Well, after much thought I went ahead and purchased the Hypertech PP III. I've had the program (I went for Level 3, the highest power level) installed on my truck for about 750 miles to this point, and here is what I have observed:

1) Power is MUCH improved, though still it has a VERY pronounced turbo lag at low speeds.
2) Transmission took a while to re-learn it's shift timing, seems OK now.
3) Smokes like a proverbial freight train when at 2/3 to full "throttle".
4) Made an overly sensitive "throttle" even more sensitive - the truck is extremely difficult to drive smoothly in heavy stop and go traffic. The throttle seems even more like an on-off switch!
5) Fuel economy seems slightly better, though I'll need to run a few more tanks through it to really know for sure.
6) DIC fuel economy information is neary useless! With the OEM calibration it usually indicated about 10% better economy than hand calculated. With the HPP program installed, it now usually indicates about 20-25% better economy than actual!
7) The one thing the HPP wo't do for me is to allow me to raise the fuel cutoff - the way the truck runs now the 95 MPH cutoff is rediculous!

Any comments?

TIA

Thanks for the review! It helps all of us when folk report their findings on newly released modifications. Or for that matter, older mods and how they affect the LLY.

Any barking on shifts?

I've seen "twitchy" throttle on other tuners for the LLY as well. I call it "tip in", the way it handles the first small amount of accelerator pedal travel. BD and PPE have tip-in trouble also.

I wonder why they didn't allow you to remove the speed limiter? Bullydog, PPE, TTS, Predator all remove it.

None of the tuners address the ECM fuel mileage program error. Perhaps there is no variables to allow for it's adjustment. Dunno.

Thanks for the reply.

About the "bark" - since I'm a green-horn newbie when it comes to diesels, I'm unsure about the bark. Last night, on the way home from work, I heard a l rather pronounced sound of some sort. It was raining fairly hard, and I was turning left onto a road from a side street and had to get on it pretty hard to merge with traffic. My truck began sliding sideways, so I had to work the throttle fairly rapidly a couple of times to help control the slide. As I released the throttle I heard what may have been a turbo bark, but I dunno???

I have the Hypertech also, level 1, don't waste your time. I leave mine on level 2. On #2, no smoke, unless I stand on it, shifts great, fuel mi. up about 1 or 2mpg. DIC fuel mileage is unchanged. Hand calc. 17-18. The best part was yesterday when that shiny black mustang had to suck diesel exhaust from 0 to 65mph. :) Make sure you look both ways before you launch, there might be a cop around. 04.5 D/A cc sb.

Great info, fb0308!

I may try level 2 myself soon, though it's GREAT fun to smoke someone out when they're tailgating me or otherwise pi$$ me off.

On the other hand, since I prefer a programmer rather then a hardware install, I may look into another unit which WILL allow me to disable the 95 MPH limiter.

Any suggestions? I like to add power, reprogram for my larger tires, disable the speed limiter etc. I'm not prepared to upgrade the Allison!

I too had no desire to upgrade the allison. I had too many problems with the edge with attitude so I took it off for good. Hypertech level 3 is comparible to edge users running level 3. Remember, level 3 is all you can run with the edge with a stock tranny so whats the point? Hypertech gives more low end tq. right off idle. Wheel slip is more pronounced now especially when raining or turning hard in each direction. It took me a while to get used to the throttle response. Power is good and definately has turbo lag throughout the entire power band. The tune for 33's or 285'2 didnt work for me. Now the speedo is off by 5 the opposite end now reading faster than my actual speed. I may try for 31's ad see if that evens it out. It, at times seems a bit sluggish with this winter blend of fuel. I'm starting to humger for more power again. I dont really care about the speed limiter. I dont think a 7000 lb 4x4 needs to break 100, plus its running too many rpms. I have cars to do that. Overall I'm satisfied with the hypertech but this month, is our year anniversary together so a trip to the dealership for an inspection, oil change, and rear diff. fluid change. Hypertech makes it easy to put it back to stock. I would be interested to try the diablo sport. Thats what I initially wanted but werent out yet for the LLY. Anyone had a chance to compare the 2?

Oops, I forgot to post that MY Hypertech did near perfect on the tire size change. My speedo WAS reading about 5% low with my 275/70R17's. After the HPP reprogramming I checked it against a 30 mile section of highway mile markers and it read about 0.5% high - good enough for me!

If you don't like the Hypertech but like that type of programmer try the Diablo Predator. It readjusts the speed limiter and gives some cool diagnostic tools as well. Just my .02

for some reason i wanted to break 100mph, on your tire calibration screen(hypertech) program in a smaller tire than you have on your truck and you'll go faster, your speedo will be off but you'll break 100, i know this works because i did it with a gps. with 31.50's on my truck I set the programmer for 26inch and I went approx 117mph at 3200 rpms, I set the programmer for 24in tires and it kept throwing brake fault codes.

I got rid of the hypertech because it didn't do the limiter. Looking forward to purchasing a predator soon.

If your using stage 3 with Hypertech you may wanna do the airbox mod. to improve airflow or get one of the custom applications, IE: AFE 2 , AIRRAID , Trueflow ,Volant.
Heres a link to the mod page :

2001 boxes had snorkels into the inner fender. GM Service Bulletin # 01-06-04-050 deals with problems associated with resultant poor air flow, filter minder on, SES light illum, and codes P0101/P0103, water stained filters, fouled MAF sensor etc.
The fix was to replace the box and reprogram ECM. MANY trucks did not receive this update, and when power enhancing devices (chips) are added, this condition is aggravated, and the chip is blamed for the problem.
Some GM dealers will do these updates as a coutresy, but since the bulletin is quite old (10-19-01) most will charge you. The air box can be modified as shown in this Tech Tip, but the programming updates need to be done by a GM dealer or myself.
I suggest that all updates be performed to the ECM (engine computer) and TCM (transmission computer) whenever possible. The dealer can give you a print out of the updates installed. Here is a 2001 air box with the snorkels removed and the side cut framed out. The entire side is basically removed:

http://www.kennedydiesel.com/images/Air_box_cutout_side_view.jpg

On all boxes, the side of the box has a nice, large, triangular area that can also be removed by cutting as shown:

http://www.kennedydiesel.com/images/Air_box_cutout_triangle.jpg

And resulting in:

http://www.kennedydiesel.com/images/Air_box_cutouts_completed.jpg

I then cut out the cross quadrant ribs resulting in long floor pockets rather than multiple small pockets. I drill a 3/16" drain hole in each of these and add a Uni Foam Air Filter Element (http://www.kennedydiesel.com/detail.cfm?ID=139) and reinstall the box!

http://www.kennedydiesel.com/images/Air_box_assy_with_filter.jpg

http://www.kennedydiesel.com/ click on tech tips.