[adamjwilson]

Originally Posted by Camaro fanboy

because i'm a tight ass.

[KMPrenger]

Originally Posted by jamala00

Interesting... I store mine in my storage unit all winter. Non heated, on concrete. Never had this issue.

I don't think tire flat spots are the OPs problem since he said it ran fine for the first 20 mins of the trip (unless the speeds during that time were not at highway speeds).

But anyways, I park my car on doubled up carpet pads pretty much all year round (especially winter) because the tires get bad flat spots. These are the stock SS runflat high performance summer tires, although I'm running the rear size tires on all four corners on aftermarket 1LE replica wheels. That keeps them riding nice. Otherwise they get to vibrating so bad I begin to wonder if a lug nut is coming loose lol.

[jamala00]

Originally Posted by KMPrenger

I don't think tire flat spots are the OPs problem since he said it ran fine for the first 20 mins of the trip (unless the speeds during that time were not at highway speeds).

But anyways, I park my car on doubled up carpet pads pretty much all year round (especially winter) because the tires get bad flat spots. These are the stock SS runflat high performance summer tires, although I'm running the rear size tires on all four corners on aftermarket 1LE replica wheels. That keeps them riding nice. Otherwise they get to vibrating so bad I begin to wonder if a lug nut is coming loose lol.

Ah, that's probably why. I run all seasons, so it gets parked for the winter on those. I've never owned summer only.

[ctrlz]

Everything I read says that "bad fuel" causing "vibrations," "shudders," etc. is all due to misfires. the car typically detects misfires before you can feel them. i think prolonged misfires would post a CEL. but I would still hook up a scan tool.

[len125]

sounds like transmission shudder....get flush or trade in camaro and get a new one before its too late

[arpad_m]

Originally Posted by len125

sounds like transmission shudder....get flush or trade in camaro and get a new one before its too late

You do realize he has an aftermarket torque converter from Circle D, right?

[WhiteMale]

If you're getting a misfire you'll get the flashing CEL

Too, flat spots when I've seen them from overnight on a set of Kuhmo ASX tires, they come out rather quickly but the ride the first 5 minutes or miles was pretty choppy.

[ctrlz]

Originally Posted by arpad_m

You do realize he has an aftermarket torque converter from Circle D, right?

I suppose it wouldn't hurt to ask if he switched to the newer spec ATF. That wasn't clear in post #1. I like to think we don't have to ask, but...

[arpad_m]

Originally Posted by ctrlz

I suppose it wouldn't hurt to ask if he switched to the newer spec ATF. That wasn't clear in post #1. I like to think we don't have to ask, but...

That is a fair point... the correct fluid came out in Jan 2019, so I assumed there was no way anyone touching the trans would risk older spec fluid, but he may actually have done the TC upgrade prior to that date.

[Darth Martel]

FYI I used Mobil 1 LV ATF HP for trans fluid. I had the work done to swap out the torque converter Summer of 2020. I bought the trans fluid for the shop that did the work to use. No way of knowing for sure if they actually used it but, don't see why they wouldn't since I supplied it.

I filled up on 93 after work and drove home 30 minutes. Still had a shudder. It's supposed to rain today so drove my truck into work. Thursday looks good so will drive the Camaro then. We'll see how that goes.

It's just odd that this shudder materialized after vehicle storage for several months. Which is why I was thinking it was the e85 that sat all winter in a half empty tank. Flat spots in tires work themselves out after 5 or 10 minutes. Those are relatively new tires as well. Michelin Pilot Sports.

What about the rear differential? Could that cause a shudder? I have changed that fluid in the past but, it's been awhile. Only 22k miles on the car though so not sure it would need changing again. The shudder seems rpm dependent. Once I hit a cruising speed it'll start shuddering but, I can push through it by accelerating. Definitely feels transmission/torque converter related but I don't know jack.

[Darth Martel]

Drove it in this morning. Still shuddering. My check engine light did start blinking for a little bit a few minutes into my trip. I turned into a neighborhood to turn around and head back home but it went off. Drove towards home a little bit but, the CEL never came back so turned around again and drove it all the way into work. If I kept it around 1500rpm+ it seemed to drive ok. So I kept it in 6th gear most of the time and dropped it to 5th when I had to drive a little slower. I'd put it back into D every so often just to see if cruising in 8th would shudder and it did. It would shudder slightly after I got through a few gears during acceleration from a stop too. I'm guessing from the temporary CEL trigger that it was misfiring so, that does support the old e85 theory being the cause. I thought my exhaust sounded a little louder than usual as well when I first fired it up this morning but, I could be imagining that. I'm going to keep driving it, hopefully not triggering a CEL, and try to burn through this tank of fuel. I'm at 3/4 a tank now. Will let it go as low as possible and then fill up on 93 one more time. Hopefully, a tank of mostly 93 will clear up the issue. Might help to swap in a new fuel filter as well. If it continues after that, I'll get it up in the air and check the exhaust and make sure that's all tight. Probably give it an oil change. Maybe change the rear differential fluid. And if the shudder still persists, I'll do a transmission fluid flush. If all that still doesn't do the trick, I'll have to get the transmission and torque converter checked out. I'm not sure what else to do. The car was sitting with the battery disconnected from the vehicle and on a trickle charger. Would that affect the tune? I wouldn't think so but, I'm trying to think of all possibilities.