8a8mfh

iTrader: (3)

I had installed some used 3.73's but for some reason the front pinion bearing spun and made the pinion questionable, I ran it anyway with a new bearing, all was good, quiet, but it was getting to my head.

I installed some Motive 3.73's today, made in Italy.
They seem to drive ok but decelleration is noisey, I did install all new bearings this time and set up was right on with their specs.
Backlash .008-.012, I got .010. Pinion preload is 24 inch pounds.
They say to use 75w90 non synthetic for break in.
I've installed a lot of used gears and other new brands but this is my third 7.625 rear and it's the most noisey one I've done.
Might it get quieter? Maybe after break in and going back to mobil one 75w90?
I have pics of the contact pattern if anyone wants to see them. I have to resize the pics first.

Scott@DrivelineSolutions

iTrader: (22)

Decel gear noise indicates the gear may be to deep, ie too thick of a pinion shim. What was the thickness of the shim you used? Did you check the pattern on the gear with marking compound?

I just installed a Motive perfromance gear 2 weeks ago and it was dead quiet. I set up with the stock pinion shim but wil Koyo bearings if that helps any.

8a8mfh

iTrader: (3)

I did check the pattern. According to Yukon gear the pattern I had was acceptable.
The original shim was .033, I don't remember whats in there now but I think it's about half of that.
I did use Koyo bearings too. I honed the old one out for a set up bearing and measured old vs new overall thickness and it was within .001.

8a8mfh

iTrader: (3)

Here are the best pics I can do.
Not sure where to go from here. I was actually up at 2am driving around. No noise at all when driving or accellerating, but a little more than coast and off the gas it whines. It also makes kind of a hissing noise like somethings rubbing the driveshaft but nothing is rubbing.
The pinion bearings are new, I set it up with honed out set up bearings and installed the new ones one time only, I would think they are still good.

Please help, if your advice is to push the car in a lake I might take it

chicane

As the paint shows in the above pictures, the pattern is still slightly "crossed up" and is actually short..... not too deep. Meaning that coast is too deep and drive is a little short.

I would add 0.002" in depth and re-set lash to center up the pattern before leaning on the lash to tighten up drive.

You are looking for a pattern that looks similiar to these patterns. The left pic shows the pattern centered with the correct depth and the right pic shows the pattern with the lash tightened up for a "performance" drive setting..... which is very important for a 7.5" set up to combat ring gear tooth deflection. Keeping in mind that with the pic on the right, the coast pattern needs to be centered after the lash is tightened up.

8a8mfh

iTrader: (3)

Well I took a .014 shim out of it and put in a .018. It made little to no change in the coast side but it made the drive side worse.
Then my bearing puller broke and there it sits.
I did take a good used inner pinion bearing and hone it for a slip fit, also took a pinion nut and grinded the crimps out of it, now I can swap out shims quicker and easier.
My motivation has dropped to zero at this point.

One thing I don't understand though. When you move the pinion in or out doesn't it change both the drive and coast sides? And you have to stay in the manufacturers .008 to .012 backlash range right?
Is that enough range to make a change in the pattern?

Scott@DrivelineSolutions

iTrader: (22)

Adjust pinoin shim to .036 and set backlash to .009. You are not deep enough as to the pics you posted. I just finished up 2 gear installs this morning and one was a 3.73 10 bolt Motive performance.

chicane

Complex compound, hypoid gear sets can be a little tricky to read. If you move the depth in or out, one thrust surface might change more than the other. Sometimes it will even move in the opposite direction that you shim, but only to a point. So far, you have not gone too deep as I see it.

Secondly, you do not have to run between the manufacturers recommendations..... it is merely a guideline, but it should be adhered to unless you have the experience, knowledge and reason to do otherwise. I have run a 7.5" into 0.005" just because the pattern wanted it. But for a range example, I run 0.0006 to 0.0009" on Top Fuel differentials and upwards of 0.018 to 0.020" on topkick differentials that run ISO 175 to 250wt gear oils.

