Gear mesh reading

[hoogiesngrinderz]

Ring and pinions aren't something I spend a great deal of time with. The last couple sets have worked out well, no noise and within spec. But, the gears in this 98 have me questioning myself.

Usually you can get an OK reading on the coast side of used gears. Not the case with this set, both coast and drive side are wiping the grease clean from heel to toe, but I think the pattern is a little high on the flank. Backlash is .007", gears are GM 3.73 that were purchased in late 2011 along with a install kit and Eaton Trutrac. No idea who installed them, I only have the receipts that were given to me with the car.

The reason I ask is because the gentleman I purchased the car from didn't say anything about it. Then again, I don't think he drove it on the street before he pulled the engine/trans. Buying parts from another guy I found out he was the one who sold it to the person I got it from. He said I'd need to have someone to look at the rear end.

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Please excuse the lithium grease. My gear marking compound is nowhere to be found, more is on the FedEx truck as I type this.

Move the pinion in .002" or just run it? I have new axle bearings and seals sitting on the shelf that I might put in for the hell of it, very little play in the current ones and didn't see any leaks.

Thanks!

[Detroit Gearbox]

The pattern with grease is unreadable. You need gear marking compound to preform this task. Is this gear used? (It looks like it) If so, your wasting your time trying to check the pattern, as nothing you can do will change it. Keep you lash as is and run it (as long as bearing preloads are correct).Rich

[hoogiesngrinderz]

Thanks for the input! Gears are used. I picked up the car as a roller not too long ago, just got the engine and trans installed a week or two ago. I was told there was rear end noise so I wanted to look everything over. Lithium grease was only thing I had that was somewhat visible. Searched high and low for my marking compound but it must have been tossed, more will be here tomorrow.

At first I was really concerned that the wear pattern was very high on the flank. Upon further inspection, wear seems better than I first thought. Backlash is within spec @ .007". Axles were not worn but new axle bearings and seals went in this afternoon just because I had a spare set. Both c-clips were badly grooved, hopefully the new ones show up Friday. If it still makes noise after that, oh well, I'll just build up the spare rear housing over the winter

Thanks again!

[hoogiesngrinderz]

Also have a solid pinion spacer kit on the way, I thought I was going to tear this rear apart.

Rich, if I do install it, do you have a preferred method of setting them? Such as measuring the crush sleeve and stacking the sleeve to the same height or plus a couple thousandths? Really curious about it. I set my last one by trial and error.

[Detroit Gearbox]

Also have a solid pinion spacer kit on the way, I thought I was going to tear this rear apart.

Rich, if I do install it, do you have a preferred method of setting them? Such as measuring the crush sleeve and stacking the sleeve to the same height or plus a couple thousandths? Really curious about it. I set my last one by trial and error.

Measuring the original crush sleeve is a good starting point. Some of the solid shim kits I do not like because they actually "crush" when you tighten them...which changes the preload. The hardness is incorrect on the thick spacer (ratech brand?) . If you install one and take it apart, you will see what I'm talking about. The large spacer will have a visible mark on the end. As for installing solid spacers or a crush sleeve, I do not suggest re using the pinion bearings. I always start with new. Use a inch pound torque wrench and get the turning preload about 25 inch lbs (light coating of gear lube on bearings).

[hoogiesngrinderz]

Finally took the car our for a spin the earlier this week. It howls, but doesn't get audible until 15 mph or so. At 60 it screams like a banshee, sounds like a supercharger. Quiets down a bit on decel, howls during cruise/acceleration. No play in the pinion and I tightened the pinion nut about 15° as a Hail Mary. Short road test - no dice. Preload didn't feel any different though

I have a new Timken bearing set that will be here on Tuesday. I guess I can't leave it alone I'm starting to really like this car more (overall) than the blue one. I'd like to get it right.

I'm half tempted to have a shop do it just because I don't feel like having the car stuck in the garage, other cars need attention before the white crap accumulates. What would a shop charge for labor to change the bearings and putting it back together? I always hear great things about you, Rich, but you're so far away :\

I no longer have access to the in-lb dial torque wrench I always used in the past, so there's $138 for a 0-75 dial or $45 for a 0-60 beam torquer. I can press the pinion bearing off/on here in the shop but I can't pull the diff bearings. $90 for the side bearing puller. $135 minimum investment. Then again, I need to do bearings/seals on my Jimmy soon as well

[Detroit Gearbox]

Finally took the car our for a spin the earlier this week. It howls, but doesn't get audible until 15 mph or so. At 60 it screams like a banshee, sounds like a supercharger.

You either have a bad ring & pinion or no back lash (no pre load on the carrier?) A whine or howl is a gear noise.
If the pinion bearings are bad, you not only can feel them grumble by turning over the pinion by hand, but you will hear bad pinion bearing start to make noise at a walking speed (5mph). If the pinion was loose ("0" preload and the pinion moves in and out/up & down) it would make noise on de-acceleration.

[hoogiesngrinderz]

You either have a bad ring & pinion or no back lash (no pre load on the carrier?) A whine or howl is a gear noise.
If the pinion bearings are bad, you not only can feel them grumble by turning over the pinion by hand, but you will hear bad pinion bearing start to make noise at a walking speed (5mph). If the pinion was loose ("0" preload and the pinion moves in and out/up & down) it would make noise on de-acceleration.

.007 back lash, no play in the pinion. R&P, diff, and bearings were installed late 2011 or early 2012 going by all the receipts that were given to me with the car.

I'll look into a new gear set. Any recommendations? I know a lot of people like OEM (AAM) gears, which DTS has for $207.35

I was going to tear into it today but there was a deer hanging in my stall. I'll check the preload on the carrier when I pull it apart, do a thorough inspection of everything.

[Detroit Gearbox]

I prefer the AAM gears.
Even though you have .007" lash, do you know if the carrier moves left or right?
When you get the cover off, Try prying the diff case (gently) right or left to see if it moves.
Once the axles are out and caps are off (do not forget to mark the caps)
See if the carrier just pulls out by hand or if you have to use a large pry bar to get it out. It needs to be preloaded.

[hoogiesngrinderz]

I finally pulled the rear end out last week and tore it down. I bought a 3.42 open diff rear end and swapped the Eaton TrueTrac in from the noisy rear.

The carrier was tight in the noisy rear, good preload. The carrier bearings were very nice as well. What wasn't so nice was the odd wear on the pinion and ring gear. Possible oil breakdown due to heat?

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[c0ncEpT]

Are all the teeth starting to pit or is it just the camera?

[hoogiesngrinderz]

I wouldn't say pitted, etched would be a better word to describe it...it isn't rough to the touch. It looks as if the oil may have broke down. The pinion gear is interesting, how that odd wear fans out from the leading edge towards the center of the tooth.

The rear I put in the car is quiet, backspace of .009-.010. I'm happy enough with it. I'm just curious to figure out why this gearset was so loud, and I always like a learning opportunity. I'm going to guess and say the pinion was too shallow...

[WMCCjames]

Looks like the gear set wasn't broke in properly. The surface looks like it never got hard.

[1BADAIR]

Looks like the gear set wasn't broke in properly. The surface looks like it never got hard.

X10

[hoogiesngrinderz]

They guy probably beat the piss out of it right off the bat. I was told the guy had a really stout LS1 in the car.

Is it normal to have the wear on the pinion so far from the heal (I think that's the heel side on the pinion)