I've posted about this issue before but didn't get much to help me with. I figured I'd try again and maybe have some luck. Fluid was flushed on trans and I THINK that's when this started; but don't remember for sure. What the problem is; is that when the truck is cruising at 65 or higher all is ok, but under that the tach will all the sudden jump up and then come back down; basically as if the torque converter's unlocking and then locking again? If I REALLY baby it and barely stay on the throttle it won't do it, but hit about 5 lbs. boost and it'll do it when it wants to. I know that when you hit the brake pedal it's suppost to unlock the converter and rise rpm's..mine does not. But brake lights work fine, and when it's high idling during warm up, the pedal de-activates that. I talked to some guys and heard something about a torque converter lock up solenoid, and also about a speed sensor that would cause this? I'm guessing that w/e this is, is electronically related inside the transmission controls because I don't think it did this before my flush. Can anybody help me this time because it's really gettin annoying now. Also if this matters, my fluid isn't dark or anything like that with clutch or w/e, it's still nice and red/pink after my flush and smells fine.

Hopefully somebody can help me this time.

Thanks

 

I've seen several where the Transmission Range Sensor (TRS) starts to fail and causes this problem. The TRS is the sensor on the driver's side of the trans with the wiring harness plugged into it. Some people call it the neutral safety switch.

There is no good way to diagnose it. If you haven't put a new one on lately I'd replace it.

 

i'll take a look under the truck once i get a chance and look for this sensor; thanks for your input.

 

well mark, i just looked under the truck to glance at it and the only connector i saw on the driver side was the one that the gear selector is hooked up to, with the rod going up to the lever in the cab. it's like a 4 or 5 wire connector. that's all i noticed on teh driver side of the transmission(didn't pay attention to anything behind on the transfer case). is this the sensor your talking about or is it located elsewhere on the driver side that i'm just not seeing?


thanks again
by the way-you said there's no way to make sure it's workin properly or not; so my best bet is to just buy a new one and see if the problems goes away?

 

If you have a scanner, tuner or AutoEnginuity you might try pulling the codes to see if anything shows up. I'm no where near a transmission expert so I'll defer to ^^Mark^^.
Just a thought, Joe

 

That's the sensor.

It won't set a code until if fails completely. Before it fails completely it usually destroys the trans with all the extra shifts. I'd replace it and hope for the best. It's not the best diagnostic technique, but for this issue it's the only way I know.

 

i checked again after i posted that--seems the sensor i described has about 8 or maybe 10 wires..but it's the one that changes position as you select your gear , correct? any way you could get a pic so i know i'm replacing the right part?

 

Yes, that's the right sensor. It's the ONLY sensor on the driver's side of the trans. There is zero chance that I'm getting under a truck any time soon to get a photo.

 

i only ask cuz i saw another one that was towards the top of the trans..2 wire sensor-just makin sure that's not it. so this trs sensor is ford only im assuming; is that what fords terminology for it is? transmission range sensor?

 

what transmission is it? E40D or 4R100?

 

It's a 4R100. It is the one on the side with all the wires. The one near the top is the turbine speed sensor. It is called the TRS, or Transmission Range Sensor.

 

i'll call ford tomorrwo and get a price and hopefully pick it up! any special procedure for installation?

 

anybody recomment a special "additive" to put in these tranny's to help them out? i dont wanna just throw in any old thing off the shelf. maybe people have better luck with a particular one, or these tranny's work well with a certain type? any suggestions?

 

MERCON V ATF. That's the best thing to put in the trans. These transmissions don't work that well with the snake oil trans additives.

 

hmm...wen i flushed i was told by ford parts dept. that mercon III is what i should use...so i did..truck is an early 99. could this be what is causing my lock and unlock issue? hooked up to a scanner; everythign is workin as it should electronically; so my problem is hydraulic or mechanical. i asked botu fluid and additives because when it's cold; the problem is less persistent. but if i had overfilled it during the flush; or mercon 5 is what it should have; could this cause my problem possibly?