vibration

[jmwilso2]

Hi everyone I just got my gryphon a week ago and have been on a road trip half way accross canada since then I've been trying out the different canned performance tunes and am finding that the 87 towing gives me the best over all driveablility and fuel economy but both it and the 93 performance have a small but very noticable vibration when in 4th gear and under load. For example when accelerating gently, it occurs immediately after shifting to 4th. Or if going up hill at lower speed like 35-45 mph. Once I get up to highway speed the vibration goes away. It feels like it is coming from the tranny but I cant be certain. Has anyone else experienced this and if so did it go away when you got your custom tunes?

Thanks

Joe

[jmwilso2]

Hi everyone. I just installed an S&B cold air intake this morning. I started the truck up and everything seemed fine until I took it for a test drive. The intake does seem to add a little extra oomph and my average fuel economy is .8 better than before but the vibration I described in the previous post is 10times louder. It happens under the same conditions but at first I didnt even realize it was the same noise because it is so loud. I assumed it was the intake drone that I have heard the S&B has sometimes and was trying to think of a way to deaden the vibration in the air intake when I got thinking about the vibration I was already experiencing. I set my gryphon back to stock and all the vibration/droning went away. So now I am wondering if the noise I felt/heard in the original post was coming from the factory intake and the larger more resonance prone cai tube just amplifies it. I really dont know. Tomorow I will try two things first is to rev the engine while in park with the gryphon set to 87 tow and see if it makes the noise and then I'll try test driving it in tranny only. If anyone has any suggestions I could sure use the input. I'd like to make sure I'm going to keep this intake before I send in my hex code.

[Longshot270]

If the vibrations go away when tuned back to stock then it sounds like a tuning issue. I'll try to get Bill's attention to see what he thinks.

[jmwilso2]

Ok, thanks, its sure got me puzzled, if its just a tuning issue that is great because when I get my custom tunes it should eliminate the problem.

Thanks again

Joe

[Longshot270]

I'm not completely sure what it is but it sounds like a tuning issue. Normally the canned tunes dont cause any trouble.

[jmwilso2]

I did some playing around with it today. With the truck in neutral there is no vibration regardless of rpm and programmer level. When driving though there is only normal intake noise with the gryphon set to stock and a slightly louder with it set to tranny only, but in 87 tow it howls whenever there is load on the engine. Cruising along there is no abnormal noise but if you accelerate or even go up a small hill with the cruise control on it makes enough noise that you have to raise your voice to talk. Im still not sure if it is coming from the intake though i think it must be because the noise was very subtle until I installed the cai.

[Jackpine]

Now you're describing "intake drone". Bill can adjust the tune to minimize this or even eliminate it, but it WILL require an adjustment (new tune). A simpler solution is to install the DIY Gotts Mod intake which has NO drone and requires no special tuning, and it also give you an increase in power.

The earlier vibration problem could be something known as "tranny shudder" which used to be an issue a couple of years ago. I think Bill can make minor adjustments in your present tune to get rid of this.

- Jack

[jmwilso2]

Hi Jack, I'm still running the canned tunes I wanted to make sure all my bolt on mods were going to be staying before I get the customs written. If it is just intake drone why would it go away when set to stock or tranny only. I am seriously considering the gotts mod I would definitely do it if I had the chance to do it over again. I might call S&B to see if they'll take back the intake. I'm just having a hard time understanding why it only does it when there is load on the engine and set to 87 tow but under no other circumstances. Your idea that my first issue and the air intake issue are completely seperate sounds pretty likely to me now that I am thinking about it more. I am relatively certain that the vibration prior to the cai install was coming from around my feet and after the install it is higher up in the engine bay. I am also relatively confident that the loud noise after the cai install cannot be tranny because anything that loud coming out of there would have to affect drivability. So that leaves the question as to whether the original vibration was coming from the factory intake and is being amplified by the cai or if they are indeed seperate issues.

Thank you for the input I really appreciate any advice I can get about these things.

Joe

[jmwilso2]

Ok Ive reached a decision. I'm going to return the S&B and do a Gotts mod if it doesnt measure up (but I think it probably will from all I've read about it) I'll try to find an airforce1 intake.

Joe

[Jackpine]

As far as I know, the canned Lvl 2 and 3 tunes modify fueling, timing and probably other parameters that effect how air is moved through the intake.

Because air is moved through the intake in discrete "pulses", each time an intake valve opens, there are pressure waves created that can reinforce each other at certain frequencies and these create the "drone". The helmholtz resonators on the stock intake are designed to cancel these out, even when they occur on a "tuned" engine.

The commercial CAIs were also designed for stock tunes. Anything that modifies the intake timing, is outside their design parameters. When Bill adjusts the tune to get rid of intake drone, it's my understanding that he sets the intake timing back to stock.

All of these conflicting requirements have the effect of reducing the benefit of a commercial CAI.

Since the Gotts mod retains the stock design, while removing the "bottleneck" at the snorkel you don't get the adverse effects.

- Jack