View Full Version : Gear Ratio
11-23-2006, 11:08 AM
Happy thanksgiving all.
What gears would be the best for a 1/4th mile pick up truck out of the 3.42 gears or the 3.73 gears? i have the 3.42 ones just wondering if it would be better if i put 3.73 gears in it instead? because i like my gears alot right now and have been beating other trucks thats have the 3.73 gears? whats the differences betwenn the two?
11-23-2006, 11:33 AM
When you are in OD you want to add the difference in gear to your RPM. For example if you went from a 3.08 to a 3.73 your cruising RPMs would change about 600 or so RPMs. I wouldn't go from a 3.42 to a 3.73. I son't think they is enough gain to be there to make the swap worth it. Unless you are going to add a posi at the same time and needed new gears then I would. I did go from an open unit and 3.08s in a Blazer to 3.73 and an Auburn posi unit. I dropped almost one full second. There is alot to be said about rear end mods. Think about going 4.11
11-23-2006, 11:50 AM
Go with 4:10's!! Likewise 3:42's and 3:73's aint that much of a difference.
11-23-2006, 02:24 PM
what kind of difference am i looking at with the 4:11 gears- compaired to what i have now??
11-23-2006, 02:58 PM
Add about 600 rpms to your cruising speed is what will be affected the most. Take a 4.11 and a 3.42 and subtract the two and that will give you a good idea of what to expect.
11-23-2006, 05:35 PM
yeah but power wise...... will i see a huge increase in speed and power?
11-24-2006, 12:16 PM
You wont gain any power or gain or lose speed at all with a gear change, but your truck will have a greater mechanical leverage than with the higher 3.42 gear.
You will notice higher revs at the same speed on the highway, and acceleration will be more brisk.
I went from 3.08's to 4.10's and surely noticed a difference but it wasnt a crazy big different. I dropped about 2-3 tenths in the 1/4 mile, and also lost about 2 or 3 mph.
60ft times dropped by about3-4 tenths.
City driving is much better, and hills on the highway are a breeze, no TCC unlock or downshift like with the 3.08's. Overall thee truck FEELS lighter and much less throttle angle is needed to accelerate while driving.
With the 3.08's I would trap in 2nd gear at 5500 rpm.
With teh 4.10's I trap at 4800-4900 rpm in 3rd gear.
The fastest I have had my truck was 122 mph which was 4200 rpm in OD with 4.10 gears and a 28" rear tire. I had lots left but the tires I had installed werent in any shape for a top speed run, so I let off.
For drag racing or street driving for that matter I wouldnt go 3.42 to 3.73 unless you broke the 3.73's or got them for free. If I were you I would go directly to 4.10's as they are ideal for the 1/4 mile. 4.10's were a little low for my 28" tires on the freeway however, 2500 rpm only gave me72 mph, 2250 gave me 65mph. I liek to crusie at abot 75 mph and the revs would be around 2600 rpm, tahts just a tad high for my liking. The same 2600 rpm with 3.73's would give me 83 mph, or 2350 rpm for 75 mph with 3.73's and a 28" tall tire.
Its all a matter of preference and exactly how you will drive the truck.
If its primarily drag use, then for sure go 4.10's, and Richmond gears are teh best IMO. I have broken several GM geads and only 1 set of Richmonds. Teh Richmonds finally broke after 4 seperate incidents. the Richmonmd ring and pinion gears digested 1 set of spider gears and 3 Powertrax Lockrite lockers. i simply ground down teh rough edges, reinstalled them and got another 100,000kms of driving out of them. I broke them doing a TC stall test in teh driveway. Best gears I have used.
Here is a nice reargear/tire height calculator that I use all the time.
11-25-2006, 03:05 PM
Take tire height into consideration, and where your particular vehicle makes peak power. I am staying with 3.42's, I run a 27" tire and have a basically stock L05 w/ bolt ons. My Z28 however, I run a 28" tall tire with 4.10 gears, I'm actually considering going up to 4.30's in the future.
The major difference, my L05 is out of breath around 4100-4200, and my Z28 pulls all the way to 7100-7200. If I decide to spray again, I'll have to drop gear in the car.
11-25-2006, 05:53 PM
alrighty, thanks guys... i think im going to keep the gears i have now. Prob in the near future ill get PCM tuned but Ed Wright, after i get some borla headers. well see how it goes.
11-25-2006, 06:47 PM
I would get eitehr 3.90's which I had in my 97 before I sold it or 4.10's IMO
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