Small RPM Drop in 4th Gear
05-23-2018, 08:25 PM
#1
Advanced
Thread Starter
Small RPM Drop in 4th Gear
I’ve noticed that during light to moderate acceleration, the RPM drops slightly when the engine gets to 2500 RPM in 4th gear. The drop is about 100-200 RPM. My car is a 2017 Z51 A8 and it just hit 3000 miles. I didn’t notice it last summer but it is very consistent now. I haven’t tested it under heavy acceleration. I usually drive with the exhaust mode set to track but tonight I set it to automatic because I was driving through some quiet neighborhoods and coincidentally, the dip in RPM occurs the same time the valves close.
I’m sure it’s nothing but was wondering if anybody else noticed this?
I’m sure it’s nothing but was wondering if anybody else noticed this?
05-23-2018, 08:53 PM
#5
Burning Brakes
Do you notice any vibration/shudder when it happens? Does the rpm just dip or go up and down 100 rpm or so while in gear? The AFM exhaust valves close when you go to v4 mode so it sounds like it is happening when it switches to v4 mode. You can test by putting it in manual mode, which disables v4/AFM mode then just use the paddles.
When I had the A8 TC shudder issue on my Camaro SS it would happen when cruising on the highway when it kicks into AFM mode. The TC slips to remove the vibration of v4 mode but fails at doing so. You wind up with a triple flush to get different fluid and if that doesn't work they replace the TC.
When I had the A8 TC shudder issue on my Camaro SS it would happen when cruising on the highway when it kicks into AFM mode. The TC slips to remove the vibration of v4 mode but fails at doing so. You wind up with a triple flush to get different fluid and if that doesn't work they replace the TC.
05-23-2018, 10:13 PM
#6
Advanced
Thread Starter
Do you notice any vibration/shudder when it happens? Does the rpm just dip or go up and down 100 rpm or so while in gear? The AFM exhaust valves close when you go to v4 mode so it sounds like it is happening when it switches to v4 mode. You can test by putting it in manual mode, which disables v4/AFM mode then just use the paddles.
When I had the A8 TC shudder issue on my Camaro SS it would happen when cruising on the highway when it kicks into AFM mode. The TC slips to remove the vibration of v4 mode but fails at doing so. You wind up with a triple flush to get different fluid and if that doesn't work they replace the TC.
When I had the A8 TC shudder issue on my Camaro SS it would happen when cruising on the highway when it kicks into AFM mode. The TC slips to remove the vibration of v4 mode but fails at doing so. You wind up with a triple flush to get different fluid and if that doesn't work they replace the TC.
Last edited by Wemattson; 05-23-2018 at 10:15 PM.