d22019

I drive an '01 379 with a 6nz Cat turned up to 550hp(was 475 originally) with a super 10 and 3.55 rears. I'm use to driving acerts that pull hard around 1400 rpm where this engine pulls at 1850-2300. To me it seems too fast but I don't know. It averages 3.8-4.3 mpg all the time hauling hay (big square bales 77-85k) on a double drop. I also noticed it smokes more than any other truck Ive driven, mostly accelerating and jaking. Not a lot but you can see a pretty good cloud cross the road when the wind is blowing the right direction. It seems to have a slight miss around 850-100 rpm, nothing major but you can tell its there. Any of you guys have any input on this? The engine has just been serviced and has 735k on it.

NE frmhnd

A non-ACERT Cat will sound more relaxed at 1900 RPM than an ACERT will at 1500. You'll find most pre-emission engines are like that.

The super 10 an overdrive? You still want to cruise at lower RPM if you can.

Sounds right on fuel mileage. I ran several 3406E at 435 and a C15 at 450, and it was a really good day (or a day I fueled in the south after Katrina and got high-sulfur fuel) that I hit 5. Course they was geared all wrong, too. RPM at speed was over 1550-1700.

d22019

I believe it is an overdrive transmission, 1550@72. The truck could really use a 13 speed. Going across I-40 in western OK its hard to keep it in the powerband. It lugs in 10th at anything below 65 and is turning 2k in 9th at 65.

NE frmhnd

Yeah, I wouldn't put anything less than a 13 behind a Cat. It should pull pretty good down to 1350-1400 RPM.

d22019

So I put a resistor in the plug for the fuel temp and its a different truck now. Its averaging 4.9-5.3 and it will pull most hills in 10th now (barely). It still needs a 13 or 18 speed.

2006BLKMegacab

Whose resister did you buy?

I've seen enough of them listed on ebay but I havent had the guts to try.... although I'm getting tempted haha

d22019

I bought a pack of 5 150 ohm from radio shack for $1.75. Its just taped in the fuel temp plug for now. I was really surprised at what it did performance wise.

2006BLKMegacab

ok, thanks, I'll give it a try