Just purchased a 2003 C4500 LB7 Duramax 300hp Allison 1000 tranny.

According to the spec sheet for the truck, the speed limiter of 75 mph is a $24.00 part. If they can add it why am I finding it so hard to get a straight answer on how to remove it?

This is a vehicle used for personal use (not a business) it's a private hauler.

GM say's it can't be done (I think it's a liability issue on their part).

I have already purchased one programer (that claimed to be able to remove it)...needless to say it is being shipped back this week.

I am also going to post this in the LB7 thread.

Please help!

whouldnt a bullydog power pup take off the speed limiter?

Did you try it on yours?
Did it work?

ohh i dont have the truck yet...
but it worked on my uncles but his is a 3500

Been told the limter is there for the tires. My build sheets if I read right UPC=15 88 road speedhas a prt #10284728 the truck has michlin tires I think the xlv they are regroveable tread type .

I have an '05 C5500 with a limiter of 75mph. I have tried to have it removed and it can't be done right now to my knowledge. The 4500 and 5500 have different programming than the 2500 and 3500, hence why the programer you bought did not work. Christian at BD Power is working on a box that will remove and I was told they should be ready within the next few weeks if all goes well. I will post when I have more info.

My 03 C5500 with 4.44:1 and Michelins is factory set at 85 mph. (Momma was racing tractor-trailers with it on I-95 one day and was complaining that it did not want to go any faster for some reason. Looked down and she was pegged. Told her to slow down an watch her speed.....tsk, tsk, tsk).

When I ordered, I paid attention to the choices of tires, and their max speeds, which is why the extra $$$ for the Michelins over stock. I also looked at the rear-end ratios closely for rpm-to-speed as a fuel saving measure. (When it comes to physics, its very hard to get away with cheating. Either it works or it does'nt, no in-betweens, no work-arounds).

If you've got a very low ratio, over-riding the speed limiter and boosting HP will result in poor fuel economy, and you may find yourself increasing the population of highway gators. Which is fine, if you can live with that.

RF

I would be fine with a 85mph limiter instead of the 75mph limiter I have. I ususally cruise at 68-70 for the most part. Just nice to be able to pass or get out of the way. I agree, prolonged high speeds eats fuel and could result in a tire failure.

BD Power has the Kodiak C4500/C5500 boards in for more power and more. They should have the wiring harnesses done in the next few weeks to remove the speed limiter.

http://www.bd-power.com

Limiter (speed reader)is in the Allison trans,If it by passed The speedO won't work.Truck might run in limp mode or not at all. I had my high idle rewired as per GM tech line and wrench/tech with a wire cutter and a PC laptop.Idle would Kick using Deck and speedo jump to 60 MPH while setting still.In the end I picked up 2 MPH truck would run 77 and 80 down hill.Tech said he couldn't unhook bypass reader speedo wouldn't work and the 75 MPH limit is a Law on all medium duty trucks

My friend has a C4500 4X4 that also use to do only 75MPH, he has the PPE lly programer and now he says it can do over 95MPH.

Thats fast for a big truck....:eek:

Does the PPE programer raise the fuel rail pressure? I would like to buy a box for my 4500 LLY but am scared of the increase in rail pressure. Has anyone gutted the cat on there MTD?

check with PPE for sure, but I don't think any manufacturers programmers raise fuel pressure....:)

PPE is advertising the speed limiter removal. From their web page......
-----------------------------------

GMC Duramax 4500/5500 TopKick

GM's large size truck comes fully powered with a Duramax engine which means more power. PPE's line of Xcelerator and Enforcer performance chips can boost this stock 300HP truck well over 500HP. The Xcelerator now removes the 75 or 85 mph limiter on 2 or 4 wheel drive C4500/5500 GM TopKicks


http://www.pacificp.com/duramax.htm#topkick

TechProf