Hi everyone, this is my first post as this forum seems to be where Ive found the most help in the past.

I have a 2000 F150 4.2L v6 rear wheel drive with the 4r70w auto tranny in it. The truck has 108k miles on it and I don't believe it has ever had any transmission work done to it. I've driven it the past 70K miles and the previous owner kept a log of all work he ever did and I have not found anything dealing with the transmission.

Not to long ago I started noticing a knock when going into overdrive or accelerating hard and it shifting out of overdrive into 3rd. The idea of transmission problems scared me into buying a new vehicle (OK fine, it was a convenient excuse and the lifted jeep WAS necessary!). Now that I've spent to much on my jeep I would like to sell the f150 for a decent price but with transmission issues I don't expect it to sell for anything, so now I have a solid daily driver I am wanting to take on fixing the problem myself if possible.

The transmission issues started to effect 1st to 2nd gear as well which also worried me so I started with a quick fix which was adding some of the lucas transmission additive and it completely fixed 1st to 2nd. However overdrive is still an issue. When I am driving at about 50-60mph if I need to accelerate hard it gives a major knock when downshifting. I ran an OBD scan at my local parts shop and it didn't show any issues on any sensors or any codes on the transmission.

I was thinking my next step would be to change the filter but a local shop said I might damage it more by changing the oil. I understand that could be an issue if I was planning on doing a full flush but should it be a concern if I am to just drop the pan inspect for large chunks of metal and replace the filter?

Outside of the filter change what are my next steps towards fixing overdrive knocking?

Thanks everyone!
Brando

 

I would do a complete fluid change - drop the pan and drain the torque converter. If you see chunks in the pan, start shopping for a rebuild.

Don't be concerned about the filter, it only filters out big chunks and is good for the life of the transmission. Same with the pan gasket unless it's damaged.

 

Ok sounds good. Thank you. Since the filter and gasket are only $15 is there any harm in replacing them? Also best way to drain the torque converter by undoing a radiator hose and turning the truck on correct? Or are you referring to just what will drain out when dropping the pan?

 

The 2000 should have a drain plug on the torque converter. My 2000 5.4 did with the 4R70W. The OE gasket is a much better gasket than the aftermarket gasket that comes with the filter. It is a life time gasket and I would not change it for a cheap replacement.

 

Pull the inspection cover under the bellhousing and turn the engine over till you see the drain plug.

 

Thank you guys for the reply i just found an awesome guide for draining the torque converter. I have 5 quarts of fluid right now so i guess first step is to go get abut 8 more before taking this job on! I have also been told the transmission or motor mounts may be the issue. It seems odd that they would only effect overdrive but worth looking into while im doing the work I guess!

Thanks again

 

If the guide says to disconnect a cooler line, that's not necessary on your truck, you have a drain plug.

 

The guide explains draining it the exact same way yall have described it using the drain plug. will likely be this weekend before I can dig into it but Im excited to get it figured out, just hoping I dont find a broken spring or anything when i open it up.

 

Update on my f150, I dropped it off at a transmission shop to have them diagnose the issue and their response was "somethings coming apart in the converter, I cant tell you what it is until i get in there and it will need a rebuild somewhere between $1400-$1800"

Does that sound right to y'all? to me it sounds like he doesn't have any idea but just wants to do a rebuild for the cash...

Thoughts?

 

Hey Brando, Just seeing where you ended up with this as I am having the same problem on my 03 Supercrew 5.4, 4R70W. I took it to the dealer who found no codes which I believe and claimed they couldn't duplicate the problem which is BS. I drove the truck on the freeway the next day and the same "thunk" at about 50mph. As someone on the internet suggested, I turned off the overdrive and the problem went away. Turn it back on and there it is. I'm hoping this narrows down the fix but???

 

Sounds like we are having similar issues. I have not had it fixed yet, but I did learn that it is the torque converter that is causing it. You can test this by going about 50mph, instead of punching it and feeling the "clunk" quickly tap the breaks then hit the accellerator, this should take the torque converter out of lockup and you shouldn't feel the clunck anymore. Once the transmission is opened up if there isn't large metal chunks in the sump pan it can likely be fixed just by replacing the torque converter, if there is large pieces of metal in the sump pan then it will require a full rebuild. Hopefully this helps. Once I learned all this I parked the truck and am preparing to do the torque converter swap myself.