C7 Transmission Triple Flush
Melting Slicks
Joined: Feb 2018
Posts: 2,183
Likes: 1,049
From: North Texas
Just like you can't reuse safety wire even if only a few turns are loosened to remove a bolt.
Airplanes are not like cars concerning maintained, even new once used bolts get replaced.
Burning Brakes
Joined: Apr 2011
Posts: 1,149
Likes: 107
I did my triple flush myself. Before I did the first flush I bought a new trans pan and welded a low-profile bung onto it. Dropped the pan, replaced the filter, installed new pan with drain, refilled. Did it two more times just using the drain plug.
Burning Brakes
Joined: Apr 2011
Posts: 1,149
Likes: 107
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
If he works on planes under 135 rules then he has to replace filters and gaskets when they are removed, it's required by the FAA. Grey area, if the filter / gasket was just installed and had to be removed immediately for some reason, maybe not. Only the inspector that signs off on it can decide.
Just like you can't reuse safety wire even if only a few turns are loosened to remove a bolt.
Airplanes are not like cars concerning maintained, even new once used bolts get replaced.
Just like you can't reuse safety wire even if only a few turns are loosened to remove a bolt.
Airplanes are not like cars concerning maintained, even new once used bolts get replaced.
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
Question. Considering the triple flush is a "1 off" and we do transmission service every 50k, isn't this a large expense for that kind of service? Or am I mistaken?
Burning Brakes
Joined: Apr 2011
Posts: 1,149
Likes: 107
It was still way cheaper than letting the dealership do it. If you have ever dropped your pan to drain the ATF and change the filter the small cost for a pan and bung is waaay worth it. IMHO
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
Not for me. I don't have any welding tools 9r remember the skills I had 30 years ago so I will have to hire a welder. From what I see, it's the same as any other pan drop I have done except this is 3 pan drops, right? We used to loosen all the pan bolts, put the drain pan under the pan and loosen the bolts more to empty the pan as much as possible before removing the bolts altogether.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
Why? It's a 50K service. How often do you hit 50K? If this is an oil pan, I agree that loosening the bolts and all that is not a good thing. This is a 50K service so what does it matter? They plan for a shop to service it not DIY.
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
2. Prepare the Transmission:Ensure the vehicle is parked on a level surface.You may need to elevate the vehicle to access the fill and guide plugs.Consult your owner's manual for specific instructions related to your vehicle.
3. Add Fluid:Insert a funnel into the fill plug opening.Add the specified transmission fluid (Mobil 1 synthetic LV ATF HP for the 8L90).Add fluid until it starts to trickle out of the guide plug.This method prevents overfilling.
4. Check the Fluid Level:You may need to start the engine and cycle through the gears to get an accurate reading from the guide plug.The transmission needs to reach a specific temperature (depending on the vehicle and usage) to ensure accurate fluid level readings.
5. Important Considerations:The 8L90 transmission was designed to fit within a six-speed transmission case, which can make fluid and filter changes more challenging. Avoid overfilling the transmission, as it can cause aeration and foaming, which reduces pressure in the clutch packs.
Last edited by aklim; Aug 21, 2025 at 10:14 AM.
Burning Brakes
Joined: Mar 2018
Posts: 1,172
Likes: 218
1. Locate the Fill and Guide Plugs:The fill plug is on the top passenger side of the transmission.The guide (or level check) plug is on the front driver's side.
2. Prepare the Transmission:Ensure the vehicle is parked on a level surface.You may need to elevate the vehicle to access the fill and guide plugs.Consult your owner's manual for specific instructions related to your vehicle.
3. Add Fluid:Insert a funnel into the fill plug opening.Add the specified transmission fluid (Mobil 1 synthetic LV ATF HP for the 8L90).Add fluid until it starts to trickle out of the guide plug.This method prevents overfilling.
4. Check the Fluid Level:You may need to start the engine and cycle through the gears to get an accurate reading from the guide plug.The transmission needs to reach a specific temperature (depending on the vehicle and usage) to ensure accurate fluid level readings.
5. Important Considerations:The 8L90 transmission was designed to fit within a six-speed transmission case, which can make fluid and filter changes more challenging. Avoid overfilling the transmission, as it can cause aeration and foaming, which reduces pressure in the clutch packs.
2. Prepare the Transmission:Ensure the vehicle is parked on a level surface.You may need to elevate the vehicle to access the fill and guide plugs.Consult your owner's manual for specific instructions related to your vehicle.
3. Add Fluid:Insert a funnel into the fill plug opening.Add the specified transmission fluid (Mobil 1 synthetic LV ATF HP for the 8L90).Add fluid until it starts to trickle out of the guide plug.This method prevents overfilling.
4. Check the Fluid Level:You may need to start the engine and cycle through the gears to get an accurate reading from the guide plug.The transmission needs to reach a specific temperature (depending on the vehicle and usage) to ensure accurate fluid level readings.
5. Important Considerations:The 8L90 transmission was designed to fit within a six-speed transmission case, which can make fluid and filter changes more challenging. Avoid overfilling the transmission, as it can cause aeration and foaming, which reduces pressure in the clutch packs.
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
Burning Brakes
Joined: Jun 2018
Posts: 756
Likes: 172
From: SC
To me, logically, requiring a triple flush and all the steps, effort to fo it by the Service Bulletin, the overall point is to rid the whole system of the old bad fluid. Given that and knowing a filter of any kind holds a certain amount of the fluid it's immersed in, why would anyone, leave the filter with old fluid, in ? It doesn't make any sense.
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
To me, logically, requiring a triple flush and all the steps, effort to fo it by the Service Bulletin, the overall point is to rid the whole system of the old bad fluid. Given that and knowing a filter of any kind holds a certain amount of the fluid it's immersed in, why would anyone, leave the filter with old fluid, in ? It doesn't make any sense.
Yes, I was next to the guy at the parts store when he asked for fluid for a transmission fluid change. Parts guy suggested a filter. This will kill you. "Nah. I'm selling it and if the fluid looks clean, they won't check the filter.". I wonder why I am so skeptical about sellers.
Burning Brakes
Joined: Jun 2018
Posts: 756
Likes: 172
From: SC
Unless I am selling it tomorrow, I would think that after the 3rd pan drop, I'd change BOTH the gasket and filter.
Yes, I was next to the guy at the parts store when he asked for fluid for a transmission fluid change. Parts guy suggested a filter. This will kill you. "Nah. I'm selling it and if the fluid looks clean, they won't check the filter.". I wonder why I am so skeptical about sellers.
Yes, I was next to the guy at the parts store when he asked for fluid for a transmission fluid change. Parts guy suggested a filter. This will kill you. "Nah. I'm selling it and if the fluid looks clean, they won't check the filter.". I wonder why I am so skeptical about sellers.