rckt

I do notice the car runs smoother with the Range. Never had shudder but could feel it shift from v8 to v4, not anymore. Love the Range.

Makitso

I agree with this recommendation from my own experience. Last fall I had a new set of Michelin AS3+ ZP's installed
on my Z51. Several weeks later while driving on the highway, I notice a cyclic vibration coming from the back of the
car. This scared me, knowing about the A8 issues and I had been using a Range from day one. I went back to
Big O where I purchased the tires and had them check the balance which was spot on. Then they did a road force
balance test and found the right rear tire registered a 33 lb. hard spot in the tread. So with 375 miles on the tires,
Michelin replaced the one tire and the vibration was gone. Much relief that is wasn't an A8 issue!

us3rname

Just a quick update. In a previous post I said that I didn't feel the flush improved the shudder. well after about 1200 miles of daily driving and beating on it I'm glad to say the last 200 miles have been mostly shudder free. Seems to be improving with every drive. One thing I observed during the winter is that the hotter I got the trans the less noticeable it was (possibly cooking the moisture out of the fluid??). As it's been getting warmer my trans is running hotter and also improving with each drive. Now there are to many variables and no evidence to support my "hunch" but if my hunch is anywhere in the ball park maybe the shudder will come back in the winter when it cant get hot enough to burn the moisture off. Or maybe the new fluid will not retain moisture and the shudder will not return. I kinda wish I held off on the flush so I could compare it and try and relate the shudder to long term trans temps.

matthesf

Has anyone linked this to the delayed engagement issue? I'd like to knock out 2 birds with one flush

MrClean21

Makes me wonder if they actually did a "triple" flush? Maybe they cut corners and some of the old fluid is still in the tranny.

Roastum1

I thought they just do it once now?

MrClean21

See bulletin #18-NA-355 . It calls for flushing the system three times all on the same visit.

See https://gm-techlink.com/?p=11127

us3rname

That's totally possible, I dropped it back off yesterday to have them evaluate it again. Yesterday morning it was fine on my drive to work and then on the way to the dealer the shudder was back. Kinda wild how before the flush it would consistently shudder and after a flush it does it randomly. If it continues this way ill just bite the bullet on a new billet converter and a trans tune. Warranties are only good if they can resolve the problem.

Gearhead Jim

Unfortunately, the part I put in bold is hugely important.

Hopefully, you won't have to take that step.

Gearhead Jim

Yesterday I had some other work done on our car (2017 Z51 A8), and showed the bulletin PIP5337E to the Corvette Tech, asked him if it was still relevant. He said that bulletin/information is obsolete and the current diagnostics and tolerances are shown in the bulletin from January 2019, which makes no mention of rpm variations as a problem or aid to diagnosing problems.
Of course he could be wrong, but he's a sharp guy who pays attention to the details. I've even seen him at work checking on Corvette Forum to help diagnose problems with non-GM parts in customer cars.

burneyr

You guys ready for this???

After I posted in this thread last month my issues which included delayed gear engagement, hard 1-2-3 shifts, and acting as the transmission was in neutral occasionally from a dead stop haven't been fixed by the PCM reflash or the recent fluid change. The tech believes the valve body is going out, but the GM techline would not authorize the repair until we drove 300 miles on the reflash.

OK- I had contacted the GM Customer Care executive office seeking assistance with my problem. They contacted the dealership, arranged rental, and told me when to take the car to the dealership. I did this as instructed for the above mentioned reflash that did nothing.

After a week passed the GM rep called to check if I was satisfied with the repair so that the open case could be closed. I told her nothing was fixed, but I was willing to give them the benefit of driving the 300 miles after the reflash. She calls again by which time we put over 300 more miles on the car with the same issues. I ask her what is the next step? She says she will contact the dealer again and let me know.

