Controlling overdrive transmission

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Headintheclouds

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Changing 904/727 to A500/A518 I'm investigating the subtleties of controlling overdrive and lockup when gently accelerating on the freeway.

Both the PATC kit and the delay relays option drop overdrive and lockup together when the throttle is opened. I'm wondering if the TC lockup and OD are equally fragile and if it would make for a smoother drive if they were controlled independently - perhaps using vacuum for the lockup and throttle position switch for the overdrive.

Can anyone tell me what happens on a factory car with overdrive and lockup when the throttle is eased open when cruising at 60 to 70mph? how much does the pedal go down before LU and OD switch out? Do they go together? If not, which goes first and how much more pedal is required for the second change?
 
On my ‘91 Dakota with LU and OD, it definitely does them separately. LU comes in last when getting up to speed and drops out when pulling a hill long before it kicks out of OD.
 
Headintheclouds said:
Changing 904/727 to A500/A518 I'm investigating the subtleties of controlling overdrive and lockup when gently accelerating on the freeway.

Both the PATC kit and the delay relays option drop overdrive and lockup together when the throttle is opened. I'm wondering if the TC lockup and OD are equally fragile and if it would make for a smoother drive if they were controlled independently - perhaps using vacuum for the lockup and throttle position switch for the overdrive.

Can anyone tell me what happens on a factory car with overdrive and lockup when the throttle is eased open when cruising at 60 to 70mph? how much does the pedal go down before LU and OD switch out? Do they go together? If not, which goes first and how much more pedal is required for the second change?
Click to expand...
The governor in the trans varies the pressure and is directly related to the speed of the car.
I plumbed a cooler line from the governor port up to the back of the intake where I mounted two adjustable pressure switches from Nitrous Express.

Those two switches (one for OD and one for Lockup) activate relays, which in turn activate OD and Lockup at whatever speed I set them for.
On the back of the intake makes it easy to change engagement speeds with an Allen wrench.
Then I added two rocker switched inside the cabin to enable or disable the relays.
With both switches inside in the “auto” position, overdrive and lockup engage and disengage at whatever speed I set them for completely automatically.
As those pressure switches are set right now my car goes into OD at 50mph and lockup at 70mph.

I used an adjustable vacuum operated switch for kickdown.
When manifold vacuum drops to your set level, the vacuum switch breaks the ground for the lockup relay causing lockup to disengage.

I can turn off either or both switches inside the car and it will only shift 123.
One thing to note is that OD will ONLY engage once the trans is already in 3rd, as OD uses the hydraulic circuit of 3rd to engage.

I found that the vacuum kickdown stuff really isn’t needed.
The trans drops out of lockup once below 70 and OD once below 50 all automatically.
If I ever need to stand on it that hard I just turn the switch inside the car off.
I run 3.55 rear gears, so if I’m doing 80mph I really don’t need to drop to third anyway.
Passing in OD and or lockup is not a problem anyway.:D

Or, just buy an expensive controller.

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DionR said:
On my ‘91 Dakota with LU and OD, it definitely does them separately. LU comes in last when getting up to speed and drops out when pulling a hill long before it kicks out of OD.
Click to expand...
My 96 Dakota is a 4 wheel drive and only a 3.9 V6 so when it kicks down on a hill the CC drops out first followed by the O/D but when the cruise is on it almost happens at the same time due to the throttle position. @lkopaska , have you retrofitted any O/D transmissions?
Headintheclouds said:
Changing 904/727 to A500/A518 I'm investigating the subtleties of controlling overdrive and lockup when gently accelerating on the freeway.

Both the PATC kit and the delay relays option drop overdrive and lockup together when the throttle is opened. I'm wondering if the TC lockup and OD are equally fragile and if it would make for a smoother drive if they were controlled independently - perhaps using vacuum for the lockup and throttle position switch for the overdrive.

