i am getting rear end gears this spring for my lo3. i was just wanting opinions on what ratio to order. i have some mods done so far and i plan on doing alot more. the transmission will probably come next

 

For a TBI car you cannot go wrong with a 3.42 gear. If you have cam plans in the future and expect 6000 rpm shifts you may wish to consider 3.73's. A 3.42 gets my vote and is a great gear to utilize the low end of the LO3.

 

shifty: i am swapping cam(226/232 @ .05 114 lsa) and i have concerns about my 3.05 gear while cruising at 72 mph at 2000 rpms. i suspect it will surge or exibit some not so nice manners. assuming the car develops max HP at 5600-5800 rpms would the 3.55 be the smallest ratio i should run? my buddy had a bad experience with 3.73 and advises against that ratio? also what rpm do you think i will turn at 72 mph with a 3.55? see sig.

 

What rear end do you have? Is it a 9 bolt? Also tire size, and tranny will ultimately determine what RPM's you will run at. Fill me in on that and I can tell you a good rpm approximation. Or you can experiment yourself and check out the calculations section of this site.

 

if you have an auto you have 2.73s, manual: 3.08, 3.55s are not an option for a 10-bolt. Either go with 3.42s or 3.73s, and if you have a good amount of miles on that rear you might want to get duluxe rebuild/installation kit and youll definately want posi. Since you have a 92, you should definately have 28 spline axles meaning you can use the SLP 4th gen take off posi, they are only $99 from www.slponline.com . I went with 3.73s and i have no regrets, although i have never driven a TBI with 3.42s i cant really compare, but the 3.73s are giving me some nice quarter mile times.

 

this is a vette rear end. i think a dana 36. 1984. 95,000 miles. had only one failure. oil slinger fell off and was riding on pinion shaft making a clinking noise. disassembled inspected and reassembled. that was at 80,000. no other issues. with manual and Z51 i think it is 3.05/3.08. will get build sheet and look up but car in barn. it may even be the 2.7?. but not sure. the 2.7? was the standard issue and the Z51 got a diff gear but eeven that changed 1/2 through production. regardless i am taching 2100 at 72 mph. if i had my druthers i would say 2500 at 72 mph would be my preference. car has posi. keep in mind independent rear suspension. my buddy says 3.55. his 3.73 had anoying whine in both rear ends he tried. both came from supposed qualified rebuilder on exchange. 2nd one on warrenty. same issue. his was a 72 vette.

 

It's not the gear ratio that would make the gears whine, certain gear types are known to whine. Gears also have to be installed with perfect tolerances to keep them from whining. I'm running 3.42's and like them a lot. Correct me if I'm wrong but I think it might be Richmond gears that tend to whine. I bought a 2002 Camaro SS posi unit with the gears on it already off of ebay and it doesn't whine at all at any speeds.

 

Richmonds are known to whine because of the way that they are cut. GM and gmmotive gears typically do not whine at all.

 

my richmonds gears whine pretty loud but im used to it

 

i already ordered the posi and i was looking at a 4.11 gear since i do not do to much highway travel and is not a daily driver would this be to low for my car

 

Yes. That is way to much gear for your 305. Your car will be slower with them. You need to keep your RPM's down low. That gear would have them way out of the power band of your motor.

 

my richmond gears while a little biut whn my foot i off of the gas. they were that way when i had a good shop install them but again thats normal for the matial there made of of but i wont run anything else.

 

ok well just got off the phone with summit and ordered the 3.73s

 

You will be much happier.

 

thanks alot i would have been pretty upset if i spent all that money and went slower