Kriss

will chek that when i get back to the truck this week.

Kriss

already done, didn't work.
speedo not working. and that speedo thing on the transfercase is kind of frankenstein looking, no intention to fix that thing right now, Thats why i didn't botter with anything and got straight to a direct switch. ( i use an app on my phone to check speed)

but thats weird my orange wire is grounded by default. From what i understood from the shop manual, the solenoid get powered only when all condition are met in the circuit. So its not right as it is now... anyways i just want it to overdrive when i need it too.

I ordered a solenoid from rockauto for 39$ cdn

will install the solenoid, with a direct switch in the cab and see if works or not.

nonrev

I'm not sure about your truck but my 92 with the A518 would not go into overdrive unless the speedo was working.. had to fix the reducer that spins the speed sensor then all was well.

NJTman

If the Speedo isn't working, the pcm won't ground the orange wire out, but he's already got a wiring issue,with a grounded orange wire , which is the strange part. If he's lucky, replacing the solenoid will fix him up....
Maybe his solenoid burned up being energized all the time

Unlike myself, who had to have the trans rebuilt

Kriss

that's what i think too.
how much you paid for the rebuilt?


And yes why not repair the speedo thing after all. anybody got a link where i can find the parts?

Mr-rookie29

All of this is great information and this works great but I have one question. If I forget to flip the switch back before the tranny wants to downshift , What will happen to the tranny ?

ScubaSteveCA

I had the same question. Buddy sent me to learn how a torque converter works, cleared up my concern. I forget to take it out of OD and it just lags around 30-50mph range reminds me to take it off.

cougar

According to my transmission manual, OD can't occur until it is in 3rd gear. The valve body prevents it. If your concerned about it, I'd install a pressure switch in the governor port. Hooked in series, it will give you a minimum speed upshift to OD.

ScubaSteveCA

It normally doesn't, but if you bypass the tps, it 100% will shift 1,2,4. The OD solenoid is separate from the valve body, my understanding is that the trans doesn't know the difference between 3 and 4th (OD) except that the electronic OD solenoid releases and allows spring tension to engage 4th.

cougar

It is going through 3rd, it happens so fast you don't notice it. OD gets its hydraulic pressure through the 3rd gear valve. The only thing keeping OD from happening at that point is the solenoid.

Mr-rookie29

That is why I am asking. I bypassed the tps and didn’t know if something bad would happen to the transmission if I didn’t flip the switch back off so the overdrive kicks out before it went to 2nd

cougar

Premature wear on the bands and clutches.

ScubaSteveCA

No because your torque converter is not coupled when your foots off the accelerator. Thats my understanding. Not a transmission guru, but I did a fair bit of research before I put my OD on a footswitch.

ScubaSteveCA

Can you explain this? Because it seems that using the transmission downshift to slow down would actually cause more wear?

cougar

I've been sitting here thinking of how to explain how this works in simple terms. In an automatic transmission, gears have no teeth. The transfer of power is dependent on friction applied by clutches and bands. The amount of friction depends on the amount of hydraulic pressure applied to the pistons and servos operating the clutches and bands. Like all hydraulic pumps, pressure is produced by RPM. The higher the RPM, the higher the pressure. At a normal idle speed, the pump doesn't produce enough pressure to apply much force on the clutches and band resulting in little friction if set to manufacturers specs. Increase the RPM and pressure increases and then does friction. It is this friction that wears your clutches and bands. Now think along these lines. Friction is the difference between something moving and something not. At a stop, all of the moving force (engine torque) is applied to a non moving force (stopped) = max friction. In a decelerating or compression braking situation engine RPM is high and so would be the hydraulic pressure applied to the clutches and bands. Question: how much torque do you need to apply to break the applies friction thus causing slip? Or, how much friction are you creating by simply increasing RPM or upping the line pressure? Hope this helps.