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.

 

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.

 

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.

 

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

 

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.

 

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

 

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.

 

ok, thanks, I'll give it a try