Hello so I have a 2008 lmm duramax. It has 144k on it I use it every day and I two with it every month various distances. I tow a heavy fifth wheel. At 120k the exhaust plugged on me I bought it bone stock. So of course I wasn’t in the best financial state when it happened. I bought mini max from a friend that was brand new for a couple hundred and took a sawzall to my exhaust. Worked just fine. That was last summer. So it still has the egr intact and stock air intake. It’s been runningreat. I tow on 60 hp and daily drive it on 120hp. I average over 20mpgs in the highway and around 15-16 with a trailer. No complaints other then soot all over underneath the truck and it’s loud. So the problem:
A couple months back I noticed that the transmission had a slight shake to it when I was at wot or a high throttle in 5th gear and it feels as tho it is slipping in 4th too. The truck runs great. Everything checks out. The only code it has ever thrown was a low rail pressure when I hammered on it I know that the truck needs a lift pump well I have that now just have not installed it. So I have babied it since I figured I prolly messed up the trans. Everyone I talked to agreed. I even had a guy at a trans shop a couple weeks back drive it and he somewhat agreed. So I am about to purchase a PPE stage 4 build kit with the converter and a billet stator. I figure that’s enough for me. I am never gonna take the truck passed 550hp and was told this kit would be great. So before I buy this kit I had the guy who is gonna install it hook his computer up and log the transmission while he drove it. He came to the conclusion that he doesn’t think it’s my transmission. He thinks it’s something with the motor. That being said what do you guys think it could be? If it was something internal with the motor I feel like it would run like shit or I’d definitely know. If it was fuel related wouldn’t it throw me a code? When I got the rail pressure code I know it was because the system couldn’t keep up with the amount of fuel it needed from the tuner. I know I don’t have a head gasket issue I have no symptoms of really anything. The truck runs awesome you really don’t know there is a problem until you get into the throttle. Is it possible that maybe the exhaust got to hot could that cause issues I’m at a loss. So tomorrow I’m paying 150 bucks to have a mechanic data log and do his diagnosis on the motor Any ideas would really help. Again the truck runs amazing. Smooth idle always starts no matter the weather good mileage. Great power. I just think maybe the trans guy got it wrong. And he didn’t completely rule it out he just said it seemed like a strong trans and the hesitations were not the trans.
A couple months back I noticed that the transmission had a slight shake to it when I was at wot or a high throttle in 5th gear and it feels as tho it is slipping in 4th too. The truck runs great. Everything checks out. The only code it has ever thrown was a low rail pressure when I hammered on it I know that the truck needs a lift pump well I have that now just have not installed it. So I have babied it since I figured I prolly messed up the trans. Everyone I talked to agreed. I even had a guy at a trans shop a couple weeks back drive it and he somewhat agreed. So I am about to purchase a PPE stage 4 build kit with the converter and a billet stator. I figure that’s enough for me. I am never gonna take the truck passed 550hp and was told this kit would be great. So before I buy this kit I had the guy who is gonna install it hook his computer up and log the transmission while he drove it. He came to the conclusion that he doesn’t think it’s my transmission. He thinks it’s something with the motor. That being said what do you guys think it could be? If it was something internal with the motor I feel like it would run like shit or I’d definitely know. If it was fuel related wouldn’t it throw me a code? When I got the rail pressure code I know it was because the system couldn’t keep up with the amount of fuel it needed from the tuner. I know I don’t have a head gasket issue I have no symptoms of really anything. The truck runs awesome you really don’t know there is a problem until you get into the throttle. Is it possible that maybe the exhaust got to hot could that cause issues I’m at a loss. So tomorrow I’m paying 150 bucks to have a mechanic data log and do his diagnosis on the motor Any ideas would really help. Again the truck runs amazing. Smooth idle always starts no matter the weather good mileage. Great power. I just think maybe the trans guy got it wrong. And he didn’t completely rule it out he just said it seemed like a strong trans and the hesitations were not the trans.
