97 expedition transmission slipping in 2nd gear.

[IMINYOURCHAIR]

Notes: 288k miles. 4.6w 4R70W trans with 3.31 LSD rear.

Driving home past Friday, tried to overtake and it felt like it was slipping but also had a miss so I couldn't quite tell. fixed issue with ignition.

driving home today and truck is running perfectly. try to accelerate up a hill after loosing speed. down to 50 mph so I stomp it. she grabs 2nd and begins slipping on and off. no radio on and ac off windows down and I can hear the engine mostly so I can tell she is running well. the slipping seemed to stop halfway through the rev range and she started to accelerate as normal before going to third where I let off the throttle as I had gotten to the speed I wanted to be at. I didn't need to accelerate again like that so I don't know if it is going to continue to slip or not.

I did check the trans fluid after the first incident but found it hard to get a reading. my heater hoses sit right over the dipstick handle. from what I could tell, it was somewhere between the two holes but above the first one.

Is it time for a new trans? what's the word on a manual swap?

 

[IMINYOURCHAIR]

update: Climbing the same hill as yesterday, I gave near the same amount of throttle and couldn't get it to slip.. it went into 2nd and pulled strong accelerating me past 50 quite quickly. what would cause it to slip one day but not slip the next?

 

[JUST4FUN]

When did you change the trans fluid last ? On this trans I im correct you can change all of the fluid by pulling the rubber plug on the bell housing then rotate the engine till the plug on the converter lines up then it all comes out

 

[IMINYOURCHAIR]

I haven't touched it. too much hearsay about high mileage trans failure after replacing the fluid. anyone here have that problem before?

I did notice the little inspection plug on the trans but didn't think about a drain bolt on that.

 

[IMINYOURCHAIR]

I got it to do it finally. one problem. I actually looked at the revs this time since I was driving an easy part of a road. they didn't rise/fall with the loss in power. Seeing this, I found a scan tool program called forscan. paired it up with my bluetooth code reader and got these codes and after clearing and driving they persist.

P0325- knock sensor circut malfunction. (should be able to diag on my own when I get time)

B1410 - LF window motor circut failure (all windows work properly, auto down functions too)

B1352 - ign key in circut fault ( dinger doesn't go off with key in and off, broken connector that I'm not worried about)

C1917 - Air suspension Electrical variable orifice (evo) out of range
( no clue here, air suspension seems to work as normal with no check sus light after POST)

 

[IMINYOURCHAIR]

additional symptom. while idle reading codes after drive, the truck somewhat lightly stumbled and lowered the revs for a few seconds then returned to what I know as normal idle for this truck. I did check for vac leaks when I sprayed the plug wires to check for a voltage leak there.

 

[JUST4FUN]

how does the fluid look, smell, feel, if it smells burnt or looks brownish then I would change it

 

[JUST4FUN]

https://www.youtube.com/watch?v=-OXegCB2nZw this guy it right about what happens to trans fluid

 

[IMINYOURCHAIR]

fluid looks/feels/smells normal. it even looks better than my last car did at 100k... I will go ahead and put back for the fluid/filter but I have a heater core to put in before it gets any cooler.

I will watch the video later tonight. also, after noting the revs aren't rising when I feel power loss, I am beginning to doubt the trans as the culprit... I wonder what the chances of a bad knock sensor causing the ecu to cut power slightly as a fail safe are seeing as that code comes back even after resetting the codes.

 

[IMINYOURCHAIR]

Update, So far, a tune up has solved the issue. see my thread in engine & performance section