2009 Eleanor

A buddy of mine is trying to decide whether he would benefit from going from 4.10's to 3.55's. He has a turbocharged gt with an auto trans and 29" tall tires.
Please let me know what you think.
Thanks in advance

SpartaPerformance

Benefit in which way?

2009 Eleanor

He is wondering if there will be a performance gain. I know he will get much better mpg and I know manuals would benefit from 3:55's because they would be in the boost longer. But what about automatics?
Would 3:55's be an overall (performance, mpg, streetability) upgrade or downgrade?

retfr8flyr

How big is his turbo, what rpm is it fully spooled, what stall is his converter? The 3.55 gears will load the turbo better then 4.10's will but if he can't get the car moving they wont help.

I went from 3.73's to 3.27's on my car and turned the exact same times. I was several MPH faster with the 3.27 gears but couldn't get the car to launch worth a dam. I was doing 1.9 60' times because my converter was too tight and it took a long time the get spooled up. I have a new converter that allows me to footbrake to 3000rpm and higher compression engine now and it will be interesting to see how this setup does.


Earl

NuclearMuscle523

65mm
Around 3700-4000
3000rpm tci single disc
315/35/20 nt05r breaks traction easy on the street.

retfr8flyr

A 65mm should spool before 3700 rpm, is he on the stock engine?. I would think, with his setup, that 3.73's with a 29 inch tire, would be a great gear for his car. If he wants to go with a smaller tire the 3.55's and a 27 inch tire would also be good.

I went from a 28 inch DR to a 27 inch DR on mine for the track. I still run a 28 inch DR for my DD tire in the summer months.



Earl

NuclearMuscle523

I am looking for more time in first gear, better traction, much harder pull through gears.

NuclearMuscle523

And earl your windage tray and driveshaft are still doing incredibly well, thank you!

retfr8flyr

Glad to hear everything worked out for you. The lower gearing will definitely help with traction and will load the turbo well. I like my 3.27 gear, 27 inch tire combo and can't wait to try out the new setup with a higher stall converter and higher compression engine. I was tuning 130 mph but only doing 10.90's, due to launching so softly with the previous converter.


Earl