Friday (almost two weeks later) I get a return call from this GM rep, and she tells me she talked to the service manager. He is upset I picked up the car and wants me to pay a diagnostic fee for the attempted repair and for the two days of rental car charges. I about lost it. ''What are you talking about? Ma'am? They called me saying the proceedure authorized by the techline was carried out, but they believe the transmission needs a valve body replacement GM would not authorize. I went to the cashier, asked to settle my bill, and was informed it was warranty service, and I owed nothing. My invoice says ''warranty'' and a zero balance. What are you telling me here? Are you telling me I call YOU for help, YOU arrange for me to bring my car in again, YOU handle the rental, my car isn't repaired; I'm presented with an invoice that says I owe nothing, and now you call me almost a month after the fact telling me the dealership wants payment?''

It's obvious she has no clue what's going on. Then she says the service manager must have me mixed up with someone else and she will call me back and let me know the resolution. Just bizarre...

The only thing I can think of is maybe GM denied the warranty claim after the fact, and now the dealer wants to charge me for the reflash the service tech performed under the GM techline's direction.

All I know is the transmission is still not working properly, it's getting worse, and it appears from my last contact that calling GM Customer Care and allowing them to arrange a satisfactory repair is just a backdoor to put out of pocket expense on the customer for a car well within the warranty period.

I'll chime back in this thread when I get more news. Sitting at 26000 miles now and not four years old yet...

matthesf

That's a damn shame! I hope you're able to get it resolved.

AmmoVet

OK now my turn. Took my 2016 Z51 in today for third time. First time they did not have the fluid and ordered it. 2nd time the fluid was mistakenly not ordered. Today I take it in at 8 am and just got a call that it was ready 1210 pm. I made the comment that it was fast and he indicated they did not need to drop the pan to flush it three times. When I dropped it off I asked them to replace the filter on the third flush. I asked them to look at page 26 of the service bulletin because my fear was that they did not see the specific instructions for the Corvette. He then stated the tech told him they had a new service bulletin that was dated March and the new process deleted the need to drop the pan.

Has anyone heard of this. Can anyone vouch for a new SB dated March 2019?

.

pkincy

I have not heard of it but he should be able to print it out to you with little effort if it exists.

MrClean21

Nope. Call him back and ask him for the bulletin number. I spent about 30 minutes and a new bulletin is nowhere to be found. That doesn't mean it doesn't exist. It just isn't appearing anywhere. I even specifically asked if TSB 18-NA-355 has been superceeded. I did find new bulletins for March but nothing on this topic that I could tell.

Found more. This page says the 18-NA-355 is from March 1, 2019.
https://www.repairprocedures.com/bul...5/5181942.html

#18-NA-355 - Shake and/or Shudder During Light Throttle Acceleration Between 25 and 80 MPH (40 and 128 KM/H) at Steady Speed - (Mar 1, 2019)

javenius

The January version of 18-NA-355 references US only (see page 1). Pretty sure a dealer told me the March update only adds applicability to Canada, not a change in procedure.

AmmoVet

thanks Mrclean and javenius, attached is the last sheet of the updated SB Dated Mar 1, 2019, showing changes.

got the car back took it for a 30 mile spin, no shudder. Time will tell. They did have a copy of the SB ready for me. They told me they did not drop the pan to do the flush but did run the full 24 quarts into/ through it. So worst case is I get shudder again and take it back.

snomuncher

From the reading I've done, delayed/harsh engagement is a separate issue related to any of the following: fluid leakdown of the torque converter, excessive crankshaft end play, or TCM calibration. There are separate service bulletins related to those items.

Bulletin 18-NA-355 addresses only shake/shudder.

carriccp

For those that have had the latest fluid, how is your shudder (or lack of) now with some mileage on the cars? I'm looking at a new GS before the month ends and contemplating an A8.

us3rname

Its better after about 1200 miles but not totally gone. It seems like the speed range it happens in has been narrowed by about 15mph so its a big improvement but again, not 100% corrected.