A good rule of thumb for lash is 0.001" for every inch of ring gear diameter. But 0.008 to 0.010" is about the norm for passenger car differentials. When you get into tuning lash for gear oil weight.... there are no rules.

I wish I had my 'little black book' here at the house.... I have probably 200 entries for Italian Motive, 3.73 gear sets along with the other setting I used to get them set-up.

The Elvis8tor Z28

iTrader: (3)

I just had some Motive 4.10s (made in Italy) installed earlier today at NLP and they’re noisy on deceleration, and I also here a weird loud hissing sound as I accelerate. What should I have them do?

Scott@DrivelineSolutions

iTrader: (22)

Any pics of the pattern? What was the installed pinion shim setting and backlash?

3800RS

iTrader: (15)

hey i dont mean to hijack but scott i had gears installed and they make a weird whine noise only on right turns like on exit ramps. can u pm me some advice ??

The Elvis8tor Z28

iTrader: (3)

I don't know anything, they wouldn’t let me watch.

8a8mfh

iTrader: (3)

I'm at a loss here. I've tried every pinion shim from .022 to .044 in .003 increments, and backlash with each one between .008 and .012 and I cannot get the coast side out of the toe of the gear. And it always has the shape of the picture I posted above on the left.
Whats going on here?

Scott@DrivelineSolutions

iTrader: (22)

Thats just the way the gear was cut, does the drive move when you add pinion shim? You may want to just center the drive and let it go.

Scott@DrivelineSolutions

iTrader: (22)

Sounds like they didn't preload the carrier bearings enough and the case is actually floating around. I have seen it before in a Ford, everytime you made right hand turn it made noise. It ended up ebing a bad bearing.

8a8mfh

iTrader: (3)

Yes I can get the drive pattern to move, I guess I'll just set the drive side as good as I can.

chicane

Dont just look at where you actually applied the paint, the "wipe off" will tell you all sorts of information.

Take a look about every 90* at the wipe off and it will give you a better indication of what you actually have. Sometimes "run out" will give you a false impression of the actual pattern..... as strange as it may sound..... it might even be at the major wipe off areas of the ring gear. Some times its not a bad idea to pull the carrier out and set it back into the housing clocked a few teeth differently.

Other than that, have you checked the "run out" of the carrier flange ??

And just for ***** and giggles, try a set up with 0.015"...... it may just want that much. And dont worry, a good straight 140wt oil will provide the cushion for an increase in lash beyond 0.012". 0.015" isnt extreme anyway.......

BTW, I normally ship all differentials with at least an ISO suspended-moly, straight weight 140...... in all street chassis. The only thing I run 90 weight in, is front end differentials in colder climates.

8a8mfh

iTrader: (3)

I didn't check the runout of the carrier flange, the markings seem consistant though, I should check it.
I was going to ask about the wipe off of the compound, it seems to be more right than whats worn through the compound that was put on it. It seems to come close (close as I can get it) with a .031 shim and .013 backlash.

So it was noisey at coast, off the gas, very little at light throttle, none at any throttle. This was with .036 shim and .013 B/L.

Is noise always a sign of a gearset thats going to be weak, and might wear quicker?

Thanks to all for the advice.

chicane

No, noise doesnt have anything to do with strength. Most of the time it has to do with material hardness or incorrect "mesh" of the gear set.

Nor does it have to do with wear..... unless it is really set-up incorrectly..... but that would be visible thru the paint 'picture'. The gear face will "work harden" throught a few heat cycles.... after that, there isnt too much that can be done in respect to noise.

The Elvis8tor Z28

iTrader: (3)

Did you find out what the hissing sound is, because I have the EXACT same noises you described. Whining on deceleration, and a weird hissing sound as I accelerate. I think the whining is a little too loud, it kind of sounds like a little jet plane is behind me when I decelerate. They told me to bring my car back in tomorrow at Noon, and I have to go to work at 3:30pm, what exactly should I tell them to do so I can get to work on time. They’re not going to charge me anymore money to fix it are they, because I already paid $420 for the install. Thanks!