stevens1994f150

i have searched the forum for similar problems to mine but mostly i find people experiencing no overdrive at all and it just revs. my problem is different, my overdrive does work but its shifting on it own at about 55-60, i can get it to shift earlier at about 40-45 by taking my foot off the gas slightly. secondly when it shifts it revs for about a second then overdrive takes over. i have no CEL and no blinking on my trans light. i checked the fluid and its at full mark and good color with no burnt scents (smells like crayons) i believe the transmission is a 4r70w by looking on the sticker in the door. if anyone could shed some light on this i greatly appreciate it

stevens1994f150

bump....

Manuellabour247

1. Has the transmission ever been flushed? It could have good color and smell, but dirt and debri could have built up over the years restricting flow in the valve body.

2. When was the last time the transmission fluid was changed, and did they do a full filter change with it? Again, the old filter could cause a restriction in fluid flow or not be sealed properly to the transmission causing limited pickup of fluid.

3. Are there any vaccuum leaks? I've found on some vehicles that vaccuum leaks cause all sorts of goofy problems. My old 75 had a modulator valve that was vaccuum driven. Not sure on a '94 if it's vaccuum driven or not.

stevens1994f150

thanks for your reply, i do not know the last time the fluid was changed or flushed since i just bought the truck about a month ago but i will check it out. there are no vacuum leaks engine runs cherry

im not 100 percent sure but i think the computer controls the shifts.

ill get some fluid and a filter and change it out this weekend she how she does and report back

stevens1994f150

alright guys im debating on weather to do this myself or have it done incase the trans does not have Mercon V in it i would be mixing fluid in it so im thinking ill need to drain all fluid torque convertor too. i have changed fluid/filter a few times on my other vehicles but never drained a TC. with my experience level should i attempt this myself or have it done?
anybody know what i would pay to have it done? BTW i have confirmed i have a 4r70w trans by stamping on side of case by MLPS RF-F4ZP-7006-AA

Crownman

It doesn't matter if it doesn't have Mercon V in it. I use regular old Dexron III in my '95 4R70W. Mixing the fluids won't hurt anything. Just pull the pan and replace the filter and gasket. You can fill it back up with Dex III or Merc V whether you drain the converter or not. It won't hurt anything.

Manuellabour247

First off, NO!!! Different brands and different types of fluid have different detergents in them. Some do not mix well with others. I've been dealing with oils for 15 years in the military and automotive shops. Do not ever mix different brands/types of fluid unless you absolutely have to. That's why I asked if you had flushed the transmission. it pulls the old fluid out and puts new fluid in. If your transmission requires Mercon, then put in Mercon. Ford and Chevy transmissions are different on the internals. The different fluids have detergents that work with the internals of each.

And just because you haven't had a problem doesn't mean that everybody can do that with no consequences. Transmissions are expensive, don't risk it.

stevens1994f150

i have not done anything yet..still waiting on my paycheck but what do you suggest i do? should i take it to a shop and have it flushed and changed? as stated before only knowledge of transmissions service is just changing the filter and putting fluid back in the pan, i never flushed a system

how much do you think ill pay to have it done?

qdeezie

The 4R70W has a drain plug on the torque converter. It is very easy to access. Draining the TC and the pan should get roughly 90-95% of the fluid out of the system.

Regarding whatever fluid you go with, make sure it is a high quality fluid that meets the Mercon V specs if that's what your trans calls for.

Manuellabour247

I used to make coolant and transmission flushing systems for BG before we lost the contract. They hook up a machine that puts fresh fluid in the return line of your transmission while pulling the old dirty fluid and putting it through internal filters. If you are unsure of the fluid that's in there, I would try to drain the TC like said above and let the main body drain as well for a few hours if possible. Then I would fill it up with the proper fluid to minimize any cross fluid contamination. Just remember that it won't run correctly with the TC empty. I'm sure you could partially fill it with a bottle and hose, but it will run rough for a minute or two. Just make sure you are checking the level every so often to make sure it doesn't run completely dry. It will take a bit at idle and running through the gears to get the majority of the air bubbles out of the system.