First, I want to apologize if there's a thread already somewhere. I tried searching but didn't have much luck finding this particular problem.

When the truck is cold, it runs top. Never misses a beat. Once it's up to operating temperature, it skips 1st and starts in 2nd gear, every time. Manually shifting to 1st doesn't help. In fact, it feels like the trans is hanging up. Barely wants to move in 1st.

basics on the truck:
95 F-150
136,500 miles
5.0 engine
4r70w trans
4x4
4 inch suspension lift + body lift
35x12.5x15 inch tires


When hot:
Reverse is solid.
2nd, 3rd and OD always work.
Lockup works
No check engine or flashing OD Light.
OD switch functions normally
If I pull over, turn the truck off and start it immediately, I get 1st gear back every time. This can also happen if I run to the store. Then, once it shifts out of 1st, it's gone again. This works every time, without fail, so I use it if I really need to beat traffic at an intersection.

Basically, when it's hot, it just starts in 2nd gear and manual shift does NOT give me 1st.

What I've done:
Trans filter change
Thermostat (running hot and thought that might help)
Electric fans(because clutch fan was bad too)
Range sensor
Output speed sensor
VSS on pumpkin
Recalibrated PSOM for 35s(which did help with overall shifting, but no fix for 1st)

I used a friend's snap-on scanner
KOEO:
121 - closed throttle pos out of range
552 - air management 1 ckt problem

KOER:
121 again
321 - therm air system not working bank 1

Per that tool, closes throttle is showing .73 volts and WOT is showing 4.48 volts. I read somewhere that the spec is .75 to 4.5.. not sure though because I don't have a proper book, only a Haynes manual.

I was told by a friend of a friend that it sounds like a bad deal on a clutch pack causing blowby once hot. This doesn't make much sense to me, because key cycling gives me a 1 time fix.

I feel like it's electrical. Problem is, I have no idea where to start actually. I only started throwing sensors on it because I figured if I had to rebuild it, I'd be replacing most of them anyway.

Could it be the shift solenoids? Doubtful because I have OD still and I know(from one of these forums) how they cycle for shifts.

Could it be some other switch or solenoid in the trans?

Obviously the TPS is going bad, could that actually be the problem??

I also have a hard time buying that anything about the AIR system would cause a trans problem. Especially since it's not bad enough to trigger a check engine light.

​​​​​I really don't want to rebuild, but will if I have to.

I've been hanging by head about this for over a month now.. any help would be greatly appreciated.

And if someone can straighten me out and it turns out to be a simple, cheap fix, I may even consider a 12 pack. Lol

EDIT::::
​​​​​​Need to add... I can reproduce this without even driving. If I let it get to temperature, manually shift to 2nd, then to 1st or Drive, 1st is gone and it wants to start in 2nd.

 

Ok, so the throttle position sensor is a problem. Probably not a problem that will cause the transmission to start out in 2nd gear, but a problem. Start there and get that right.

My bet is valve body as long as the range sensor is good.

Can that scanner see commanded gear while driving?

D

 

Yea, it's the snap-on mt2500. I didn't drive it though, didn't think I had to. I got it hot before even testing it because one of the tests required the O2 sensor to be warmed up a bit. By the time I got deeper, it was operating temp.

While it was giving me the problem, I looked at that. All positions read as they should. Even manual 1. I honestly forgot what each readout was, but it looked right. I apparently deleted the pic I took. In manual 1, I think the voltage was .69 or something. Which I believed to be low.(I read somewhere). So I replaced the range sensor already too. Went with Standard brand, as I've always had good luck with their parts and I couldn't get my hands on a motorcraft brand. It had the neutral alignment mark and I went full OCD and used a mirror to make sure my initial alignment wasn't skewed by angles. It already has the new style connector, oval-ish with the single locking clip.

I will be getting the new TPS next week, along with a short piece of trans cooler hose. Apparently, while manipulating the radiator to get the fans on, I wasn't careful enough about the rusty line, cashing a pin hole.

You mentioned the valve body? Whatcha thinking?

Also.. anything else in there I should check if I have to go there? Since I'll have the pan down again.

PS: I'd seen you reply on another thread and you mentioned having history with these transmissions. While I'll take any input I can, I was kinda hoping you'd see this. Lol. Not trying to sound creepy, just that diagnosing transmissions was never my strong suit.

 

I want to add.. I don't like to question those who obviously know more than me.

Having said that, I keep coming back to one thing. The problem can be temporarily remedied by turning the truck off and starting again. I do this at a stop sign if I need to beat traffic. Then, once it shifts from 1st to 2nd, the problem stays until next restart, or when it cools down. It works like this every time. This led me to believe that the problem is electrical in nature. Some solenoid, switch, sensor, etc. Am I over thinking this? Could it be some hydraulic problem? I would thought something hydraulic would have been either permanent, no matter what the temp of the truck. Or, it would have been more random overall.

Again, not questioning to be a D.. it's just my nature to learn as I do this sort of stuff.

 

I would look at the commanded gear while driving it. That's exactly where I would start.

