Several years ago I was seduced into believing that a 4:10 was the key to rip-snorting power delivery. With a near stock engine, the mix was hardly optimum. Too much noise, shifting more frequently, and an overall sense that the car wasn't quicker or faster anyway.

So, I put the 3:42 back in...until I built the engine with an LT4 heads/intake and HotCam package. Now the power-band moved and I had off-idle performance issues and found the perfect gear in my 3:73.

Add another year, and I was scouting for more power. Having decided it was time for a P1SC and installing. It took about 20 days before my pistons came apart and I was into a full-engine rebuild.

Since the engine was all apart, I decided that a 383, -31cc JE dish pistons and a mild cam were in order. Now the 3:73 is too low and the car years for a taller gear.

So, after 150,000 miles, my axle was grinding and splitting my ear-drums apart. I did a full rear-end rebuild: seals, bearings, new axle and a 3.42 R&P set.

The car is back to stock gears and I love it. I can take 1st gear through an intersection, can wind 3rd to a hundred, and the car feels smoother and quieter. Better gas mileage too!

Gears need to be matched to the engine's design. In my case, the 114 LSA/super charged 383 simply wanted taller gears.

 

Whats your RWHP? I currently have a 383, and am looking to put on a D1SC with about 12 psi of boost (With a custom cam coming, and rest of the motor work, probably between 600-650 RWHP all said and done). I currently have 3.73's in my 12 bolt, but I am wondering with the large power increase I am about ready to change to, if I should bump down to the stock gears or lower? Or (I am sure depending on the cam), should I stay with the 3.73's for a good RPM for the highway? The cam I have right now, is a mild one but the car does't like to be driven in 6th until at least 75 mph. I am just curious to what you think.

 

My car is only putting down ~420RWHP. It is a P1SC with 8#, but the 383 drops the output to about 6# at 5800 RPM.

As for the 3.73 or 3.42, I think your cam has a lot more to do with it, but with my 383, the power band drifted southward and I felt a need for a taller gear. Check with your cam manufacturer and get their take. I am sure someone else might disagree with my selection, but I use my car for the street, not the strip and only occasionally actually blast through the gears at full romp.

If I was to change the cam to move the powerband northward and/or change the pulley or go with a high-boost D1SC, then my gear selection may change again.

 

I sure like my 2.73's (honestly).

 

Again, it will depend on the cam I would guess. The more agressive cams might not like to hold highway speeds at 2k on the tach, they may need 2500, in which I would probably stay with the 3.73's. However, if it didn't mind holding highways speeds at 2k or less on the tach, and it spins the tires still at 80 mph under WOT, then I might drop down to some 3.42's or possibly even some 2.73's. Honestly, if 2.73's would work I would love to have them, that way I could wind out 5th gear, and for track runs, leave it in 4th.