Thinking about 4.10's

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plumkrazee70

plumkrazee70

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Hi everyone. I have a 70 dart with a 340 and a A500 (42rh) OD trans. I have been playing with the rpm calculator and with my 25" tires and a final drive of .69 at 65 mph, rpm sit at 2400.

I know I will eventually step up to a 27" tire,which drops the rpm to 2200. My question is that too low?

My cam is a 340 stock replacement with a duration of [email protected] on a 110 LSA, with an operating range of 1500-5500 rpm.

The intended use for the car is a fun driver.
 
What do you have for gears now?
 
You would be happy with 4:10 and OD. I run 4.56 with 833 OD. A bit steep but its still ok on the highway
 
fklskv said:
You would be happy with 4:10 and OD. I run 4.56 with 833 OD. A bit steep but its still ok on the highway
Click to expand...

Thanks, I think I will be happy also. I just thought I read somewhere that you have to take into account your cam range and final drive rpm.
 
plumkrazee70 said:
Thanks, I think I will be happy also. I just thought I read somewhere that you have to take into account your cam range and final drive rpm.
Click to expand...
No! Not to low.
You'll like it A LOT!
You forgot to take into account the converter slippage. But don't worry.

That cam duration is slated to start making power right about at that cruise rpm you listed with the bigger tires. You'll be OK.
 
rumblefish360 said:
No! Not to low.
You'll like it A LOT!
You forgot to take into account the converter slippage. But don't worry.

That cam duration is slated to start making power right about at that cruise rpm you listed with the bigger tires. You'll be OK.
Click to expand...

Thank you! Getting excited to get the body work and paint done so I can put this thing back together.
 
No, none at all.
Well, maybe excessive tire smoke issues. This may cause a lighter weight wallet.
There's also the real possibility of doctor visits because of pain in the jaw/face from prolong smiling.
Do be notified that your local police department may have you pay an extra happiness tax for speeding. I know that one allways sucked to donate to. But it happens.

Remember to get a new speedometer gear for the larger tires based on a 1:1 ratio with the 4.10 gears.
 
rumblefish360 said:
No, none at all.
Well, maybe excessive tire smoke issues. This may cause a lighter weight wallet.
There's also the real possibility of doctor visits because of pain in the jaw/face from prolong smiling.
Do be notified that your local police department may have you pay an extra happiness tax for speeding. I know that one allways sucked to donate to. But it happens.

Remember to get a new speedometer gear for the larger tires based on a 1:1 ratio with the 4.10 gears.
Click to expand...

Thanks so much! I forgot about the speedo gear. I will have to add that to my list of things to get.
 
plumkrazee70 said:
Thanks, I think I will be happy also. I just thought I read somewhere that you have to take into account your cam range and final drive rpm.
Click to expand...

You mainly have to worry about cam selection when you go higher gear, lower gear like 4.10 will work with any combo.

I'm running 4.10 w/ 28" tires on my 727 & it's a daily driver, you'll be fine for sure on a fun driver w/OD & 4.10.
 
Thats a great gear with an overdrive. I know this isnt a Mopar but my 72 vette has an OD trans and I run 4:10's and its a lot of fun in town or on the highway. I can run 70 at just around 2500 RPM's. When in town i never go into OD. To me its the perfect gear. Go for it! As was said earlier the smile will never come off your face! Best of luck.
Rod
 
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