1996 F350, 351, E4OD, 4x4, 4.10 axle ratio. 135,000 miles. Transmission fluid changed about 10,000 miles ago. Fluid level is right where it should be.

Truck goes through all gears just fine when put into D. When put into 1, it'll take off just fine and hold the gear, then when manually shifted into 2, it seems like it begins to slip. RPMs will go up and the truck is not moving like it should. If I then manually downshift back into 1, it will take off. If I manually upshift from 2 to D, the slipping stops and the truck will then actually go into second gear and take off like it should. It will then shift normally shift from there to drive, and then into overdrive.

If I'm going down a hill and want to downshift, when I press the OD button, it drops into drive like it should. Then if I want to downshift further, I will manually put it into 2. When I do this, it's almost like I'm putting it into neutral. RPMs drop to under 1,000 and truck is just gliding down the hill without any downshift occurring. I will then apply the brakes to slow the truck down, and then manually downshift into 1 and it will go into first as it should.

So basically, everything seems normal with how the transmission is operating, except when manually put into 2. It will "slip" in 2 when manually upshifting, and seem like it's in neutral when manually downshifting into 2. Otherwise, things are fine and truck runs, idles, and drives normally. OD light does not flash, and speedometer and tachometer both work as they should.

I thought maybe the MLPS was going bad and not giving the signal that it was manually being placed into second gear. I replaced it but there is no change to above-described condition. Does anyone have any ideas? Anything else I should be checking? Could it be something with the solenoid pack? Or is this a sign of an internal issue and that its time for a transmission rebuild? I've been researching but haven't found anything with this specific condition. Thanks.

 

Before randomly replacing parts, check for codes. That can often point out where to start the diagnosis.

 

The MLPS needed replacement anyway - my reverse lights stopped working a couple months ago. That is now fixed with a new MLPS, but the transmission concerns remain.

I ran codes this morning:

KOEO:
hard faults:
111 - system pass
memory codes:
172 - lean condition in cylinder bank 1 (passenger side)
332 - insufficient EGR flow.

These 2 memory codes have existed on and off for several years and I don't believe they would have anything to do with the transmission.

KOER:
4 - engine ID (8 cylinder)
172 - lean condition in cylinder bank 1 (passenger side) - same as above

So I don't believe these codes help to identify my transmission issue? Anything else I should be checking?

 

The only difference between automatic second and manual second is that the intermediate band is applied in manual second. The only thing that makes sense to me is that the intermediate band hydraulic circuit has a leak.

You can test for this with a 0-300 PSI gauge installed in the test port. The test port is on the driver's side of the trans, towards the front, just above the pan. It has a black hex head plug in it from the factory. The thread is 1/8" NPT Dryseal.

If I'm right, the pressure in manual second will be quite a bit lower than the pressure in automatic second.

 

if this was the case, the problem would be most likely in the valve body if the OP were to find out that it does lose pressure, yes?

Also, i would ask and wonder if the shift indicator is fully accurate and adjusted and the shift cable has no stretching, and that the adjuster block on the bracket at the transmission is fully locked in place. as well as the shift cable bracket being squared to the case (not distorted)
I could see a small stackup of issues hiding a mispositioned indicator and thus position, but not just one individual part

 

It could also be a leak in the servo that applies the intermediate band.

 

thanks. Just trying to expand my understanding of how transmission works

 

Not to say that Ford bands break, but I've worked on enough older transmissions that bands do break.

 

Thanks. That would make sense. I imagine I would need to figure out a way to run a line from the test port to a pressure gauge in the cab? That way I can see the pressure as the transmission shifts while I go down the road? Or is there a way to do this from underneath the truck while it sits in the driveway?

 

You could lift the rear wheels off the ground and do it in the driveway, or you could run the gauge to where you can read it from the driver's seat.