4r70 swap : what rear gear ratio?

[DVEST8R]

I know the 4r has a taller 1st gear than the 5r55s. With that said will my combo of 3:73 and 28 in tires still be good to go? Combo is built motor/200 shot of nitrous, circle d stall

 

[dysan]

That's the combo I ran the last 2 years with my 4R70W trans. It really comes down to what rpms you want to cross the stripe at and how much power you're making. I was about 630rwhp and 590 rwtq with this combo and was crossing the stripe around 6300 rpms at the end of last year in pretty good air.

Now I don't know how it will work with spray since I was in boost on the 2-step but you will be spraying on/after the launch. I've never used nitrous so I don't have any first hand experience.

 

[DVEST8R]

That's the combo I ran the last 2 years with my 4R70W trans. It really comes down to what rpms you want to cross the stripe at and how much power you're making. I was about 630rwhp and 590 rwtq with this combo and was crossing the stripe around 6300 rpms at the end of last year in pretty good air.

Now I don't know how it will work with spray since I was in boost on the 2-step but you will be spraying on/after the launch. I've never used nitrous so I don't have any first hand experience.

Nitrous will come on with the release of the transbrake. I assume you are saying you were 6300 at the stripe in the 1/4? I only race 1/8 since thats all we have here

 

[dysan]

Yes, 1/4 miles racing where I'm at. Can't help you at all with 1/8 mile comparison. I just don't know how the converter will differ since I'm already loading up my converter when I'm on the 2-step being in boost but I suspect it should be similar since it's all about the converter design and the flash/stall it's set at.

If I was only 1/8 mile I would have my 4.10's back in my car without a doubt.

 

[05moneypit]

4.10's with the 2.84 first gear of the 4R70 is pretty steep, depending on power level it may be challenge to get the car to hook. I run 3.90's with a 28" tire and often think I would be better with a taller tire(29.5") , less gear (3.73) or the 2.40 first gear of an AOD.

If you can get the car to hook the 4.10's would be good for 1/8 mile racing

 

[lindertw]

edward, you were crossing the stripe in 3rd gear with your 5r55 auto, right?

rpm = (mph x final gear ratio x 336)/tire diameter
rpm = [101 x (3.73*1.55) x 336]/28
rpm = 7000

does that jive with your notes?

4r70 gear ratios are: 1st: 2.84 :1 2nd: 1.55 :1 3rd: 1.00 :1 4th: 0.70 :1 Rev: 2.32 :1

with the new trans, will you cross in 2nd or 3rd gear at the 1/8th stripe? If you cross in 2nd gear, there's no change to the math from above. If you cross in 3rd gear with the new trans, 4.10's would have you crossing at like 5000 rpm...

 

[DVEST8R]

edward, you were crossing the stripe in 3rd gear with your 5r55 auto, right?

rpm = (mph x final gear ratio x 336)/tire diameter
rpm = [101 x (3.73*1.55) x 336]/28
rpm = 7000

does that jive with your notes?

4r70 gear ratios are: 1st: 2.84 :1 2nd: 1.55 :1 3rd: 1.00 :1 4th: 0.70 :1 Rev: 2.32 :1

with the new trans, will you cross in 2nd or 3rd gear at the 1/8th stripe? If you cross in 2nd gear, there's no change to the math from above. If you cross in 3rd gear with the new trans, 4.10's would have you crossing at like 5000 rpm...

with the 5r55 it was shifting into 4th 2 car legenths b4 the 1/8 mile mark