pflan

My '99 F-150 Extended Cab 4.6 V8.. is having some transmission problems. I do not know the past of the truck (maintenance, etc.). Truck has 167,000 miles on it. Transmission usually shifts fine through town and everything, but when I am on the interstate or a faster backroad, the truck just does not like to downshift.

For instance.. if I am going around 70 and the truck is in 4th gear, say I begin to hit an incline. So to keep my speed, I hit the gas a little harder. Well the truck struggles to keep speed because it doesn't downshift. To get it to downshift, I have to really give it some gas and it downshifts hard (makes a loudish thumping or clunking noise).

Also, in that same scenario, when the truck shifts back into 4th, it sometimes shutters into gear.


I've checked the fluid. The level is fine and the color seems to be a good pinkish red.

So what would be my first step in trying to correct this issue? Maybe changing the fluid? Flushing and replacing or what?

I have also heard that a clogged up catalytic converter can cause transmission issues. Is this possible?


Thanks guys,

pflan

POltman42

Hey, I own a 98 F-150 4.6L screw with 155,000 miles on it and I'm having the same issues, I know a good transmission guy I am taking it to and I'll let you know what I find..

Also for the catalytic converters, we used to have a 97 F250 with the 460 in it, that had horrible transmission problems and even after we rebuilt the tranny, tore of the catalytic converter, which were plugged and weighed about 300 lbs each when we pulled em, after that the truck ran like new and tranny shifted awesome, so the problem may be there, the best way to check that is to feel the airflow coming out of the tailpipes with someone revving the engine, if flow is lacking or impeded it is very possible that is the problem. But that is not the cause of it on my 98 F150

pflan

Hmmm.. well let me know what you come up with man! Thanks for the input. Once you get back to me, I'll get the cats checked because my fluid seems fine!

POltman42

Sorry for the delay man, took me awhile to get my truck in the shop, got real bust with work... That shudder in my truck that feels like the transmission is actually more of a "lug" from lack of power in our style F-150s, mine was cause by poor airflow coupled with old spark plugs.. Which I only found the bad spark plugs because they weren't able to keep up after I installed a K&N 57 series cold air... They found 3 spark plugs that were hardly firing creating a lack in power that only manifested itself by the transmission not shifting because the computer is telling the engine that there should be enough power to keep up but there isn't... Changed out all 8 plugs and have driven nearly 2000 miles in the last four days and the "shudder" hasn't shown up at the speeds where it was before and believe me I tried my damndest to get it to shudder.. So as my mechanic/tranny specialist said "it's not a tranny problem but an engine power output issue , but it will ruin the tranny eventually if not fixed."

So I would suggest doing a little once over of the engine and maybe a little tuning and see wht you get but I'm not going to say yours is the same situation with certainty, hope this was a little helpful

pflan

Hmmmmm, thanks man! Changing the spark plugs and air filter would be much cheaper than transmission work! I'll look into it.

greenheadkiller98

Do not flush the transmission! Drop the pan and change the fluid, filter and gasket. (30min-hour job, easy skill level) i was having the same problem at 125k miles and i did this and it shifts like new now. The cause was my filter was clogged and barely sucking enougn fluid to shift properly. Hope this helps.

ColtRice17

Mind wouldn't downshift either and when I had itbin the shop they replaced the front passenger wheel speed sensor and throttle position sensor and now it runs just fine. Nowbi just need a new O2 sensor. Know where I can get a new one for cheap?