3.91 gears w/ 3.23 speedo

after my trip to a bodies only car b que the total mile on my new set up,(engine, trans, and rear) reached 1024 miles. i have 3.91 gears and my speedo is set up for 3.23 gears. does anyone know the conversion to find out my true mileage. also at 3k and 4k rpms what would my true mph be? also when can i start useing a synthetic oil, or oil additive like lucas in my motor? i plan on doing an oil change this comming weekend.

Tony with 3.91 gears and your 26" tal tires (275-50-15s right ?) you'll be spinning 3278 rpms at 65 mph, 3795 rpms at 75 mph and 4298 at 85 mph.

http://www.quiknet.com/~ke6vut/rpmcalc.html

Your motor should be broken in enough to change to synthetic oil.

why don't you just get the right spedo gear... they are cheap and really easy to install....

Yeah thats what I would do, or should do :D

I would find out wich gear you need for 3.91 gears and G60-15s. They should be the same hieght tire so it should work perfect.

thanks :salut: . do you know where i can find the right speedo gear?

Whats the right speedon gear for a 8 3/4 with 4.56's i hav now a stock open 7 1/4 with 2.73's :scratch:

you are good for synthetic oil now. My builder said after 300 or 400 miles your good for a synthetic.

i changed mine after 600 miles

i had my dart out last night.. it has 245/60/14 tires on it and i was doing about 50mph at just under 3000 rpm. the spedo seems pretty damn close. not sure how accurate the tach is though....

here is a couple charts. the link goes by how tall your tire is and the pic. is tire sizes...

http://www.moparts.org/moparts/tech/pages/speedo.html







http://www.dodgecoronet.com/~abodyjoe/Misc.%20car%20info./spedo%20gear%20chart.jpg

thanks for the charts guys :salut:

Zombie the right gear depends on tire size and gearing.
Becuase 4.56 werent factory offered you"ll need to do some math and figure out what tire size and gear combo will rev like your 4.56s and your gear size.

zombie, if you are going to use those gears on the street you better buy a gas station. it would be cheaper. i get 6 mpg with 3.91's :shock: and if you plan on driveing that to the next car-b que next year from where you live you better leave tomorrow. :D

does that gear just pop in and out of the trans?

there is a single bolt that holds it in... be prepared . fluid will come gushing out if you don't drain the trans.

im most likey going to run a 255/60x15 for her set up or a 245 im not sure yet,my dad had the same set up with the same rear end in the garage he said on high way he was at around 4800-5000 :cheers: :scratch: :salut:

i know this much about my mph

2k in second around the neighborhood
2500 on the highway around my house
and 3000 on the interstate

that seems to get the job done

16dartandbroke, what gears do you have in rear?

3.91 with a 275/60 - 15