2015 - differential gear whine at hwy speeds

hirdlej · April 13, 2016

I'm sorry to hear of all the troubles you're having. It sounds to me like a technician that is inept at diagnosing and doing his job properly and overlooking the issue at hand.

Again, this isn't an attempt to hi-jack your thread but as promised I'm updating you with the findings on my truck which exhibit the same identical symptoms as yours.

I took mine into the dealership this morning and met with my tech. We went for a test drive and he immediately acknowledged there was an issue.

By the time I got home, he had sent me a text message stating the backlash of the rear differential was .012". Too loose for his liking. My truck only has 650 miles on it. He's now deciding if he wants to put new gears in or readjust and have me try it again. The last I heard he was going to take the axles out, check pinion preload, pattern, etc. to come to a final conclusion. I'll let you know what he does and if it corrects the issue.

Just remember, there isn't a finer art when working on a vehicle than setting up a rear differential. If it's off one little bit, they don't run right. I'm wondering if you just had a bad/shoddy technician who overlooked the real problem in the first place.

pm26 · April 13, 2016

Did 1936 Chevy truck differentials whine at road speed?

darkfox1 · April 13, 2016

Frankly, I imagine it was a diff problem all along in my truck and could have been fixed with a FULL new axle assembly being installed from the factory.

However, instead, they tore into my transmission and diff with bench techs.

At this point if they were to try to force me to take it back, I would want a new factory transmission and new factory differential.

I think they know this, and I think that's why they're looking at a different angle.

Sometimes I feel like I'm being childish? But.. I think its more like.. what I pay for vs what Im getting.

Sure. The loaner truck is nice. It's an LTZ, leather, crew, LED headlights and all that, a real pleasure to drive, but.. I have this incompleted thing hanging over my head. Some people tell me I may have to shell out thousands of dollars to do this or see my credit dive, or be left holding an unsecured debt with my bank, or having my payments go up.. it keeps me awake at night. I didn't ask for this problem.

hirdlej · April 16, 2016

Darkfox, I just wanted to give you an update on my truck. Our symptoms were identical from the get-go and here's what my technician came up with. Again, I'm not trying to rub salt in a wound, but hopefully this information helps you or someone else that stumbles across your thread.

Upon disassembly my tech found that the backlash of my gears was .013". Once the gears were cleaned up, he checked the pattern to see what the whole story was. The cost side of the gear was "ok" but that drive side, eek! (see pictures below). It was obvious that when he went to do a total teardown what the problem was. Speedy Gonzales didn't have the pinion nut tightened properly which allowed the gear to shift back and forth. My guy said when he put the impact on the nut to remove it, it just spun right off without even doing a ""brbrbrbrb". Whoever the dumbass was never set the final pinion preload!

When my guy put the new gear set in, we found the factory shims were spot on. Could this have been a fluke? Maybe. However, we feel the parts put in were right, it just wasn't "finished". At any rate, I'm currently breaking in the new ring set (no towing for 1000 miles and he wants me to keep the speeds under 60mph for the first couple hundred miles) which I absolutely do not mind.

My problem is completely fixed, now I'm starting to enjoy my new truck. We'll see if my whine comes back after a few hundred or thousand miles, but I feel confident everything is taken care of.

darkfox1 · April 16, 2016

I figured it had to be something like that. I'm nearly absolutely sure thats what was wrong with the 15.. But.. for whatever reason, their bench tech couldn't fix it it.

They need to find this factory guy and fire him out of existence. This is not only laziness its a safety problem. It also threatens the longevity of something we pay a LOT of money for and cannot afford multi-thousand dollar repairs later in the vehicles life resulting from the failure of some yahoo in a factory that wont tighten a nut!

This is disgusting. How far GM's quality has fallen.. I mean GM has always had quirks (leaky rear main seals in SBCs, piston slap in early LSx motors.. 4L60Es being made of cheese..) but finger tight bolts? Really???

Thank you so much for the update. I will continue to update with mine as well.

Though GM as a whole has greatly disappointed me in this, the dealership has gone an extra 10 miles to make sure I am a satisfied customer. Once this is all over with, if things go the way I feel they should... I will be.

hirdlej · April 16, 2016

Another item I forgot to mention, the axle u bolts were only at about 30 ft lbs. They had to retorque everything there as well. Best of luck to you man.

darkfox1 · April 17, 2016

Your truck was a Friday afternoon before a long weekend "Do this and you can go home" truck it sounds like.

Guess mine was too..

