What gear to use with the 402/th400??

[gregbr]

Don't understand cam specs or stalls at all. How much does the th350 converter stall compared to a th400. The trans builder told me to use the th350 converter in my th400 for less fluid usage and slightly more stall. Can you explain what my cam is and how the stall would help?

Is going from a 3.07 to a 3.42 rear ratio a big change? It doesn't sound like much as compared to changing from a 3.07 to a 3.73.

['72customdeluxe]

Your cam basically bleeds off cylinder pressure at low rpm, therefore making less power until it revs up. The higher stall converter (an aftermarket 2000-2400, that 350 stall won't do much for you) slips more and doesn't stop slipping at as low of an rpm. So it lets the motor get into the power faster. Get it? That small of a stall will drive almost exactly like stock, meaning it won't just let your motor slip to 2400 rpm going down the road. Here's some good cheap ones.
http://cgi.ebay.com/ebaymotors/ACC-1...Q5fAccessories

http://cgi.ebay.com/ebaymotors/ACC-2...Q5fAccessories

['72customdeluxe]

Also because you said you're not worried about mileage, I would skip the 3.42's and go straight for the 3.73's. 3.08 to 3.42 isn't a very big change.

[capev86]

nothing beats an aggresive rear gear coupled with an overdrive. i planning on going from a 4.57 to a 4.10 on my 72 burb and adding the overdrive unit to the saginaw 3 on the tree. i will have good towing power but with the overdrive and big tires i will be cruising at a lower rpm than all you guys just running a straight 3.08

[capev86]

you could beef up a 2004-R to replace that 400 and it would be a bolt in overdrive replacement. if you wanted to run a 700-R4, 4L80E or allison 5 or 6spd auto, you'd have to get more drastic with a custom length driveshaft! there is also the aftermarket aux overdrive route, but you still have to cut the shaft or get a custom one.

['72customdeluxe]

Originally Posted by capev86

nothing beats an aggresive rear gear coupled with an overdrive. i planning on going from a 4.57 to a 4.10 on my 72 burb and adding the overdrive unit to the saginaw 3 on the tree. i will have good towing power but with the overdrive and big tires i will be cruising at a lower rpm than all you guys just running a straight 3.08

That's exactly my plan. 4.10's and a 2004r. My 3.08's suck on the highway and in town and you can tell the converter still slips even at 2500+ rpm. I used to want 4.56 gears but if I ever got a real motor it would run out of gear in the 1/4.

[gregbr]

Thanks for the great ideas.

[TBone1970]

Originally Posted by Daves72'GMC

I have a 402BB 30 over with turbo 400 and 3.54 dana 60 and an edelbrock cam a little bigger than stock and good on the highway and quick from the start and good milage.

Hello Dave,
I have the same setup in my '70 C20. However, my RPM's get up to over 3K when on the freeway. Where does your truck run for RPM's doing 65?

Would you know how to bring the RPM's down using the same tranny and diff, maybe gearing? Any feedback/input is appreciated.
God bless,
TBone

[CG]

Originally Posted by TBone1970

Hello Dave,
I have the same setup in my '70 C20. However, my RPM's get up to over 3K when on the freeway. Where does your truck run for RPM's doing 65?

Would you know how to bring the RPM's down using the same tranny and diff, maybe gearing? Any feedback/input is appreciated.
God bless,
TBone

Dave hasn't logged in since 2010, he might not get back to you. Pretty old thread. But ... Maybe?