Engine/Transmission (1994 - 1998) Something different happened today?

[BigYellowIron]

IO was driving along about 65 mph and all of a sudden my rpms went up to like 2800 and my truck bucked hard.

Felt like a down shift only harder.



I looked at my OD switch and the little light was lit.



I did not push it and I was by me seld so no one else did.



Anyone ever had that happen?



It must of been my gost companion!!!



Adam

 

[Missouri Mule]

Adam'



You sure you did not tap the brake pedal accidently?



Sometimes the brake switch has a hair trigger. The good news is it can be adjusted.



Also I have read that the vacuum line being pinched or leaking could cause this but this would be more permanent.

Mite be electrical but that would be more permanent problem also.



Good Luck !



P. S. Do not try to Heel and Toe in Overdrive.

 

[Extreme1]

Originally posted by Missouri Mule

Do not try to Heel and Toe in Overdrive.

LOL!!



"That just happens sometimes". No, really. It's happened to me twice in one day on a long trip and then it won't happen for months. Summer, winter, rain, dry, totally random.



I bet you had to change your shorts though, huh?Oo.

 

[Cummins Corvette]

What would the brake switch have to do with that?

 

[illflem]

The ghost has also pushed my OD button a couple of times. I think it's just a PCM glitch. Don't worry about it until it starts happening all the time.

 

[Missouri Mule]

Nothing I was thinking cruise. Sorry!



But if your coolant/trans fluid was getting a little warm I believe the PCM will Kick it out of Overdrive.

The transmission speed sensor, transmission tempature sensor.

your favorite throttle position sensor,vehicle speed sensor and coolant temp sensor ( I think that's all of them) all feed data to the PCM which of course controls when the trans goes into/out of overdrive. The PCM has preset specs, if anyone of these sensors sends data to the PCM that is not with in the the specs spread the trans won't go into overdrive or will come out of it.





From 96 service manual



" The control switch indidcator light illuminates only when the overdrive switch is turned to off position, or when illuminated by the transmission control module. "

The trans temp sensor description was the only one that mentioned that when it causes the PCM ot kick trans out overdrive and engages converter clutch. According to third gear converter clutch schedule.



Still not a good idea to heel and toe in overdrive.

 

[DavidGardner]

Been there done that . Happens to me about 3 or 4 times a year. Just driving along about 65 mph and all of a sudden the truck slows rapidly and the RPM rises sharply. Next time this happens just push the overdrive button (which will be lit up) and everything will return to normal. When it happens to me I always think something is realy broke bad. Like -did I just blow a differential - or U-joint? Enjoy your truck, this is just one of the quirks. Standard transmission guys if this happens to you - time to worry!:--)

 

[Blakers]

It happened to me twice last winter. Never since.



Blake

 

[RottnDogue]

Hasn't happened to me, but Anyone else notice that so far everyone that it has happened to has a 95' ??



Darren

 

[Extreme1]

My cruise is always on when it happens. It always looses the cruise setting.

 

[dseabaugh]

Actually there has been a lot of that lately. It has to do with the wind vortex caused by alien space vessels looking for Powerstroke Diesel window stickers.

 

[Greg W]

My 95 does the same thing about 4 or 5 times a year too! It gives me a scare every time although each time I get the OD button pushed a little faster and faster. I always figured that I had just gone through an area with very high power RF transmissions. RFI or something else causing the PCM to freak. It is good to hear that I am not the only one having that happen.

 

[rrausch]

I have a '95 too.

the first time it happened I puckered up the seat covers real good and sweat bullets for 5 miles wondering what the heck happened.

Second time I thought Hmmmmmmm.

3rd time I thought "Ho Hummm... yaawn. "

I guess it has happened 4-5 times in 3 years. I don't even worry about it anymore. Like Greg, I am getting faster on the draw on that O. D. button.



Interestingly it hasn't happened since I got my ATS Stage IV. Maybe it is just waiting for me to get comfortable before it tries to scare me again.

 

[Blakers]

Originally posted by dseabaugh

Actually there has been a lot of that lately. It has to do with the wind vortex caused by alien space vessels looking for Powerstroke Diesel window stickers.

It only happens while driving east. I think it has something to do with the angular velocity of the earth's rotation. Perhaps a safety feature to prevent the earth's rotational speed from being affected by too many CTDs accelorating in the same direction?



Oo. BlakeOo.

 

[redramnc]

Good one



Now, if you are in the Southern Hemisphere would it occur only when going west?



Does this mean we now need to BOMB a shield to the PCM housing? I have some lead sheeting somewhere... .....

 

[HoleshotHolset]

... . happened to mine about 3 times since I bought it...



I was on the phone driving up the highway at 70mph when it did it last weekend..... I calmly hit the OD switch and continued on.



As long as it doesn't leave me stranded... I'm happy.



I do seem to remember this problem being focused on the pre-47RE trannies..... ('94, '95).....



Matt