70mph gearing

[Dinosport]

Hi guys. I know some of you know how to calculate rpm. I do not so Ill ask, lol
I have a 700r4 Im going to install. Its non lock up because I know thats good for about a 300 rpm loss.
I have 25inch tires I believe the 700r4 over drive is .70,
I need to know what will the engine rpm be with the .70 gear and 25inch tires at 70mph
with 308 gears, 342's and 373's
I have 308s now but I'm trying to decide if I want to swap the gears when I put the transmission in the car.
Thanks

 

[pontiacgp]

this is easy to use to figure it out, with your current set up and the .70 4th gear you'd be at 2000 rpm at 69 mph

http://www.apexgarage.com/tech/gear_ratios.shtml

 

[MrSony]

Those seem ideal. I wouldn't go quite as steep as 3.73 though but on a 700r4 the gap between 1st and 2nd is steeper than on a 200r4 so that would help. Sidenote, I have 2,29 in my car with half bald 195/70/14 tires, a stock th350 and I'm at 2500rpm at 65-70mph on an engine with a redline of about 5,500.

 

[Qdub24]

Best calculator to use that I've found so far: https://www.ringpinion.com/calculators/Calc_RPM.aspx#TireHeight
3.08

3.42

3.73

 

[V8 Rumble]

Is your trans set up for non lock up? Or are you making it?

You will need this if you haven't done so already. This will give you proper flow to the tc when going non lock up.

https://m.summitracing.com/parts/tr...RuKRKmF-VuryGPbvUSNI6u2e6pSLPQnlgwaAkRS8P8HAQ

 

[Dinosport]

Thanks guys I figured out what I wanted to know. I would love 373 but I think Ill stick with 342's When I take trips with the family the engine will be at a nice comfortable RPM.

 

[Dinosport]

Is your trans set up for non lock up? Or are you making it?

You will need this if you haven't done so already. This will give you proper flow to the tc when going non lock up.

https://m.summitracing.com/parts/tr...RuKRKmF-VuryGPbvUSNI6u2e6pSLPQnlgwaAkRS8P8HAQ

transmission came with a B&M converter and the lock up eliminated. If it had it I wouldve left it. I couldnt pass up
the deal

 

[Dinosport]

Those seem ideal. I wouldn't go quite as steep as 3.73 though but on a 700r4 the gap between 1st and 2nd is steeper than on a 200r4 so that would help. Sidenote, I have 2,29 in my car with half bald 195/70/14 tires, a stock th350 and I'm at 2500rpm at 65-70mph on an engine with a redline of about 5,500.

I was looking for a 200r4 for that exact reason. But the 700 fell in hands at a really good deal. Built trans with low non racing miles, B&M converter 2200 stall. 200bucks, I had to take it

 

[565bbchevy]

With a 25' tall tire I am guessing that these are low profile mounted on a 17" or larger rims?

 

[Dinosport]

With a 25' tall tire I am guessing that these are low profile mounted on a 17" or larger rims?

There 18's.