Hello, a couple of months ago I've bought a 1989 F-150 5.8 with what I thought was an AOD. I made the mistake of not researching before buying so I knew NOTHING about the truck other than "does it run and drive?' I've recently found out that it's been swapped with a 5.8 and the PO put in a C6 tranny. the problem I'm having is that once I get driving and get the truck warmed up, it will make a grinding/sucking sound. it started when I was on the highway going about 60MPH. but once I got off, I didn't hear it again for a couple of weeks, so I didn't think anything of it. however, its recently started to make the Nosie again. only when in drive, only when you're on the throttle lightly, and only around 2100-2300 RPM.it also gets louder or more frequent the more you drive however, I did hear it one night when I revved it up in neutral, but only slightly. the transmission is definitely leaking a small bit. but not leaving any drops under the driveway. also, I've noticed the dipstick will push out of the tube a bit after driving it, only a little bit. but if it's not the transmission, could it be something in the engine? the PO removed the EGR system and put an aftermarket exhaust on it. at idle I can hear a noise coming from under the hood. not like from the motor but from like the water pump or something, it's like somethings loose and is rattling around somewhere. the only way to describe the noise form what I suspect is the tranny is like chains dragging on the ground. the transmission also seems to shift WAY to early. as in I'm in 3rd gear at 20 mph.
So, what do you guys think? Tranny or something else? let me know if you need any more info and I will give it to you.

 

Automatic transmissions do not make a grinding sound when they fail. There are no "gears" to grind.

 

if it is pushing the trans dipstick out of the tube a bit, i would inspect the trans vent for a blockage.

 

Then how do they create the different ratios?

 

It's not often that I've heard automatic transmissions making grinding noises, but if that is the case, it's usually better to start by rebuilding a used transmission. The noisy ones are really beat up.

 

Sorry, I'm a bit ignorant. how would I go about checking if the vent is blocked? just go poke something in there? lol

 

Well, OK, in fact their are gears in the planetary gearsets, but they are not "traditional" gears like in a manual trans. I personally have not ever seen one of those fail to where there is a grinding noise, have you?

 

yup.
That is what I do with a piece of wire.

 

They are wheels with teeth on them just like in a manual transmission. I think what you may be thinking about is that the gears in an automatic are always in mesh. They do not go in and out of mesh like in a manual transmission.

And yes, I've heard failing automatic transmissions make grinding noises.

 

OK, I have news lol. yesterday I was inspecting and cleaning the tranny. (Its leaking a little bit) and I took the vacuum modulator off to clean around it. And ended taking it out to clean the outside of it. and like 2.5 Quarts of fluid came out, all over me and the driveway. long story short I ended up putting 2.5 Quarts of fluid in it. and when I was checking the level with it running, I heard the fuel pump. (the one on the frame rail) and it was abnormally loud. when I was right by the door I heard the noise, but only for a split second. I'm thinking it's the fuel pump. I got to wait till I get paid again then I'm going to replace it.