[Jmcmanus626]

Hi, question for anyone who's dealt with the transmissions. Is it worth swapping from the 8 speed to the 10 speed? Is it simple as just that or does there need to be an update to the ecu as well for such? Is it even worth doing? I know the 8 speeds could have issues, as some have had with sluggish performance or just hard shifting. Or is it just worth upgrading the clutch plates and such for performance. Long and short i have a 17 2SS with the 8 speed I'm building on and was curious if anyone ever swapped them, or what they did. Thanks!

[arpad_m]

I'd be very interested to hear of even one successful 8L90 to 10L90 swap.

That said, it must be enormously expensive for what you'd gain, I would definitely not want it for my car. The only advantage the 10-speed has over a properly tuned 8L90 is the extra gear between 4th and 5th, giving it a slight edge in drag racing (because of the gear ratio drop wih the 8L90, rpms drop a bit below the engine's powerband on the 4-5 shift). Actually, shifting with the paddles is also somewhat faster on the 10L90, but it istill isn't Porsche or Koenigsegg fast, there is going to be a delay.

My 8L90 wasn't bad to begin with and is now perfect thanks to Ted Jannetty's tune, no shudder, no sluggishness, no weird shifts, no slipping, plus I get to enjoy several proper "bam" WOT shifts one after another (unlike the 10L90 that only does one or two in real life, and that's if you're able to launch properly in 1st gear).

[Joshinator99]

Agree with Arpad, complete waste of time to try a swap. My stock 8L90 held 900-1000 WHP for 4 plus years and a stack of mid 9 second time slips. I don’t know many transmissions that can do that successfully, including the 10L80/10L90. And also to Arpad’s point, the tune is critical to a long lifespan and good performance.

[KingLT1]

Yes there is a company offering conversions now. It's been popular for the CTS-V3 and Truck crowd. It makes the most sense if your vehicle has a A4/A6. Everybody shits on the 8l90 but I think they are great with proper tuning. The A10 would be a little faster 60-130.

https://www.powertrainswapsolutions.com/

[Jmcmanus626]

Originally Posted by arpad_m

I'd be very interested to hear of even one successful 8L90 to 10L90 swap.

That said, it must be enormously expensive for what you'd gain, I would definitely not want it for my car. The only advantage the 10-speed has over a properly tuned 8L90 is the extra gear between 4th and 5th, giving it a slight edge in drag racing (because of the gear ratio drop wih the 8L90, rpms drop a bit below the engine's powerband on the 4-5 shift). Actually, shifting with the paddles is also somewhat faster on the 10L90, but it istill isn't Porsche or Koenigsegg fast, there is going to be a delay.

My 8L90 wasn't bad to begin with and is now perfect thanks to Ted Jannetty's tune, no shudder, no sluggishness, no weird shifts, no slipping, plus I get to enjoy several proper "bam" WOT shifts one after another (unlike the 10L90 that only does one or two in real life, and that's if you're able to launch properly in 1st gear).

I appreciate the info. I was planning on swapping in monster clutches and such and tuning the transmission for what i want. Just wasn't sure if it was worth it or doing a straight swap or what all the advantages or disadvantages would be. This was very informative, so thank you.

[jlaudio11]

It really depends on what you're trying to do. Something more mild the 10 spd will help it accelerate quicker, getting into big power I'd build the 8 speed and if you're going to swap then swap to a th400. I believe Tim King bought a built 8 spd car and swapped it to 10 spd but he builds transmissions for a living and wanted his build in the car.

[KingLT1]

TH400 is race car stuff. There are so many other platforms that you can turn into a race car easier and cheaper than a 6th gen. What makes the 6th gen nice is how comfortable it is and how well it drives/handles. The multispeed automatics compliment that part of them.

[Jmcmanus626]

Originally Posted by jlaudio11

It really depends on what you're trying to do. Something more mild the 10 spd will help it accelerate quicker, getting into big power I'd build the 8 speed and if you're going to swap then swap to a th400. I believe Tim King bought a built 8 spd car and swapped it to 10 spd but he builds transmissions for a living and wanted his build in the car.

