Today, the automatic transmission in my '96 F-360 7.3L behaved strangely momentarily. The previous owner replaced the transmission about 15,000 miles ago, and this issue is one that I've only seen a few times in the 6 years I've owned the truck. I'll explain:

I was approaching a stop light today and began slowing down from about 65 MPH. When I had slowed to about 15 MPH, the light turned green, so naturally, I stepped on the accelerator. Upon doing so, the truck began to accelerate having clearly down-shifted to 1st gear during the immediately-prior deceleration. That's where things got strange, in that the transmission did not want to shift out of first gear. The engine revved to just over 3,000 RPM, and acceleration continued, but it didn't want to shift. I eased off the accelerator, and the RPMs dropped to about 1,500, and then I pressed the accelerator again. That's when the transmission appeared to be "hunting" for the right gear. It shifted quickly from 1st to 2nd gear, then almost immediately to 3rd. Vehicle speed and engine speed were very low, and the truck had poor acceleration (due to being in 3rd gear to soon). In an attempt to force a down-shift, I pressed down on the accelerator, which caused the transmission to shift back to 1st, and then finally to 2nd gear at what seemed to be the appropriate time.

For the next 15 minutes, the truck drove fine and the transmission behaved normally. Then, suddenly, at another stop light, after having come to basically a complete stop (speedo said 0 MPH, but I was still barely rolling), the transmission didn't want to shift out of 1st gear again when I attempted to accelerate. It did the same as before, but without all the "gear hunting". I had to really rev the engine, then let it rev-down still in 1st gear, and then press the accelerator again and the normal shifting would return. There was power during the entire time in 1st gear, so it wasn't a huge "slip" between gears or anything like that.

This issue has only happened 5 or 6 times during my 6-year ownership. The transmission is new (approx. 15K miles), and is only driven occasionally (only 2,000 miles this last year). The tranny temp gauge never read more than 180 degrees during this recent incident.

Any suggestions on where to start diagnosing? It was late when I got home, so I didn't do anything to diagnose it. To me, it sounds like a sensor or something electrical is the issue, but who knows... There is no "check engine" light showing on the dash during this strange behavior, and the Overdrive indicator on the shifter does not flash. Aside from this strange intermittent transmission issue, the truck has been virtually problem-free. I bought the truck with 136K miles from the original owner who was meticulous with it's maintenance (my boss at the time of purchase), and the truck only has 152K miles on it now. The previous owner did not have any problems with the original transmission, but simply replaced it as a precautionary measure because he used to tow heavy loads quite frequently. I know that to be true since I was working for him both when he replaced the transmission, and when I purchased the truck.

Please help!
Thanks in advance.

 

I'm gonna guess you maybe have something occasionally sticking in the valve body. It's a guess though, I'm no trans expert. Let's see if Mark stops in here, he's the former trans engineer that is on this site some.

Any flashing OD light on the shifter?

 

It could be a sticking 1-2 shift valve, it could be a failing intermediate one way clutch, or a problem in the intermediate clutch.

 

Thanks for the suggestions. Now, are sticking valves something that's LIKELY, especially for a transmission this new, or are they being suggested simply as something that COULD be?

If the problem is sticking valve(s), what's the likely cause? Also, what is the fix for such a problem?

Any help is appreciated, as my knowledge of automatic transmissions is not great.

 

As far as electrical goes check your brake lights (bulbs - connections) as they can cause weird transmission shifts, especially if someone before you has hardwired connections (not factory).

 

Good suggestion. I just ran and checked all the lights and bulbs. They're OK, but you reminded me of an issue I had about 4 years ago (the first time I had a shifting issue): As part of the Centurion customization package, there is a secondary RV/camper connector in the bed in addition to the factory Ford one at the back bumper. One day while driving home from work, I suddenly got a check engine light, OD light flashing, and "gear hunting" from the transmission. I immediately pulled over and checked any electrical connector I could think of and I found that the center screw of the extra RV/camper connector in the bed had come out and was shorting out 3 of the connectors in there. I re-installed the screw properly and things were back to normal. A quick check just now shows it is still in it's correct position.

I'll keep looking around and checking electrical connections. The odd thing is that the strange shifting only happens very intermittently.

Thanks for the suggestion.

 

What is the conditionn of the fluid?nice and red or turning?

 

I can't help much with the diagnostics, but I just put a Transgo Tugger valve kit into my transmission this weekend with the help of a good friend who is a tranny guy. Wow! What a difference. It's like a new truck for me. All the shifts are really clean, the massive "clunk" I was getting going into 4th is gone, good power, etc. I dropped the pan and pulled the valve bodies, took it to his house where we did the kit (all but a couple of parts) and then took it back to my house and installed it. The whole thing was probably 4 or 5 hours. I highly recommend it for anyone whose tranny might need a little perk up. My fluid was basically cherry koolaid so I know I get a good bit of help just from that alone, but I really like the shifts now. Whole thing with labor for my friend ran me $400 - a reasonable price to pay for what feels like a new tranny.
Good luck.

 

The last time I checked the fluid was about 4 months ago, and it looked perfectly clean, like it just came out of the bottle. No burnt smell either, and the level was correct. I've only put about 300 miles on it since that time. I'll take another look at it.

That's great to hear that something so relatively simple made such a big difference. All in all, my shifts are very crisp with no clunking or slipping. It's just this occasional desire that the transmission has where it seems to want to stay in 1st gear too long that has me perplexed--especially since the transmission is basically new... 15K miles ago, it was a brand new transmission from Ford, not a rebuild, hence my confusion.