01sbc

Okay...so no input here. I could really use some help. Seems that with as many members there are on this site I would get some input. Guess not.

dan1stgen

sounds like it would work to me check it out b4 you go buyin stuff though

wannadiesel

As long as you can find the wiring harness it should work.

01sbc

Okay just wanted to make sure it would work. The wiring harness should be on which side of the transmission?

wannadiesel

Driver's side.

01sbc

goes in right at the back? I'll take a pic in the morning just to make sure.

JWood

intersted in doing this to by pass my computer on my '93.

if the VSS fails, even with a pot for the TPS, the truck shifts out of OD, so you're stuck going 55 down the freeway with earplugs in.

I like the OD override swith to still be usefull though, so I tought about using a latching relay to apply power to the circuit. with the relay closed, power is applied to the OD solenoid allowing the pressure swith to complete the ground... with the relay open, no power and no OD.

you could even use another set of contacts on the relay to drive a "OD OFF" light.

feedback please... thanks in advance
Justin

Darchangel

OK, I just tried this mod on my dad's truck, which I'm currently driving. The ECU died a year ago, and I've since put in a stand-alone alt regulator, and a manual switch for the OD. I ran across Feets' post from the Tech FAQ section.

First, I want to make absolutely certain that I'm using the right pressure port on the trans. It's this one (circled) right?:

Also, exactly which pressure switch did you use? I cross-referenced the AC Delco part number and got Murray part #35752 from O'Reilly's. It closes at about 30 MPH, which pretty much means the OD kicks in when it shifts to third, and it doesn't open until almost stopped (checked with multimeter.)
Since that wasn't right, I ordered an actual AC Delco switch, part number 15-50078, straight from AC Delco. That one closes at about 25 MPH, and doesn't open until almost stopped. Incidentally, it also has 35752 elsewhere on the box.
Before I hit up NAPA for 207616, any clue what I'm doing wrong. Are both of these switches out of spec?
Incidentally, AC Delco 15-50078 crosses over to NAPA 207083, according to NAPA's website.
Another oddity I noted was that the Murray 35752 switch said "ON: 3.3kg CLOSED: 0.6kg" on it. If they meant kg/cm^2, that equates to about 47 PSI and 8.5 PSI, respectively.

I'm thinking about hooking up an oil pressure gauge to the circled port temporarily to see what's actually happening there.

Either these switches are way off spec, or the transmission is.

PS: Kevin (feets), this is goofy, but I know who you are. I keep running into you on the web ever since you brought your Belvedere out to an informal meet in Irving way back when, and here you are again! Weird...

Kevin Wright
http://www.wright-here.net

unixcowboy

I've got the NAPA 207616 and have it hooked to my locking TC...
It kicks in at 45 and drops out at 33.....

Don't understand your results...

feets

I used the Napa switch. Perhaps my cross reference was wrong. It still works in my truck.

Howdy Kevin! Small world, eh?

Darchangel

unixcowboy - that's exactly what I want to hear! I'll try the NAPA one. There's a NAPA a couple shops down from the O'Reilly where I got the first switch. Wish I'd tried it first.

feets - small world no doubt! Love that Belvedere...

I'll bet that the other switches I have will work in the intended application, but have different actual specs from the NAPA part. The AC Delco and the 35752 both show to be for a variety of Mopar vehicles, including K-cars. Apparently the actual pressure values aren't considered all that critical.

Thanks for the responses; I'll let y'all know how it goes.

sdstriper

You can get an adjustable Hobbs switch if you would like to dial it in more. The switch you have might even be slightly adjustable if you pick the epoxy off the screw...

http://content.honeywell.com/sensing...scorp/P3_6.pdf

Darchangel

Well, I got the NAPA switch and had an opportunity to put it in last Saturday. No real change, unfortunately. It closes at about 25 MPH, according to my multimeter.
First, I need confirmation that I've got it in the right port on the trans (see picture in post a few above.)
I plan to get under there and connect up a mechanical oil pressure gauge to see exactly what's going on, but I messed up my back Saturday evening, so it'll be a while before I'm fit to crawl under the car.

Pacer

so how do you hook up the switch to turn off the OD? it sounds like its got 2 grounds? one wire is tapped into the ground wire for the OD solenoid and connected it to the pressure switch and the other one wire from the pressure switch is plugged into the rocker and grounded the rocker using the screw for the parking brake handle. does it not need power? i wanna do this but im kinda lost on that part???

Darchangel

You just run the output of the pressure switch through the toggle switch, then back to the transmission OD solenoid. That way the pressure switch is still doing it's thing, but you can interrupt the ground signal with the toggle to prevent OD. So the wiring is ground -> pressure switch -> toggle switch -> OD solenoid.