wanted know if any one swapped from a 3.42 to a 3.73 and if it was worth it? difference in ET's? 60ft? mpg?

i do a lot of expressway driving im running a 28" tire since i plan to lower the truck 4/6 or lower, last lq4/4l80e truck had a 4.10 and mpg sucked was turning 2800+ rpm any time i was on the highway so thinking of maybe a 3.73 or just keeping the 3.42?

 

I have 3.73s already and want the 4.10. If your going to change it. Buy once cry once. I would definitely look at the 4.10s

 

how much does the race times actually matter to ya? if it's a lot, you'd want to calculate what rpm your trans / diff / tire height puts the motor as you pass through the trap so as to wind each gear out without an extra shift at the end. if it don't matter that much, do what works best for your average driving.

with 28" tires, i don't think 3.42s'd be too bad on the highway. 3.73s'd be a small change to justify the swap unless you're having to rebuild your rear anyway (or at least that's a lot of peoples' takes on it). another factor is where your power band starts... if you've got some donkey-dick cam, you might need 2800rpm to keep it from falling on its face.

 

i'd personally look at 4.11s just due to the strength difference of 10 teeth & 41 teeth versus 9 teeth & 37 teeth in the same size ring.
or at least that's how i understand it... anybody feel free to correct me if i'm wrong.

 

i cant speak for times, but like ive read a hundred times on this site "dont fear the gear". It was always said to me each ratio you go up is roughly 200rpm. So cruise the highway at 70 or 75. However i can speak from experience in my rcsb 4.8 4.10's and 24's i use to have. huge improvement obviously around town and to my surprise turning 2400ish on interstate still managed to get 18.4mpg. 28' tire and 73's might be middle of the road any other mods?

 

im putting in a lq4 with 243's and btr stg2 n/a cam tbss intake 92mm tb hooks headers tru dual exhaust 2600 stall

i just wont do another 4.10 with a short tire, the engine was seeping oil from just about every gasket that was on that engine in my last 04, 80mph was 2800/2900 rpm just to high when your doing 100 to 200 miles a day

no plans on rebuilding the diff just adding a auburn unit, if i do swap gears id rebuild it tho, et's are important to a point this will be my daily so that has to be kept in mind, just really be a street with a little heat under the hood for a fun truck

the reason im asking i was running 3.73 in my c5 zo6 had it down to RPM trans for same day service they found i wore the splines on the output shaft and pinion only thing they had on hand was stock 3.42 or 3.90 i picked the 3.90 and it made a huge improvement from the 3.73 so wanted to see if going from 3.42 to 3.73 is kind of the same?

 

the M12 gearing in the Z is wildly different than your 4L60 regardless of almost running the same size tires (i'm running 27s on my C5) and having 1000lb more to lug around, so it won't have as much seat-of-the-pants feel... but it'd still give you more mechanical advantage. the question is how much it's worth to you. with your short tires, you're still gonna jump about 200rpm @ 70 going to 3.73s (2000 vs 2200) and 80 = 2500rpm (vs 2300 now). but based on my 5.3 with the BTR Stg3 truck cam coming on around 1800, your smaller cam in a bigger engine should do fine either way - especially with the looser converter. by my uneducated guess, it sounds like to have your cake & eat it, too, you're better off keeping the 3.42s with the stall (but take it with a grain of salt... i'm a stick-shift guy).

 

truck has a 80e swap already should of mentioned that i guess

yeah i drove my z daily weather permitting (winters suck here) for a few years just got tired of being in traffic with it thats the reason i actually bought this truck as a daily

not running the truck cam its the sge2 ls1/ls2 cam 227/234 .614/576 113+2, the heads and cam im using is what i was using in my ls6 it put down 475/415 wheel n/a, pulling the ls6 for a 416 so since i have them just going to put them in the lq4, its not the best choice for the truck but its not costing me any thing to use them hoping to make 380+ hp 350+ tq @ the wheels. in the car power came on around 2500 rpm not sure what its going to be going true the 80e thats why im wondering about the 3.73

 

 

the heads are tsp prc cnc 243 2.5's like i said i have them on hand so on they go, like i said i know its not the "best" setup but its what i have to work with down the road a few years id like to turbo the truck so if i did it would all get changed. my last truck was around that rpm with the 4.10 around 80mph not wanting to go down that road again