HEllo i am new to this site and a new F150 truck owner. I just bought a 1991 Ford F 150 4.9l 6cyl 2wd truck for $800. It drove perfect back to my house from where i bought it which is about an hour expessway trip. Once i pulled in my driveway i noticed some leaking from under the truck. i looked underneath the truck and there was about a 1 1/2 inch round hole on the transmission. Which had dumped all the trans fluid, I cannot find anything about a plug for the bottom of the trans. I called my local autozone and he suggested theat it might be a freeze plug. So i bought one and installed it which it fits snug so maybe thats it. I checked the oil and trans levels with the truck off and they both read perfect. I was going to start the truck let it run for a minute and then check the trans fluid again but when i started the truck it was knocking very very loud. Could this be because the trans is empty? also the fluid was red/brown is that trans fluid? or do i have a bigger problem? any suggestions or advice would be greatly appreciated.

 

To answer your problems, the hole is just an access and had a rubber plug in place.
The leak is a bad seal.
If the knock is not in the motor it is the converter making the noise.
See this in an 85 my son has.
Unless you can get trans sealer to work after about 300 miles, it will keep leaking but the noise may stay.
The trans needs to come out and a decision made to rebuild or just take a chance on servicing front seal and put in a converter.
I think you bought problems the seller knew about.
Good luck.

 

Howdy and welcome, yer in the right spot! Yup, like he said, just an access up to the torque converter drain.

Which tranny do you have?

PRND21 wich is a C6
PRN(D)21 with an OD lockout button on the dash which is an E4OD.

When you say it dumped all the fluid what do ya mean? The E4OD holds about 20quarts and if i remember right the C6 about 15quarts.

For the knocking id say it's time for six new motorcraft plugs and wires, a distributer cap and rotor, and a fresh oil change with a Motorcraft FL1A filter and some 20w50.

Adrianspeeder

 

i dont think there is a bad seal. like you guys said that drain was the leak. that is where all the fluid came from. i have the PRND21 wich is a C6 trans. and the knocking started after all the fluid leaked from the drain whole. so i guess my question is if i refill the trans will the knocking stop.

 

No, you misunderstand, the hole is just an access to the the torque converter drain. The original rubber plug is just to keep dirt out. Have someone spin the motor by hand until you can see the drain plug on the TC through the hole and then make sure it's tight. Or it could be the front seal of the tranny leaking. The fluid collects in the bell housing and just happens to leak through the access hole in the bottom.

I still think a basic tune up will solve the knockin'. What's the mileage? Keep in mind it's only a 5digit odo so that first number could be 0, 1, 2... ext. How well was the truck taken care of.

Also interesting with the C6 being in yer truck. This is the first '91 half ton I've ever seen the C6 in. Mostly by '90 they were all E4OD. Good news is it's about the third of the cost of an E4OD if it does need rebuilt.

Adrianspeeder

 

maybe im not understanding or not explaining it right but the hole im talking about on the bottom of the transmission, if i look up in it i see gears or at least 1 gear. so i dont think this is just a dust cover that came off but i could be wrong. so i just got home and i put more fluid in and started it and the same noise is coming from under the truck. im not good at explaining noises but as far as i can tell it is not actually a knock its more of like a clicking noise. i put it in drive and it went forward and put it in reverse and it went back then i parked it. it is way to loud of a click to drive it and it really sounds bad.

 

The clicking could be a noisy lifter. Does the sound seem like it's coming from the engine or transmission?

In either case, 20w50 would be too thick for my taste. 10w30 would be fine or if it's really cold where you live then 5w30. 20w50 would only be a band aid to the ticking noise and could only hurt you in the long run as opposed to 10w30. But as long as there's some kind of oil in the old 300, it won't matter. They are indestructable which makes me think the tick could be not be a serious motor problem.

If you drove it for an hour on the expressway, it must have kept all it's fluid in it while driving. If it did, then I wouldn't suspect the TQ drain plug. I would suspect it's the front seal on the trans.

Keep us posted

 

mj,
the transmission has a pan on it's bottom that holds the fluid.
If that had a hole in it all the fluid would drain out except what is in the converter.
The hole in the bell houseing; you may see the flywheel ring gear the starter uses to crank the motor over with.
That area would collect fluid from a front seal leak or even a rear main bearing seal leak.
Since you discribed the color of the fluid as reddish, it is transmission fluid.
Take another look at it and you will see what I am saying.
A converter can go bad to make the noise you are hearing.

 

That's correct. You are not understanding. There are NO freeze plugs in an automatic transmission.

The hole is to access the torque converter drain and attaching nuts. The gear that you see in there is the ring gear. The starter engages the ring gear when you start the truck. A rubber plug belongs in this hole, and it's function is to keep dirt out. It doesn't seal to keep fluid in, because there shouldn't be fluid on the other side of the plug unless the front seal has failed.

There are a lot of things that can make that noise. Without hearing it for myself I'm not going to make a guess.

 

Yes, that is just a "dust" cover that goes in that hole. There should never be any transmission fluid coming out of that hole. If so then there is a leak for sure.

The gear you are seeing is the gear that is driven by the starter and is on the outer edge of the flexplate. This is at the very front of the transmission in the bellhousing and is the plate that attaches the engine to the torque converter and thus the transmission. So behind the flexplate is the torque converter which is a sealed unit. These parts sit in an area called the bellhousing which is separated from the rest of the transmission internals by the pump, which is a sealed unit and has the seals on it that seal the transmission in that area. If you have transmission fluid in there then you either have a leaking torque converter drain plug, a leaking pump to case seal or a leaking front seal. If you have engine oil in there then you have a leaking rear main seal.

Everything in that bellhousing area rotates directly with the engine. So the knocking is probably the bolt on the freeze plug that you installed into this hole hitting the torque converter.

Hope that explains it.

Darrin

 

Thank You all very much for the great information. I now understand (embarressed) sorry it took so long for me to get it. I have a friend that owns a shop so I am going to take it up there and have him give me an estimate. So the dust hole that i see is that on the transmission or the bell housing or something else? sorry like i said im not good with this stuff. Also the engine seems to run fine and the body is strong and in good shape. Taking that i paid $800 for the truck would it be worth it to try and fix it or should i try and persue this guy for my money back? any opinions i would be gratefull for and again thank you so much for the help!

 

You should check the trans with the engine hot with it running in park.

 

Or just note whether it is hot or cold and use the appropriate hash marks on the dipstick.

Darrin

 

Well you guys were right it is leaking from the front seal on the trans. Also the engine is leaking from the rear main seal and the valve covers to expensive to spend on a $800 truck. Me and the the Seller are going to small claims court but thats a whole other story. But i did buy another F150 so i'm still in the club lol. I bought a 1998 Fi50 v8 triton super cab manual trans with 130,000 miles for $4000 i hope this turns out to be a ok deal.