97 vs 98 GEM and PCMs

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I replaced a bad 97 (4L) transmission with one from a 98 (3L). Both 5R55E.

Speedo doesn't work and shifts aren't quite right because the 98 transmission doesn't have the VSS on it.

I believe I need to get the VSS signal from the rear diff ABS sensor, to the PCM but am not sure how best to do this?

Putting the 98 GEM into the 97 didn't change anything. And the engine really didn't like using the '98 3L PCM in the 4L '97. I presume because of the different engine sizes?

I'm GUESSING if I put the 98 wiring harness, and GEM into the 97, and got a 4L 98 PCM all would be well? But, is there an easier way? Splice ABS diff signal to 98 GEM? Would 97 PCM be ok with that?

Thanks!

 

[RonD]

Welcome to TRS


3.0l Vulcan engines only came with 5R44E autos(or A4LD or 4R44E), and bolt pattern for trans is different, so no you didn't bolt a 3.0l trans to a 4.0l engine, auto or manual

4.0l engines are the only ones that got the 5R55E or 4R55E
3.0l/2.3l/2.5l engines got the 4R44E or 5R44E automatics

Info here on that: http://www.therangerstation.com/tech_library/AutoTrans.shtml

These transmissions all have integrated Bell Housings, so 3.0l trans will not bolt to 2.3l engine or visa versa, or 4.0l for the same reason.
4R is 4-speed
5R is 5-speed
44E is light duty, 3.0l and 2.3l engines
55E is heavier duty, 4.0l engines only

Yes, 1998 to 2000 Rangers used the Rear axle ABS sensor for speedometer and computer, and of course ABS, so 1998 to 2000 trans won't have speedo hookup

Check if your '97 has rear ABS, so a Speed sensor on the rear axle housing
seen here: http://www.therangerstation.com/tech_library/speedometer.shtml

You can use that with this: http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/prd126.htm
And run "corrected speed" signals to speedo and computer

Since I assume the automatic you did use did bolt in and does work, then I would look for a 1995 to 1997 trans and sell the one you have now.
That would be the simplest

Right, you can't change PCMs from different engine sizes and expect good results, the computers are programmed for the engine size.
GEM could be swapped but in the end you will be better off with stock setup if there are any future problems.
If you start swapping out wiring harness's you can compound current problem and will compound future wiring problems

 

[tab a]

Ron, you're right--even I'm confused about the tranny I put in. It's a 5R55E from a 4L 2000 Explorer.

Yes, as I mentioned I do have the ABS sensor on the 97's diff.

< I would look for a 1995 to 1997 trans and sell the one you have now.
That would be the simplest >

I'm in the middle of nowhere, so finding another transmission wouldn't be easy, and I'd so much rather play with wiring than remove another transmission, though granted most of the aggravation of extremely rusted/stuck bolts would be missing.

If I put the 98 GEM in, and run wiring to it from the ABS sensor, it should be happy right? Then the question would be, would the 97 PCM recognize the signals sent from the GEM as appropriate, or does it deal with them in a totally different way from the 98 PCM?

Extensive web searches have unearthed very little about this so I'm very appreciative of your help!

Thanks!

 

[RonD]

1998 to 2000 GEM also needs to be programed for Tire size, so one size doesn't fit all

But yes, VSS sensor has a + and - signal, "-" is common ground so will already be at GEM, speedo and PCM locations.

Go to this post to get GEM wiring: http://www.therangerstation.com/forums/showthread.php?t=162915

The incoming signal from VSS(pin 9) and out going VSS to speedo and PCM(pin1) are "the same" except corrected for true speed.
Ford basically just cut the wire from old VSS on trans and spliced GEM in the middle

PCM gets this corrected signal on Pin 58(VSS in)

 

[tab a]

So if I'm understanding this correctly, since the 97's rear axle sensor has Light Green/black that is continuous with ground, all I need to do is splice the other, Red/pink (+) wire to pin #9 (VSS input) of the '98 GEM?

That sounds way too easy.

Thanks again.

 

[RonD]

Light green/black is the "low" wire, Red the high

Go to this thread and get the RABS file: http://www.therangerstation.com/forums/showthread.php?t=169106
In this diagram is shows BOTH spliced into VSS wires and going to GEM on a 1998

 

[tab a]

Yes, I'd found that schematic in my searches.

Since the rear axle sensor is the same part for both 97 and 98, I would guess its connections to the RABS(s) would be the same? So I wouldn't change that.

I would only splice in/ADD the VSS input to pin 9 of the GEM, using the red/pink (although the schematic seems to indicate either can be used).

Am I missing something?

Thanks.

 

[RonD]

1997 GEM also got VSS signal(on pin 9) so you may already have it there.
But it didn't modify it and send it out(pin 1)

I think the 1997 only used VSS signal for 4X4 so GEM 2WD may not have it, but some models did lock the doors when speed was detected, manual trans

1997 GEM here:

 

[tab a]

I've read that the 98 GEM outputs a square wave to the PCM, etc.

It sounds like you're saying the 97 GEM puts out a different type of wave (sine?) to the PCM. Which means even if I put the 98 GEM in, its VSS output would not be appropriately recognized by the 97 PCM?

Which makes the easiest course your original suggestion--just putting in the Dakota 'box' and keeping everything else original?

I found 97 and 98 PCM pinouts here
http://www.therangerstation.com/forums/showthread.php?t=116012

Mostly the same though a couple differences probably would matter, if trying to use a 98 GEM?

Thanks again!

 

[RonD]

VSS or OSS are Variable Reluctance(VR) sensors so actually output an AC signal, sine wave, called a DC-coupled square wave, hence the confusion
Sensor 'reads' a tone wheel, tone wheel looks like a gear so has teeth, each time a tooth passes near the VR sensor it creates a signal that rises as tooth gets closer then drops off as tooth moves away, so smooth wave up and down, but you can clip them to make a better digital signal.

Hall effect sensors(needs 3 wires) are squared waves

Image here: http://www.daytona-twintec.com/sensor_data/CKP_Sensor_Waveforms.gif

Ford has always used VR sensors for speed, so there is no incompatability as far as the sensor goes, "true speed" is another story

GEM wouldn't out put a true square wave it just changes the frequencies to reflect true speed

 

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OK, I've got the Dakota Dig. converter on the way.

I need to keep the original signal from the RABS sensor for the brakes, but at the same time run converted signal to PCM, GEM, speedo, and speed control servo.

Do I just need to splice into the GY/B at the RABS sensor, and run that to Dak.D. input, then DD output to GY/B at original VSS connector that used to attach to transmission?

Thanks again.