Alright, my GTA pulled a 14.6 totally bone stock. Now if I upgraded from the factory 2.73 gears to 3.73 gears from a same year Camaro, what kind of change in my quarter miles time can I expect? If I look for a used set of 3.73's exactly what parts do I need for a complete swap?

I already have the part numbers for the gray gears for recalibrating the speedo but I don't even want to bother with the swap unless I'm going to pick up like a half second or so....

Thanks!

Alex

 

I'd opt for 3.42s. You'd definately drop some tenths with that. I'd think with a stock TPI intake, even with the SLP runners, you'd be revving out of your power band with 3.73s. At the MPH you ran in your sig, you'd already be turning 4800 rpms with 3.73s.

 

Same here, go for 3:42s it will match your powerband better. With those expect to knock off .4-.6 in the 1/4. I went from 2:73 to 3:73 and didn't gain anything cause I mismatched my gears to my powerband.

 

3.42's it is then!

So anywhere from a .4-.6 of a gain huh? Good, that's about what I was hoping for....

 

Shouldn't your car have 3.23 now? If so I don't think you'll be seeing those gains going to a 3.42 ratio but if you got 2.73 I say go for it.

 

Hey -

I have an 88 Formula 305 TBI 5-spd, and 3.08 gears.

I have sitting in my garage, 3.73's waiting to be put in. Did I make the same mistake??? Or is my powerband different than yours???

Will these gears help me for .4-.6? Will they help me at all???

My car's barely modded at all ... check the sig.

Kzad

 

Good point, I was referring to if you had 2:73s

One thing to remember when picking gears, look at the specs of your cam and find it's power band. A cam that doesn't make power past 4500 rpms won't do good with 3:73s.
That's for 1/4 wise though.

If you're interested in stop light racing or distances shorter than 1/4 mile then this doens't really pertain to you.

 

Yes, your powerband is different. TBI power band is a little easier to stretch, not to mention a lot cheaper. If his TPI is stock, it probably runs outta breath around 4,500 rpm. It looks as though your engine probably falls into the same range though, depending on how much your open element did for you. IMO, go with the 3.73's as long as you plan to further mod your engine, i.e. intake manifold, headers, cam; or if you just like to race from street loght to street light. If you aren't planning on any future mods and are purely looking for quarter mile times, then go with numerically lower gearing, like 3.42s. In any case, I'm guessing you don't have a posi, which will complement gears greatly. A posi combined with gears may get you .5 seconds off the e/t (from what I've observed), and is usually the biggest SOTP gain for the $$$.

 

In most cases these rear end gear changes do not help more than 2 tenths maximum in most cases, I have seen 3-6 tenths drop with the right torque converter. Depending on what kind of driving you do, will determine the rear end gear ratio you need. I would do the TC first, unless you already have the rear end gears now. Check around to verify what I say is true.

 

r90-

My 373's that I have in the garage ARE posi. That's one of the main reasons that I purchased them.

Pro Built -

I may be mistaken, but I have no TC considering I have a Manual Transmission, correct?

Thanks for you help...

KZad

 

KZad,



No you do not have a torque converter. Where(rpm's) and when you let off the clutch is roughly the same principal

As far as your 3.73s go, I hope you mean that you have a new posi differential as well. It is not the gears that are posi.

As far as e/t times go, from reading the TBI board, most experiance between .3 to .5 of their times with new gears (usually 3.42s or 3.73s)