98 F150 Offroad 4.6 w/4R70W and approx 124K miles,
Greetings, I recently noticed the tranny "slipping" when driving in high gear w/the OD off. It's especially noticable between 35 & 45 mph. The slip doesn't last long, perhaps 1/2 a sec or less and the rpm increases for the same amount of time. It doesn't slip in OD.
It also has had a sloppy 1st to 2nd shift seemingly since I had the fluid flushed & refilled at 55k miles. The filter was replaced and the fluid used was Mercon V.
The truck sits alot now and only avg's less than 50 miles a week (usually on Saturdays).
I've heard a leaking seal on the 1st to 2nd accumilator piston may be the sloppy 1st to 2nd shift cause and that the fluid could just be old and contaminated.
Can the accumilator be accessed without dropping the valve body and will a simple fluid and filter change correct the slip?
Thanks

 

The 1-2 accumulator can be gotten to by just dropping the pan. It is right beside the valve body. Look for a big snap ring.

I would get the parts to replace everything inside the accumulator bore before you drop the pan because the parts aren't that much and you could use them anyway. You need the accumulator cap, the accumulator and an upar and lower spring.

When you have it apart make sure to inspect the accumulator bore and use a scotchbrite pad if you find any rough spots.

On whether the fluid and filter change will fix your other issue? Impossible to say through internet diagnosis unfortunately.

But, you might also want to replace the MLPS (neutral safety switch is what a LOT of parts stores call it) to see if that helps anything. That is another inexpensive part that is easy to install. You just have to make sure you install and tighten it down with the transmission in neutral and the neutral alignment marks lined up on the switch then make sure they are still aligned after you are done.

Not that this will fix your issue because I honestly don't know what the issue is, but this is a cheap part that often causes a lot of problems. You can likely get out the door with all these parts, including fluid and filter, for less than $130. So, I think it's worth a shot.

Darrin

 

Thanks Darrin
I'm to the point to where I'm either going to do a pan drop and fluid and filter change or let the dealer do it.
With the high mileage I've decided against the power flush.
If the parts price out cheap enough I may swap out the 1-2accumilator but since it hasn't gotten any worse and if the pan has alot of debris in it, I just may let it ride until rebuild/replacement.
Alot depends on what the tranny looks like inside.

 

There's no such thing as a power flush. There is a flush, but it isn't powered. It's the best way to change all of the fluid in the trans.

You can change most of it by dropping the pan and draining the torque converter. Your '98 will have a drain plug in the torque converter.

 

Thanks Mark. I've heard them refered to as "power flushes" as that is how the filter got cleaned too but in any case I'm not going with a flush. Matter of fact the service writer at the Ford dealer didn't recommend the flush as he said a tranny that hasn't had it done regularly @ 30k intervals, would probably do more damage than good. He also recommended the pan drop and TC drain/refill.
A couple more questions.
1) I see where the 4R70W holds approx 13.9 qts. Roughly, how many qts will just a pan drop and TC drain need to refill?
2) I'm assuming that the TC won't fill unless the tranny pumps the fluid in, if this is correct how many qts should be put in before starting to allow the pump to fill up the TC the quickest.
I'm concerned that running the TC dry for too long could cause some damage.
3) Is Penzoil Mercon V a good brand to use for the refill?
Thanks

 

You'll probably get about 12-13 quarts by draining the torque converter and pan. That's not a bad way to do it. Later trucks didn't have a drain plug in the torque converter, so the flush is the best way to change the fluid on those trucks. I don't believe it will do any harm to flush a trans that hasn't been done regularly, but the torque converter/pan drain will do just as good a job.

The trans pump fills the torque converter. Put 7 quarts in and run the engine for 90 seconds, then shut it off. Time this with a watch, the time is critical. Then add four more quarts and run long enough to warm up the trans and check and set the level.

 

An update,
Finally got around to serviceing the tranny. Apparantly sometime in 98 Ford must have done away w/the drain plug on the TC as I couldn't find it. I know I manually spun the engine at least twice.
I then decided to take it to have it flushed as I didn't want to chance damageing it by disconecting the return line to "power drain". I went to the Ford dealer as I had a coupon.
The flush and new fluid fill seems to have corrected my problem. 1st to 2nd shift is much better and there was no slipping w/OD off and under 40mph.
In talking to the tech afterwards, he seems to think it could have been some debris built up on the TC lockup solenoid causing intermittent or incomplete lockup. It also made sense because there were no failures in OD.
So in my case, having my tranny flushed at 124K miles when it hadn't been done in nearly 70K miles did not make it worse, it actually made it better.
Your use may very.....
Thanks to those who responded.

 

Good to hear it fixed your problem. I'm in a similar situation. 145,000 miles and not sure if the "flush" is a good idea. Sometimes my tranny seems like it can't make up its mind to downshift. The rpms go down, then up, then down, then it seems like it makes up its mind or finally hits a power band, or I don't know, maybe the TC finally locks up (not really sure how they work) and the truck will take off.

 

I was told up front that a flush was a gamble but when I discovered there wasn't a TC drain plug then I decided to take that gamble.
I also decided to go w/the Motorcraft branded Mercon V. At $4.10 a qt it was in the middle of the prices of other brands and since it nearly lasted 70k miles from the last flush, I figured it was good enough to go back in
From what I understand the shift pattern on the 4R70W goes,
1st-2nd-3rd-TC lockup, 4th(OD).
W/OD off it never goes into 4th.

You may try driving w/OD off to try to localize it.

A fluid change is your 1st stage of repair and probably your cheapest.
You may try the pan drop and TC drain (if it has the drain plug) or go w/ the flush.
I mentioned a "power drain" earlier but don't recommend it. It is a procedure I've read where you disconnect the return line at the tranny, connect a length of rubber hose to it to extend it to a drain pan, have someone start the engine and immediately stop it after you start to see bubbles and sputtering of fluid into the drain pan. This way you get the fluid out of the TC too but I was/am concerned that running the engine too long without fluid in the tranny could cause more dmage than what one was hoping to correct w/a drain and fill.
Good luck

 

There is a proper way to do a power drain, Mark Kovalsky has the procedure somewhere around here.