Cold/cool weather causes my OD to flee.

[284]

I know it's there...but why does it not engage when it gets cool/cold?

Thanks for any input.


Gary

[Philip]

The trans has a temp sensor in the oil line going out to the coolers. With cold temps the PCM will lockout OD till the trans reaches a preset temp. This sensor will drop the trans out of OD if it sees a high temp condition also.

On my truck it takes about 3 miles on cold days before it will go into OD.

[284]

The trans has a temp sensor in the oil line going out to the coolers. With cold temps the PCM will lockout OD till the trans reaches a preset temp.

Thanks Philip, I'll track it down. Is the PCM the sensor you're talking about?

[Philip]

Is the PCM the sensor you're talking about

No the PCM is located behind the battery. The sensor is located in the front cooler line right in front of the trans pan.

[JD730]

The trans has a temp sensor in the oil line going out to the coolers. With cold temps the PCM will lockout OD till the trans reaches a preset temp. This sensor will drop the trans out of OD if it sees a high temp condition also.

On my truck it takes about 3 miles on cold days before it will go into OD.

Sorry to pop you bubble Phil, but that "sensor" is only a high temp cut out switch, I think it opens and disengages OD around 260*F.

The water temp is a PCM input for OD function, I think it wants to see 60* at the water temp sensor. The TPS is another source of headaches, they seem to act up more in the cold.

[284]

Thanks Philip.

The water temp is a PCM input for OD function, I think it wants to see 60* at the water temp sensor. The TPS is another source of headaches, they seem to act up more in the cold.

Thanks for the input. The vehicle was well warmed up--heater blowing quite hot--and the OD was still not working.

I replaced the TPS (throttle position sensor on top of fuel pump?) when I got the truck. But then again, the slug I got the truck from had it and gave it to me. Knowing him, it could be bad in some sort of way, but it looked brand new. The plug is at 6 o-clock, but IIRC, I thought I saw a pic of one where it was at 12?

The prior owner slug thought it was a ground to frame problem. I looked at that and it's gotta good connection. I have a hard time believing the slug tho. Musta been that $2000 complete brake rebuild that had to be done after I got it...

Gary

[JD730]

The next step I would take is to put a manual switch in the cab so you can bypass all the BS.

On the trans there is a 2 wire plug above and behind the shift linkage. One wire has +12volts when the key is on and the other is grounded through the PCM to turn the OD solenoid on. Tap into the wire that goes to the PCM and run the wire into the cab and too a switch so it grounds when you turn it on.

This will at least tell if the trans is work properly.

[dpuckett]

Philip- I now have had 2 OD autos, and they both will go into OD at 35mph, 2min after starting cold. Could mine both be defective?

284- The plug in is supposed to be at 12 o;clock when viewed from the driver's fender. That could be part of your problem. Also, there is a good page on PDR's website (piersdiesel.com) that shows you how to adjust your TPS. Look under the "tech info" or something like that. The TPS can also be disassembled and cleaned.

DP

[Philip]

JD370 is right. The OD upshift in cold temps is controled by the PCM it uses the engine temp to allow up shift. My drivetrain books says The PCM will not allow up shift to OD till it sees an engine temp of at least 60 degrees.

The sensor on the trans cooler lines is just an on/off switch. High side is 273 degrees. It resets itself at 240 degrees.

Daniel you can vary the OD shift point by what you set the idle voltage at. Idle voltage is around .75 to 1.0 volt.

What speed did the trucks go into OD at WOT.

[dpuckett]

Mom's hangs onto 3rd til about 65mph when the TPS is functioning right; current W250 goes in OD about 60mph, though WOT isnt near as strong as in Mom's old pile. Both have 3.54 gears. I have noticed that Mom's truck will rev to about 2150rpm and stay there through the gears; mine goes to about 1800 and hangs there through the gears at moderate throttle til about 45mph. Mine does drop about 3-400rpm when it goes to OD- Mom's, maybe 75rpm.

DP

[Philip]

The hanging your seeing is the converter slipping. Mine is doing it bad it doesn't like these new injectors to much. LOL

[284]

Thanks everyone for the valuable input. Busy day, so after supper and dessert w/GF, went and flipped TPS. Did a quick drive and seems to be not only driving "right side up" but getting into OD.

Had to come back because company coming over. Now, GF is across lap as I type, so more tomorrow.

Thanks everyone.

[PToombs]

[284]

:safe:

...jus sumptin wrong with that in pink.

I'll follow what was recommended...this weekend gonna do the manual OD trick to gain more control over this beast.

[dpuckett]

Philip, maybe "hanging on" was the wrong phrase. Stays in might be better. There is no real slowing in acceleration before it goes into OD with either one. I know Mom's convertor is sloppy- I did a stall test on it and quit at 2000rpm- truck hadnt even begun to move yet. With mine, the engine bogs a good deal at about 14-1500.

284 sorry to hijack the thread, though it sounds like you are a little preoccupied .

DP