D

 

Ok, thanks. Once I fix the trans cooler line and borrow the scanner again, I'll do that.

 

Darrin, I've got the scan tool. But of course it's pouring today so I won't get to the drive test. Thinking back, I'm not 100% sure it will show commanded gear, but I'll poke around anyway to be sure. I just can't remember if it gave me the info you're looking for, but we'll see.

I did get new TPS in and as thought, no fix. But, it definitely has better throttle response than before.

On a side note.. taking time away and stepping back from it, I got to thinking. Maybe it could be hydraulic? Even with the weird kink of being able to temporarily fix it by key cycling.

​​​​​​Is it possible that by shutting the truck off, I'm releasing pressure from something and it's "resetting" itself? Could this simply be an overpressure issue somewhere due to the trans getting hot and something being sticky that's simply released when I shut it off?

I know I was stuck on electrical problem, but that just kind of popped in to my head when I realized that shutting it off, also stopped the pump. Also, if I try this by neutral revving, key off/on to avoid starter use, it does NOT fix it. Only shutting it down and restarting does.

It basically made me think more simply about how they work. I could be way off, but just kicking around ideas.

Thanks for your help. I'll let you know when I figure out if the tool can see commanded gear or not. If so, I'll post results.

 

I did the drive test. Using the same MT2500 Scan tool. But before I do, I want to add that I went and checked all connections and wiring harness for the transmission, and really just about everything else I could see. Everything looked ok. Until I got to checking the bulkhead connector (Vertical harness plug on the rear passenger side of my trans) Which is a terrible design IMO. Anyway, that plug had a fair amount of transmission fluid in it. I tried to clean it out, but didn't want to do anything crazy since it's in an awkward position and I couldn't see it.

Now, for the drive test. Here's what the scan tool showed me.

When cold or hot, and shifter in D, It shows
MAN LEV POS___O/D
TR=GEAR___PRND

Through the gears cold and hot:
1st -- PRND
2nd -- DRIVE2
3rd -- DRIVE 3
OD -- DRIVE 4

When hot, it still drives like it's in 2nd. Shows PRND change to DRIVE2 at the same moment it shifts from 1st to 2nd when cold. Difference is, there is literally no shift when hot. I feel nothing, no bump, click, slip.. nada. Just carries on until it shifts to 3rd.

PARK/NEU indication shows normal. R_DL when in any gear. P_N when in park or neutral.

TPS Code gone since I replaced that. Still no new codes with KOEO and KOER tests. (still has AIR codes, but I understand they should have zero effect on anything except emission inspection)

Could the internal harness/bulkhead connector having trans fluid in it be my problem? Or am I being too hopeful at this point? Regardless, I will be checking it when I drop the pan next. I will look to get o-rings for it. Or maybe I'll just replace that internal harness, they seem to be fairly inexpensive.

I'll wait until I get some more input from you.

 

Darrin, I was wondering if you'd had a chance to look over my drive test results.

I am definitely leaning towards some kind of mechanical/pressure related problem. As I mentioned before, if I turn the truck off and start it again, it does fix it, but for one shift from 1 to 2. However, if I try to park/neutral rev, and key cycle, it does NOT fix the problem.

I could be wayyyyy off, but I'm thinking valve body and/or 1-2 accumulator problem. Not sure why either one would cause problems ONLY when hot, but who knows.

 

Discovered another temporary fix today. If I put it in reverse and goose it enough to chirp the tires, I will also get first gear back. Can also do this if I shift to reverse for a few seconds, then neutral for a few seconds, then back to drive.

In both cases, it's about a 70% success rate. Also in both cases, it's similar to re-starting the truck. It will only last until it goes to 2nd gear.

Now I'm totally confused. Could it possibly be low/reverse servo? I'm only wondering this because when it's acting up, using manual 1 makes it feel like there's a brake applied. It'll try to go forward, sluggishly. But when I let off the gas, the truck almost immediately stops.

 

So, let me just start by thanking the hell out of Darrin! And you can add this to your banks as well, just in case someone else has the same issue!

Anyway, after discussing things with Darrin, it seemed like a rebuild job was in my future. However, I decided I would be remiss if I didn't at least drop the pan and check a few things before I committed to such a big project. (For me, having never done it)

Upon dropping the cap for the 1-2 accumulator, I noticed something odd. There was no O-ring on the pan end of the piston. Springs were good though. So I consulted Google, and every image of the OE metal pistons has two O-rings, one on either end. I just happened to have one that worked AND fit into the sleeve without catching or binding. I put it back together, put fresh Merc 5 fluid in it and fired it up. At first, I was just happy to know it went in to each gear.

Then the test drive. First, in my driveway. (Already nice and hot) While before, Man 2 back to D or Man 1 would make 1st disappear. This time, it was there!!!!! On down the road I went... and maaaan is this thing alive! It NEVER dropped first. Better still, is the fact that 1st kickdown actually works again.

This thing boogies now, even on 35s!

Again, it was completely missing the lower O-ring on the pan end of the 1-2 accumulator piston!

And Darrin, thank you again sir!