Can anyone tell me what happens on a factory car with overdrive and lockup when the throttle is eased open when cruising at 60 to 70mph? how much does the pedal go down before LU and OD switch out? Do they go together? If not, which goes first and how much more pedal is required for the second change?
Click to expand...
It will make a difference which transmission model and year you have whether it is hydraulic or electronically controlled.
 
Good info, thank you.

TrailBeast - are the relays in your system time delay? I have heard of cases where the overdrive keeps switching in and out at certain speeds and I have seen a few articles suggesting a few seconds of delay
 
Headintheclouds said:
Good info, thank you.

TrailBeast - are the relays in your system time delay? I have heard of cases where the overdrive keeps switching in and out at certain speeds and I have seen a few articles suggesting a few seconds of delay
Click to expand...
Personally I have never had a problem not using delayed relays.
I just don’t hover right at the speed OD engages at.
Every once in awhile it does happen (like following traffic)
In that circumstance I just turn OD off.
I could also readjust the engagement speed on the pressure switch for OD.
OD is currently set to engage at 50mph which I rarely do.
I’m either doing 45, 65 or 80+.
When I go to CA to visit relatives I take I40 over to I5 then North.
Hang that baby on 100 and turn up the music for hours.:D
 
TrailBeast said:
The governor in the trans varies the pressure and is directly related to the speed of the car.
I plumbed a cooler line from the governor port up to the back of the intake where I mounted two adjustable pressure switches from Nitrous Express.
Click to expand...

The 42re / A500 also have a "Variable Force Solenoid" that is intended to control the pressure. Are you not using that? Does the transmission function purely on hydraulic control for the 1-2 and 2-3 shifts?

Soren
 
sorenbarr said:
The 42re / A500 also have a "Variable Force Solenoid" that is intended to control the pressure. Are you not using that? Does the transmission function purely on hydraulic control for the 1-2 and 2-3 shifts?

Soren
Click to expand...
Who's using an RE?? Most swaps are done with an RH.. To use an RE all shifts & pressures are computer controlled so you would need a control module.

I have a full schematic for automatic control of an RH using time delay relays on my other computer, I'll try to post it later.... I initially built a control without delays like Trail Beast.... Use the delays it's better, trust me...
 
toolmanmike said:
"must have 16-18" of vacuum" Has that been an issue?
Click to expand...
I never saw that till now. Looks hand written on the picture. But I’ll assume it’s never been an issue. The vacuum switch acts as a throttle valve so fluctuating vacuum with throttle opening/closing is part of how it works. “7 inches or more to shift in to overdrive” and “3 inches or less to downshift and turn off lock up”.
 
sorenbarr said:
The 42re / A500 also have a "Variable Force Solenoid" that is intended to control the pressure. Are you not using that? Does the transmission function purely on hydraulic control for the 1-2 and 2-3 shifts?

Soren
Click to expand...
Die to the posts after yours I’ll not reply directly to your questions, but more or less add to the conversation from here.

I use strictly the hydraulic functions of the 42RH.
With adjustable pressure switches I set the speeds of the automatic shifts engage and disengagement.
I also don’t use a kickdown function from OD or lockup, although it would work fine with the adjustable by vacuum switch allowing one to set the amount of vacuum it takes to trigger it.
Also, technically it would need two vacuum switches.
One for lockup and another for OD.
With 3.55 gears I certainly wouldn’t want it to drop from lockup into 3rd at 80-90 on the downshift.

If I want out of lockup for example I can either be below 70 where it comes out automatically, or just turn it off at the shifter.
Same with OD, only it turns on or off around 50.

All that said I never needed to have it shift out of either automatically, and found the possible benefit to be not worth more wires and vacuum lines.
Got to remember, my motor and trans both came from a truck that weighed substantially more than an A body Mopar, and also had multi thousand pound towing capacity.
I opted for 4th and 5th designations because “lockup” wouldn’t fit. :D

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