monte0 Posted May 28, 2014 Share Posted May 28, 2014 Ok, I've got my mind set on exactly what motor and trans I'm going with when the cars done (ls2/4l80e). Currently I've got 3.25 gears in my ford 9" and I have 3.50's in stock I could swap out, but I'm wondering if maybe 3.70 gear would be a better choice for this combo? I'm planning on staying with a full lockup converter and the 275/50 15 tires. I'm going to be racing it some every weekend but do plan on doing some traveling with it more once it's done. My old t400 with 3.25's would run around 3000rpms at 65 which wasn't bad on the shorter tires Quote Link to comment Share on other sites More sharing options...
Patrick Sheean Posted May 28, 2014 Share Posted May 28, 2014 .373's with a four speed auto will get you out of the whole in a hurry, plus you have overdrive for the highway, sounds like a good combination. Quote Link to comment Share on other sites More sharing options...
bigscaht Posted May 29, 2014 Share Posted May 29, 2014 im plotting on my gears too..you have an od tranny....that with the 373s will be fun and it will drop ya highway rpms too...i want an od tranny!! Quote Link to comment Share on other sites More sharing options...
72MC Posted May 29, 2014 Share Posted May 29, 2014 I'd go at least 3.70 something. If I were you, I would also consider 3.90. I have 4.10s and the OD drops it so it feels like a 3.08 on the highway. 4L80 have a .75 OD. 4.10s have been perfect for me and as you can see by my siggy, I have a 4L80. Just my couple pennies. - Dave Quote Link to comment Share on other sites More sharing options...
monte0 Posted May 29, 2014 Author Share Posted May 29, 2014 What size height tires are you running, that makes a difference in final rpm. Around what rpm's do you see at 65mph? Quote Link to comment Share on other sites More sharing options...
Daryl Posted May 29, 2014 Share Posted May 29, 2014 Do you plan going manual with a switch lock up or keeping it with a computer? I too have a 4L80e in my Monte. I'm using an EZ TCI TCU controller. I went with 4.10 gears and a 285 40 17 set of tires. I don't have it in front of me right now but I seem to remember from a gear calculator that it will be running 2350 rpm at 65mph. Quote Link to comment Share on other sites More sharing options...
Daryl Posted May 29, 2014 Share Posted May 29, 2014 just ran the numbers 26.5 tire 4.10 gear 65mph= 2534 rpm (my set up) 3.90 gear dropped it to 2411 3.70 was 2287 Quote Link to comment Share on other sites More sharing options...
72MC Posted May 29, 2014 Share Posted May 29, 2014 I am running Nitto NT450 275/50/17 in the rear. They are 27.88 inches tall. I don't do much 65 mph due to our speed limits being 70 mph. I'm usually running 80 mph and rpms are around 2800-3000. Daryl is right though, at 65 mph, rpms are low to mid 2000s in OD. Â The fly in the ointment for me is my stall convertor. Since I run a full manual 4l80, the convertor is non-lockup. Stall is 3300-3500 and it likes the higher rpms. If I run 65 mph, alot of the times I will keep it in 3rd. One way I learned my tranny's happy place is by the trans temp gauge. With a lock up convertor you should be fine with low gears. - Dave Quote Link to comment Share on other sites More sharing options...
monte0 Posted May 29, 2014 Author Share Posted May 29, 2014 Do you plan going manual with a switch lock up or keeping it with a computer? I too have a 4L80e in my Monte. I'm using an EZ TCI TCU controller. I went with 4.10 gears and a 285 40 17 set of tires. I don't have it in front of me right now but I seem to remember from a gear calculator that it will be running 2350 rpm at 65mph. Â Plan on dropping a complete ls2/4l80e with factory pcm setup. I've got the tuning software to tune it so that's why I'm going that route. Quote Link to comment Share on other sites More sharing options...
monte0 Posted May 29, 2014 Author Share Posted May 29, 2014 just ran the numbers 26.5 tire 4.10 gear 65mph= 2534 rpm (my set up) 3.90 gear dropped it to 2411 3.70 was 2287 Â Ok, my tire size is a 26" so I'd be a little higher on the rpm by not by much. Quote Link to comment Share on other sites More sharing options...
monte0 Posted May 29, 2014 Author Share Posted May 29, 2014 I am running Nitto NT450 275/50/17 in the rear. They are 27.88 inches tall. I don't do much 65 mph due to our speed limits being 70 mph. I'm usually running 80 mph and rpms are around 2800-3000. Daryl is right though, at 65 mph, rpms are low to mid 2000s in OD.  The fly in the ointment for me is my stall convertor. Since I run a full manual 4l80, the convertor is non-lockup. Stall is 3300-3500 and it likes the higher rpms. If I run 65 mph, alot of the times I will keep it in 3rd. One way I learned my tranny's happy place is by the trans temp gauge. With a lock up convertor you should be fine with low gears. - Dave  I'm trying to get my target rpms at around 75-80mph to be no higher then 3000. And with my shorter 26" tires I'm going to need less gear then your using. As for the stall it's going to be more then likely around a 2400 with lockup. Quote Link to comment Share on other sites More sharing options...
monte0 Posted June 10, 2014 Author Share Posted June 10, 2014 Ordered a 3.89 gear set from Richmand for my 9" and a half rebuild kit. Dropping it off to my friend to get setup and hopefully it will be ready by monday next week Quote Link to comment Share on other sites More sharing options...
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