What rear gears with 4L80E?
What rear gears with 4L80E? Will be running a 6.0L front mount kit, 76mm turbo with .96 a/r, Speed Inc. TU1 cam, stock 317's, 3400-3600 stall, 315/35/17 DR's out back, E85, etc. I would like to trap in the 130's which should obviously be very obtainable. Also do not want to spin the motor much past 6k. Car was an M6 car so it has a 3.42 rear end in it now. I can pick up a 2.73 rear 10 bolt for $25 from a buddy.
The car will be street driven and daily'd when it's nice out. Will see track use maybe a handful of times each year. Will probably see it's fair share of highway pulls also.
With all that being said, what rear gear would you choose and why? I did a few quick searches and the consensus seemed to be to stick with the 3.42's for an overall fun car. However, there are people running 2.73's or thereabouts in TH400's running sick times. I may pick up the 2.73 rear anyway and give them both a try, but looking for opinions on what you think will run faster at the track, and be more fun on the street with what I am working with.
Thanks all.
The car will be street driven and daily'd when it's nice out. Will see track use maybe a handful of times each year. Will probably see it's fair share of highway pulls also.
With all that being said, what rear gear would you choose and why? I did a few quick searches and the consensus seemed to be to stick with the 3.42's for an overall fun car. However, there are people running 2.73's or thereabouts in TH400's running sick times. I may pick up the 2.73 rear anyway and give them both a try, but looking for opinions on what you think will run faster at the track, and be more fun on the street with what I am working with.
Thanks all.
Last edited by RedRocketZ28; Apr 5, 2012 at 12:09 PM.
I ran an almost identical setup with 3.42's. It worked great but I did always wonder how it would have performed with higher gears and considered switching to 3.08's but never did it.
I ran 3.55's with my 4L80E and 3800 FTI stall. I also ran a 3.08 gear set with the same FTI stall just at 3200 so I can compare the two. This was a stock cubic inch LS1 with a stock shortblock, cam only and ls6 intake. PT76 turbo at 11-15psi.
The 3.08 pulled less rpm at cruise of course and made 3rd and 4th gear fun because of how long they were and how much it would pull against the tight converter and the long gears.
The switch to the 3.55's and 3800 stall wasn't noticeable in RPM's until I got to 60mph+. I think Greg@FTI's work with the stall has a lot to do with this and the converter's efficiency, but it is what it is. The main thing I loved about the 3.55's and the 3800 stall over the 3.08's was when I stood on it in 1st or 2nd it was a whole nother animal. It would snap the tires loose and build boost a lot faster than the 3.08's did.
The 3.08's made boost faster in 3rd and 4th gear where they had a lot of load on them, anytime I stood on the gas with the 3.55's it felt like a different car. MPG's were better with the 3.08's by 1-2mpg.
The 3.08 pulled less rpm at cruise of course and made 3rd and 4th gear fun because of how long they were and how much it would pull against the tight converter and the long gears.
The switch to the 3.55's and 3800 stall wasn't noticeable in RPM's until I got to 60mph+. I think Greg@FTI's work with the stall has a lot to do with this and the converter's efficiency, but it is what it is. The main thing I loved about the 3.55's and the 3800 stall over the 3.08's was when I stood on it in 1st or 2nd it was a whole nother animal. It would snap the tires loose and build boost a lot faster than the 3.08's did.
The 3.08's made boost faster in 3rd and 4th gear where they had a lot of load on them, anytime I stood on the gas with the 3.55's it felt like a different car. MPG's were better with the 3.08's by 1-2mpg.
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I used this calculator to make sure I would be in the right mph range at the end of the 1/4, and not over rev the engine to obtain that mph.
http://vexer.com/automotive-tools/speed-rpm-calculator
I'm limited to the rear end ratios available in my swap since it's a Lexus IRS, so it was more important to me to make sure the final ratio worked with 3rd gear in a 4L80E for my goal.
http://vexer.com/automotive-tools/speed-rpm-calculator
I'm limited to the rear end ratios available in my swap since it's a Lexus IRS, so it was more important to me to make sure the final ratio worked with 3rd gear in a 4L80E for my goal.
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