Engine slips-mechanic confused

Hello folks. I hope I'm doing this right..here goes. I'm having an issue with one of our company trucks (06 Int 8600). As I accelarate, from 1200-1700ish, the truck acts like the tranny slipping. Loaded or unloaded affects the severity, but not the frequency. New tranny last year, new turbo 3 years ago. I'm admittedly hard on it (I blame it on the nature of what I have to do, set septic tanks) but I've asked the mechanic if it's my driving and he says he doesn't think so. This has been going on for a few years, so if it was the tranny or turbo, the new one's should've fixed it right? I can add that a couple times while accelerating, my truck went beyond "slipping" and the bootom fell straight out. Happened with cruise and peddal both. Turbo chirped hard a couple times as it pegged and dropped and struggled to climb back up the RPM's. I read in a KW forum about a guy having same issues, and it wound up being the clutch. But that was auto trans, mine's a 10 speed. Could it be the clutch? Turbo pressure tests all pass. I did mange this trick, don't know if it helps: when it was below 30, if I parked outside with the nose close to the shop door and would start it, it will register an engine code and the problem goes away. If I turned it off and started it again, code goes away and problem comes back. The engine code did not lead the computer to the problem. Another funny detail, I just got it back from mechanics for oil service and to investigate this issue again, but they said they couldn't find the problem again. The thing makes it funny is, it is NOTICABLY better. They didn't adjust the clutch or have to add any fluids aside from a bit of oil, they just hooked it up to the computer, but no code so no repair. This has happened before, with varrying degrees of effect. Would appreciate any information. Thank you.

 

Hey Don, appreciate the advice. I recognize engines don't slip, just super frustrated and that's what I came up with for a title. Arg. I can say it's been a while since the clutch has been adjusted, and almost no free play at this point. Catches halfway out and rides the rest of the way. There is a tiny bit of play. This is my first gig as a driver, and it's the main truck I drive. On this truck, it's never stayed tight after an adjustment for long. A week or so, maybe two, when the other trucks hold it for much longer. I just figured that was the way this truck is. It's just hard to believe it would be the clutch and the mechanics not identifying it as that. Is this really that sneaky of an issue? I mean, after what I read in the KW feed and with your info here, I would belive it, but really?

As far as engine size, part number, and inspection cover; I will check all of that when it comes back. I broke the outrigger mounts durnig my last set, but as soon as she's back I'll gather that information and act from there. Thank you again for the help. Greatly appreciated.

 

Thanks for the info guys. Talked to the boss about the comments here and he talked to the machanics. He doesn't believe our mechanics are shady. Stupid yes, but not shady. That being said, one of the wrenches convinced his boss and mine to go with a clutch adjustment to start. He's willing to put a new one in, I have a good boss. But wants to take the mechanics advice. Any thoughts on if that's a solid step forward? And if so, any suggestions on how long an adjustment should last? I feel like the previous ones lasted, at best, less than a month before the clutch was at the end of the pedal. And that this adjustment is just prolonging the inevitable.

 

Hi guys. Sorry it's been so long, work ya know. Here's the update: got the truck back a month ago after frame repairs and servicing. Had the clutch adjusted. First 2 days it still slipped in every gear. Then one morning, it just worked. Every gear, all day for 2 days. For the next few days it was in the morning, for the first 30 min to hour on the road it would slip, then come out of it. Now it's back to slipping most of the time. I had a good 3-4 inches of free play in the pedal right after. Now down to 2ish.

As for what gear I start in and riding the clutch comments, I can tell you I don't ride the clutch and I start in 2nd 3rd or 4th depending on load. And I don't use the clutch most of the time, just float thru gears. Not sure if that's good, but this is my first and only driving gig and that's what I was taught.