Big Blue's Transformation

[85lebaront2]

Bill - I've done some comparing of the vacuum and electronic speed controls and it does look fairly easy to use the electronic in place of the vacuum, with one exception. There's this statement in the EVTM about how the electronic unit works: "Utilizing a vehicle speed sig­nal from Programmable Speedometer/Odometer Module, increases or decreases vehicle speed to maintain set speed." I ain't go no PSOM.

But, before I realized that there's a transducer input on the vacuum system and none on the electronic version I created a spreadsheet to compare the use of the three wires in the horn pad as well the one to the horn relay. As shown below, there is only one difference, and that is the BK wire on the vacuum side and LB/BK on the electronic one.

And I'm not sure what to think of that. As you can see in the schematic below for the electronic speed control, they don't show the LB/BK wire as grounded. But there are only three connections for the horn pad, and one of those is ground. Right? So, how could the LB/BK wire not be grounded?

In any event, since I don't have a PSOM I'll continue on with the vacuum speed control for the time being. But thanks for the offer.

Gary, all the PSOM does is take the pulses from the teeth on the tone ring in the rear axle and convert them to a speed signal that matches the current one in the speedometer cable. Ford did that when they went to the electronic speedometer. The output from the PSOM had to match the existing pulse count. The beauty of it is, who cares what gear you have, only variable is tyre size.

[grumpin]

Are the Bullnose squirters adjustable?

With my Bricknose I can stick a pin or something in the jet and point them anywhere I like. (Which reminds me to adjust them a bit higher)

It's way too cold to have water in my reservoir up here.

Would destroy the pump when it froze.

If anybody finds adjustable squirters for these trucks that would be great.

The squirters on my Xterra were acting up and I found some adjustable ones on amazon. They are great so far!

[Nothing Special]

Bill - I've done some comparing of the vacuum and electronic speed controls and it does look fairly easy to use the electronic in place of the vacuum, with one exception. There's this statement in the EVTM about how the electronic unit works: "Utilizing a vehicle speed sig­nal from Programmable Speedometer/Odometer Module, increases or decreases vehicle speed to maintain set speed." I ain't go no PSOM.

But, before I realized that there's a transducer input on the vacuum system and none on the electronic version I created a spreadsheet to compare the use of the three wires in the horn pad as well the one to the horn relay. As shown below, there is only one difference, and that is the BK wire on the vacuum side and LB/BK on the electronic one.

And I'm not sure what to think of that. As you can see in the schematic below for the electronic speed control, they don't show the LB/BK wire as grounded. But there are only three connections for the horn pad, and one of those is ground. Right? So, how could the LB/BK wire not be grounded?

In any event, since I don't have a PSOM I'll continue on with the vacuum speed control for the time being. But thanks for the offer.

Gary, will that give you issues when you go to add EFI? I'm pretty sure the computer will need a signal from a VSS. If you have a VSS it's easy to add a PSOM (you can still keep your old-school speedo and just use the PSOM for the speed control).

(and this might be what Bill was saying?)

[Gary Lewis]

Gary, will that give you issues when you go to add EFI? I'm pretty sure the computer will need a signal from a VSS. If you have a VSS it's easy to add a PSOM (you can still keep your old-school speedo and just use the PSOM for the speed control).

(and this might be what Bill was saying?)

Dane - I don't know about adjustable squirters, but I'd be in the market if they are available. Right now I have water-gun streams hitting the windshield. They'll work, but a targeted spray would be nicer. However, I might find the original Bricknose nozzle as it is in the shop somewhere.

Bill & Bob - Perhaps terminology is getting in the way. I thought PSOM was a module that took the signal from the rear axle and converted it to some other signal. Maybe not?

And, the EEC-V ECU does require input from the Vehicle Speed Sensor. Unfortunately I don't have those pages on the site yet under the 1996 EVTM, but suspect they'll show up later today, although I do need to make a trip to the shipping store for a large, flat plate.

I do have a whatchamacallit that plugs into the transmission/tranfer case speedo hole and provides both an output for a speedo cable as well as an electrical output. Is that the same as the output from the ring gear, although probably at a different rate? Will that work as input to the ECU and speed control?

[Gary Lewis]

Gary, will that give you issues when you go to add EFI? I'm pretty sure the computer will need a signal from a VSS. If you have a VSS it's easy to add a PSOM (you can still keep your old-school speedo and just use the PSOM for the speed control).

(and this might be what Bill was saying?)

Oh, re-reading that, PSOM is a module and VSS might be the whatchamacallit? Or the speed control sensor in the speedo cable?

[ArdWrknTrk]

Gary, will that give you issues when you go to add EFI? I'm pretty sure the computer will need a signal from a VSS. If you have a VSS it's easy to add a PSOM (you can still keep your old-school speedo and just use the PSOM for the speed control).

(and this might be what Bill was saying?)

Oh, re-reading that, PSOM is a module and VSS might be the whatchamacallit? Or the speed control sensor in the speedo cable?

Gary, the Programmable Speedometer/Odometer Module is essentially the gauge.

You can Program it to account for tire and gear changes.

The Vehicle Speed Sensor is either in the top of the pumpkin or a device added to a speedometer cable to create pulses for the computer to read.

