[anthony_n]

Hey everyone,

I drive a 2017 Camaro 1SS convertible with the 8L90 auto, and lately I’ve been running into some transmission trouble. When cruising, I’ll sometimes feel a low rumbling/vibration, and every now and then my tach will “bounce” up and down by about 50–100 RPM. From what I’ve read, this sounds a lot like Torque Converter Clutch (TCC) Shudder. GM even issued TSB 18-NA-355 back in 2019, recommending a full transmission fluid exchange as the fix.

Here’s the problem: I’ve already taken the car to my local Chevy dealer and even AAMCO, but neither one would agree to perform the fluid exchange. They both said the risk to the transmission was too high. That leaves me in a tough spot—I’m considering trying another GM brand service center (Cadillac, GMC, Buick) and asking if they’ll do it there.

Now for the kicker: I’m planning some performance upgrades down the line, including a cam swap (likely a BTR Gen V Stage 2 Supercharged cam), which will require an upgraded torque converter anyway. But that’s probably 6–12 months away.

So my question is: what’s the best move in the meantime? Do I keep hunting down a dealer who will do the fluid exchange to protect the transmission now, even though I’ll be replacing the converter later? Or would it make more sense to just baby the car and hold off until I’m ready to do the cam and converter upgrade?

I’d really like to keep the car as healthy as possible while avoiding unnecessary or redundant work/parts. Any firsthand experience with this situation (or advice on how dealers handle it) would be hugely appreciated.

Thanks in advance!

[arpad_m]

Your car is a 2017, you might as well start with the mods and get a proper transmission tune along with an ECM tune that disables AFM. It'll be cheaper to have the car tuned only once, ie when you do the cam and whatever else you want to do (intake, heads, long tube headers, E85 etc.) that require a tune anyway.

I will say, though, that I have never heard of a decent service department refusing to perform trivial, lucrative, non-warranty TSB work like this. It's as if they don't want to make money on a fully documented procedure

[Mark114]

I recommend that you get the flush described in TSB 18-NA-355 so you have the correct fluid and to reduce or eliminate future damage from the original fluid. The flush procedure requires special equipment, but any GM dealership should be able to do it as it applies to a broad range of vehicles. Since you’re out of drivetrain warranty it will cost $500 or more.

[anthony_n]

Yeah, since I’m not sure when I’ll be able to start diving into more invasive mods that require tuning (fuel system, cam, heads, FI, etc), I’ll probably go search for another service center that will be willing to help. I know I’ll still need a good transmission tune too. Hopefully I can find someone near the DC/Maryland/Virginia area that is reputable. Was thinking about reaching out to Race Proven Motorsports in Delaware.

[dmcmahan60]

I would just try and find another dealership that is willing to do the flush and go from there. I had my first one done at 21,000. Second was done because of a faulty transmission temp sensor and they had to do a drain and refill. Then another one a few months ago for maintenance purposes. The first one was free but paid for the other two. I just hit 159,000 miles this morning

[MarineDad]

I'm assuming they don't want to do a fluid exchange because of sediment concerns. Flushing the fluid may stir up sediment and effect the valve body. Sediment will kill a valve body faster than anything. See if either place will drain the transmission, drop pan and replace the oil filter in the transmission. This should take care of any sediment concerns. If there is another reason they don't want to do it, I don't know what it would be.