Valve body or deeper in?

[SoHK_alumni]

Have a couple irritating issues with the 4R70W in my Ranger. Not sure if I'm looking at a valve body problem, or if the problems are deeper in.

1st, is a massive flare when downshifting out of locked 4th at full throttle. The trans seemingly goes into neutral and lets the engine rev freely.

Under gentle acceleration, it's no problem, but a sudden push to wide open throttle and it'll flare every time.

If I hit the O/D button to turn O/D off, I can wail away on the throttle at will without issue.

2nd, day to day driving, take off in 1st is flawless. But, under impatient acceleration from a stop, I'll get a series of shudders from the drive line before things lock up solid and seem to behave correctly.

Unknown history on the transmission. Came out of a 146K mile 5.0 Explorer but was not original to the vehicle. Fluid was clean, no fragments and little "dust" in the sump. In the last 30K miles, fluid and filter have been changed a 2nd time and again, no debris in the pan.

So, do these sound like a valve body issue or a something deeper into the rotating mass? (or, is it a Saturday afternoon to replace/rebuild the TB or a weekend to replace the transmission?)

Part of me wants to pull a used 4R70W out of yard and go through it, learn as I go on a rebuild but since automatics are pretty much a black box to me, I'm hesitant to spend the coin and effort on what could end up a paper weight when I'm done if I miss something.

 

[transman304]

From what you are describing I would suspect a low pressure issue and a band failure. Could be pressure regulator valve in VB which are bad about wearing. May even be a pump issue. The only way you are going to learn about the "black box" is to get it apart and fix it. You may not get it the first time but we all started somewhere. Good luck.

 

[JK080]

Have a couple irritating issues with the 4R70W in my Ranger. Not sure if I'm looking at a valve body problem, or if the problems are deeper in.

1st, is a massive flare when downshifting out of locked 4th at full throttle. The trans seemingly goes into neutral and lets the engine rev freely.

Under gentle acceleration, it's no problem, but a sudden push to wide open throttle and it'll flare every time.

If I hit the O/D button to turn O/D off, I can wail away on the throttle at will without issue.

2nd, day to day driving, take off in 1st is flawless. But, under impatient acceleration from a stop, I'll get a series of shudders from the drive line before things lock up solid and seem to behave correctly.

Unknown history on the transmission. Came out of a 146K mile 5.0 Explorer but was not original to the vehicle. Fluid was clean, no fragments and little "dust" in the sump. In the last 30K miles, fluid and filter have been changed a 2nd time and again, no debris in the pan.

So, do these sound like a valve body issue or a something deeper into the rotating mass? (or, is it a Saturday afternoon to replace/rebuild the TB or a weekend to replace the transmission?)

Part of me wants to pull a used 4R70W out of yard and go through it, learn as I go on a rebuild but since automatics are pretty much a black box to me, I'm hesitant to spend the coin and effort on what could end up a paper weight when I'm done if I miss something.

I dont believe it will be a valve body issue, I am thinking a problem with the forward clutch, it would explain the shudder on takeoff and the flare coming from 4th gear. I bet the clutch material is flaking off the forward clutches and there is too much clearance now due to the worn clutch disks. Its a common condition I see when I tear them down here lately, matter of fact I am doing one right now and these are the clutches from the forward drum. You can see on the top one the clutch material is flaking off.

Maybe this is what you saw when you found the "dust" in the pan.

 

[SoHK_alumni]

Many thanks for the experienced opinions! I've successfully cracked into a few slush boxes over the years, but never enough to buildup any real confidence to troubleshoot the darn things.

The upside of the situation is that in day to day driving, (this thing is my daily driver after all!) it's 100% functional and since in the last 20 months/30K miles that it's been under the Ranger, the issues have not worsened so I'm fairly sure I've got time to work out a cure.

So, I think I'll try starting with a "tested good" used 'box and go through that. At under $300 for the initial purchase, add a full set of seals, frictions etc and a fresh torque converter I'll have about half the cost of an over the counter rebuild from the local parts house.

Gotta find a place to stash my "spare" 5.0 to free up the engine stand so I've got a way to hold the project 4R70W while I go through it, then it'll just be a day off the road when I swap out the boxes.

Although, maybe re-cam the spare 5.0 and stick both in at the same time? Hmmm, tempting! I've got to admit, the 4R70W really fills up the transmission tunnel and I'm really not looking forward to getting to the top pair of bell housing bolts!

Again, thank you!