New 4.56 Gears

the hammer · July 27, 2010

New gears installed, broke them in like instructed to by many forum members and websites, and there is a whine noise that gets louder as the speed of the truck increases. It also will stop when I let off the gas pedal and coast. The first day I picked up the truck with the gears it had this noise, I complained, and tech drove with me and heard it. Said it would be fine and he could adjust it out when we do the 500 mile fluid change.

Went in, 500 mile fluid change, noise still there. He said he couldn't hear it but I know he will once I go back and he rides with me. So, what ammo do I need verbally to tell him as proof that it should be quiet so that I don't have to keep arguing with them to fix it?

Help is appreciated.

Josh

J-man67 · July 27, 2010

New gears installed, broke them in like instructed to by many forum members and websites, and there is a whine noise that gets louder as the speed of the truck increases. It also will stop when I let off the gas pedal and coast. The first day I picked up the truck with the gears it had this noise, I complained, and tech drove with me and heard it. Said it would be fine and he could adjust it out when we do the 500 mile fluid change.

Went in, 500 mile fluid change, noise still there. He said he couldn't hear it but I know he will once I go back and he rides with me. So, what ammo do I need verbally to tell him as proof that it should be quiet so that I don't have to keep arguing with them to fix it?

Help is appreciated.

Josh

Def shouldn't be whining. Sounds like the ring/pinion aren't "meshing" correctly. Not sure how mechanically inclined you are, but take the rear drive shaft out and see if you can move the pinion. Side-to-side, in and out, up and down. It shouldn't have any movement. Also check for any leaking around that area. The pinion bearing/crush sleeve/seal may need to be replaced. I am chocking this up to installer error, so make sure you pressure them to fix it. New gears, within the correct tolerances, should be silent before break-in and after!

gnet158 · July 27, 2010

Your truck must hook up to the pavement like crazy... Stinks that you have the whine but hopefully the Tech will be able to fix it.

Spurshot · July 27, 2010

New gears installed, broke them in like instructed to by many forum members and websites, and there is a whine noise that gets louder as the speed of the truck increases. It also will stop when I let off the gas pedal and coast. The first day I picked up the truck with the gears it had this noise, I complained, and tech drove with me and heard it. Said it would be fine and he could adjust it out when we do the 500 mile fluid change.

Went in, 500 mile fluid change, noise still there. He said he couldn't hear it but I know he will once I go back and he rides with me. So, what ammo do I need verbally to tell him as proof that it should be quiet so that I don't have to keep arguing with them to fix it?

Help is appreciated.

Josh

Josh,

Just make sure you can eliminate other possibilities like tire noise. I'm not doubting you, but the mechanic will.

My experience with gears is that if they are noisy right away, they will only get worse. The two times I recall setting up gears myself, noise indicates that the mesh pattern is not right. If the mechanic is honest and agrees that there is excess noise, pulling the cover and checking the engagement pattern is a quick way to tell if the gears are setup properly.

The links below have some examples of proper engagement patterns. Simple white lithium grease will work for testing pattern. Other materials like white paints and similar work too.

Make the mechanic pull the cover and check the pattern and show you.

http://www.dippy.org/svcman/image/0332.jpg

http://www.blackgto.com/jeep/drive.jpg

The following are examples of an improper pattern. Note how the pattern is not centered on the flank of the teeth. Patterns either inboard or outboard on the flank of the teeth mean the pinion depth and/or backlash is improper, usually pinion depth.

http://static.summitracing.com/global/imag...o02-must_17.jpg

http://www.dippy.org/svcman/image/0335.jpg

http://www.fnc.ch/images/content/technik/GEARS.jpg

http://farm4.static.flickr.com/3049/305421..._b95121c907.jpg

pm26 · July 27, 2010

The lash between the gears is not adjusted properly. Tell them to correct it.

Spurshot · July 27, 2010

The lash between the gears is not adjusted properly. Tell them to correct it.

