pac brake has it i ordered it from i think advanced diesel when i ordered my pacbrake switch ill have to find the recipt, ive noticed a difference, i hit 50psi boost with it off when its on i can only make about 20

Transmission type makes a difference also. I don't think I've ever seen a stock, or even mildly built automatic shift over 3-3200 RPMs. A manual would be different, as you control the shifts. For a weekend sled puller, a set of 4k springs would be nice. I've got a combination set of springs in mine that fuels extremely hard to about 3k. Uses one of the 4k springs and the rest are stock. Problem is the pedal is touchy, which is also a problem with the 4k springs.

Here is what you should expect to get out of your Stock Spring setup... I would HIGHLY - HIGHLY recommend going through the side instead of the top of the AFC. Do yourself a favor and go buy a cheap set of digital calipers for when you expose the locking nut you need to know where to put it back or count the clicks - but I don't see how you can really keep track after it gets so loose...

Attachment 54578

The depth from the center screw to the washer was 0.087 on one side for me (when I installed it originally it was 0.070) and close to that on the other. After getting the cover off w/ I think a 7/8" Socket (See Photo) you crank the motor around with a 3/4 on your altanator then you crank until you see your Springs come around in that hole - then your ready to disassemble. Getting the screw off can be tricky because it is a split regular screwdriver nut with a screw in the middle... its hard to explain...

Attachment 54579

I went with a 3000 but thinking about going with a 4000. I do know there is a different pedal feel but I think if I would put the 4000 in it would make my truck lighter feeling like going from stock to 3000

I wish I could be more help but this is where I am at. Anyone ever tried going from 3000 to 4000 in there truck. Did it need less pedal to get up and go?

when i did my 3k to 4k conversion i didn't feel any difference in pedal feel. i did notice a little higher eht at 2700-3k rpm's as the truck wasn't starting to defuel at 2700 any more. i rarely turn my truck over 3100. the only reason i put in the 4k kit was so i knew i would have full fuel up until i let off the go pedal.

No big difference for me... It may be a bit more touchy but nothing dramatic. I think it runs harder at 1/4 throttle than WOT. Just smoother anyway. I will never hit that range - I just like knowing its in there for some strange reason:yeah:

Did you go from 3 to 4 ?

So are you saying " I think it runs harder at 1/4 throttle than WOT " with the 3000 or the 4000?

I think he means it revs more with less pedal. At least mine does. I went from stock, to 4k, to 3k, to a mix of 3 and 4k. With the 3k, it felt like you could hold it at any RPM. With the 4k, it would rev to 1500 with VERY little effort. This was under no-load, or "free rev" tests in park. It (the 4k kit) takes less pedal to get it up to speed than the 3k kit.

Yes - I went from stock to a 3k and about 3 weeks later I went to the 4k kit for 15.99

I can't tell a diffrence really from the 3k to the 4k but thats because I don't need or want my Cummins to reach that range. Why I put it in? I have no idea other than it was available and affordable. I would do it again and I couldn't say way. I don't think it achieves anything in my range of RPM... only if you went that high would it be proficient IMO. So the 3k up to about 3600rpm by accident I know makes a huge difference... I stay under 3250RPM - after that the 4k is something I couldn't tell you about but I did put it in and really can't make out any difference though I did remember tonight that I need to slide my AFC housing full forward again so I may have backed off some power.

In a nutshell - the 3k is a GINORMOUS difference from stock... the 4 k probably has it's difference within it's range - but you have to have a motor built for it (Head bolts, V Springs, and Gaskets, Etc. Etc...) I have the Valve springs coming - other than that I only need a good Hot Shot truck that can pull a load and make a black cloud now and again. (Oh dear God I can't wait to pull with it... :updance::hd:)

A Pacbrake should be a nice addition as well...

Good luck!

A motor built for it? All you need is valve springs so your valves don't float. As far as studs and gaskets, I don't think I've ever heard of anyone replacing those solely on the fact that they put in a 4k GSK.