Texas_Ace

Electrical short makes the most sense with all the other issues you have.

TundrastruckDave

That's what I've also been leaning towards. Especially after replacing the #1 shift solenoid (as the PO753 code said should be done) and then watching the exact same code come up again!

But like I said, any little "new quarks" just further stresses the situation - like this fluctuation in the RPM's - which scares me into thinking I should park it, rather than drive it manually (so-to-speak) until I can afford to have it looked at.

Texas_Ace

Next step you could take, and even do it yourself, would be to ohm out all the wires on the transmission harness. Tracing the wires can be a pain and time consuming but you might find the short that way. Or you could skip right to getting a new harness/making one.

TundrastruckDave

Hadn't thought about the new wiring harness idea?!

Let me make certain I understand you correctly...
There is a separate "wiring harness" which attaches to the transmission - in essence a transmission wiring harness - right. It's not "wired" into the main wiring harness (where it can't be unplugged) and "can" thereby be replaced. Am I understanding you right here?

Texas_Ace

That I am not sure of, I think it does at least connect to the main harness what I don't know is if it is seprate until the ECU or not.

Either way you should be able to buy the whole harness of the same year/model truck if you look hard enough. Best bet is to find a wrecked truck and pull it off.

TundrastruckDave

Hey Texas Ace,

I'm trying my dead-level best NOT to get taken to the cleaners - again! That said maybe you can tell me if this makes any sense to you...

Have a long lost friend who has transmission experience and he's offered to look at it for me. I've told him the "whole" story and sent him the code information and some other info he requested. He was taking that info and checking with another transmission specialist, whom I assume he trust or possibly even worked with.

In any case, he's asked me to take the truck to a local auto parts store and have them clear the code(s) for the shift solenoid. Then he's asked me to start the truck and see if the code shows up again "without" driving it. He says if it's electrical the code will show up again, but if it's mechanical, he says it probably won't show up again. He says the ECM only monitors electrical components in the transmission, of which there are 3, with all 3 being shift solenoids - 2 identical and one for overdrive. He says if it's mechanical - even something as simple as trash in the valve body or a spring or ball in the valve body that's sticking, or some "other" larger mechanical problem the ECM will automaticlally "blame" it on the only components that it monitors in the transmission. If it's mechanical, he's saying the shift solenoid that was replaced may not have even been bad in the first place?!

Any of this sound legit to you?!

Many thanks!

Texas_Ace

I am not a transmission expert by any means, still the only part of a car I have not worked on personally (automatic transmission that is). It does sound like it makes sense though. I am sure that each car reacts slightly different but that does sound like a reasonable place to start.

donomite49

i know from doing my 3.4 swap that the trans harness does go into the main engine harness on the drivers side then on to the ecu.

TundrastruckDave

So the transmission wiring harness is actually "wired" into the main harness and can't be unplug and replaced - right?!

Texas_Ace

It sounds that way, you could still replace the entire wiring harness to the truck, bet it would cost about the same as having someone track down the short in it unless they got real lucky.

See what your buddy can do first then decide what to do.