Mechanic willing to help

Thanks bud!

 

Highest mileage MX I have seen so far had 600k on it. Honestly, if it were my money, I'd buy a 500 HP MX over an ISX15. Better fuel economy and an awesome torque band. If all maintenance has been properly performed (15k OCI's, aftertreatment services, ext.), the only problems you are going to have are sensors at the most. Remember, Paccars use a Cummins aftertreatment system. When you compare the two engines, the aftertreatment is going to be moot point.

EDIT: Forgot to mention, drive it like you stole it. For some reason whenever we get a downed Paccar it's from a company like TransAm that neuters their trucks to 62 MPH and 1500 RPM shifts. Every customer that loves their Paccar openly admits that they drive the snot out of it. If you are driving a Cummins or a CAT, treat her gently.

 

Not too late. I'm fixing the cab now gotta put it back together to start it. Found a cut harness and been waiting for it to get here so we started on the body work. Thank you for the help

 

Cool, glad I could help. Was that truck involved in an accident or something?

 

Yep down in Florida. Still working on it when I get a chance. I'll post pics when it's done

 

>>>I realize the last post here is over 3 years ago, but I'm hoping your still watching this ----- and i was wondering and hoping you could help. I was going to put this in the main thread, but that last post there was over 2 years old, so wasn't sure if the thread was dead or not. anyway-----
I just bought a 2014 T680 with an MX13. it was set at 455hp. i wanted 500hp, but i was told it could not be done,??? but could only go to 485hp. So i did buy the uprate to 485hp. No i have been driving the truck a little more than 4K miles. I have 3:36 rears and I'm surprised that it won't climb the hills. She also seems to shift to early, at 75 I'm doing 1500rpm. I can't seem to get the RPM over 1600, so no torque. She seems to shift to early, to low in the RPMs, Its like, they did the Uprate but for what ever reason, nothing is unleashed.
WHY????? Were there there changes in the tranny program that should have been done also? other parameters that should have been done? I do have a copy of the current parameters that i can send you.

Also I seem to have no jake brake in 10th gear or below 12 or 1300 rpm. ( i think 1200) it just coasts until it down shifts and then the jake kicks in. so downhill i have to downshift to 9 to get my jake, not good.

and my last question - I had a ProStar Highrise for 9 yrs with a ISX15, love that motor, 475hp with 3:55 rears. Now that truck ran up the hill with 40K in the box, and compared to my T680, well the 680 is walking and i would expect the 680 at 485hp to be about the same (NO?) . anyway the last question is i have noticed in the turns on the highway, like doing 70mph down I79 she seems to lean a hell of a LOT. I can't tell for sure if its just the cab or if its the whole truck, but i have to tell you it has me a bit spooked. my ProStar NEVER leaned even at faster speeds. any idea why the hell its leaning like that or is that normal for a T680? OH, when i park, i lose the air in the cab airbags in a matter of minutes.

Please let me know your thoughts. I don't want to go straight back to the place i bought it from, they didn't seem to know what they were doing with the uprate int he first place. So i'm trying to get some outside thoughts.

 

They can only uprate to whatever the rest of the drivetrain torque ratings are. I am guessing your truck transmission was a 1650lb ft torque rating. Need to make changes in your transmission software. Need to put latest software and change settings from fuel economy to performance if that is what you are after. They have a new aggressive mode and change shift from smooth shift to fast and it will take it to max engine RPM on shifts if your foot is in it and will downshift quicker on hills. MX engine brake only works well in higher rpms. If you want aggressive downshiffing, just move selector to L. Make sure you have seatbelt on cause it will slow you down quick. Sounds like you air leak on cab air ride system. Spray bottle with soap and water and quiet area you should be able to find it.

 

Ok - wow you took a lot and condensed it on me - the air bag leak is the least I'm worried about, i was just wondering if that is leaning the leaning problem.
can you explain the Fuel economy to performance settings a little more? what exactly will that do and what will i lose? and i assume that is in the Tranny program? What is the aggressive Mode on shift?
Right now the truck on History was getting @ 7.2 mpg, i would like to stay close to it but i run 35K-45K loads in the hills and I'm dying on the hills burning up more fuel taking way to much time to climb. Also when she does shift, I lose anywhere from 3-6 (or maybe even 7) mph because it is taking so long to shift. and of course that isn't helping.
Last night i ran through I79 with the stick in M and held it in 9th, was doing 70 and she was humming up and down a lot better than it had been left in auto. heck i would have been in 8 or 7 even with it in auto and i only had 28K in the box. so yeah, need some help.

So the only way to get the Jake to really work in 10th going down a 5% hill is drop it to L? otherwise I'm coasting down the hill??
and what about the whole leaning issue? this truck leans in the turns. I have been driving almost 30 yrs and never had one lean like this. causes??
and what is P##@G me off is the fact i just bought it last week and SUPPOSEDLY they went over the whole truck. well it seems they didn't do a very good job. Im guessing either my front end or whole truck suspension issues but specifically i'm not sure what

 

I am guessing the T680 you bought is an ex fleet truck that was speced for fuel mileage. The reason your Prostar pulled hills better was rear axle ratio. With an overdrive trans and MX, 3.36 and below is fuel mileage spec. 3.42 and 3.55 is considered blend and 3.70 up is performance. They are a couple of things that can be changed very easily in Eaton Serviceranger 4 that change how your transmission shifts. By changing from standard to performance shift mode, it will let RPM's raise higher before shifts are made and will downshift quicker. It is as simple as just clicking from a drop down box to make the change. I would make this change first and see how you like it and how much fuel economy suffers. If you ease throttle in performance mode I feel it shifts same as standard unless you stand into throttle more. L is for most performance out engine braking. MX engine brake needs RPM to have much retarding effect.

 

She wasn't exactly your typical fleet truck, but it was from a small fleet of about 40 trucks. He orders 10-12 at a time every year to rotate. Im actually surprised with all the bells and whistles he did order the truck with that he didn't have it set up a little more on the performance side.
Anyway -- with 336 rears, and raising the HP to 485, wouldn't that either compensate a bit for the rears? or shouldn't they have adjusted, reprogrammed the torque in the tranny side of the programming?

So I'm a little lost as to what to do or how to handle the Jake issue. I get the MX doesn't like low RPMs to work the Jake, and i like to use the Jake going down hills as opposed to my brakes. So ..........
Do i downshift earlier to keeps the revs higher and run down the hill pretty much over revving the gear? or do i use the "L" Gear to slow it down?