Help with my truck..Please

Well what's I'd the most efficient rpm range for an isx? Is it a 870 or 871? Does that make a difference for optimum rpm range.

 

You're right, I did a lot of research before buying a truck - mainly in the specs department, and still it wasn't enough - I could have gone further in the suspension knowledge and perhaps found another truck that didn't require $4000 of upgrades.

Still - at least the guy is asking questions now -

 

He ought to be able to handle some constructive criticism. A positive thing that can help to motivate. First thing he needs to do is crawl under his truck with a flashlight and shop rag. Find the tags on the transmission and rears. Then can figure out more from there.

 

I don't understand how someone can come and post on an internet forum then get all but hurt when someone post something they don't want to hear. Suck it up and get some thicker skin. I completely agree that anyone that goes out and buys a truck with no knowledge of the industry or workings of a truck is asking for problems. Just because you have the money or credit doesn't mean you will succeed.

And I agree with what someone else said here, RPMS and MPH goes hand in hand with fuel mileage. If you are cranking your RPMS up to run 65 mph down the road, you are going to get crappy mileage. My truck runs about 1350 rpms at 67-68 mphs. My last tank, loaded to 78,500 lbs, running I-80 across IL, IA and NE I got 6.4 mph. Pulling pneumatic. But if I were to have ran faster, with RPMs pushing 1500+, I imagine I'd have dropped to 5.3 or so.

Also have to keep in mind, you can't be maxing out every gear shifting either. You don't need to act like you are in a drag race taking off. All of that behavior affects your fuel mileage as well.

 

They have a do it your/self test kit you can make use parts bought at hardware store like PVC plastic plugs with holes you drill out yourself and hook up a test gauge to see pressure drop timed at 1 min. 0 drop is best,but once you put a few # of air in block off cap clamped on rubber boot leading to turbo from air cooler, you can spray soapy water on everything till you find all leaks and fix them yourself, U/TUBE has many that are somewhat right that you can learn from but is more like C/B radio where its hard to pick good from bad advice?

 

Now that we know you have a 2.64 rear end ...
Replace your 10 speed transmission with a 13 or 18 speed, choose one with the model number ending with the letter B. Example - RTLO-18913B or RTLO-18918B. That will make your rpms go down and increase your speed ..........

 

He has a auto shift. Changing transmissions will be a big undertaking (finding all the clutch linkage/pedal setup). Changing rear gear is out , he is at almost the highest (lowest number) available. May want to find some one getting ready to replace a set of 11R22.5 tires . See if you can run them some and see if they help ( before you send 5k). With the truck he has he may have to slow down. Best of luck!