ok.. i just got my trans completely rebuilt including a few hardparts... and now it looks like my cars gonna be down a little longer than i wouldve liked because of an incident with a state trooper while my Z was in the shop.. slower car = bigger ticket.. go figure... anyway point is while its in the shop and my license in danger i figure maybe go ahead and upgrade to a 3.73 rear end gear i think i have 3.23 right now but is there any way i can tell for sure from the VIN without the car since its in the shop and i cant go under and turn the driveshaft to find out =/ and also if i have 3.23 is it worth upgrading to a 3.73 for a usually street driven car with the occasional race on the strip?
and if it helps any its a 94 Z28 with a Zoom performance rebuild kit and upgraded sprag gear bands and servos.. and an experimental valve body (long story dont ask ) but more to the point should i wait and see how the car does with the new trans before i put in 3.73's or just go ahead and drop em in while its still in the shop because soon as i take the car out of the shop its straight to my garage to put in a trans cooler anyway

thanks in advance for all the help and info
RT04

 

You can not use the Vin number for finding the gear ratio or any other options. Only the RPO's numbers can help.
With your description it would be hard to say what rear you have,,,2:73 or 3:23????? And you could be guessing wrong.

 

turns out i do have the 3.23, i figured i did just from how the car felt off the line... anyway is $600 for 3.73's bought and installed a good deal? 400 for the gears and 200 for labor... of course thats with the knowledge its being done right because its being done by the only mechanic i trust around here lol

but how streetable is a 3.73 4l60e as far as interstate trips and such.. i make a few 20+ mile trips a few times a week on the interstate, just curious how big of a difference it would make at 70+ interstate speeds...

 

You still don't really know what ratio you do have (guess 3:23)??
However; the gear choice is up to you, I would not spend the money.
Travel on the interstate with 3:73 @ 70 =2500RPM's vs 3:23 @ 2100. This without knowing all the facts about your car.

 

I paid 400 for my install so yea i guess it is.....then again it was DTS--specialty shop.

 

The local chevy parts guy told me my rear end rears from my VIN??

 

You know why... He plugs in your Vin number into the computer and calls up the all RPO's that were installed on your car. That how he does it, not by the VIN alone.

 

no i didnt guess, the guy workin on my car checked it out for me, it had 3.23 rear end so i decided it was good enough for me and not worth $600 for a car mostly driven for street use... but now with the car back im glad i didnt because the new trans throws teh rear end in the air in every shift 0_0 barks second easily around 3k at half throttle... best shiftin 4l60e ive ever seen lol now if i just had the comp programmed to set the firmess all the way up like an hpp3 does... wow.. anywayz thanks for the advice everyone
next step finish the appearance mods while i wait on the motor to go so i can rebuild it like i want it

 

that shift firmness that u did, u really need to take that out. u r just gonna burn up ur new tranny in no time. if u put a shift kit in, that is all that u need. i am sure plenty others that know , will back me up on this one.

 

i havent done it yet, but what does adjusting teh shift firmness in the pcm do? as of right now 4k and below shift HARD but after that it still feels like the pcm is holding it back some, in other words.. itll turn the tires over from 1st to second at any between 2-4k but at WOT shift at 5850 rpm it just shifts like it use to... thats why i was thinkin about the pcm, because i remember people talkin about getting a bark from 1st to 2nd at wot with that im really happy with the new trans though, i can feel it grabbin a lot harder in just normal driving in gear even, leaves the line a little harder now too, so apparently the trans was gone when i got it =/

 

yea, well, after trying to decipher all that was written, you really do need a shift kit
increasing line pressure like a hpp3 does nothing but hurt the tranny
put a shift kit in and have a blast- safely

 

you didnt decipher it too well then :-p

i already HAVE a shift kit 1 inch larger clutches for each gear stronger sprag and a new piston to press it all in, along with all the other goodies of a complete rebuild, and the shift kit is in very well because i get a tire chirp from 1st to second gear EASILY at mid rpms, but WOT it just acts similar to how it ddi before, except it doesnt bounce off of the rev limiter =/ it shifts well at wot it just doesnt shift anywhere near as well as it does at mid rpms with ample throttle it still feels like the shift points are set too high to me i mean cmon how do you get a strong chirp at mid rpms and the car doesnt even hop forward at wot?! i shouold just stick wiht the good ole th-300 and 400.. so much simpler to get them to shift hard and fast everytime ..

 

ok, didn't decipher it well enough i see

yea, but what's your shift points set at and what is your car specs?
it does though sound like your shift points are set high

 

mostly stock except k&n intake and the rebuilt trans, i dunno exactly where theyre set but its right at or after redline, and i can tell its not shifting anywhere like it does at mid rpms, wot shift is like it just... i dont really know how to explain it but it shifts sorta like it would with stock parts and no shift kit, just slow and smooth... it makes me mad because i know its getting plenty of power and is one of the best shifting 4l60e's ive ever seen. but still no good wot shift... normal driving like 1/4 throttle maybe it shifts around 3-3.5k that sound too high? my moms 87 pro/am shifts at around 2500.. it may just be that im comparing to something completely different but 3-3.5 sounds waay to high for normal driving... and 1/2 or beyond is redline shift or just under it, seems to me like just before wot it shifts perfect.. thats another part of why i was considering 3.73 to keep it around that perfect rpm.. well thx for the help

 

yea, can't really help you
but normal driving it seems like it should be shifting much sooner than 3500 rpms