8l90

[dhutton]

Originally Posted by dontlifttoshift

Right, but the ECU doesn't know what tire diameter or gear ratio you have. Consequently the shift strategy is based false information. It's close for a lot of applications but with a 31" tire it won't shift the way it should.

I was thinking the same thing. The ZL1 uses 2.85 gears with a 27” tall tire so it’s similar to 3.73 gears with 31” tall tires if I did the math right. Got me wondering what the Connect and Cruise tune assumes.

Don

[raustinss]

id have to agree , not that it matters but my 17 silverado with 3:42 gears isnt even that low lol

[vet57air]

Originally Posted by dhutton

I was thinking the same thing. The ZL1 uses 2.85 gears with a 27” tall tire so it’s similar to 3.73 gears with 31” tall tires if I did the math right. Got me wondering what the Connect and Cruise tune assumes.

Don

The install docs for the LT4 8L90 specify 3:08 to 4:11 gear and 26" to 30" tall tire. Yes I went with a 31" tire but assumed the transmission only sees the driveshaft rotation as an end result? Funny my speed to the Dakota speedo was within 5 mph first time out.

[dhutton]

Originally Posted by vet57air

The install docs for the LT4 8L90 specify 3:08 to 4:11 gear and 26" to 30" tall tire. Yes I went with a 31" tire but assumed the transmission only sees the driveshaft rotation as an end result? Funny my speed to the Dakota speedo was within 5 mph first time out.

Ya I think the rear gear ratio sort of cancels out the tall tires.

Don

[130fe]

Do you have HP Tuners? You can change it that way in the gear/tire wizard in the tune. You are using the Gen V connect and cruise pcm correct?

[vet57air]

Originally Posted by 130fe

Do you have HP Tuners? You can change it that way in the gear/tire wizard in the tune. You are using the Gen V connect and cruise pcm correct?

I am using the GM connect and cruise pcm. Is HP tuner the way to go? Are there others? What other stuff will it do?

[protour]

Originally Posted by vet57air

I am using the GM connect and cruise pcm. Is HP tuner the way to go? Are there others? What other stuff will it do?

HP Tuners is your only option with stock ecu. Where in BC are you again?

[vet57air]

Originally Posted by protour

HP Tuners is your only option with stock ecu. Where in BC are you again?

On the island, Port Alberni

[shelteredV]

Get with a really good tuner and they can make that trans work awesome with HPT. Just make sure they have experience with tranny tuning.