4r70w Problems

[BruiserOutdoors]

Installed a 4r70w that was a fresh bench build with the AA Dana 20 adapter with a a Quick Shift 4 controller. The transmission was built in 2020 and installed in 2024. It would "neutral drop" on occasion from a dead stop. I ended up getting the OK from the transmission builder to just "drive it" and see if it would work itself out. It ended up losing 3rd and 4th after 13 miles of test runs. It threw slipping error codes at max line pressure. Took it back to the transmission builder and he rebuilt it and figured it was a valve body issue. I have an additional 120 miles on it now and it has "neutral dropped" 4 or 5 times, usually at more than 1/4 throttle. It no longer seems to happen from a stop like it used to.

Stock explorer dipstick and tube. Fluid level seems good but I need to measure and verify the dipstick length.


[When I say "neutral drop" I mean the transmission drops out of gear and the engine revs up]. No error codes this time around.


Any guidance would be appreciated. Valve body issue? Controller issue?

 

[Broncobowsher]

What gear is it in when this happens? Not the shifter itself, but what is the actual gear that it is driving in?
If it is 1st gear, it is purely mechanical. You can disconnect all the wires and nothing electrical can force a neutral.
2nd gear is mostly the same, with a rare chance it is commanding 1st gear. With this transmission a commanded 1st gear will get a downshift without engine braking. There is a mechanical lockout to prevent engine braking unless the shift lever is actually in the 1st position.
3rd or 4th gear could be dropping out and going to 2nd gear (also no engine braking unless manually in 2nd gear position)

Beyond that it starts getting into data logs (Does the Quick4 data log?) and maybe doing line pressure tests and getting it to happen.
It does sound like a low fluid level issue. But I am hesitant to try changing that since you have a matched dipstick and tube.

 

[BruiserOutdoors]

What gear is it in when this happens? Not the shifter itself, but what is the actual gear that it is driving in?
If it is 1st gear, it is purely mechanical. You can disconnect all the wires and nothing electrical can force a neutral.
2nd gear is mostly the same, with a rare chance it is commanding 1st gear. With this transmission a commanded 1st gear will get a downshift without engine braking. There is a mechanical lockout to prevent engine braking unless the shift lever is actually in the 1st position.
3rd or 4th gear could be dropping out and going to 2nd gear (also no engine braking unless manually in 2nd gear position)

Beyond that it starts getting into data logs (Does the Quick4 data log?) and maybe doing line pressure tests and getting it to happen.
It does sound like a low fluid level issue. But I am hesitant to try changing that since you have a matched dipstick and tube.

The transmission builder changed the spring for more pressure during the 2nd rebuild. (55 psi sonnax lb spring)


It seems like it was in 2nd or 3rd when it happened to me. I will check with the owner when it happened to him. I think he said it was in first at a stoplight after some freeway driving.

I threw in 2/3 of a quart and took it for a spin. (Dipstick level didn't seem to change.) Didn't happen until 10 minutes in when I got on it, almost like a sump getting uncovered. I was able to manually shift from 1 to 2 to drive without issues. the issue happened when I left it in drive and did more than 1/4 throttle.

 

[Yeller]

Dumb question….. seal on the filter? I assume you’ve not been in the pan, just throwing out some of the silly things I’ve seen.

 

[BruiserOutdoors]

Dumb question….. seal on the filter? I assume you’ve not been in the pan, just throwing out some of the silly things I’ve seen.

Dropped the pan originally to install Lokar shift rod. But the whole system has been gone through by the transmission builder since.

 

[Broncobowsher]

Did they use the 4WD filter with the extended pickup, or the car filter for a flat pan? Still that is really low fluid if it is happening on flat ground.
The only way to lose drive in 1st gear is to release the forward clutch pack. And that is a loss of pressure. A loss of connection will result in a shift to 2nd gear.

The adding nearly a quart of ATF and the fluid level not changing is very strange. Makes me think even more of low ATF

 

[BruiserOutdoors]

Did they use the 4WD filter with the extended pickup, or the car filter for a flat pan? Still that is really low fluid if it is happening on flat ground.
The only way to lose drive in 1st gear is to release the forward clutch pack. And that is a loss of pressure. A loss of connection will result in a shift to 2nd gear.

The adding nearly a quart of ATF and the fluid level not changing is very strange. Makes me think even more of low ATF

FILTER (as labeled on invoice):

https://www.oregonperformancetransmission.com/product/PTM-MRK4700K-S.html

PAN (looks like this, which is an 1" or so shallower than the Dorman aftermarket with drain plug):

https://www.ebay.com/itm/3855516150...d=link&campid=5335857059&toolid=20001&mkevt=1

 

[BruiserOutdoors]

For whatever its worth, it happened twice after 60 mph pulls. Putt around town, not an issue. Get on the throttle, goes to neutral. You can manually shift from 1st to 2nd to drive without problem.

 

[Broncobowsher]

What you have is not a common problem.
You have to go back to basic diagnostics. No internet magic pill on this one.
The best clue I have seen so far is you added fluid but that didn't change on the dipstick. Next up is watching line pressure during a drive. Log data if possible.
Nobody will have a simple answer at this point. It is likely a very simple problem, but it is hiding.

 

[BruiserOutdoors]

What you have is not a common problem.
You have to go back to basic diagnostics. No internet magic pill on this one.
The best clue I have seen so far is you added fluid but that didn't change on the dipstick. Next up is watching line pressure during a drive. Log data if possible.
Nobody will have a simple answer at this point. It is likely a very simple problem, but it is hiding.

Is it likely transmission based or could it be due to the US Shift controller?

 

[Broncobowsher]

Most likely transmission. That is where you need the data logs while driving.
Until you get some data on what is commanded vs what is happening. Default is high line pressure, the controller commands reducing line pressure.