2004 48re No Overdrive

[Dick Langendorff]

Was driving from Southern California home to Northern California. Crested a grade and then the truck would not go into OD. Rpm's went from a normal of 1750 to 2350. Drove home about 300 miles that way. I had my 33 foot 5th wheel in tow.
Tow/Haul would not change anything. Checked fuses and relay. All good. Checked transmission speed sensor. No change. It is not showing any scan codes. With the key or at the mechanic with a big scan tool.
It shifts fine and runs good through 1,2 and 3re gear. Just won't lockup or OD.
Truck has 268,000 miles. Stock.

 

[cerberusiam]

Mystery switch time to see if it is electrical or mechanical. A mechanical failure will not show codes, it just won't shift to OD. Once it is verified it is mechanical or electrical check pressures on the OD circuit to see what they are.

 

[Dick Langendorff]

Thank you Cerb for the response. I was hoping you would see the post.
I have checked virtually everything I can with my limited "expertise". I took it to the mechanic who does our smog and maintenance on my wife's car. I have done all of the work on the truck which has mainly been a lift pump, brakes, water pump and lube/oil.
On Thursday I will be taking it into a transmission shop here in Brentwood. They will hook up their scanner and test drive with me in the truck to show me what is and isn't happening.
I considered doing the mystery switch, but, not sure I know enough about it to actually do it. That is why the visit to the transmission shop.
I appreciate the response and will let you know what they find. Thanks again.

 

[Dick Langendorff]

I talked to David at DNJ Components in OK.

 

[cerberusiam]

If the scanner says it is demanding OD and still doesn't go into OD then it is likely a mechanical issue int he OD unit.

Also, the trans temp\temp sensor and\or the gov solenoid going bad will stop OD engagement also. That is why it is critical to either use a mystery switch or have a scanner than can manually actuate OD to validate electrical or mechanical root cause.

Good news is that can be rebuilt separately from the rest of the transmission. At 268k on the clock might be time to consider complete trans rebuild but you do have a choice if the OD is the only thing in the budget now.

 

[Dick Langendorff]

Thank You, I will let you know what I find out on Thursday.

 

[sag2]

We're neighbors. I sent you a pm if you want to stop by and we can put the DRBIII on and see what's going on .

 

[sag2]

Checked it out, the converter is nice and tight, killed it immediately with the scan tool actuator. The DRBIII shows it is in 4th but it isn't. It must be commanding 4th but not making it. It locked up in 2nd and locked in third a couple of times. So we know a couple things. The converter solenoid works, the PCM works, and the converter clutch works. Governor pressure is reading right on the money so the transducer is also working. Speed sensor on trans and all three wheel speed sensors are reporting correctly. Trans fluid temp was at 180 degrees. Actuating the solenoids I could not hear them clicking but not sure you can through the pan and fluid. So the thought was to replace the OD solenoid and see what the inside looks like at the same time. Not that expensive and if I have the time I will stop by and actuate both solenoids with the pan off just to be sure. I guess it can always be the OD clutch, but this should eliminate the easy and inexpensive stuff first. Thoughts?

 

[Dick Langendorff]

Thank You Sag2 for what you did. I have ordered a tc/od solenoid. It should be here on Monday. Stopped by Napa and they can order, but do not have in stock.. More than double the price.
Thanks again for the support and expert analysis.
I will be in touch.

 

[Dick Langendorff]

Today I replaced the od/tcc. No change in the shifting. May have to take it to the transmission shop.
Thanks for the great input and help.