Not just the initial 3-4 shift but after it gets into 4th for a few seconds you should be able to notice when the tc flares and locks up. That is where the power drop may be noticeable. If your exhaust is loud enough you can hear everything it's doing and verify it with the tach. Or datalog with your XCal. That is really the only place a 'normal' drop in power should be noticed during a consistent acceleration. 3rd is 1:1 and 4th is .7:1 and I'm guessing the tc holds something like a .87:1 (based on the new 6 speed ratios which give a real .87:1 gear) or so for a few seconds then locks up into true 4th. If that is the case then talk to your tuner about it, I have tunes from the same tuners and they can play with the tc behavior. Otherwise no clue what it could be.

 

Alright I payed close attention to it coming home this evening and it is when the truck shifts form 3rd to 4th that the big drop in HP occurs. Guessing from reading all the posts this sounds like a 'normal' thing and nothing really to be concerned about?

I rarely get up to 4500 RPM's (can't remember last time I pushed that much). Yes I do have the 4.56 gears so that's kinda what was making me wonder as well.

 

Actually the drop in HP comes after the shift into 4th gear. Watched RPM's on my Scanguage II and saw them & HP drop slightly after shift into 4th, then RPM's and HP dropped more significantly again a couple of seconds after the shift. Speed was somewhere between 45-50 mph when the drop occured. Is this the torque converter locking up? I will admit I'm not sure what that is, but I think someone mentioned it earlier.

Thanks to all the replies.

 

that is a shame...wish I had some in my truck to experience it...I would be there somewhat often

 

It takes more HP to take off than to climb the higher gears. You can noticed that by monitoring the RPMs when doing a WOT take off and climb to 4th gear ( being careful to not crash into anything ofcoarse ) Sounds normal to me.

 

After reading this and re-reading BlackDawg's post earlier in the thread it does sound like a quite normal thing. Guess I was just worried that maybe something was up with my truck. Doesn't sound like it though.

 

I think it's from your 3.5" intake and not having your truck dyno tuned. Yesterday I had my truck dyno tuned by VMP and found that with my Troyer tunes that my A/F was way off and the truck was running really rich. With the Troyer mail tune my truck's power used to cut in/out all the time when you were accelerating. It was almost as though I left off the gas and then hit it again right in the middle of accelerating. It drove me nuts. After several hours of tuning yesterday he managed to get it right but he said it was hard due to the huge intake. Anyway, it could be because you have the 3.5 and don't have the A/F spot on. Now with the VMP tune truck runs perfect and I haven't felt the power cut in/out at all while accelerating.

Keep an eye out because I'm going to make a post about VMP in the tuner thread tonight.

 

I have the 3" AF1, not 3.5". I also have both Troyer and VMP tunes and it does it on both tunes. I've been running the VMP 87 performance tune lately, may switch back over to the Troyer 87 performance and see which one is more drastic. I'm really hoping to get the truck dyno'd soon, hopefully as early as Saturday. Gonna have them dyno both 87 performance tunes.

 

I am experiencing something similar to you. Except I have an Edge Evolution tuner. If I stay below 2800RPM's, my truck will pull like hell. Once I break 3200 RPM, it falls on its face. All sound and no umph. So you aren't the only one.

I am stock except for a drop in K&N. I have 3.73 gears on a FX4.

 

 

It sounds like your truck isn't breathing properly. Either your intake isn't right (e.g. incorrectly indexed MAF), or your exhaust is restricting higher RPM flow.