I have a 1998 F150 4x4. 4.6L with 4R70W tranny. My O/D light started flashing a few days ago. Only occurred when the truck was run on a 30 minute or longer trip. Happened twice in two days. On the third day, the truck will not shift from second to third gear. It will occassionally seem like it is trying but the engine just revs and the truck drops back into second. Had the codes read and they say it is a speed sensor. Replaced this. Same problem. Was told it could possibly be a solenoid. Replaced this. Same problems and the codes still read speed sensor. I am at a loss. I would like to avoid a tranny shop until absolutely as the one in my area, without seeing or driving the truck immediatly said they would need to rebuild the transmission. If anybody has any guesses, I could use the help. Thanks.

 

What are the codes exactly(ie. P0500, P0503 etc) Sounds like something is wrong with your direct clutch or 2-3 accumulator. Lets start with the codes first and go from there.

 

My mechanic read the codes for me. I will be trying to contact him tomorrow, but it may not be until Monday. When I do I will get the exact codes. Will let you know. Thanks.

 

The code is P1500. One other interesting thing that I found. I took the truck for a drive with the computer hooked up. The computer shows a shift 1 solenoid, shift 2 solenoid and a shift 3 solenoid. With the truck in drive, when I start driving the shift 1 solenoid is shown as on. When the truck shifts to second, the shift 2 solenoid is on and the shift 1 solenoid is shown as off. The shift 3 solenoid is never turned on and the truck never goes into third gear. The solenoid has been replaced along with the speed sensor.???? Would appreciate any guesses. Thanks again.

 

Hey derhicks

The 4r70w trans only has two shift solenoids, plus a tcc solenoid and an epc solenoid. Not sure why your scanner shows a third shift solenoid? Anyway it sounds like the shift solenoids are operating correctly. The code p1500 defenition is

DTC P1500:
Diagnostic Trouble Code (DTC) P1500 indicates the VSS input signal was intermittent.

Possible causes:

Intermittent VSS connections.
Intermittent open in VSS harness circuit(s).
Intermittent short in VSS harness circuit(s).
Damaged VSS.
Damaged PCM.

Seeing as your truck is a 4x4, there is a tsb about a loose speedometer drive gear causing vss codes. If you take the vss out of the transfer case extension housing and reach in with one finger you should be able to feel the drive gear. It should be tight on the shaft, if it loose then that may be why the code is being set.

I think you may have more than one problem that just surfaced at the same time. The p1500 code set by the erratic vss signal, usually causes erratic shifts but not a no shift condition. There is also a tsb for your year truck that pertains to an updated 2-3 shift accumulator. The original 2-3 accumulator did not fit properly in the bore on the trans, allowing fluid pressure to leak past the large seal surface. The updated part has a tighter fit.

How is the trans fluid, its not burnt is it? When you had the pan down to change the shift solenoids, was there any debris in the pan? Is your trans original or has it been replaced before?

Later

 

Xplorer,
First off, thanks for your time and all the input. About two problems at once. this may be a possibility. As i stated in the first post, the O/D light started blinking a few days before the no shift situation. When the light would blink I got very erratic shifts. Was told the transmission was in protection mode and that was the cause of the harsh shifts. So, possibly the VSS was the cause of that problem. My main problem now is the no shift from 2 - 3.
To answer your questions. The transmission fluid is clean. Just changed about two thousand miles ago. This scares me because I read some posts about guys losing transmissions soon after fluid change. At any rate, old fluid was clean and new fluid is also clean. No debris in the pan. The transmission is the original.
Having you mention "burnt" brings to mind a thought. The day before the no shift I had a "burning" smell after driving. Couldn't pinpoint it at that time. But is it possible that my second problem is a clutch gone bad? Once again, thanks for your input.

 

Hi derhicks, your welcome, I always like to help if I can.

So back to your problem, is the od light still flashing or is that fixed? If the only concern you have left is the no 2-3 shift, I would take a look at the 2-3 shift accumulator. The only bad thing is you have to take the valve body off to get at it. Your mention of a burning smell while driving, if it was a clutch pack inside the trans and you could smell it outside the vehicle, you would have major trans damage and the fluid would be badly burnt. You said the fluid is still good, so I suspect it is the 2-3 accumulator or a bad seal in the direct clutch.

Once again I hope this helps

 

Xplorer,
Not sure if the O/D light is still blinking. It would only blink when I drove the truck on a longer trip, say 25 miles or more. So, with only two gears I haven't had a chance to do that. I will take a look at the 2-3 accumulator. Back to work today so it will probably be a few days until I can do anything truck related. Will be in touch. Thanks