Could be...or also could be pinion depth. Very often, it's the pinion depth that is improper. This is because backlash is easier to change and set in most axles.

xc80002 · July 27, 2010

Gears need shiming correctly, what brand of gear?

the hammer · July 28, 2010

I had them install Yukon gears with install kit. I double and triple checked the noise to make sure it wasn't tires, as the guy already mentioned it to be the noise i was hearing. It is definitely the gears. I just want to be able to say the correct terms to the tech when I am talking about it. He is really nice and all other work I have had done there is good. If i had time I would have done this myself, but I am in med school and just don't have the time.

Should I go out to the garage and pull the shaft from the pinion and try and shimmy it around? I think it is backlash adjustment from what I have read in articles. But, alas, I have no experience with gears so I have to rely on you all to educate me.

xc80002 · July 28, 2010

I think that has a locker in the rear end that has to come apart. You need to know what your doing before you rip into it. I think there is an additive that needs to be added to the gear oil also too. This also keeps them from whining. So you might want to look at that to. Amsoil has the additive in there gear oil already. I had 456 Motive gears in my 08 and had no problem with noise. He told me about the additive.

the hammer · July 28, 2010

I think that has a locker in the rear end that has to come apart. You need to know what your doing before you rip into it. I think there is an additive that needs to be added to the gear oil also too. This also keeps them from whining. So you might want to look at that to. Amsoil has the additive in there gear oil already. I had 456 Motive gears in my 08 and had no problem with noise. He told me about the additive.

If you are referring to the G80 i do still have that in my diff. They put Royal Purple fluid in there when I had the 500 mile change last week. I don't know if the additive will help at all, cause it was in the first batch of break-in fluid anyway (I asked them about the additive, too). I really hope it is adjustable and my gear set isn't already to far meshed to get the adjustment corrected.

xc80002 · July 28, 2010

get a hold of Yukon and ask them

jro909 · July 28, 2010

i just have to ask, what do you need that low of gearing in a half ton for? do you have fred flintstone tires? towing the bismark around town?

Matt_ · July 28, 2010

i just have to ask, what do you need that low of gearing in a half ton for? do you have fred flintstone tires? towing the bismark around town?

4.56's really aren't that low of a gear for a GMT800 truck. My 4.10s with 33's was pretty weak... i didn't like its performance or towing one bit with that setup. Then, when I jumped to 35s the 4.10s were horrible and I jumped to 4.88s (which got better highway gas mileage than the 4.10s).

So yeah, i'd run 4.56s with 33's on a truck like his and be perfectly happy.

bluegmctruck · July 28, 2010

I had them install Yukon gears with install kit. I double and triple checked the noise to make sure it wasn't tires, as the guy already mentioned it to be the noise i was hearing. It is definitely the gears. I just want to be able to say the correct terms to the tech when I am talking about it. He is really nice and all other work I have had done there is good. If i had time I would have done this myself, but I am in med school and just don't have the time.

Should I go out to the garage and pull the shaft from the pinion and try and shimmy it around? I think it is backlash adjustment from what I have read in articles. But, alas, I have no experience with gears so I have to rely on you all to educate me.

i would not mess with it if i was you especially if you don't have alot of experience. i would take it back to the shop and have them look at if first so that they can't try and blame it on you.

hrspwr · July 28, 2010

As everyone else is saying the gears are not meshing and/or there is too much lash. Personally I would not touch it unless you were the one to put it in. If you had a shop do it, bring it back to them and tell them to fix it. The whining noise is caused when there is to much lash between the ring and pinion gears, caused by not shimming it correctly. You also want to make sure that they test to see where the gears are making contact, ideally you want the pinion to be mated dead center on the ring gears tooth, deeper in will bind and where quickly and on the outer will break a tooth or teeth on the ring gear when put under a load.

The whine will not hurt the gears it will just be annoying, it is the contact pattern that is the real killer