Thread: gear help

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i just did a search and could not find the thread im looking for , i think denny did the post, basicly im looking for the rear gear formula, i just did the tire turn trick and came up with i 3/4 driveshaft turns to 1 tire turn, what ratio does that give me?, im running a th350 with p215/75/15 tires and getting about 65mph @ 3000 rpms, i want more speed at less rpm`s

Originally Posted by hotroddaddy

.. getting about 65mph @ 3000 rpms, i want more speed at less rpm`s

Try going down hill. Stick in neutral and coast. I have gotten as much as 70 mph @ only 1100 rpm.

You are a funny man, unfortunatly i live in florida, flat as pancake

Originally Posted by hotroddaddy

I just did the tire turn trick and came up with 1and3/4 driveshaft turns to 1 tire turn, what ratio does that give me?

You will have to try it again. This time just roll the car on the ground. Start with the valve stem at the bottom and go one rotaion of the tires. Or else mark a tire with chaulk and go one revolution.

If you do it in the air, the tendancy is for one tire to turn in reverse while you are turning the other forward so it really doesn't work unless you can brake the other wheel. Or else you have to multiply by two. My guess is that your 1.75 turns is actually 3.5 which means you have 3.50 gears.

Originally Posted by hotroddaddy

i just did a search and could not find the thread im looking for , i think denny did the post, basicly im looking for the rear gear formula, i just did the tire turn trick and came up with i 3/4 driveshaft turns to 1 tire turn, what ratio does that give me?, im running a th350 with p215/75/15 tires and getting about 65mph @ 3000 rpms, i want more speed at less rpm`s

thats a 1:75 ratio hotrod. dont believe thats what it is.
try this.



http://www.4lo.com/

i only jacked up 1 side, then put it in neutral, left 1 tire on the ground, started with the valve stem on the bottom then spun it till it was back on the bottom, drive shaft spun not quit 2 times

Originally Posted by hotroddaddy

i only jacked up 1 side, then put it in neutral, left 1 tire on the ground, started with the valve stem on the bottom then spun it till it was back on the bottom, drive shaft spun not quit 2 times

if you want to go about 150 mph thats a good gear. if not the drive shaft should turn at least 3+ times

Here's the diffrent calculators I've been using that are pretty user friendly.

http://www.mustangii.net/tech.asp

Look in the calculators section and click the gear calculator (the RPM and tire diameter calculators are fun to play with too).

You will need to know tire diameter, RPM and speed to figure the ratio.

i did the calc it said the ratio is 3.640

If you don't know what gear it is, how can you be sure the right spedo gear is in the trans, would not count on the rpm/tire size calc. If you turned the wheel once and counted the turns of the shaft then 1.75 x 2 = 3.5. As stated above. At least that has worked for me on several ocasions.

Originally Posted by DennyW

Not by what you said in your post.

The rim is 15 inchs, the tire height is different.

http://www.miata.net/garage/tirecalc.html
27.7" tall

Yeah, nothing is matching up, according to the numbers its a 3.73 at that speed and rpm but if it turned 1.75 you would think it was a 3.5. Maybe the spedo gear is off too.

3.356, i did 47mph @ 2000rpm, tires are 26.5, so if i replaced the rearend what would you guys recomend looking for , oh its a chevy 10 bolt by the way

thanks guys, i know theres a post somewhere that explains all this i just couldnt findit again, i just want to travel down the freeway at decent speed and not running at 4grand, i dont really care if i spin the tires or not, although it really lights em up now