I need some help. I took my truck to a performance shop that does rear end gear changes among other performance things. I had them change the rear gear from the factory 3.55 LS to a Yukon 4.10 with the Detroit TrueTrac. All of the bearings and seals were replaced and then filled with Lucas oil 85w-90. The first time they installed the ring and pinion, it was fine for about the first 200 miles and then it developed a whine that started at 40 mph and went to 52 mph, with 48 mph being the loudest of the different speeds. It was really noticable when the truck is up to speed and I give it enough gas to hold that speed. I took it back to them to look at it and they pulled the cover and said that nothing is wrong and that the pattern is fine. Filled it full of fluid and give it back. Took it back to them to install a second ring and pinion, that they paid for, and after the second gear change it did the same thing. 200-300 miles and it started to whine again. They told me that most aftermarket gears have a whine to them and that there is nothing they can do other than pull the cover again and make sure nothing is out of the ordinary. So far I regret doing the swap, because the power difference doesn't overcome the whine that annoys me. Maybe it's just me being really picky, I don't know. Sorry for such a long post but I really want to get this problem solved because boating season is here and I'm ready to pull it to the lake. I would really like to see if anyone has any suggestions, other than take it back to them. Thanks Gary

 

isn't the oil supposed to be 75w140 full synthetic?

did they add friction modifier? it is a must no matter what the oil manufacturer says.

 

They shouldn't have had to add friction modifier because of it being a gear driven LS and not a clutch LS. As far as the fluid goes, I didn't know if that would cause a problem or not.

 

I think that's just the nature of aftermarket gears and LSD's. You could always install a loud exhaust to cover up the whining.

 

Already have a magnaflow and can still hear it.

 

The way I would think of it as this, you trade off a little comfort for performance. In your case, you gave up a little peace and serinity for a high performance gear ratio. It's like how you get that annoying whine when you bolt on a blower to your truck. It's not particularly pleasant to listen to but everyone now knows that you are packing some serious heat ender the hood now.

 

I guess that's one way to look at it. I just want to make sure it doesn't explode on me 10,000 miles down the road.

 

A good setup on quality gears shouldn't whine. I doubt if the gear lube would cause it but maybe it's possible. Did you follow recommended break in on the new gear set? If so I would suspect improper setup.

 

It was babied for the first 1000 miles. The hardest I get on it is pulling my boat.

 

Anyone else have an opinion on this issue? I have heard alot of people say that some aftermarket gears do that but I would think that an aftermarket gear should be as good of quality as an OEM. Any and all help would be appreciated. Thanks Gary

 

I hope you figure out the problem bc im getting 4.88s installed in my truck and if this happens i will flip out...from what i understand from people if they make whine its bc the install was not done properly or improper break in so i dont know what else it could be

 

In all my stangs i had a gear swap with FRPP and never had a whine so maybe its either the parts or the installer?

 

I'd suggest you get them to change the gear oil to 75w-140. And since you have the trutrac installed as the limited slip, then the friction modifier isn't necessary due to it being a gear driven limited slip.
I also have a 4.10:1 setup in my truck with a trutrac. Some noise is there, but not much. Another thing to mention, the factory 3.31 setup had a whine at certan speeds before the gear change.

 

The mechanic that did my gear swap said that quality gears set up properly will not whine. I have Ford OEM 4.10's with 1,500 miles or so on them now and not a sound.

 

I took it to a local Ford dealership today to have their rear end specialist take it for a spin and he said that he couldn't hear it whine. He put it on the rack and checked it with a stethescope tool and said that it didn't make hardly any noise. So, appearently it's my hearing. Like I said, it might just be me being paranoid. Thanks for all the replies. Gary