My '95 T100's 3.4 would Knock or rattle when I accelerate harder then normal when the engine was cold. I noticed it in 2nd gear mainly. I figured it was probably piston slap because it wouldn't do it after it fully warmed up. I heard that sound for a few years but the motor had over 200K so I chocked it up to ware. I just figured they expanded and filled the bore when up to operating temp. Anyway I replaced that motor with a JDM engine, a 2000 or newer by the front oil dip stick. There usually (suppose to be) lower mileage motors but it makes that sound even louder then the old motor! It stops when its warmed up but I certainly wasn't expecting it. Don't get me wrong, it runs great and has all the power or more then the old one its just a sound you don't want to hear! Is this common to 3.4's? Does Toyota used forged pistons? I'm just curious.

 

I haven't seen anything about piston slap on the 3.4L engines at all. Are you sure that's what yer hearing? Shoot some video and post it up.

What kind of oil are you using?

 

I'm running 5W30 supertech oil (wallmart brand). It won't do it by just reving it up. It has to be under a load. I'm not sure of what the sound is but it is heat related because once its fully warmed it won't do it. I can't do a video, wish I could, I just wondered if it was a common sound. It sure runs good, I'll just take it easy till its warmed. I plan on rebuilding the one I pulled out so I'll know more when I tear it down, get some measurements. But that project has to get in line with the rest of them! I'll post about it when I do.

 

[quote= Is this common to 3.4's? [/quote]


no. mine does not make noise.

is it an auto trans?

 

Carefully inspect the driveline...you might have to take the drive shaft off to test the U-joints and the other stuff.

 

Its either a cracked flex plate, or you've got a slight exhaust leak somewhere.

 

It's a 5 speed. All new exhaust gaskets. I might be hearing a little valve train noise. The new motor had a little looser clearance (just looking a the wear pattern on the cam lobes, I didn't measure them). That may be why it seem louder then the old one. I should do a proper clearance check but for now its just nice to have my truck back on the road and for that motor to earn its keep. I'll post some clearances when I can get to it.

 

Piston slap? No, your looking for valves, exhaust leaks, pinging from pre-detonation, or a misc demon rattle. Piston slap is not somthing to suspect.

 

could be a cracked manifold. Gets warm and seals.

 

Good point, an air leak at cold temps would cause some pinging or knocking. Then taper off as the motor heats up and seals the leak.