PSOM's didn't come about until well after the Bricknose trucks, but Bricknose trucks had a VSS because of the RABS.

[Gary Lewis]

Gary, the Programmable Speedometer/Odometer Module is essentially the gauge.

You can Program it to account for tire and gear changes.

The Vehicle Speed Sensor is either in the top of the pumpkin or a device added to a speedometer cable to create pulses for the computer to read.

PSOM's didn't come about until well after the Bricknose trucks, but Bricknose trucks had a VSS because of the RABS.

OK, I got it. Well, I got it for a while. PSOM is the module, and VSS is probably the whatchamacallit.

So, will the electronic speed control really need the output from a PSOM? Or will it work from a VSS? Again, the '96 EVTM says "Utilizing a vehicle speed sig­nal from Programmable Speedometer/Odometer Module..."

It appears the ECU will work from the VSS, so I think I'd be happy with just the VSS feeding the ECU and running the vacuum speed control, assuming the electronic speed control does take the PSOM. But can the vacuum speed control be fed by the VSS, which might bypass any issues with speedo cables as it is prior to the cable? Sure would be easy to plug that guy into the t-case and run two wires up and bypass the current speed sensor.

[ArdWrknTrk]

OK, I got it. Well, I got it for a while. PSOM is the module, and VSS is probably the whatchamacallit.

So, will the electronic speed control really need the output from a PSOM? Or will it work from a VSS? Again, the '96 EVTM says "Utilizing a vehicle speed sig­nal from Programmable Speedometer/Odometer Module..."

It appears the ECU will work from the VSS, so I think I'd be happy with just the VSS feeding the ECU and running the vacuum speed control, assuming the electronic speed control does take the PSOM. But can the vacuum speed control be fed by the VSS, which might bypass any issues with speedo cables as it is prior to the cable? Sure would be easy to plug that guy into the t-case and run two wires up and bypass the current speed sensor.

If it's reading from the speedo cable and the gears are right I suppose it's okay.

A VSS in the pumpkin is just reading magnet pulses from the tone ring and can't know what size tires are on the truck.

Bill or Shaun is going to have to help you there....

[Nothing Special]

Gary, the Programmable Speedometer/Odometer Module is essentially the gauge.

You can Program it to account for tire and gear changes.

The Vehicle Speed Sensor is either in the top of the pumpkin or a device added to a speedometer cable to create pulses for the computer to read.

PSOM's didn't come about until well after the Bricknose trucks, but Bricknose trucks had a VSS because of the RABS.

I mostly agree with what Jim said. The only difference might be "just semantics" (but an aside here, since "semantics" is defined as "a branch of linguistics... concerned with meaning", and since the entire point of talking or writing back and forth between people is to communicate meaning, then isn't saying "just semantics" equivalent to saying "just the entire point"?). Anyway...

Yes, the VSS is the vehicle speed sensor on the rear axle in stock form. But a sensor elsewhere (like on the speedo gear at the transfer case output) can do the same thing.

In my '97 the VSS signal is used by the PCM, the RABS and the PSOM. If one or more of those three weren't there the VSS would still be needed and would still be read correctly by the other(s).

Can the PCM correctly understand the signal from a different VSS than the stock one? I don't know. But I'm sure that info is out there.

The one semantics issue I have with what Jim said is that I'd say the PSOM converts the VSS signal to a signal for the gauge rather than say it essentially is the gauge. The gauge is just one thing that uses the PSOM output. The speed control is another. And the PSOM should be able to happily provide a signal to the speed control even if the gauge isn't there.

The PSOM can be reprogrammed up to 5 times. This ordinarily only be needed to compensate for changing the tire size, but it should be able to compensate for a different VSS rate. But be careful as it can only be reprogrammed 5 times. Then you apparently need to get a new PSOM.

[ArdWrknTrk]

I mostly agree with what Jim said. The only difference might be "just semantics" (but an aside here, since "semantics" is defined as "a branch of linguistics... concerned with meaning", and since the entire point of talking or writing back and forth between people is to communicate meaning, then isn't saying "just semantics" equivalent to saying "just the entire point"?). Anyway...

Yes, the VSS is the vehicle speed sensor on the rear axle in stock form. But a sensor elsewhere (like on the speedo gear at the transfer case output) can do the same thing.

In my '97 the VSS signal is used by the PCM, the RABS and the PSOM. If one or more of those three weren't there the VSS would still be needed and would still be read correctly by the other(s).

Can the PCM correctly understand the signal from a different VSS than the stock one? I don't know. But I'm sure that info is out there.

The one semantics issue I have with what Jim said is that I'd say the PSOM converts the VSS signal to a signal for the gauge rather than say it essentially is the gauge. The gauge is just one thing that uses the PSOM output. The speed control is another. And the PSOM should be able to happily provide a signal to the speed control even if the gauge isn't there.

The PSOM can be reprogrammed up to 5 times. This ordinarily only be needed to compensate for changing the tire size, but it should be able to compensate for a different VSS rate. But be careful as it can only be reprogrammed 5 times. Then you apparently need to get a new PSOM.

I agree Bob.

It adjusts/infers the VSS signal for the gauge to read properly, but it also provides input for things like antilock and speed control.