I have always been under the impression that OEM (AAM) gears were the best gears around when doing a gear swap due to their quality. However just recently I have been told that they are a complete PITA to install due to their tight backlash requirements
(3-6 thousandths) and almost always have some sort of whining due to not being able to achieve the proper backlash w/ aftermarket shims. I have a set of new OEM 3.73's that I am now considering swapping for a set of Yukon 3.90's.

What are you guys thoughts on this?
Anybody have any experience installing OEM gears?
Also for those that are running Yukon gears or 3.90's what are yall opinions or impressions of them?

 

i love my yukon 3:90's

 

Any gear noise or whining? I have heard once you swap to a 4.10 or higher there is almost always gear noise even if the the gears are setup dead on? Just curious if that is the case w/ 3.90's as well...

 

if they are set right then you will hear no whine! However i have a slight whine, hardly noticeable. Some people say that they cant hear it. But anyways i have my backlash set at .006 im sure i would have no whine at .007 but the more surface area the gears have on one another the stronger the gear but the louder they will be.

 

Makes sense man. What are you running RPM wise on the freeway w/ the 3.90's? 70-80 mph?

 

i beleive its 2400rpm, ill check for sure in the morning

 

I use yukon or motive gears 75% of the time. I haven't had any problems with either one. I worked at the dealership for 13 years and only had trouble with one set of oem gears and that was in a 9.5 inch rear axle. It had a mismachined housing that had to be replaced. I would find a shop you can trust and have them install the gears they have had good luck with. If you insist on a certain brand and they make noise its on You. If they pick the gear its on them. I run a 4.10 gear and 285-60-16s they seem a little low at 80mph but its not to bad once you get used to it.

 

Original OEM gears are a pain only for a shop that doesn't know what it's doing. If a shop is complaining about the difficulty of installing AAM/OEM gears, I would take my vehicle elsewhere.

I had the stock 3.73's in my Avalanche replaced with AAM 4.10's and had absolutely zero issues. However, the shop that did the install does differentials only and pretty much owns the market in San Diego. They also put in moregrip's G80 replcement.

I've heard other branded gears are fine and lots of people have used them with no problems, but I would not put anything except AAM gears my GM vehicles. They're a little more expensive, but no more than the equivalent of a good dinner out.

 

So you're gonna swap from 3.73 to 3.90? Doesn't seem worth the effort. Or are you saying you have a set of OEM 3.73's that are laying around that you will trade for some 3.90's? Then I assume you have 3.23/3.42 now?


I went with AAM gears (4.10) No whine, no issues...other than traction. Had a gear shop do the install.

 

I have 3.23's now and a new AAM 3.73 gearset awaiting install. However I keep hearing about how hard it is to achieve the required backlash w/ aftermarket shim kits, so I was contemplating selling them for some Yukon 3.90's. Anybody know if you can buy GM shims specific to the gear set you are installing. I have heard that the factory uses specific carrier shims for certain gear ratios to aid in installation from the factory. Possibly a GM carrier shim kit?