The ground problem is primarily the starter. If the engine ground is bad the circuit will find the next best path to ground. That can be through the transmission. None of the electricity using parts of the trans carry enough current to cause this problem.

 

That makes "more" sense, but still doesn't quite add up. IIRC that is what Jack has focused in on in past discussions (unfortunately my memory is not good enough to have recalled that in detail). The question then is why not ensure proper grounding of the starter ground path in preference to actually adding a potential electrical path between the frame and the transmission. Rhetorical question really.

I do recall that most people tried to build the case of an internal transmission electrical short causing it - and I just couldn't see that.

 

Thanks for all this, guys. I didn't know how important that starter ground is and didn't treat it any differently when I swapped in the tranny on my bus. Apparently, I lucked out and haven't had problems, but that's just the kinda bonehead stunt I usually pull to hose myself.

 

If you want to ensure a good ground for the starter, connect both batteries directly.

The familiar story >> The ground problem is primarily the starter. If the engine ground is bad, the circuit will find the next best path to ground.

And I'm still waiting for the explanation of the transmission path for years.

When we have a failing ground connection at the lower front of the engine block, the first thing to blow is the 12ga braided wire from the frame to the body tub at the passenger footwell since both batteries are connected to the frame. The next wire series to that is the 12ga braided wire from the body tub firewall to the engine block, which rarely blows because the lower one does first. I experienced that when the Ford dealer put in a rebuilt motor. Early trucks had that issue from the assembly line as a TSB was noted. They did not include the lower cable, but that is the one that people most find blown out.






All years Ford Body Builder Book has stated to not connect a negative or ground strap to the transmission case. While that is generally for added power equipment associated with body installers, why would you do that? Connecting the frame to the transmission adds a pathway that was not there before.

We do not see the selector cable for the transmission welding up; as some GM products had happened, the older F-Body vehicles come to mind. We also don't see any parking brake cables or elements welding up, the metal pathway from the body tub to the rear axle, driveshaft, and transmission.


Again, where is the continuity. These were informal, from discussions elsewhere. Round three was when I was told the continuity function wouldn't work with resistance.

 

I think the ground path when the original ground is bad is from the engine to the trans, through the driveshaft to the rear axle, to the springs and then to the frame.

 

The springs and shocks are rubber mounted with bushings, which is why I get zero continuity from the transmission to the frame, where the battery negative terminals would be connected. And why I mentioned the parking brake cables.

 

Wow thats a ton of information to absorb. To xcrsp440, i used the sctx3 and i have an older innova?(i think) code reader. So i am limited on what i can tap into there. I also have put a test gauge on it and its 0 psi for all gears. As of now i plan to pull the transmission and replace the pump with the one out of the original. Then before i run it check into this possible ground issue. Oh and one other thing, it had a canner tune downloaded with the sct, and after installing this transmission it will not return to stock. Any thoughts there?

 

F350 1990, just checked ground connections. From trans to cab it was great everywhere i probed, but trans to engine was iffy and trans to frame i could not get one anywhere. I suppose this means i need some ground straps.

 

lol ............ unbelievable. The myths and superstitions prevail.

 

A 4/0 cable should suffice.

Trans to body and trans to frame comparison makes absolutely no sense since both the body and frame are connected cables to the battery. You would either have no power in the cab or no lights at the rear of the truck.

Trans to engine connection is with several bolts holding the rear adapter plate on, then several bolts connecting the trans to the adapter plate. All bolts would have to be out and then you still have the locating dowels to each.

Attaching a cable between the trans and the frame creates a current pathway to the starter where there wasn’t before.

 

well i got busy and forgot to update, i changed the pump, cleaned up all the grounds and it all went how it should with the exception of the threads in the test port giving up on life. Tapped it out and its been all good since. Many thanks to everybody

 

I have a 2006 f350 srw fx4 with the sotf t case and 5r110, i have recently had an ATS trans installed (probably a bad choice considering it is the 4th one from them) and new trans to pcm harness installed. I have driven allmost exactly 2,200 miles on this trans (it is not the same trans as the original i kept having problems and requested for them to send one without me sending my old one back to be sure that is wasnt the same one). I was towing today (14,000lbs) and just crusing on the freeway at about 65mph when out of the blue i felt as if it flipped a switch and went into nutral. I pulled over and tried all the gears and just free reving in all gears except reverse(reverse had no responce to pressing the pedal) and tow haul was flashing. I would apprecciate some guidence i wont be able to scan for codes till tomorrow and i have a feeling it might be somthing odd like the EPC solenoid.

 

I dont kniw enough about it to dive very far without diagnostic tools, running the codes is going to give you the answer pretty quick I bet. Hopefully someone that has some tricks up their sleeve replies

 

Anyone is going to need codes ....

 

I hate to be the one to tell you this, but the codes are not going to be much help. Something mechanical failed.

If the truck will roll in park, the transfer case or rear differential have failed. If park holds, either the transmission has failed, or possibly the flex plate has broken.