Name that noise! (V2 CTS-V autotragic)

Uuuuuuuuuugh.

2010 CTS-V auto. 130k miles.

Several months ago, it developed a weird “honk” when shifting from 3rd to 4th that SOUNDED like it was coming from the rear. A few weeks ago, I mentioned this to the guys at LSXperts, hoping it was a common problem with an easy fix. They looked perplexed. The owner asked if it shifted normally otherwise. I told him the revs have a tendency to hang between gears on WFO acceleration, but I ASSumed it either had something to do with “torque management” or perhaps the car was breaking traction and the traction/stability control was freaking out momentarily.

He told me this should not be the case, and that I should at least have the trans serviced and go from there.

2 weeks ago, I brought the car to the local stealership for an oil change. They’ve always done me right, and I have no qualms about having them do maintenance/minor repairs.

Still convinced that the noise is coming from the rear end, I had them service the diff with the oil change.

Pulling out from the dealership with the trans cold, I got on the gas hard, and sure enough, the 3-4 noise is still there. I’ve been “driving around it,” shifting manually at low RPM, but this weekend, with my brother in the car, I deliberately produced “the noise” to get his opinion. It was markedly worse than “normal.”

I’ve also noticed (and maybe it’s been happening all along, but I’ve typically got the radio blasting from the moment I get in the car) that rolling from a stop in 2nd gear (the “default” gear in “normal” driving mode from a stop) that the car is “lurching” a bit when cold in second. Also, it’s “howling” a bit from the rear when turning while cold...which definitely(?) points toward diff.

I’m having the trans serviced Monday and politely asking them to “check their work” on the diff (correct oil/topped off/limited slip additive if necessary?) but in the meantime, any thoughts? On top of the rear-end issue, does it sound like *maybe* torque convertor, and not new trans time? 

Poopie, you're berkeleying up.   you have LSXperts at your disposal.   give them the car and let them figure it out.  maybe it's not in their wheelhouse, but they're certainly going to be more attentive to figuring it out than the stealership will be.

AngryCorvair said:

Poopie, you're berkeleying up.   you have LSXperts at your disposal.   give them the car and let them figure it out.  maybe it's not in their wheelhouse, but they're certainly going to be more attentive to figuring it out than the stealership will be.

Matt swears to me that when we were there they said they farm out any transmission work.

In reply to poopshovel again :

hmmm, ok, but do they farm it out to someone like themselves?  either way, best of luck my friend!   i hope it's nothing major.

I know a lot of these developed jacked-up rearends because people didn't follow the break-in procedure. GM said no more than half-throttle for the first 500-1000 miles, and you would have guys who would leave the showroom with their foot sticking through the grille. Jump forward a few months and the rearend would be making all sorts of ugly noises due to it.

Also, off-topic, but don't be so quick to paint all dealerships as liars and thieves and shiftless ne'er-do-wells. Working at a dealership, I've seen it cut both ways, plenty of work from independent shops that was completely butchered. When the independent shop has someone sink $500+ into vehicles and then it still isn't fixed and they send the customer to the dealership who fixes it correctly for $600, who was doing the stealing, the guy who charged $600 to fix it right, or the guy who took $500 and the vehicle still wasn't fixed (or worse)? Sorry, just a pet peeve that I see on here a lot and kinda burns me as a dealership employee

In reply to NickD :

Quite the contrary!!!!! I only say “stealership” as it’s part of the lexicon here. The guys at Day’s Chevrolet here have been AWESOME! ...Hennessey Honda of Woodstock, not so much

Hopefully my post didn’t come off like I was slamming the dealership. They’ve always done me right.

In reply to AngryCorvair :

Thanks dude. I’ll have it serviced first, per their recommendation. When that doesn’t do squat, I’ll give them a call. Silver lining: If it needs a tranny I’ll have them go ahead and swap in a TC...and likely cam...and maybe a nastier exhaust than the borla.

In reply to poopshovel again :

It wasn't particularly aimed at you, it was more just in general.