I have a 2000 ecsb with 150,000 miles.

Has 3.42 gears and stock transmission

Every bolt on and cam to come soon 210/218 .584 .584 116lsa

The cam will work fine with stock stall

Could I do a 2600 stall and 3.23 gear so it'll get better highway millage but still pull around town?

 

What size tire?? It will play a big factor...I say go with a 30.5" tire and 3.73 gear with a stock coverter for mpg

 

31" the 3.73 will get worse highway than the 3.42 rpms are higher

 

No you wont get worse fuel economy because the crappy 3:23's factored with a cam factored with a converter lug the motor making it work harder to move the truck. Put gears in it and the truck will loaf along no problem and you very well may see a increase in fuel mileage because the motors not lugging. Gears are a necessity for a converter to work efficiently and correctly.

 

You will never save enough money on fuel by switching to different gears to pay for the swap. The only way you could is if you had a massively mismatched combo, like 5.13s on 28s or 3.08s with 35s, or if the gear swap enabled you to take advantage of other fuel-saving methods (we have a member wh swapped his 3.08 to 3.90s, allowing him to tune his Active Fuel Management to run four cylinders at higher speed and load, and he experienced quite the improvement).

 

What kinda mileage do you get now?
Ive got a 2000 ECSB 1500 with 3.42s and 265/65/17 All terrains and i can get 24mpg on the interstate if im easy on it.. average about 15mpg on my commute to work from all the idiots on the interstate here..

If you got a good tune then your ok if you have a light tire..


with a 31" tire and goin from 3.42 to 3.23, your looking at 100rpms difference.. thats not a big difference at all to see a gain.. plus goin to a 2600 stall its gonna be loaded up more trying to get it to go with the higher gears and tall tires.

 

I get +-23 at 75mph around 16-18 city depending on coasting or stop and go driving. I have 20's with the Michellen LTX tire P275/55 R20

I know It'll take 50,000 plus miles to get my money back lol

The main reason for the gear swap is the posi unit. I just don't want to do a swap and get worse gas millage

What about 3.55ish range gears and no stall?

 

just checked online the 275/55 r20 is a 31.91inch tall tire

 

The lower (higher numericaly) u go on gears the less lug on the engine. If the converter has a good lockup it wont effect mpgs much at all. I had 3.42 gears to start with on my truck got about 21 mpg then the rearend let go so i rebuilt with 3.73 still got about the same mpgs. Decidedbi wanted to go faster so i swapped to 4.10s and a 28" tire compared to the 29" i was running before. Truck was now running 2500 rpms at 70 mph and fuel mileage dropped to 18 mpg then i swapped to 4.56 got 17.5 mpg went to get it retuned again detuned a bit took it on a 1200 mile road trip over the weekend put on some 29" tires and i got 19mpg average. Its more about the tune i think. my truck ran 2600 rpms down the freeway so rpms dont hurt the fuel mileage as much as some think cause the engine has that.much.less load on it

 

I wouldnt worry about it.. theres not enough differnce in the ratio for it to matter..
Just throw the posi in and go.. i put my Eaton LSD in my truck almost 90K miles ago.. the gears have 255k miles on them now.