Hi,
Just follow the steps that you will find in the Griffin website for adjusting the ITripe with the IPOD. I used to have the same problem but i solved using this manual. I'm quoting the steps here. Just make sure that you have the volume set to 50-70%. This is important.
' iTrip Support
My iTrip stopped broadcasting. How do I get it working again?
Step 1
First, reset the iPod by holding down the Menu and Play buttons (Menu and Select buttons on the 4G iPod and iPod mini) at the same time for about 5-10 seconds until you see the Apple logo appear.
Step 2
Once it displays the main menu again, play a song and make sure that the volume on the iPod is set between 50% - 70%.
Step 3
Then follow the procedure for retuning the iTrip. Basically, select the iTrip station that you want the iPod to broadcast on. When the station starts to play and LED light in the iTrip starts to flash rapidly, immediately tap the Play/Pause button to pause the iPod and it should lock in the station. You will know that the station is locked in if the iTrip LED light blinks slowly 3 times after the rapid flashing stops.
After you see the iTrip LED light blink slowly 3 times, press the menu button to navigate back to the main menu and then when you play your music it should be broadcasting on the new station you programmed.
How do I tune my iTrip?
To get the most performance from your iTrip you need to tune it to the correct radio frequency. These detailed instructions show you how to how to select the best frequency to use with your iTrip. You can also view our iTrip Tuning Tutorial Video by clicking on the link to the right.
Note: These instructions assume you've already run the iTrip Installer that came on the CD-ROM with your iTrip, and you've synched your iPod with either iTunes or MusicMatch. If you haven't, please run the iTrip installer and sync your iPod before continuing.
The iTrip comes preset to 87.9 on your FM radio. If a radio station in your area is broadcasting on that frequency, you need to find a different frequency for your iTrip. Scan through the FM dial on your radio until you find a frequency with nothing but static. Depending on where you live, there may be many open frequencies, or only a few.
Once you've found an available frequency, you need to find its matching iTrip station file on your iPod. The iTrip Station file is a special, five-second music file that tells the iTrip the frequency on which it will broadcast. You want to 'Play' this file, but only this file. Here's how:
1. Navigate to Playlists, and then to iTrip Stations on your iPod.
2. Scroll down this list of station frequencies until you find the matching frequency.
3. With this station highlighted, press the iPod's Play button or the button in the center of the scroll wheel.
4. When the light on the iTrip starts flashing rapidly, press the Pause button, to stop playback. (The Pause button, which is also the Play button, and has a right-facing arrow and two vertical bars.) This step is very important because the iPod will continue on to the next station file if the Pause button isn't pressed, and your iTrip won't know which station to use to broadcast.
5. After you've pressed the Pause button the iTrip's light will flash slowly three times, and then remain on. This tells you the iTrip has been tuned to the new frequency and is ready for use.
You’re now ready to listen to your iPod on any FM radio., so select your music and rock on! But make sure the volume on your iPod is set between 50 and 70% of maximum; any lower, and iTrip won’t be able to hear your music; any higher and you may hear distortion.
That’s it! iTrip will remember your new station until you decide to change it. You can change stations as often as you like. Please note that you may have to play around with several different frequencies before you find the one that gives you the best sound quality.'