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Need Help With Engine RPM Signal For TCM
- Thread starter mynewtoy
- Start date
Nobody?
6.2 machanical with 4L80E 4x4
www.dieselplace.com
On the HMMWVs they have a unit in place of a vacuum pump that sends some type of signal. Might be worth looking into.
Can you send me a picture of what I'm looking for?
Thanks
Keith_J
Well-known member
My finger is pointing to the terminal that is for the tach module buffer. It is a snap on boot. Driver side alternator. This is an alternating current with frequency proportional to engine RPM. The Dakota Digital module will convert this to a tach level signal of pulses per revolution which is adjustable.
Thanks Your the best!!
Barrman
Well-known member
As pointed out the CUCV alternators have a tachometer signal already. Some vacuum pumps generate a signal as well. But, that signal might or might not talk to your tachometer or TCM.
Your transmission control module should generate its own engine speed signal because it gets the input shaft speed reading from the sensor inside the transmission. At least my Compushift TCM works that way. However, it won't export that signal to a tachometer or its own read out.
I have used the Dakota Digital converter box to go from a CUCV alternator to an Autometer analog tachometer on my M715 with a CUCV engine and dual alternator set up. I also used a Dakota Digital converter box on my Cowdog Suburban project. I have a Delco CS130 serpentine belt alternator on that truck and used the Dakota Digital box to get a good tachometer signal to my gauges and for read out on the TCM display.
If you get a diesel pulse adaptor for a digital timing light with RPM read out. That will give you an exact engine RPM that you can adjust the Dakota Digital box to get your tachometer exactly dialed in.
A Snap-On MT480 or MT1480 "Lummy Mag" timing set up will also give you an exact engine rpm from the slot in the harmonic balancer as a baseline to set your tach or TCM.
Your transmission control module should generate its own engine speed signal because it gets the input shaft speed reading from the sensor inside the transmission. At least my Compushift TCM works that way. However, it won't export that signal to a tachometer or its own read out.
I have used the Dakota Digital converter box to go from a CUCV alternator to an Autometer analog tachometer on my M715 with a CUCV engine and dual alternator set up. I also used a Dakota Digital converter box on my Cowdog Suburban project. I have a Delco CS130 serpentine belt alternator on that truck and used the Dakota Digital box to get a good tachometer signal to my gauges and for read out on the TCM display.
If you get a diesel pulse adaptor for a digital timing light with RPM read out. That will give you an exact engine RPM that you can adjust the Dakota Digital box to get your tachometer exactly dialed in.
A Snap-On MT480 or MT1480 "Lummy Mag" timing set up will also give you an exact engine rpm from the slot in the harmonic balancer as a baseline to set your tach or TCM.
Barrman
Well-known member
I was typing while you asked your question about the stock CUCV tach signal. It was for the STE/ICE diagnostic suit case they used back when the trucks were new. Think all analog OBDII with no real information from a 4 digit digital read out. I went to the trouble to find one that worked and used it once. It is now a novelty in my opinion for these trucks. However, the adaptors that come with the STE/ICE can be used to check all kind of PSI readings with real gauges attached to them.
chevymike
Well-known member
Or you can use something like this optical tach, which is what I used to set the RPM's for my Speedhut diesel tach. Worked great and is cheap.
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Buy AGPtek® Professional Digital Laser Photo Tachometer Non Contact RPM Tach: Tachometers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
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Keith_J
Well-known member
Certain transmission control modules use both engine tach and transmission input shaft speed differential to delay torque converter lock up when there is slip in the converter. If the engine tach signal is not calibrated correctly, it can prevent TC lock up or create harsh lockup.
I have been reading and searching just thought I’d pick some brains before I dug in. The oil pump drive with the engine speed sensor is expensive which I’d buy if someone could tell me if it would work. I even called MSD but the tech wasn’t very helpful. Im going to try again and hopefully get a more knowledgeable Tech.
Barrman
Well-known member
I forgot about the oil pump drive way. I had one of those and tried it first. It leaked oil out of the plug housing when I test ran the engine. Then my serpentine belt drive vacuum pump froze up soon after. I went with a CUCV vacuum pump and promptly forgot all about the speed sensor back there. The Dakota Digital converter box for the alternator signal was a lot cheaper than a replacement cam drive tach signal generator and I haven't looked back.
I have one of the oil pump drives but the sensor is gone. It looks kinda like a tach cable could be adapted. One day I'll follow up on that. Cable drive tachs are vintage neat.
