Just trying to find out what gear ratio would give me the best performance results from my combo.Don't have the $$ for a nice manual overdrive tranny so I figure I might as well get a rear end to work with my current transmission. Also was wondering if anyone could tell me the different freeway RPMS i'd be turning with the different gear ratios? The rear end will be going along with my th-350 that has a 2500 hughes stall converter. If I left any info out that you need to know let me know.

What engine? Use of the car? How tall are your rear tires? What are your goals? Any other details or mods that have beed made? These things need to be answered for someone to give you a quality suggestion.

Originally posted by camaroman7d:
What engine? Use of the car? How tall are your rear tires? What are your goals? Any other details or mods that have beed made? These things need to be answered for someone to give you a quality suggestion. My rear tires are 275/60/15's, I just would like this thing to run up to it's potential, if it doesn't seem fast enough after that, i'll just have to build another motor. I just know it's not near where it should be considering the hp/tq #'s that have been estimated from this combo. I'm hoping to get it in and have it tuned on a dyno soon also. The car is my daily driver.My engine combo is as follows:

GM 350
9.0 or 9.5:1 compression (might be higher due to switching heads)
trick flow 23 degree aluminum heads
comp cams 268XE
1.5 scorpion anodized roller rockers
performer rpm intake
holley 3310 carb
msd pro billet distributor
msd 6AL box
dynomax cerama coated 1 5/8" headers
TH-350 w/ 2500 hughes stall converter
dual 2.5" exhaust with 2 chamber flowmasters

Well since it is your daily driver, I would suggest 3.42's if you have an 8.5" or 3.55's if you have an 8.2" rear end. That is about as much gear as you will really want to run on the street without an overdrive. If you jump up to 3.73's the engine is going to buzz pretty high on the freeway. I have run them before and that is just slightly to much gear for a true street car (IMO). There are sites that have rpm calculators on them and you can determine how many RPMs you will turn with a given gear ratio. You tires are probably just under 26" tall. Hope this helps.

this was in an earlier post;
http://www.bgsoflex.com/auto.html

I was wondering what kind of difference there would be in ET with 3.42 or 3.55 gears vs. running 3.73 gears. Would there be a performance difference be worth dealing with some more RPMs on the freeway?

Originally posted by Luke805:
Would there be a performance difference be worth dealing with some more RPMs on the freeway? Only you can answer that, really. I personally think 3.73's are the max for daily street use. I don't mind 3000RPM on the freeway, but I only drive mine on nice summer days and I've got alot of "not so streetable" items too.

Figure a tenth or two between 3.42 and 3.73.

You may want to plan ahead for the future. If you can buy an OD tranny later, stick in some 3.73's and deal with it for now. If not, I'd do 3.42s or so.

You will be surprised, the ET difference between 3.42/3.55 and 3.73's is not that big. Of course the more torque you have the less the difference will be. I agree 3.73's are about max on the street without OD but, it really depends on how much highway driving you do. If you are mostly on surface streets and don't take long road trips then 3.73's might be good for you. Just be honest with yourself on how you drive the car and make a choice that suits your needs.

I love my M-20, 3.31's and about 25.5" to 26" tall tires...

I can turn a tire but yet don't buzz all that bad on the highway running 65 to 70 mph..

pdq67

What would the difference in RPM's be between 3.55 gears and 3.73 gears at 65mph if I was running a th-350 and around a 27" tire?

2.73 - 2,208 rpms at 65mph
3.42 - 2,766 rpms at 65mph
3.55 - 2,872 rpms at 65mph
3.73 - 3,017 rpms at 65mph
(Based on 27" tire)

As others mentioned, if you can possibly budget a 2004R in the future then go with the 3.73, else stick with a 3.42/3.55
I have a 3.73 and freeway 75mph speed its burning 3615 rpms with 26" tires!! Not fun, but once I get the car back from the paint shop the next project is a nice BowTie Overdrive 200R4 Level 3 trans.

Ratio calculator used
http://www.idavette.net/tech/ratioc.htm

BowTie Overdrives Level 1 Transmission starts at $866!! (http://www.bowtieoverdrives.com/catalog/catalog.php?Action=GETSUBCAT&CATID=C)