rattling
 

when im in 2nd gear, and i give my truck gas, it makes this horrible, loud rattling noise. but when i let off the gas, it stops. we put it on a dyno and when you pull down on the driveline in the back, the noise stops. any ideas? also it sounds like there is a rattling towards the front too. like right under the driver seat. almost thinking its the catalytic converter or the heat shield my mechanic put on because he tought it needed one. there wasnt one there before and he did kind of a half ass job. not bolted on very well. its a 1996 Tacoma 4WD, 2.7L thanks. its so annoying i dont even drive it. please help!!!!

When you say pull down on the drive line are you talking about the rear axle? The transfer case? My first guess would be a bearing but why only in 2nd gear. If it only does it in 2nd gear I would think it would be the transmission.

rattling in the front could also have something to do with the alignment. Rattling is never a good sound for your Toyota Tacoma to make!