I know diagnosing noises is tough over a list but I thought I'd throw this out just to see if it rings a bell with anyone. I've got a 91 F150, 4.9/I6, E4OD, 4X2, EFI, all stock as far as I know. Bought the truck about 2 1/2 mos ago and have been learning a lot from this site. Sorry, don't know the towing/work history of the truck. So here goes...

In the last two weeks the truck has been making a new noise. Usually happens after a cold startup when in low rpms in Drive or Reverse. (I've been trying to hear it in Park too but haven't definately heard it yet.) The sound seems to be coming from the back of the engine or the front of the tranny - in that general area. It's louder inside the truck than outside in the engine compartment (because of additional engine noise? I don't know).

Description of the noise: a lower, semi-grinding or unlubricated metalic noise. I know that doesn't give anyone much to go on, but I want to try to catch this early if it's something bad. The tranny has been exhibiting "normal" E4OD characteristics such as some soft shifts and some hard shifts. OD works great and has always shifted smoothly. Recently I've noticed a little more of a hard shift here but have been doing some abnormal types of travel lately (more stop and go leaving OD on rather than having it off).

At first I thought I might have spun a bearing and/or had a rod ready to go but my oil pressure guage reads on the high side of normal and does move so I assume it's working (getting ready to put in the mechanical guage). Also, it's a 300/6 so that seems unlikely. The noise doesn't really seem to be coming from the block either. My next thought is that it's the torque converter. Anybody know what this sounds like when it starts to go?

So, any opinions on what this might be? If it is the torque converter can that component be replaced or am I looking for a new tranny?

Thanks,
Guy

 

You might inspect the tubes and hoses that connect the smog pump to the rest of the exhaust system,including near the catalyst converter. Also,the shield that wrap around the exhaust system and body may be rattling only under the torque of the engine in gear. Finally,a sagging/broken motor mount will allow the exhaust pipe to come in contact with the frame,near the manifold,causing such come and go noises.
Phillip

 

As I've listened to this noise more it seems to happen loudest and most noticably when I'm coming to a stop. So as I'm slowing to a stop the noise starts and then stops when the truck stops but it doesn't seem to follow the rpms of the engine. Is there anything it could be when the truck is downshifting?

Haven't checked the suggestions above yet. Thanks.

Guy

 

Sounds like it's coming from the tranny. When did you last change your tranny fluid and filter?

Sounds like you need to change it and evaluate the condition of the stuff that came out.