no overdrive till it's warm

[jerrethomas]

i have a 93 d350 2wd nothing done to it except for a k&n air filter and a 4'' exhaust. this problem just occured a couple days ago. it seems as it won't go in to overdrive till it warms up. you can drive it for 10-12 miles till it will go into overdrive. it didn't used to do this and on another note, the speedo doesn't work when it's not in overdrive and when it is in overdrive the speedo bounces around quite a bit. just wondering on everybodys thoughts about what this might be.

 

[PPeters]

I'll jump in here and others can correct me if I'm wrong...



My understanding is the shift for 3-4 is temp controlled. Don't have the manual with me, or I could give you the temp at which it will shift. Mine will do this even now (warm weather) on days where the temps are between 50 and 60F but usually only for about the first 1/4 mile leaving in the morning or coming home from work. The short distance gets the ATF to temp, satifies the sensor, then OD is clear to operate. If ambient temps are higher (70 and up), usually don't see it at all.



On the speedo not working then working, I would suggest checking the electrical connections at the speed controller, clean with good contact cleaner, put back together with dielectric grease and see if things clear up. Same treatment for the temp sensor on the transmission. Just a place to start.



Pat

 

[cerberusiam]

If the speedometer is not working or erratic you will have a problem getting it to shift into OD. From the description the speed sensor is either bad or not making connections. Clean the connectors on the speed sensor and pull it from the trans to make sure the gear and shaft are good and see if that helps. Even if the speedometer is working you may still have erratic shifts in and out of OD which is a good indication the sensor is not putting out the full voltage needed. If all else fails you can bypass the PCM controlling the shift and use a manual switch to engage/disengage OD. The temp switch could also be a problem if it is not funtioning correctly. Like Ppeters said clean everything up and use dielectric grease and see if that helps. If that doesn't work try washing the engine and trans at car wash and see if that cures the problem for a while.

 

[jerrethomas]

good stuff guys, you people are great. can somebody give a ball park to look for the temp sensor and the speed sensor for the transmission.

 

[paccool]

For the temp sensor, look at the front part of the transmission where the line takes off headed for the cooler. Should be a Tee there with the sensor screwed into it.



The speed sensor is in the tail shaft housing close to where it bolts to the transmission main housing, drivers side. ( This is from memory (which is failing me fast! It may be in the main transmission housing next to the tail shaft housing. )

 

[jerrethomas]

i thank you much

 

[BushWakr - RIP]

The speed sensor will also create havok with cruise control too... .



bob.

 

[CoreyPerez]

My 94 did the same thing. 2 options. figure out what was wrong with the sensor, or put in a resistor so the truck "THINKS" its warm. I just fixed my sensor.



Best of luck.



Corey

 

[RamAZ]

No OD till warm.

I have 92 that use to have the same problem. I changed the temperature sensor in the trans line, I also had a broken nut that holds the speed sensor to the transmission and a TPS that had a mind of its own.



I changed the temperature sensor out for a new one, changed the speed sensor out because of the broken nut and took apart the TPS and cleaned it and reset voltage to . 8VDC. Things are great now and have been for going on two years.



If you take a look at the design of the speed sensor it is bound to wear and eventually fail. I suspect there is a carbon wiper running on a segmented disk, the faster the rotation of the wiper the the faster you are going in MPH.



I would first of all clean all connections with contact cleaner and apply dielectric grease to all the connections. What is your TPS voltage set to now? If it is set high (1. 4VDC) then when you press the go pedal it thinks you are at WOT and will not shift to OD till you let up on the pedal or will shift into OD and stay there till you give it a little more fuel and then drop out this is an indication the TPS voltage is to high.



My trans shifts into OD around 40MPH in city traffic and when giving it the go pedal it shifts around fifty. I prefer to control the shift (button) into OD when carrying a load and will always let up when it shifts into OD just to save the OD clutch packs some wear and tear.



Jim

 

[Greenleaf]

My 2 Pennies

Driving in wet weather once I lost my speedo/odometer. At the same time,also lost OD. Upon reaching my destination the truck sat while. When I left, everything worked fine all the way home [11/2 hour drive] That next day I removed the speed sensor to find the shaft square, so cleaned the connections and added dielectric compound.

The TPS has a mind of it's own. Most times I get OD but sometimes I'll have to pull my foot off to allow for a shift. The TPS is nearly 6 months old now. I make frequent adj to it with the 10mm wrench with some luck,but still have to "help"it shift sometimes. I have also loosened the TPS mounting screws to gain additional adj.

Mine seems to shift even when cold. Can't say I remember when it didn't. Will add this. I live at the bottom of a long hill. To get out of here it's a climb. If I put my foot into it I never will get OD till I reach the top or 60/70MPH. If I take it real easy, it will go in. But thats no fun. I'm enjoying the ride to the top of the hill [where I work] awakening the neighbors with the help of the straight pipe :-laf :-laf :-laf Oh yah, I lower the passenger side window too