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F150 Transmission Neutralizes on Sweeping Left Turn!

My 2003 F150 Crewcab transmission neutralizes after a sweeping left hand turn, like the turnaround under an interstate. I slip it into neutral, wait about 30 seconds, then back to drive to fix it, or, give it a lot of gas and it smacks back into to gear (sometimes). It’s been doing this for some time and the ford dealer was at a loss.

I suspect that a fluid pick up point is cavitating and sucking air because of centrifugal force, but the transmission level is fine. Maybe a small hole? or a bad oring?

How many miles are on this transmission? Did the mechanic do a line pressure check? The pressure should be checked in forward gears and reverse. If the pressure is low in reverse, you may have a problem with the pump.

It does sound like the pump is losing prime because air is getting into the oil intake passage somewhere. This could be at the filter; as the passage passes through the valve body; as the passage exits the valve body to enter the case; or from the case to the pump. I don’t know if how your filter is installed but on GM products the filter pipe goes into a receiver passage in the case. There is an Oring which seals that pipe to the passage – yours might be similar and could be leaking air. In addition to checking the line pressure, you could have the valve body bolts tightened to spec and/or replace the valve body gaskets.

Maybe ‘transman618’ will pipe in with more specific knowledge of problems and weaknesses of your transmission.

I looked on Alldata at the parts explosion of your transmission. The filter does use a standpipe to bring the input oil up to the valve body or maybe the case. There appears to be a seal ring at the joint between the standpipe and valve body/case. However, the pipe is on the right side of the transmission so the condition that would most likely cause air draw is with a sweeping right turn which would bank the trans oil to the left presenting a higher lift head for the pump and be the most likely condition for air entry. It is possible that the filter is unsecured and moving to the left on a sweeping left causing the seal ring to breach and admit air.

I was not able to pull up a hydraulic diagram for this transmission so I could not see if there was an air bleed in the line pressure passage. A lot of transmissions have a ball covering an orfice that will drop and allow air in the high pressure side to escape. If this is not working in your transmission, it could explain why the pump does not recharge unless you go to neutral or rev the engine.

Also I was wondering if it is possible that the transmission is not really up to ‘hot full’. I am sure that the dealer’s mechanic would know the procedure for checking the fluid level. But, it is possible that something is wrong with the dipstick. Maybe try another dipstick that matches your transmission and see if it reads the same. Alternately, I guess you could measure the oil level above the bottom of the pan and compare it to the same transmission in another F150.

Again a line pressure check when the transmission ‘neutrals’ would narrow down the search for the problem.

Get back to us with the solution for this problem. TNX