ok, lets break this down for you

i have the 16" rims on my truck, but i think they are 31" tires and at 2k-2100 im doing almost 80, and i KNOW that i have the 3.55 gears so it would seem like the 3.92 is correct for what you have

YES!!!!

i dont think that my truck has ever gotten that hot, even sitting in stop and go traffic w/ the a/c on, (i have the heavy duty cooling w/ the tow package) check to make sure your fan clutch is good (spin it by hand if it goes more than 3/4 or one turn the clutch is shot) and make sure the e-fan is working properly, it SHOULD go on when the engine gets that hot, or whenever the A/C is running

btw i dont have temp degree labels on my gauge, but the needle stays almost dead straight up and has NEVER made it to the hash mark on the right hand side

 

thanks Shtr.
I am pretty sure I don't have the electric fan? 1999 4x4 slt 5.9l. I just went out to the truck and confirmed, no elec fan.
I also checked the fan/clutch. The fan turns nonstop in either direction. Bad fan clutch? In which case, what do you guys recommend for a Heavy Duty Fan Clutch?

Can I put the 180 tstat in with no ill effects?

What also still puzzles me is that the build sheet states 3.92 gears and the tab on rear diff says 3.5

Until I hear from other users, I'll have to go with your statement and assume I do have the 3.92 gears.

thanks!

 

the 3.92 makes the most sense, unlesss the previous owner changed them(if its a 4x4 they would need to have done front too which gets expensive), as the dealer build sheet is seldom wrong (in my experience), get a new fan clutch from az or similar, i would get the HD if you do a lot of towing, and expect it to be VERY LOUD at first start up after you have a new clutch in, the new clutch will make itound like a diesel truck for a while when you start it up on colder mornings,

and the 180* stat is fine many people use them i know the 3.9 (the baby brother v6 to the 5.9) is supposedly makes more power w/ a 180* stat, but i cant prove that, nor do i know if this applies to the 5.9 but i would assume so, and dodge only used the 190 (or 195 whichever it is) because they needed it for emissions reasons.

HTH shrpshtr325

 

1998 and 1999 didn't come with electric fans. That started in the remapped 2000-2003.

You need to replace the clutch fan. I would not get an HD fan because I've heard they never shut off but I'm not sure. There should be resistance on the fan and it should turn either way. If there is no resistance then replace.

180 F T-stat is what you want to run with those heads because the heads were never built to handle the heat. OEM is 195 for emission purpose. Yes 15 degree's makes a difference. If you tow a lot then go High Flow T-stat. I like the one Hypertech is selling. The colder the air intake and cooler motor = more power hands down.