Tranny question Bill?

[Tholt34]

Bill,
I know you were at Ford for a while and I think i have an electrical issue with my tranny and I was wondering if you might have an idea. Here lately my Od light will flash when i come to a stop and it feels like the truck falls out of gear. You can barely role the truck and you will feel it set back down into first and shift fine through overdrive. No slipping or mis shifts or anything. Sometimes when you stop and put the truck in park it will rev up a couple hundred RPM and then drop back down to normal idle. Well the code I get is a P0720. I know this is the OSS and i first just replaced it. Still didn't fix it. SO i got a scan tool from a friend and started looking at things. Well i noticed with the scantool in datastream mode, the transmission gear says its in 2nd when and shifts 2-3-4-invalid. The transmission switch on the scantool reads correct to whatever I have the shifter in. So if i have it in overdrive it says overdrive, Man1 it says man1. So i'm wondering why my pcm is thinking the truck is in 2nd when i can feel the truck is physically in 1st and mechanically the truck shifts fine. Also when it feels like the truck falls out of gear and i can manually put the shifter in 1st and the truck goes into first and no issue. I have pulled the whole transmission harness out of the truck and checked for broke or cracked wires and ohmed wires out and have fount nothing.
I have heard of interference from like alternator or some power wires can cause issues with this but i'm just trying to pinpoint everything else before I go any further. Just wondering if anyone has heard of anything and I figured you knew the electronics pretty well Bill so i figured i would ask.

Sorry for the long post. Any info is greatly appreaciated.

Tim

[hayjayhorses]

what year truck? how many miles? stock or modded tranny? Any tunes? What dose your tranny fluid look like? Dose the ATF smell burnt? Is your ABS light on or dose your speedometer needle ever bounce around? If you post the answers to these questions you will give the people who read this forum a little more info to help troubleshoot your issue.

When you say "falling out of gear" dose it fell like the tranny is going in to neutral, as in no drag on the engine at a stop; at this time dose the engine idle up?

As for putting the truck in park and reving up a couple hundred RPM. Sound like the (1) Torque Converter (TC) may be pulling harder then it should, or the (2) PCM thinks the truck is still moving,

(1) In my '00 F550 about 1500 miles before my tranny blew:cursin:, a few times I noticed at a few stops I had to really push on the brake like the TC was pulling hard and the engine sounded/felt like it was fueling more to maintain an idle, when I put it in Neutral the engine would rev up then go back to idle. Have you heard any growl noise from the tranny?

(2) when I put my truck in to Neutral while still moving it will rev up, but it will rev to 1600-1700 rpm.

Good luck, I hope it's an easy fix, My tranny came apart 1000 miles from home with 9 horses in the trailer.

PS: this is why I am putting a 6 speed in my F550:cheesy smile:

[Tholt34]

2000 year truck, stock tranny, php tunes, does it whether chip is on the truck or stock. Tranny fluid smells fine and is red ad not burnt. Its never been overheated. It almost feels like it go in between gears. My converter isn't dragging, I know what your talking about there but thats not it. Why is the scan tool telling me that my pcm is reading my truck in 2 when its actually in first and then when it shifts in overdrive the scan tool says it is invalid.

[hayjayhorses]

could have a sticky valve or leak in the valve body


I sent you a PM

[Power Hungry]

The transmission will default to 2nd gear any time it feels there is a problem with the low/reverse clutch assembly. Unfortunately, there are several things that could cause this and I'd be very hard pressed to offer a solution or even begin to tell you where to look.

My best advice... Call Brian's Truck Shop (870) 422-FORD (3673) and see if they might be able to offer some possible pointers. Because this issue could be either mechanical or electrical, you may have some hunting to do.

I wish you the best of luck and hope it's something simple and easy.

[Tholt34]

Thanks Bill. Been trying to call brian, He's a busy guy to catch up with which i understand. I guess there could be a line pressure issue there, but as far as mechanically how the tranny works, it works great. Shift fine and solid and doesn't slip. Pulled the pan last night and there were no material on the magnet, fluid was still good, I couldn't find any sticking valves in any of the valve bodies. I've read a couple post on rfi interference. Do you have any ideas on that? like alternator being good but causing interference?


Tim

[Power Hungry]

I've never seen that, but doesn't mean it can't happen. It's possible that the MLPS (shift position sensor) is flaking out on you and I'll try to locate the tests for that and get them over to you. Other than that, I just don't know. :shrug:

[Tholt34]

I'd really appreciate that Bill. I have been wondering how to test and what it exactly does. Thanks.

[Tholt34]

I talked to brian at bts finally. He thinks that since i keep getting a 720 code and something is interferring with the signal from that sensor. He recommend alternator so i test drove it with it unhooked and no problems. So i bought a new alternator and so far its been good. He was great to talk to and really helpful with information.