I recently repaired (and reworked) my UPD. Last night I tossed it on.

I've only driven about 60 miles so far, but I've noticed that my part throttle shifts are a little "confused". An example would be when I went to pull onto a busy street this morning - the truck upshifted from first to second quite early, and the truck fell on it's face. It's never done this stock. I put my foot down, and the tranny kicked down so hard that I got a good amount of weight transfer. It's never done that either.

I was getting odd shift points the first time I had it installed, but I assumed it was the cracked intake tube throwing the fueling off.

I've noticed the confused shifts last year, when I was trying to 'redesign' the stock airbox in my old 5.3. I ran a lot of miles testing, and the shifts never got better. I assumed I just took away power, and converted back to stock.

Now I'm not so certain. What causes this?

I heard something about the MAF being related to the way the tranny shifts. Is this the issue here?

Or is it a difference in power output (slight loss in lowend?) that the PCM can't quite adjust to?

Can either be weeded out in Edit? I know little about tuning with it, but I don't think it's an actual shift point issue. Something with the MAF and fueling tables?

 

This is the problem I would bet. This probably could be weeded out with EDIT, but would cause a tuning night mare and be VERY inconsistant. You should fix this before you do any tuning. Any leaks in the air intake should be fixed for more reasons than just this.

 

Hey marc,
Give it a few days to a week to relearn fuel trims and such before you decide the intake messed it up. I've noticed sometimes the PT shifts are a little funny after a flash with Edit. Also, if your tune is stock, your probably running lean...
On the MAF affecting shifts - the Edit tables for shifts are mostly based on throttle position (%tps) and RPM. Neither of these is affected by the MAF. The only shift table I'm aware of that might come into play here is the Base Pressure vs Torque table. The PCM could be using MAF to calculate torque...

 

Thanks guys.

I caught a post a while back, might have been on the car side of the fence, but someone poorly ported their MAF. The vehicle was running strange, and the shift points were off. I'll try to dig it up.

The intake has been completely repaired... It cracked on me shortly after I put it on the first time around.

The 'rework' I did was smoothing out the airflow in the UPD's lid - The collar where the MAF slips on had a 3/16-1/4" ridge sticking up around the inside surface of the lid. I mixed up some epoxy, stood the lid up on it's side, MAF collar down, and poured the epoxy around the collor to smooth the airflow. I DO notice a bigger improvement over stock now at the mid to higher RPM's. Still feels a little soft down low, but I'll give it more time.

It's not like the thing is shifting horribly bad or anything. I'm just used to being able to set my watch with the bone-stock setup.