Hello all,

Yesterday I noticed that there was a tapping/knocking sound coming from my truck. It occurs faintly at idle, gets louder and faster as I approach shift points, and sometimes gets a little louder when I let off the gas (I may not here it when cruising at 1500 rpm, but when I lift to slow, there it is). I popped the hood, no noise from the top. I climbed under and it sounds like its coming from near the transmission. The noise occurs in gear and in park, increasing with throttle either way. I have seen many posts regarding noises like mine coming from rods, exhaust manifold leaks, catalytic converters, etc... but none of the posts mentioned when the noises occurred ( idle, rpm, in/out of gear, etc...) so I am hoping that maybe somebody here has some experience and knowledge about this. Thanks a bunch in advance.

 

Need some more details to be able to help you. First what year is it and is it a rear wheel or 4 wheel drive?

Have you changed the transmission fluid recently or checked it?

 

Just curious how your next response will differ depending on what engine he has and whether or not he's changed trans fluid.

 

I have the 5.4 FX4 4 wheel drive package. I have not changed the tranny fluid recently.

 

Also, from inside the cab it sounds like a lifter tapping. But I've listened under the hood and there is no noise from the topside. It's not very loud, but gets noticeably louder right at the shift points then fades once it shifts. Its hard to tell if it's rpm based or transmission/shift point based. Oil pressure/temp/etc... are all good.

 

I did not ask him what engine he had, I asked him whether it was 4 wheel drive or rear wheel drive. As for my response if he's never checked his transmission fluid it could be either low or full of particulates that may induce a clicking sound. My uneducated guess is there is something wrong with the transmission but based on his description it could also be stemming from the transfer case. One other possibility is that the slip yoke needs to be greased. Louder at the shift points suggests something in the transmission but there are a couple other places the noises could be stemming from.

Without actually being in the location to actually hear the problem we have to use a process of elimination and knowing where in the drive-train the noise is coming from for certain will help improve the chance that he gets the help he needs.

Also keep in mind that the transmission is slightly different in the 1997 version of the F150 than in the 98 and newer as well. Does it have bearing on the problem.......most likely not but it may.

 

Thanks a bunch Aragorn, it is most definitely louder approaching a shift and quiets immediately after. But, sitting in park it can be heard at idle and increases as I rev. Could that still be tranny related? Makes it seem to me that it's not, but i know very little about transmissions.

 

It may be still transmission related but as Tackle pointed out I don't know WTF I'm talking about. That being the case I'd suggest getting a mechanics scope and scoping the transmission. The scope should help you locate more directly where the noise is coming from.

Here is my reasoning, your transmission always has moving parts even when in park. The torque converter always spins when the engine is running. There are a lot of other moving parts in the transmission that continue to move regardless of whether or not the vehicle is in motion.

Reasoning on the mechanic's scope. It's a little old school but can be used to track down where exactly the noise is coming from. It could be from the oil pan which would indicate the CAM is making the noise. It could potentially be from the transfer case. Once you locate the actual source of the noise it is easier to troubleshoot.

Just my uneducated opinion though.

 

Good to know. Looks like a trip to harbor freight is in my very near future. I appreciate your help, its making me nervous. Its weird that it literally started making noise overnight. I'll get the scope and see where that takes me. Thanks again

 

Once you know let us know and others may have suggestions on how to repair it. Personally I'd check your transmission fluid first and possibly change it.