Been trying to troubleshoot an issue that has arisen in my 98 F150 with a 4R70W. This problem began late Monday afternoon AFTER pulling an enclosed trailer full of furniture and such. I did not have ANY issues WHILE pulling the trailer, it was after the truck sat for a few hours and i had to run to town, with no trailer attached.

Also it may be unrelated but a few weeks back i had an issue wehre the converter would not unlock and would stall the engine at idle... gave her heck a bit and it corrected itself.. go figure...

What it will do now... the converter will not lock from a standing start. It will creep in gradually, with an ever so slight shudder and about 1500 - 1800 rpm you are fine. Shifts to 2nd are sometimes soft, sometimes firm and shifts to 3rd and OD are fine (btw, transgo shift kit installed 25K miles ago, without any issues to this point). downshifts are fine and there is no slippage once i get going. If i come to a stop sign, do the 1 2 3 or rolling stop and take off there is no slippage, it is business as usual, even if you come to a complete stop only momentarily... it acts normally. if you do stop for any appreciable amount, say 10 seconds or more of time you run into the same issue with the failure to transmit power to the trans.

I have checked fluid level, it is fine, the fluid was replaced about 10K miles ago, mercon V... it is not burnt. I reset the computer last night, still does it... i have no codes thrown.

opinions on where to look to next.. whether it be the range selector on the side of the trans, some other sensor, or do i have to drop the pan and take a look inside of the valve body or accumulator spring?

This all began sunday when backing the trailer up a hill to load it... in reverse it did not really want to "go" i thought nothing of it since it was moving by about 1000 - 1100 rpm... Earlier that day it did get dropped into forward from reverse prematurely but at about half a mile an hour...

this beast has 193,000 miles on it and honestly i have never had so much as a hiccup out of her other than an AC compressor clutch grenading itself...

Thanks for the help and ideas...

Jamie

 

It is possible the converter could be coming apart. Any noise at all>??? Maybe want to drop the pan and take a look. If the fluid was changed 10,000 miles ago it should be pretty clean. -Mat-

 

i've considered this scenario.. and honestly if it has to be in the driveline i'd rather have to replace the converter than take the tranny apart... i'm in the process of moving into a new home... this is kind of a PITA to have happen, know what i mean?

BUT on the other hand... if the converter was weakening wouldn't it not want to lock up under load even in higher gears? it's only a 1st gear thing at this moment... which leads me down the electrical road in my mind... but maybe not...

just trying to be proactive... i love this truck.. it's been good to me... but man what i wouldn't give for something a bit "stouter"

J

 

The converter does not lock in first gear. It is supposed to slip in first, that's what it is there for.

 

i'll buy that it does not "lock up"... so what would cause the symptoms that are occuring?

 

Low fluid, a loose filter, or a worn pump could do what you're seeing.

 

fluid level Check, filter... well we'll see tonight... bad pump... wouldn't you see a low line pressure code?

 

There is no such thing as a low line pressure code.

 

You have describe my slipping problem to a T I will be sure to follow your post.