They find any crushed beer cans in there?

hirdlej · April 18, 2016

Well Darkfox, the joke is on me, I've been babying this thing all weekend long. Short trips not exceeding 20 miles at a time and never over 60 mph. I also made sure to let the differential cool at least a half hour between each driving session. I put a total of 120 miles on this weekend. Tonight with about 110 miles on the new gear set, I took the truck back up to 65mph again to see how things were. Low and behold it's in the early stages of starting to whine again. It's extremely faint and just starting, but nonetheless it's there. I'm going to call the dealership tomorrow and see what they want to do again. I know my technician set the backlash on the gearset to .006". The GM spec calls for .003-.005" on NEW gears. Why he set it to .006" is beyond me, but I ran it anyways. It's WAY better than it was, but it's not perfectly quiet either. I drove my brothers truck tonight with 10k miles on (we have the same truck and bought them at the same time). His is perfectly quiet so I know it's not inherent of the design of the differential.

darkfox1 · April 18, 2016

My truck only did the whine from EXACTLY 70 and up. I dont know how mmuch faster it would whine, it was at its loudest (over the radio loud) at 74. I live half an hour form the interstate but I drive a LOT for work so I had to warm it up on back roads ~40-65mph (depending on how many tractors there are on country roads..... ) and then get on the interstate.

With cruise traffic things would speed up and wind down, every time I touched it, it'd whine, ever time I let off, it'd moan. It was louder on loads like going up hill.

This got fainter for a few days after the swap but the problem came right back.

They then said transmission.. don't let them tear into your transmission! IT DOES NOT FIX IT EITHER. The sound is CLEARLY behind you!

One question for you, do you have the 17" rims and bridgestone HT tires?

hirdlej · April 18, 2016

I won't let them touch the transmission. I will make it clear to them that the problem was temporarily resolved with the new gear set until I put some miles on it. Again, it's in the very early stages, but it's coming back. This morning was worse than yesterday even. The first time it took 30 miles off the lot for it to whine, this time it took about 110 miles to whine. It whines in 5th and 6th gear manually shifting so it's not the transmission. Again, it was temporarily resolved.

My body configuration is a regular cab, standard box, 2wd with 3.42 gears (9.5" 12-bolt ring gear) and I'm running the 20" blackout wheels with the Continental 275/55/20 tires. This truck is smooth as glass at any speed. The whine almost sounds like tire whine at first, but when you positively or negatively load the drivetrain, it goes away. At a steady cruise "floating" the gas pedal to maintain speed at 65 is when it makes noise.

darkfox1 · April 18, 2016

Huh.. well thta throws one of my theories..

The '15 that I had was sdoing this, and the put me in a '16 loaner for a while tht was doing it too until I complained about it.(it was a long wheel base short bed and I can't work with a city bus length vehicle..) now I'm in a '16 ltz that does not do it.

all 3 are GU6/G80 trucks. GU6 is 3.42, G80is locker.

There is NO HINT of the sound in the LTZ. The LTZ hsa the 8 speed however and 18" wheels with goodyear SRAs, where the 15 and the 16 LTs had 17s with bridgestone HT tires.

darkfox1 · April 19, 2016

Well.. I am LIVID right now.

I just got off the phone with GM. They are telling me that they are basically giving me an upsold trade-in rate, and that I have to "Buy" the new truck.

I have to pay more than $1500 out of my own pocket, plus insurance, tax tag title fees on the new truck, AND I have to finance it as a new finance plan at my now lower credit score caused by buying the 2015 in feb.

All of this will cause my payment to increase OR I may not be able to find financing that meets my terms at all..

I AM GETTING SCREWED!!!!!

I dont know what to do... I can't afford this.

darkfox1 · April 19, 2016

This whole process has left me frustrated and anxious.

If GM does not waive this fee, well I'll have to borrow the money.. because I dont have it..

and I will tell you this.. this will be the last new GM vehicle I or anyone in my family buys..

They waive this fee, they make this right and all is well, but.. until then.. this is an irreconcilble relationship.

if I didn't have negative trade equity from my honda, I would do a refund and go buy another brand. and this comes from someone who has owned like a dozen GM vehicles in ~18 years and have always been a fan..

hirdlej · April 19, 2016

Well.. I am LIVID right now.

I just got off the phone with GM. They are telling me that they are basically giving me an upsold trade-in rate, and that I have to "Buy" the new truck.

I have to pay more than $1500 out of my own pocket, plus insurance, tax tag title fees on the new truck, AND I have to finance it as a new finance plan at my now lower credit score caused by buying the 2015 in feb.

All of this will cause my payment to increase OR I may not be able to find financing that meets my terms at all..

I AM GETTING SCREWED!!!!!

I dont know what to do... I can't afford this.

Ok, correct me if I'm wrong. But are you saying that they are willing to take your truck back and sell you a new one (2016) with the same trim level and options for a $1500 exchanged price? If what I'm reading is true, I would do that in a heartbeat to get out of my truck. Not that you should have to, but that seems fair to me.

That $1500 should however include the taxes, license, dealer fees, etc.

Another question, I'm not a credit expert but why would buying a 2015 vehicle in the year 2016 lower a credit score? I'll have to do some research on this.

This isn't an ideal turnout, but think of it this way. For the cost of a few lost payments you can jump ship and put this shit-heap of a truck behind you. I would bail on mine and go to another truck for even a $3000-$5000 difference. Sadly the trade-in's on these suck. I feel like I'm stuck with mine for a long while.