How does it work?

[n_spect_r]

I have spent quite a bit of time looking for this answer but so far no luck. If it is already posted please point me in the right direction.

I am trying to get a better understanding of what happens inside this transmission (4r44e). I purchased a core with the intent to rebuild it and swap what is in my truck. In the process I have come to believe the problem is the valve body and nothing in the main gears. Will outline that later.
What I have discovered is that this is a truly marvelous contraption, yet I am still baffled by one item. I have discerned the following;

Rotation from engine/torque converter comes in through the input shaft. That connects directly to the overdrive planet carrier. The OD output is driven by the OD sprag at the same speed as the planet carrier. Stopping the drum with the OD band causes the sun gear to stop and the planets now drive the OD ring gear which moves the OD shaft about 30% faster than the input shaft so the OD shaft slips past the sprag, providing overdrive. The coast clutch locks the OD shaft and input shaft together so there can be no slip on the OD sprag and provides engine braking. Really cool! The OD shaft directly drives the forward drum. Closing the direct clutch will connect the direct drum with the forward drum, and closing the reverse band causes the sun gear attached to the shell to drive the planets in the rear carrier, moving the rear ring gear in reverse. The output shaft is driven either by the forward planet carrier or rear ring gear.

Now for where I am stumped. In order to get any forward motion, the forward clutch must engage. At this point if I close the forward clutch and either the reverse or intermediate band, the sun gear on the shell stops and causes the ring gear to drive the forward planet gears which drive the output at about 1.4:1. Release all bands, and close the forward clutch and the direct clutch effectively locks the sun and ring gear together so the planet gears can not move and I have 1:1 output. What I can not figure out is where first gear comes in. Closing the forward clutch and nothing else does not produce any output. What am I missing here?

 

[Anduiril]

Well I know the 4r55e is mechanically the same as the A4LD but I'm not sure about the 4r44e but I would think it's the same. I can't remember if what you were wanting to know was covered in this thread http://www.explorerforum.com/forums/showthread.php?t=146956 or if there was a link to the information. It's a good read especially since you are looking to rebuild the trans yourself. I've started on mine.
I see you're in Florida, near Orlando?

 

[JK080]

Input shaft to the overdrive planet to input sprag to overdrive hub, this drives the forward drum and this drives the front ring gear and causes the forward planet to turn the output shaft.

The low sprag will hold the low reverse gear train and this will allow the front planet to drive the output shaft.

The low sprag does the same thing as the low band, in manual low the only difference from drive low is the low band is applied to support the low sprag.

This is why you will have no forward in drive if the low sprag has failed, it will move in manual low because the band supports the drum like the sprag should do.

 

[n_spect_r]

Thanks to both replies, I am in Melbourne. I still do not grasp where first gear comes in. As I see it the low sprag simply prevents the reverse drum from turning backwards, freewheeling in forward. I will make a mock up of it and play with it on the bench tonight. As far as the rebuild. I may go ahead and do the internals and just keep this in storage or sell later. Primarily I am doing the valve body. Ordered the Transgo kit and gaskets.
Symptoms are hard shifts, every gear operates, including OD. I occasionally get a flashing OD light, especially after hard breaking. I believe there is a pressure bleed over somewhere in the VB.
I bought the truck used and knew there was a trans issue, was cheap. At the time of purchase it would not go into OD. Crawled under and found the band way out of adjustment. Reset to spec (I think 120 in/lb then back 2 turns) and OD started working. But at the same time, if I try manual low the truck just sits and lurches a bit. Same thing if I push the OD button on the shift knob. Considering this only happens with the OD band adjusted it appears the the OD band and coast clutch are both engaging, could be wrong but this seems logical to me.
A local guy told me the problem was the OD sprag was bad, yet if that were so it would either slip and I would have no forward drive or lock up and OD would drag. Since both are working I am inclined to believe the top part is OK and focusing on the VB. Plan to install the rebuild on Mem day weekend.

 

[n_spect_r]

OK, I made a mock up of the bushing on which the rear sprag rides and the light bulb has lit. I now understand that first gear comes from the reverse ring gear driving the shaft forward and not from the forward planet carrier as 2, 3 and OD do. As I said before, a truly amazing contraption. Will put up some youtube videos soon. Thanks again.

The first video is up, describes how the OD assembly functions.

http://www.youtube.com/watch?v=3xdPUiUBY-k&feature=youtu.be

Second video is now up. Three forward and reverse.

http://www.youtube.com/watch?v=xTRjm-Kp_Jo&feature=youtu.be