Best highway RPMs on an LS3?
02-05-2021, 09:44 AM
#1
Best highway RPMs on an LS3? As the title states what is the Best Highway, RPMs for an LS3 with a 4L70 transmission? I have installed this in my 1970 two Wheel Drive Blazer. I am running 275 40 20 rear tires at a height of 28.5”. I presently have 3.08 rear end gearing in an open differential. In the future I plan on installing a true track Posi traction unit. The online calculators say with 3.73 gears I would be running at 22XX RPMs and with 4.11 the RPMs would be 25XX at 75 MPH. I will not drag racing or auto crossing but I am just wondering what would be the better RPMs out of those two? I am open to other suggestions. I might possibly go with a slightly larger tire in the future. Maybe an inch? The online calculators did not show much of a difference with that small increase.
02-05-2021, 11:19 AM
#2
TECH Senior Member
You looking for fuel economy or just not winding too high? My stock Tahoe runs at about 2000rpm at 70mph with 3.42 gears (stock) and 275/55-20 tires (OEM size).
02-05-2021, 01:25 PM
#3
Do you tow at all with the truck? That will help determine what you need, FWIW my L92 in my T56 TA likes to be anywhere between 1700-2000 but there is obviously less drag/weight with my car than your truck would be so maybe shoot for 2000-2300? Unless towing then I'd maybe try for 2200-2500.
02-05-2021, 01:27 PM
#4
Every engine has a sweet spot where it is not revving to high and not working too hard. Just wondering what that sweet spot is. With that being said it won't see a lot of highway time. Building for me to keep forever.
Some pictures from today.
Some pictures from today.
02-05-2021, 01:28 PM
#5
No towing, just purely a "fun" full convertible truck!
Do you tow at all with the truck? That will help determine what you need, FWIW my L92 in my T56 TA likes to be anywhere between 1700-2000 but there is obviously less drag/weight with my car than your truck would be so maybe shoot for 2000-2300? Unless towing then I'd maybe try for 2200-2500.
02-05-2021, 05:44 PM
#6
TECH Fanatic
iTrader: (7)
Wow...some nice parts in your build.
That being said, I ran a 5.3L/4l60e 3.73 28" tire combo in my wagon before I went to a T56. I thought the 3.73's were a great gear with that combo...
That being said, I ran a 5.3L/4l60e 3.73 28" tire combo in my wagon before I went to a T56. I thought the 3.73's were a great gear with that combo...
02-07-2021, 11:38 AM
#8
You're not commuting in it, and if you tow it shouldnt be in OD. Gear it on the deep side so its not sluggish with big tires. If it were mine, id want improved throttle response from a deeper gear in a "toy"
for reference my daily is a stock 4x4 silverado 5.3 3.36 gear, great on the highway 2000 rpm at 80mph, but pretty doggy at a stoplight. Loaded trailer in third gear 25-2600 rpm, 75-80 mph, and it loves it.
for reference my daily is a stock 4x4 silverado 5.3 3.36 gear, great on the highway 2000 rpm at 80mph, but pretty doggy at a stoplight. Loaded trailer in third gear 25-2600 rpm, 75-80 mph, and it loves it.
02-07-2021, 01:40 PM
#9
You're not commuting in it, and if you tow it shouldnt be in OD. Gear it on the deep side so its not sluggish with big tires. If it were mine, id want improved throttle response from a deeper gear in a "toy"
for reference my daily is a stock 4x4 silverado 5.3 3.36 gear, great on the highway 2000 rpm at 80mph, but pretty doggy at a stoplight. Loaded trailer in third gear 25-2600 rpm, 75-80 mph, and it loves it.
for reference my daily is a stock 4x4 silverado 5.3 3.36 gear, great on the highway 2000 rpm at 80mph, but pretty doggy at a stoplight. Loaded trailer in third gear 25-2600 rpm, 75-80 mph, and it loves it.
02-07-2021, 02:38 PM
#10
02-07-2021, 07:15 PM
#12
TECH Senior Member
6L80E ratios are 4.03, 2.36, 1.53, 1.15, .852, and .667. It has no direct gear.
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