posi ?

mixedbreedx · #1 03-03-2004, 01:09 PM

what is a posi rear? I don't know much and I hear it alot, but I don't actually know what it is, or how the different size gears help. Could someone explain this for me?

fritcr · #2 03-04-2004, 08:33 AM

Basicly speaking when you have a positive traction rear end that means that when your car starts to loose traction with one wheel then it puts traction to BOTH back wheels at the same time. My 96 TA has a posi track and when I punch it from a stop both rear wheels/tires lay rubber. It also likes to get sideways in the road if your not careful. The advantage is of course...better traction from a stop. A side advantage is if it don't start sliding you get better traction in the snow and wet too. Hope this helps a bit. I don't know a lot about the gears but this can change the ratio so that your car might be quicker with one rear end gear ratio than another that might make your car go faster on top end.
Rob

Jm93 · #3 03-04-2004, 07:12 PM

He explained posi well.

the gears are well, for different uses.

For example, a 4x4 jeep made for offroading may use 4.10 or higher. higher the gear, less top speed, more acceleration and low end power
a dump truck, same thing, high gear
a 6000 hp funny car, obviously a low gear.

understand? it also affects gas mileage. if your car had 2.73's and you got 40 mpg on the highway, now you swich to 3.73's and youll get maybe 30. this is because of the rpm's in top gear. with 2.73's say your rpm in top gear (overdrive in most cars) is 2000, with the 3.73's it will be more like 3000. therefor burning that much more fuel.

95fbird · #4 03-04-2004, 07:24 PM

where exactly could you go to buy a posi... would jegs have it? and what kind of price range is it in?

mixedbreedx · #5 03-05-2004, 10:36 AM

very helpful, thanks

violator6090 · #6 03-09-2004, 08:42 PM

anyone here know if i have 2 series or 3 series carrier in my 98 Trans AM automatic. 2 series has 2.73 gear and 3 series has 3.23 gear stock. at 60 mph cruising my rpm are at about 1700 so maybe that would give you some idea

tomminajar · #7 03-11-2004, 07:22 PM

Quote:

Originally Posted by violator6090

anyone here know if i have 2 series or 3 series carrier in my 98 Trans AM automatic. 2 series has 2.73 gear and 3 series has 3.23 gear stock. at 60 mph cruising my rpm are at about 1700 so maybe that would give you some idea

Ummm Make sure the car is NOT in over drive (you would have about 1.48 gear ratio)

this should help you out...
http://www.dodgecharger.net/tech/RPM...alculator.html

violator6090 · #8 03-11-2004, 10:13 PM

how exactly would my car not be in overdrive its and automatic and theres no over drive on or off mode
also what is the width of 98 trans am tires

tomminajar · #9 03-11-2004, 11:19 PM

You should have "P R N D 3 2 1" ON your SHIFTER"or maybe a "D" with a circle"O" around it and a plain "D"---3 or plain D is 1:1 ratio while the O-D is overdrive -You need diamter of tire not the width R16 or R17 =16' or 17'

Hope that clears it up - post w/any more questions

violator6090 · #10 03-12-2004, 10:09 AM

ok so i did it in gear 3 instead of D cuz i dont have the O-D and crusin at 60 mph my rpm was at 2400. im still not sure what my diameter of my tire is so i just put in 20 and that gave me 2.81 gear. so im assuming i got the 2.73

tomminajar · #11 03-12-2004, 01:54 PM

Quote:

Originally Posted by violator6090

ok so i did it in gear 3 instead of D cuz i dont have the O-D and crusin at 60 mph my rpm was at 2400. im still not sure what my diameter of my tire is so i just put in 20 and that gave me 2.81 gear. so im assuming i got the 2.73

http://www.dodgecharger.net/tech/RPM...alculator.html

go to that page and enter the number from your tire side wall such as
"195 60 R16" To calculate you diameter- its half way up the page...
Calculate Tire Diameter
Tire width - Series - Wheel Diameter
Example 275 - 60 R 15
Tire Width
Tire Series
Wheel Diameter

Tire diameter in inches

Then go to the end of the page and punch in your info for gear ratio
"this is approx doubt the factory tach is "right on"""

Let me know now I'M curious.....

violator6090 · #12 03-15-2004, 12:47 AM

well...i couldn't find that number you told me to look for on the tire but i assumed it was 27. i drove my car in 3 since my car automatically goes into overdrive in D and my rpm were at 2400 at 60 mph. i put those numbers into the calculator...(27 diameter 2400RPM and 60MPH) and it came up with 3.21...which would mean i have the 3.23 however i dont know if driving in 3 is the reason. what do you think?

violator6090 · #13 03-15-2004, 12:52 AM

then again when i assumed the tire diameter was 23...i came up wth 2.74 so yea this is a pain in my ass

DrivinSidewayz · #14 03-15-2004, 02:06 AM

your 98 has 245/50/16 stock, stock tire size is about 25.5 inches,

and you can hold your tranny in 1st(you said there is a 1 on your shifter), indicating that you indeed have the 3.23 gear out back

tomminajar · #15 03-15-2004, 12:00 PM

Quote:

Originally Posted by violator6090

then again when i assumed the tire diameter was 23...i came up wth 2.74 so yea this is a pain in my ass

Pain in the ass? You can also pull the diff cover off and count the ring and pinion gear teeth and divide . Or look on the axle housing tubes and scrap all the rust of and look for the axel number . Trust me this is a LOT less messy (P.S. you could also pull up the drivers side back seat cusion and under it SHOULD be a build sheet telling you EVERYTHING you would want to know about the car All options) I think that where they usally are....

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