Had a TSP 216/220 112lsa .600" cam installed at the end of march. I've been enjoying the truck with no issues since, except for when I had new tires put on a couple weeks ago. I previously had a 265/70/17 P metric tire, and switched to a 285/70/17 LT (18lbs heavier per tire). I immediately felt the difference when pulling out of America's Tire. Whenever pulling away from a stop, at very low speeds (1-3mph), I notice this shaking/hoping occurring. It happens every time, but goes away at anything over 5mph. Zero vibration at highway speeds too, which rules out a wheel balance issue.

Did a couple searches, and it looked like it could have been the U joints. I hopped underneath, and saw the driveshaft moving around a bit (snapped some videos), and replaced both U joints for the rear shaft. Took it for a test drive after and did the same thing.

Friend of mine thinks it's the motor mounts, but the motor doesn't seem to move that much (had it in gear, brake depressed, and jumped on the throttle a few times, and minimal movement).

What I've found out, is that if I have one foot on the brake, and give it some gas before releasing the break (only increasing the rpm's to ~1000), there's no shudder.

Could it be the idle is set too low? It's currently around 650 or so. I'm thinking that maybe the duration/overlap is what's causing the truck to hesitate when taking off from a stop without giving it gas, becuase it's very rhythmic when it does it. And I didn't notice it before because the tires were much lighter. But now with the added rotational mass, 45% more more tire (40lbs to 58lbs), it's substantially more apparent.

If it is the cam, is this what a higher stall would fix? What about gears? It's currently got the 3.08's, which I am thinking about swapping for 3.73's or 4.11's. Obviously I could raise the idle, but I dig the lope. lol

Video doesn't do a great job of showing what's going on, but you can see it a little bit, especially in the leaf springs in the second clip.

 

Seems like a tuning issue to me.

Without seeing the tune and data log it's hard to pinpoint but it surely seems like it's a issue from where it comes off idle and transitions to driving.

 

I agree with FFDP. That's a tuning issue. A 112lsa at 650rpm's is going to body rock the **** out of that truck and make it seem like it's running poorly.

IMO, up the idle to 750 or so. You're going to have to play with it to find something you like.

Mine idles at 950 just because that's where it idles better and it's a bigger cam.

 

That sounds like the tune is off and it may timing causing the surge. LSA doesn't cause surge by itself, overlap does. That cam is -6 overlap and should idle and drive fine in that.

 

950? What size cam in what motor?

My 230/242 115 idles at 725 no problem.

 

YUP...Just swapped in a bigger cam as well and set to get her tuned on Monday after the LSXRT is installed. Having just a tad bit of hesitation issues but nothing too serious

 

226/232 @115.

But that's where I want it.