I just pulled the leaky 305 for a 355, it has flat tops, RHS Pro-Torker heads, 1.94/1.5's, 67cc chambers, comp XE-256 212/218 449/454 with 1.6 rockers, ported TPI, stock runners, 24lb injectors and PCMforess tune. It has stock manifolds and y pipe that wont be there for long. The car runs great, its not running to reach/lean and I'm not getting any codes. I can feel a big difference from the 305, its just that I have a 700 with the stock 2.73's in the rear and its still a little doggy, I'm still looking for a rear out of a 98-02 with 3.42's but its hard to find one in my area for a decent price. My question is, is it really going to be that much of a night and day difference? I know the cam is a little small but these gears have got to be killing me. Any input? I've never swapped rear ends so I dont know what to expect.

 

from wht ive heard, yes, it is like day and night. find some 3.73's if you can

 

I believe that low first gear in the 700R4s helps get off the line without having to change to a lower gear in the rear. A real low gear on the street with a fast engine just turns the tires into smoke anyway.

Also, the breakage goes up with a 3:42 or lower gears and our rearends are weak to begin with. I still get consistent 23mpg in mine and I am not nice to it.

 

I would upgrade to at least 3.23s. 2.73s are not quick gears. I'd go even deeper than 3.23s though, they're what I'm running now.

 

Yep. Droping a set of 3.42's in will be like someon droped a bb under the hood when you had your head turned compared to the 2.73's.

 

Yeah the low first gear is nice but the, and bigger tires solve alot of traction issues, 1st to 2nd is a big drop, 3.06 to 1.63 is alot. 3.42's will help mask that. Plus I'm switching to a rear from a 98-02, 28 spline axles and zexel torsen posis that dont wear The LS1 it was behind probably made more power than my 355.

 

Well its kind of an interesting thing. Steep rear ends are usually a big help and there is no question that steep rear ends will allow you to launch harder however there's more to being fast then getting a hard launch. One exception to the steeper rear end is better rule are TPI motors. Because they are such torque monsters they like lower gears as they run out of breath in the high RPMs. Maybe not 2.77 low but 3.23 or 3.42s as a max. Although i have to add if with all your mods your still feeling a little doggy you might have a problem as TPI motors were well known for there great throttle response and peppiness.

 

Dont get me wrong throttle response and torque is amazing, the car runs awesome, its just after first you can feel how ridiculously long the gears are especially with the 2.73's. The nose lifts damn high when in it in first but once it goes from that 3.06 1st to the 1.63 2nd the 2.73's really show there ugly face.

 

Yea thats my biggest complaint about the 700r4 the difference between 1st and second. Ive heard you can pick up about .5 seconds in the 1/4 mile just by switching to a different trans siting the gearing as the reason why. You could get steeper gear it would help kind of but again i wouldnt get too steep as again TPI motors dont run well in the high end.

 

I have a stock 350 with 3.23 gearing. I haven't driven a 3rdgen with 2.73 so can't compare. However my car launches real hard and does good into 2nd & 3rd until it runs out of breath. Most people here seem to say 3.23 or 3.42 are best for TPI.

Are you planning on making more HP in the future? Our stock rear ends seem good to around 300hp and can be built up to 400hp with better splines, girdle, torsion pin, etc. It's torque that kills the stock rear end due to small housing size. Costs around $1,200 for all parts. Stock auto tranny is good to around 350hp. Some people do ok with beefed up engine on stock while others fail. You can build up stock auto but price could be anywhere from $400 to $1,200 depending on if you are doing work or not.

Does your rear end have disc brakes, posi? If not upgrading to 98-02 rear end with those and a better gearing would make sense $$. Maybe you can find a tranny with better gearing from a junk yard car too. If you go 383 engine or bigger, will need new rear end (moser, stange, dana).

Otherwise a new gear set is around $200. Check out this sticky.
https://www.thirdgen.org/forums/tran...ing-axles.html

 

I bought my car with 3.73s in it, n Mine goes like no tomorrow, I ran my uncles ws6 TA(2002) with his "borla" exhaust n hypertech programer and k&n filters n its not even close, he is slower comin off the line n on top. So I feel that the 3.73 is the way to go, but then again i dont know whats been done to the inside of my motor. I have driven my cuzins totally stock showroom condition iroc and it is no where even remotely as powerful as mine so I dont know if its the gearing or motor. will find out this winter when I pull it apart!?!?