New2Chevy

iTrader: (11)

Hey guys.

How much of a difference will I feel when I swap the gears from a 3.27 to a 3.73 in my 350 tpi IROC?

Will it be a noticeable difference?

Worth $700-$800 to have a shop do it??

New2Chevy

iTrader: (11)

Anyone??

New2Chevy

iTrader: (11)

Anyone?

//<86TA>\\

iTrader: (14)

you will notice a difference, it wont be earth shaking, but it will be there. 800 bux, i dont think its worth it. If yolu could do it yourself and just farm out the work involved in pressing bearing on and off, then thats a different story.

For that matter, you could but a complete rear with 3:73 gears for less and just sway the whole thing. Maybe upgrade to a 4th gen rear, get a better posi and better brakes at the same time, though you will probably only get 3:42 gears, but they are a good choice too

New2Chevy

iTrader: (11)

Hmmm....maybe I should just go with the 3.9 gear, rather than the 3.73. I mean, my Borg Warner 9 bolt should hold up to the mods I am doing, which won't bring the engine over 450 hp.

89IrocZ350TPI

are you ditching the TPI?

New2Chevy

iTrader: (11)

No, I am not ditching the TPI.

I just figured it would be a good idea to change the gears to get more "oomph" on the street.

SDIF

I don't think you will like the change.

The TPI is rpm limited in the power band.

If the engine made more power higher in the rpm band ok. But this one does not.

There have been post on this before.

I would not recommend it.

New2Chevy

iTrader: (11)

I'll reach the rpm limit too quickly or what?

If so...

What about with a HSR and Vortec heads (and new camshaft)?

Cuz that is my plan for mods.

REDTAIL

iTrader: (1)

I hope you know how to tune with a laptop with those future mods


personally I couldn't really tell much of a difference with my rear swap but I never tried to see what gears I had in there. I had bought the rear to go into my old RS but wrecked it before I had a chance to put it in. The only reason I swapped rears into the iroc was for the limited slip and rear disk brakes.
but remember most people will never be content with there performance and will want more power (like me). so if your planning on keep building your car up you may want to look into a stronger rear end all together i.e. ford 9" or a chevy 12". although there are some stock rears out there that can handle 10" slicks at a full throttle launch and there are others that have broke with normal driving. also $700-$800 for a shop to change gears seems a little pricey after all i think i paid around $300 with shipping off of ebay. but this just my .
one other thing that most people on this board will say is get rid of that forth gear WOT lockout

89IrocZ350TPI

3.73 is too much gear for a tpi intake. Look into some 3.42's.

84ls1_transam

Swap to an LS1 with a T-56 and 4.10s, then add a 300 shot zex direct port like I did. You will feel that difference.

afremont

I hope you have good brakes, gawd that must be fun to drive. I'm not into bottles personally, but still...... Do you actually ever use first gear?

84ls1_transam

LS1 brakess all the way around. Drilled and slotted. It is a really fast and fun car. I have only let one other person drive and he says drives like a newer car. He was supprised. I use first gear to get moving. I love the 2 overdrives though. What a sleeper the car is. Without the loud exhause no one would know. Even still, most people think it is a just a 305 with pipes. I was never really a fan of the bottle either. I don't if it was because I thought it was bad for it or what. But now I love it. You go through it like candy though. I'll send you some pics. I'm now done with it yet. Paint next year.

afremont

I'd like to know what "newer car" he drove that ran like that. Is he a NASCAR driver? ;-)

89IrocZ350TPI

What times are you running with an Ls1 and the 6-speed? I would think a mid 12 with slicks wouldnt be out of reach?

New2Chevy

iTrader: (11)

Ya think??
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OK, to get back on topic, what if I go with the Holley Stealth Ram and Vortec Heads with a cam?

THEN would the 3.73 be a good idea?

84ls1_transam

He just means it is really smooth and feels like a 4th gen more that a 3rd. Not power wise.
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I haven't taken to the track yet. Too many little things to finish up first.

84ls1_transam

I think gears all depend on what you are looking for. If you want good accel, go with a 3.73 or 4.10. If you want good top end, go with a lower numerical number. I had a carbed 350 with a 700R4 and the 4.10s and it was fine. Highway gas milage wasn't great. I'm thinking about 4.56's now.