Gearing

[gub]

Right now i have 4:11 gears with a c4 3speed trans.
At around 70mph its revving around 3700rpms-3900rpms.

If i had 3:73 gears, would i be able to go on the highway without stressing out my motor? If so, where would you estimate my rpms at, at 60mph?

thanks

 

[foxbodydave]

you would probably be at about 3 to 3500 rpm's depending on tire size

 

[gub]

wow thats still high, i wanna be around 2k-2500, what gear would be good for that?

 

[foxbodydave]

308 or 3.27's

 

[foxbodydave]

i had a 3.27 and a 5 speed and was still at 2300 on the freeway doing 75mph

 

[gub]

that means ill lose all my take off, huh?

 

[foxbodydave]

yea, you want the 4.11's for the launch. it all depends what you wanna do with the car

 

[gub]

Well also with this setup that i have right now, if im at 40mph and I punch it, then it will stay in 3rd and go from there. i want it to downshift into second if im going that slow. Would changing the gear change the trans downshift?

 

[foxbodydave]

to an extent it might, because itll get the rpms up, but you should be able to downshift on the shifter manually

 

[gub]

Somethings wrong with my trans where it wont go into low anymore. =[ It used to but it doesnt anymore, what could be the prob?

 

[foxbodydave]

lol yea that could pose a little bit of a prob..is it a stock c4?

 

[gub]

yea with the Cruise-O-Matic shifter

 

[foxbodydave]

have you checked your cable? and have you tried to put the shifter in "1" and start?

 

[gub]

What cable? And my shifterhas P R N Small dot then a big dot for drive then it has L for low. ( yea its pretty odd)

 

[foxbodydave]

the shifter cable itself. that goes to the trans.

 

[gub]

Is it hard to find? wheres it at?

 

[Detroit Gearbox]

gub, what type year vehicle is this. it sounds like your decribing a 64-68 ford with a green dot, and they dont shift 123nrp, they shift 1d2nrp

there's lots on on line calculators for figuring gear ratio & engine rpms
Here's one i remember
tire height times pie divided by 12+x
x divided by 5280 = y
y times gear ratio = rpm @60mph

 

[gub]

Yea it is the green dot 1, but for some reason with my low, it only goes into 2nd.

 

[gub]

more help/ input needed please.

 

[Detroit Gearbox]

gub, what type year vehicle is this. it sounds like your decribing a 64-68 ford with a green dot,

a little more vehicle info is need gub. year make & model for starters, type of transmission, floor or column shift? has anyone changed the shifter or type of transmission that in the vehicle? does the shifter handle move into low, or does it stop before it. does the shifter feel sloppy? your problem sound very simple to fix, and odds are its not a internal transmission problem. its most likely out of adjustment or something is blocking the movement of either the steering column linkage or floor shifter.