yeah, I have some more shims coming today and if I can come up with a .028 shim combination for pinion depth, I may try that and see what it looks like. But I’m leaning towards the .027 setup too. That would reduce the pinion depth .005” which should make a difference. Whether good or bad on noise remains to be seen.

 

[dvw]

.001"-.003" isn't going to make much difference in my opinion. The change is very minor. Good luck.
Doug

 

[AR67GTX]

I’m going to finish playing around with trial setups today and decide how to go. If nothing else it’s educational. Now my latest curiosity is after pulling my inner set up bearing and installing the new, permanent bearing - how does its installed depth compare to the set up/older bearing since if different, that will affect pinion depth. Hopefully they are pretty close. I’ll try to measure and compare them after I knock the old cone out.

 

[AR67GTX]

I was hoping tapered bearings would be very consistent in dimensions between manufacturers but apparently not. After spending several hours calipering my old bearings used for setup and my new assembly bearings I’m dealing with apples to oranges on shimming. The new bearings are dimensionally shorter than the old ones and as near as I can tell I need to add .002“ to the pinion depth shimming and maybe .004” to the pinion preload shimming. So here’s hoping I don’t have to press that new inner bearing off again to correct the pattern.

 

[5.7 hemi]

When you check the pattern, put some drag on the carrier. You’ll see a difference with and without drag.

 

[john-9]

there usually is some difference between a used set up bearing and the new bearing -- best way to determine that would be to measure accurately from the carrier saddle ( boss where the bolt attaches ) down to the head of the pinion with the .027 shim installed , mark the point on the pinion head you took the measurement from , then install the new bearing and measure down again at the same point , pinion bearings have to have some preload when doing this ,, if you are within +/- .001 old bearing to new bearing i would not worry about changing anything as far as pinion depth is concerned .recheck your pattern if you have doubts.

 

[AR67GTX]

That’s a good idea, I’ll use it to check my results. I sat here for an hour on a granite counter top measuring these bearings at 90 deg points, over and over and averaging results until I was getting a repeatable figure. And it’s not as easy as just calipering their depth - you have to measure from the rear seat area of the cone to the roller bearing shoulder abutting the pinion head - something I’ll call effective depth for lack of something better. It was a surprise when in this mix of different bearing suppliers, in both cases the new bearings are .002” thinner in effective depth than the old ones. I was expecting the reverse.

5.7 Hemi - yes, I do put as much drag on the gears as I can when rolling the gears. On drive side I restrain the pinion yoke with my left hand while rolling the ring gear forward with my right against the resistance. On coast I restrain the ring gear as hard as I can while turning the yoke against the resistance. Good isometric exercise.