Avoiding OD Downshift on Dyno

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wilmesbm

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Apr 12, 2010
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I had my truck on the dyno last month without the lockup switch and as soon as the guy stomped on it she downshifted out of overdrive, ran through the rpms, the shifted back into overdrive. The numbers were still pretty decent, but I want to see how much they would differ if it doesn't downshift.

So, I re-installed my lockup switch. It works in a drag racing sense, meaning I can lock the converter in 2nd now, but not in a dyno sense. Once in OD with the switch engaged I can make the truck downshift by standing on the throttle. The converter stays locked obviously, but the truck will not remain in overdrive.

I've got a built 47re with an aftermarket ATS valvebody which requires you to install a valvebody assistant which ties into pin 29 and pin 32 of the PCM. Could that be the reason the truck is able to downshift with the lockup switch engaged? If so, how do I avoid that?

If I remember correctly pin 21 (brown wire) controls the OD solenoid. Is it possible to "manipulate" that solenoid the same way we are manipulating the lock up solenoid when using our lock up switches?

Basically, I want to be able to control OD. I do not want it to be able to downshift when on the dyno, regardless of what RPM I stomp on it at.

Can anyone offer some insight?
 
I think we dynoed ours in 3rd gear (D) with the converter locked and turned the O/D off to keep it from engaging. Any reason you want it in O/D on the dyno?
 
sledshaker said:
I think we dynoed ours in 3rd gear (D) with the converter locked and turned the O/D off to keep it from engaging. Any reason you want it in O/D on the dyno?
Click to expand...

Now that you say that yes I dyno in 3rd too. As long as you are direct drive you are good. Only advantage to running it od is being able to load the truck harder in higher gear.

from phone
 
That's correct, just for more of a load depending on the type of dyno. In the past we typically run it with od off once and od on once and then compare.

I'm gonna spray this next time tho and I'm worried that with od off i may run out of rpms too quickly.
 
Either wire your OD on a toggle, or just run in 3rd. With the converter locked in 3rd, you can start low and it will load pretty well.
 
I don't run fancy lock-up or overdrive switches, I just put it in gear, run it up to about 80 MPH and let it settle before hammering down on the load pedal. Never had it kick down or unlock...seems to work fairly well on my set-up.
 
Not all valve body's are the same. Might work on one truck but not another

from phone
 
Ok I figured out that you can control the overdrive solenoid the same way you can control the lockup solenoid. I was told its pin number 6 on the transmission, but I wasn't able to figure out which wire it is on the firewall. I was told you just wire it up to a ground just like a lockup switch.

It's worth a try. Does anybody have a service manual that can tell me which wire it is on the firewall?
 
Just get a bunch of switches and wire them in until you get the right one. What's the worst that could happen?
 
I would try it of the plug on the transmission, one is OD, one is Lockup, one is ground. Bypass the computer all together
 
ahale2772 said:
I would try it of the plug on the transmission, one is OD, one is Lockup, one is ground. Bypass the computer all together
Click to expand...

I may end up going that route. I would like to know which pin it is on the firewall though just for future reference.
 
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