Matching rev-counter signal to speed output.

[DickWells]

Anybody know what form the signal takes from the tach drive (alternator) on my 95 Suburban 6.5? I need to know how many pulses per revolution in order to adjust my new Quick 4 transmission controller to match the speedometer output. Everything's working fine, shift-wise, except that I'm showing codes on the display, indicating that I have slippage which doesn't exist.

If I know the frequency (pulses) I can enter the program and chose from the list (4 pulses, 8 pulses, etc) and match them up using the calibration program.

[JohnC]

Since no one else spoke up... I think the tach works off the frequency of the AC produced by the alternator. I doubt it would be suitable for your purpose. I'm thinking you're going to have to tape some magnets to the crank pulley or something. (Wasn't there an RPM signal generator that ran off the old vacuum pump drive?)

[Robyn]

The 95 Burb does not use a signal generator.
The oil pump drive does not have one.


The front speed sensor in the tranny provides the engine speed to the original ECM

The rear sensor provides the output shaft speed and combined they allow the computer to know wasssssup


The crank sensor will provide (should) a 4 pulse signal per RPM

That sensor should give you what you need.

What does the instructions for the controller say it needs ???


John is correct me thinks as to the Tach signal coming from the alternator not being suitable


Does the controller have a plug for a signal ??


Speedo output signal comes off the output shaft of the T CASE

[DickWells]

Quote:
Does the controller have a plug for a signal ??

Yes. The Vehicle Pin Out on the controller is called tach input. All of the data that's furnished says that you simply hook up to the tach signal. Trouble is, it looks like you are both right about the signal from the alt. It's running the dash tach just fine, but there's a total miss-match with the VSS output at the T-case, indicating slip that isn't occurring. I know this, cuzz I've driven it and there's absolutely no indication of slip in any gear-change action or in lock-up, or anything between. Trans temp hasn't exceeded 160 F. Their data would get me right where I want to go, --- if I had a gas Suburban!

I talked to US Shift for over an hour on Friday and they are nice to talk to and helpful in most respects, but come up short on specific data for things like GM color codes for wires and exact procceedure for hooking up the speedo and tach/engine speed, etc. No-one there knew what the frequency is from the tach output (white wire, connector P) at the tach. Fact, I haven't even seen mention in their manual, or on their disk of the engine speed sensor that you mention, Robyn. Am I right in recalling that this sensor is located at the low-left-front of the engine block? Most importantly, do you know what the frquency of that output is?

While I'm liking the new shifting, more or less, I'm not quite sure I'm going to like functioning through all the doggon electronic hassle for getting everything sorted. The "Old Fart" ain't cut out fur no dang compuker driven vee-hick-ull!

Thanks fur listnin.:D

[sctrailrider]

You may want to send a message to "john8662" here, he may be able to help ya....

[DickWells]

Got it!!! Almost on my own, actually. Well, I got help by looking through my old DP 6.2 - 6.5 manuals. The 99 Feature Articles book first got me looking for the oil pump in an article by one Jim Bigley , where, on page 81, he shows a picture of it and describes the four pulses per rev. That got me to checking wires, and I found that I'd actually used a gray wire from the the oil pump sensor to ground for the 100 ma coil in the 40 A relay that I'd used many years ago to relieve the load on my oil pressure switch. (Article by Pete Sutsos on page 9 of same book.) There are three wires from the crank speed sensor (at the oil pump, I guess) ; the gray wire for ground, orange with 12 V, and a tan wire that gives 5V when running. I tapped onto that tan wire and viola!, the slip codes disappeared and shifting improved tremendously.

For once, I had taken notes (on page 9) and marked out my wiring, so that I could refresh my thinking. I've now added other notes in the margin to help me, down the road, when I will surely forget what I did today.

Thanks, guys and gals.