rear end and trans rebuild

[ronscuda]

I am looking to rebuild my rearend. I believe as it is now it is an 8-3/4 4.56 gear with a spool in a 742 case connected to a 3-speed trans. I would like to make it more driveable, I am wondering what set-up someone would recommend to make it more streetable. I am afraid to go all the way down to a 3.55 especially if i wont be able to do at least 70 under 3000 rpm's, really afraid to lose any performance. Does anyone have a 3peed setup and can tell me their gear size and the top speed around 3k.i also want to get rid of the spool does everyone say go with a suregrip (probably not a good question to ask) or does anyone run a detroit locker, or Auburn Gear locker, if so what do you think.also am rebuilding the trans (727 torque flight 3 speed ) i won't be doing this myself as it is beyond my skill level does anyone have any tips i should know just so i have something to go off of when talking with the transmission guy. or does anyone live in the detroit area that has recommendations i can check into. Thanks for reading this extremly long post

 

[74 challenger]

I was told the 3.91 gear set up was the best set up for driving and jumping on it. 4.10 and your whining out on the express way.Never had the chance to try it.Good luck and let us know what you go with.

 

[moparleo]

Dump the spool.

 

[moparleo]

3.91 great for off the line accelleration. Around town driving only, unless you have overdrive. 3.54 much better for all around driving both on the hi-way and the street. Type of suregrip depends on what you plan on doing with your car, street or strip. Spools are for the 1/4 mile only. Check with DetMatt1 on local Detroit area contacts.

 

[ronscuda]

Thanks for replying guys.i appreciate the info. I plan on making my car street but I don't want to get walked on if I decide to step on it

 

[moparleo]

performance calculators

http://www.wallaceracing.com/tire-aspect-calc.php

http://www.wallaceracing.com/calcmph.php
:3gears:
http://www.wallaceracing.com/calc-rear-tire.php

:read2:If you use these calculators, you will find that a 28" tire, 1:1 final trans ratio and 3.54 rear gears will give you about 70 mph @ 3000 rpm.

Just insert data for tire diameter, punch in final drive ratio, which is 1:1 unless you have overdrive,
then add the speed you want to give you the rear ratio to get that number.



These calculators should be in everyones saved folders.

 

[ronscuda]

Do you think that a 3.54 will still have a good launch to it or will it not have enough to leave a couple strips in the road. i think i am leaning toward a 3.73 probably from moser. what are thoughts on a gear manufacturer

 

[moparleo]

What engine/horsepower are you using ? If you just want to burn rubber, put some bald tires on it.

 

[moparleo]

The most important decision with the trans will be the stall speed of the torque convertor. Which will depend on the weight and gearing of the vehicle. The the engine torque curve etc... The reason you go to low gears(high numericaly) is to turn the tires at a low wheel speed to keep from breaking the tires loose. People that burn rubber, lose races. Burning rubber just means you are not getting any traction. For longevity you want to keep rpm's below 6500-7000 rpm for a street motor unless you like rebuilding engines . Put a line loc on it and you can burn rubber any time you want from a stop.