YouTube – Grand Theft Auto 4 – Vehicle Swingset Glitch Tutorial.
Much clearer explanation, from the video’s page:
This is a fast and simple vehicle swingset tutorial.
Follow my steps in the video, so you know how to do the swingset glitch.
The steps are also in the video description on Youtube.
This works on both the PS3 and Xbox 360 as of now.
___This is the location of where the swingset glitch is.
___This can be done by any vehicle, but it is hard to do this glitch with a motorcycle because there are high chances of you falling off.
You have to go slow onto the swingset with your car.
Once you reach the middle bar, hold X (PS3) or the brake button.
While holding the brake button, hold R2 (PS3) or the accelerate button.
It sometimes works without holding R2.After a few seconds you will be catapulted across the map.
Williamo's Blog 
This is my video :D. Thanks for sharing it on wolffmyren.com because I got 20 views from it, lol.
Awesome! Glad to hear you got some hits! I’ve been playing with this glitch all day at the office, so thanks for making the video tutorial, and for sharing!
No problem. More glitches will follow soon.
It’s a pretty awesome “feature” of the game. We even found one guy on youtube (we try to find some of the best GTA4 videos on youtube on our site) who did it with a bus!!!
Check it out: http://gtastud.com/2008/10/04/redonculous-videos-of-the-week-bus-skydiving/
Where is it? My internet crapped itself and I can’t see the video
i did this, once launched i died in mid air 😀
i keep on dieing
@Tou-Latu: If you try walking in to it, or using a motorcycle, you’ll probably die. Try a bigger vehicle. Buses are especially fun. =)
mi cuzin showed me this b4 i saw this vid
Grand Theft Auto ForEVER!!!
Nice video.Keep posting more.
This wasn’t fixed yet, was it?
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nice information, i really like that game.
Good post. Thank you for this.
VERY USEFUL POST.THANK YOU FOR SHARING THIS.
Is there a new glitch?
Awesome
where is it at I just got GTA IV
its patched, if you try to do it now you will fly out of the car.
cool! does this still work?