Buying a used 2018 X15

[Camstyn]

It’s a 2018 IHC LT625, 450hp efficiency. It has 6000 hours and 200k miles. I’m not new to X15’s, this truck is replacing my 2020 Pete with 565 Performance. I’ve kept up on 15000mi oil changes with 15-40, annual EGR tuneups and did the overhead at 300k mi (it was good, jakes and exh valves were just slightly tight). This truck was always babied by me, run at 1500-1800rpm and seldom exceeded 20psi boost. No excessive idle time, 7300h and 340k miles.

I don’t know the maintenance or driver history of this truck, but it is freshly serviced. What would you suggest doing immediately besides an EGR tuneup and maybe run the overhead? The spec of the truck should be a money maker, 16spd direct drive autoshit with 2.64 rears so same final drive as my Pete with 18spd/3.73’s. I’ll manually control the transmission to keep the RPM’s up and the boost down.

[tree98]

Probably add an oil bypass filter to help keep carbon packing at bay. Also check the aftertreatment history to see how full the dpf is.

Sounds like your other truck is still in great shape, why are you parting ways with it for somewhat of an unknown?

[Rawze]

(12-11-2021 )Camstyn Wrote:  ...
16spd direct drive autoshit with 2.64 rears
...

just my opinion...

you'de be hard pressed to get that thing to stay in the 1500-1800 RPM rage like it should be driven in a pull w that auto-s$itter. On top of that, it will not get out of its own way when heavy vs the 3.79's you have in your other truck. .. Its geared too tall in the back-end, and it will suffer fuel economy issues, torturing the engne by lugging it into an agonizing death everywhere it goes. I see it loosing easily, 0.6 - 1.3+ mpg across the board on it vs. a decent driver who knows how to shift and a decent set of rears instead of the garbage you mentioned, if your running 80k loads. Thats several thousands of $$$ a year going straight out the tail pipe for likely, no good reason.

[Camstyn]

(12-11-2021 )Rawze Wrote:  

(12-11-2021 )Camstyn Wrote:  ...
16spd direct drive autoshit with 2.64 rears
...

just my opinion...

you'de be hard pressed to get that thing to stay in the 1500-1800 RPM rage like it should be driven in a pull w that auto-s$itter. On top of that, it will not get out of its own way when heavy vs the 3.79's you have in your other truck. .. Its geared too tall in the back-end, and it will suffer fuel economy issues, torturing the engne by lugging it into an agonizing death everywhere it goes. I see it loosing easily, 0.6 - 1.3+ mpg across the board on it vs. a decent driver who knows how to shift and a decent set of rears instead of the garbage you mentioned, if your running 80k loads. Thats several thousands of $$$ a year going straight out the tail pipe for likely, no good reason.

It’s a direct drive transmission, so final drive will put me at the same RPM at the same cruising speed as my other truck with 3.73’s and 18 double over (1400@62mph in top gear, 1500@58mph down 1 gear). I guess I don’t understand what the difference is, other than it sounds bad on paper without taking the transmission ratio into account.

I’ve driven an ultrashift before, you can operate it just like a manual using the toggle rather than letting it do it’s own thing, which would result in a lot of lugging. Other than losing the physical clutch pedal and shift tower I should be able to replicate the same driving habits with the ultrashift. I do plan to control the RPm’s with the toggle to avoid what you are describing.

[Camstyn]

(12-11-2021 )tree98 Wrote:  Probably add an oil bypass filter to help keep carbon packing at bay. Also check the aftertreatment history to see how full the dpf is.

Sounds like your other truck is still in great shape, why are you parting ways with it for somewhat of an unknown?

My other truck is in great shape, I’m selling it for a few reasons. The market is strong right now so I’m getting a nice sized cash out with the equity from it. My work has changed where I have to run faster than 57-58mph to keep a legal log book, so fuel economy is starting to suffer more with the 389, combined with running 50% more miles than before (625-665 per day vs 435 before), and having to maneuver into some very difficult spots on a regular basis now is proving near impossible some days with a 260wb 389.

I have coworkers running 2018+ Volvos with DD13/12spd AT getting over 20% better fuel economy than I am, and it’s not my driving habits. This would be 2500+ per month that I want to stop throwing out the window and hold onto. I’m hoping this LT will get me there.

So it’s a combination of wanting to increase my profit margins, lower my overhead and make my life easier. I’m still very profitable running my 389 but I can’t ignore how much extra it costs me to run a truck like this, and it’s time to put a stop to it.

[Rawze]

(12-12-2021 )Camstyn Wrote:  ...
I guess I don’t understand what the difference is, other than it sounds bad on paper without taking the transmission ratio into account.
...

because the taller rears have a lot of excessive torque transfer, therefore losses in them to the road.

Believe me when I say that I have driven all kinds of trucks with all kinds of rears and trannies in them.. you can just simply feel that the thing will not get out of its own way vs. something geared properly when someone has directs and those tall arsse garbage-can rears in them once the truck is fully loaded.

You have been warned ... I guess that Some peple just don't want to hear reality. Next thing he will be on here in a few months asking how to turn up the HP on the engine.. because it feels sluggish, and that is far worse than re-gearing it properly to begin with. It is always a bad business decision to Turn up the HP on the most expensive component in the drive-line rather than fix the problem properly... but who am I, just some shmo in his driveway trying to help people.

[Camstyn]

It’s not that I don’t want to hear it, I’m just trying to understand. I’m here to learn, I don’t think I know everything, quite the opposite.

That was a good explanation. So what gears would you suggest to be optimal with a direct drive transmission? I run at 57-63mph, lots of steep hills but I run light, around typically only 40,000lbs gross. I just would have assumed that the final drive being equal to a 0.73 18th gear and 3.73’s would result in the same performance since it is equal mathematically.

I don’t plan to turn the truck up, I expect it to feel sluggish when I’m used to 500+ hp and 1850 torque. I haul light so I don’t need big pulling power.

[Camstyn]

(12-12-2021 )Rawze Wrote:  

(12-12-2021 )Camstyn Wrote:  ...
I guess I don’t understand what the difference is, other than it sounds bad on paper without taking the transmission ratio into account.
...

because the taller rears have a lot of excessive torque transfer, therefore losses in them to the road.

Believe me when I say that I have driven all kinds of trucks with all kinds of rears and trannies in them.. you can just simply feel that the thing will not get out of its own way vs. something geared properly when someone has directs and those tall arsse garbage-can rears in them once the truck is fully loaded.

You have been warned ... I guess that Some peple just don't want to hear reality. Next thing he will be on here in a few months asking how to turn up the HP on the engine.. because it feels sluggish, and that is far worse than re-gearing it properly to begin with. It is always a bad business decision to Turn up the HP on the most expensive component in the drive-line rather than fix the problem properly... but who am I, just some shmo in his driveway trying to help people.

I’d really like to know what rear end ratio you think would be optimal for my application with the direct drive transmission. Cruising speed 57-63mph, lots of elevation change but extremely light loads. I’m not opposed to regearing this truck if I decide I want to keep it for an extended amount of time, which is quite likely if it turns out to be a good truck. I’ll be taking delivery of it this week and hoping for the best.