Yea I'm going for getting into bigger power, wasn't sure the pros and cons. Sounds like building the 8 speed i have is the route to go

[Lt4zl1]

Originally Posted by arpad_m

I'd be very interested to hear of even one successful 8L90 to 10L90 swap.

That said, it must be enormously expensive for what you'd gain, I would definitely not want it for my car. The only advantage the 10-speed has over a properly tuned 8L90 is the extra gear between 4th and 5th, giving it a slight edge in drag racing (because of the gear ratio drop wih the 8L90, rpms drop a bit below the engine's powerband on the 4-5 shift). Actually, shifting with the paddles is also somewhat faster on the 10L90, but it istill isn't Porsche or Koenigsegg fast, there is going to be a delay.

My 8L90 wasn't bad to begin with and is now perfect thanks to Ted Jannetty's tune, no shudder, no sluggishness, no weird shifts, no slipping, plus I get to enjoy several proper "bam" WOT shifts one after another (unlike the 10L90 that only does one or two in real life, and that's if you're able to launch properly in 1st gear).

I am in east tennessee myself and got a 10l90e swapped ctsv here at the shop now and let me tell you how much better this car is because of the 10 speed. I build both of these locally in dandridge do gm tuning here building some pretty fast cars. This car is much quicker then a car I had here last year on almost the same build but still stock a8. Zero rpm drops always in the power band and way stronger trans. The a8 is probably the worst gm trans ever build as its got so many built in flaws you will see when get some miles on it and the valve body is slap worn out. Now I will say I tune a z 06 that has gone 8.2X on a stock 8l90 3.45 60-130 on the street and its finally needing a build after a year of destorying 1800whp mustangs in south florida on the street. ITs actually going up for auction with trc here soon. Just ran 8.90 on 93 and detuned so trans would make all the shifts.
We also did a 17 m6 zl1 over to a 10l90e and you wouldnt know the car ever came manual as its so perfect. Went from 9.2x m6 to 8.5x auto and the m6 did go a 1.38 60 foot. So it is possible and well worth it especally if making decent hp. I got a 2300 on my zl1 we should meet up so I can show you how a properly tuned car runs lol I have retuned behind ted and gone much faster on the same build. Soon as cools off a little I was gonna go to knoxville and bristol. Ran 6 flat last year at knox on the 1.7 and 9.4 in bristol on the same 1.7 at 15 psi. I make 26 psi now on the 2300 so its alittle quicker.
Back to trans I will say this I can build a 10l or 10r to hold 1400whp way cheaper then can a a8 to hold 1300 as that is about the limit on them if want it to stay alive anyway and not be throwing parts at it every season. Maybe will see you sometime out.

[KingLT1]

The 8l90 is far from the worst trans GM ever built. Plenty of 7-900whp cars out there on the stock 8l90 doing fine. I see a lot of 10l80's failing. When you start talking 1300+ whp and 1/4mi racing that is when a TH400 enters the chat. Even built 10l90's are on borrowed time at that point. But yes the 10l90 is GM's best transmission. But to say the 8l90 is GM's worst is crazy talk.

[Joshinator99]

Originally Posted by KingLT1

The 8l90 is far from the worst trans GM ever built. Plenty of 7-900whp cars out there on the stock 8l90 doing fine. I see a lot of 10l80's failing. When you start talking 1300+ whp and 1/4mi racing that is when a TH400 enters the chat. Even built 10l90's are on borrowed time at that point. But yes the 10l90 is GM's best transmission. But to say the 8l90 is GM's worst is crazy talk.

Agreed. My stock 8L90 took 5 years of being supercharged ( 4 years at 900+ WHP!) and a stack of mid 9 second timeslips before needing attention…pretty damn impressive if you ask me. I grew up with a TH700R4 in my ‘84 Firebird back in the day that couldn’t handle 300 HP without coughing up parts, so I’ll take the 8L90 everyday of the week and twice on Sunday.