where can i find a calculator that will tell me how far the rpm's will drop on a shift? i found a few but they don't take into count the rear ratio. does this not matter? we are trying to figure out what gears to put on the 4.3L truck. its turbo'd and when he shifts the rpm drops pretty far down and the turbo looses boost. and when its below 2000rpm while cruising it doesn't like it too much so it needs gear to hold it above 2000rpm for cruiseing at 70mph.

 

There is no exact calculator because of the converter slip. I would suggest getting a higher stall converter though. That will allow you to stay in the power band much better.

Chris

 

sounds like you need a converter, not gears

 

my bad guys i thought i posted it. its a nv3500 5spd stick.

 

Try this...

http://www.f-body.org/gears/

 

Sorry about that, I just assumed. If you changed to an auto it would solve the problem, just a thought

Chris

 

i said the same thing but he like the 5spd.

 

Get a BOV on there if you don't already. That will help between shifts. Also what gear ratios does the NV3500 have that the rpms drop below 2000rpm after a shift. Is he short shifting or something? I say get a BOV, do the drill mod, get a short throw shifter and powershift the SOB. Then look into changing gears.

 

Well, I use these for the nv3500 and they seem to be pretty accurate... My truck seems to hit a brick wall in 3rd gear til it wraps back up into the 3500 range...

1st- 5.61
2nd- 3.04
3rd- 1.67
4th- 1.00
5th- .75

 

You could use the calculator that was sticky'd at the top of this section and then change the gear ratio's. That will tell you what speed and rpm you are at in each gear so you should be able to determine where you will be on the shift based on that.

https://www.performancetrucks.net/fo...d.php?t=396210