Cruise Control?

[Kevin Means]

Our 1998 M1083 is a pre-ECU version. I would like to install an aftermarket cruise control. Has anyone done this on a pre-ECU LMTV/FMTV? The mechanical installation looks pretty straightforward, but I'm most concerned about how to get speed info to the cruise control's brains. A couple of companies make "universal" cruise controls, but, so far, the only ones I've seen require a mechanical linkage hookup at the transmission. Does my Alison transmission have such a hookup? Can speed information for these aftermarket cruise controls be obtained by tapping into the wires at the rear of the speedometer? Any other ideas?

Thanks
Kevin

 

[Ronmar]

There is an output speed sensor in the transfer case. This outputs a pulse per mile output signal(sensor reading an intermediary gear tooth). it feeds thru the transmission controller, thru the VIM on an A0/WTEC2 truck and on to the speedometer and then on to the CTIS controllers. On a WTEC 3 truck with 3116(started phasing in the WTEC3 in 199 there is no VIM, so directly from TCU to speedometer and onto CTIS...

The feed to CTIS simply drives the overspeed sense, that forces it to inflate if you are running too fast for a lower pressure setting. If you are running eco hubs, it will never work again unless the CTIS controller is re programmed to trigger at 1/2 the input signal rate...

At any rate, You could probably use the CTIS signal to feed your cruise control as long as its sense input is high enough impedance to not load it down so far as to affect the speedometer. a severe load down would affect transmission controller as it uses that signal along with turbine speed and input speed(engine RPM) to determine if the trans is operating properly... I don't have the numbers in front of me for pulse per mile rate, and you would have to determine if that rate is within the limits of the CC controller to accept...

 

[Kevin Means]

Thanks Ronmar... I think I'm with you after reading your post several times. I've learned that many cruise control systems use pulse per mile inputs to determine speed but, so far, I'm finding it difficult to find info on the pulse per mile output from the transmission or speedo. I'm sure its in the pubs somewhere. Thanks again

Kevin

 

[Ronmar]

Thanks Ronmar... I think I'm with you after reading your post several times. I've learned that many cruise control systems use pulse per mile inputs to determine speed but, so far, I'm finding it difficult to find info on the pulse per mile output from the transmission or speedo. I'm sure its in the pubs somewhere. Thanks again

Kevin

You are not missing it, it is not in the books... I actually got in and counted the gear teeth that the sensor looks at. I can look in my notes and give you a rough idea of PPM when I get home this evening...

 

[Kevin Means]

Wow! That would be great. Thank you. BTW, I really enjoyed your youtube video about manual tire inflation. I've got a used CTIS controller coming my way to replace the dead one that came with our rig, but it's the last one I'm going to buy. If it fails, I will be going manual. Thanks again.

Kevin

 

[Ronmar]

Ok with stock wheels and 2:1 hubs(7.8:1 total ratio, at ~60MPH the driveshaft is spinning an insane 3375 RPM. If I recall the output speed sensor is sensing a 36 tooth gear, so that would be 26 pulses per revolution or 121,500 pulses per minute. Since 60 MPH is 1 mile per minute that is also the PPM output…

minus the 2:1 hubs it would be half that 60,750 PPM @ 1687 driveshaft RPM…

EDIT: I think I typed that 26 in error in a past posting, I found another reference indicating 36 teeth on the gear which agrees with my memory when I counted them...

 

[GeneralDisorder]

Not sure on the A0's WTEC-II, but on the 3126 and C7 trucks, the ECM value for PPM (pulses per mile) is 62,618 (or 31.309 with ECO hubs).

It seems..... odd to me that the older truck would have a higher PPM number unless it's looking at a different sensor/trigger wheel or it's being adulterated by the TCM.

 

[Ronmar]

I could always put a freq counter on it and drive to be certain of the final output, but on my A0 it does sense a 36 tooth spinning gear(i have counted the teeth) and the DS RPM is pretty easily calculated...

OOPS: 36 teeth, not 26 teeth...

 

[Ronmar]

OOPS, I screwed that up. I was thinking it was 36, but found one of my other posts on the subject indicating 26. I think I typed that wrong way back when, as having counted them I was immediately thinking/remembering 36. Sure enough I searched a little and found a different post indicating 36 teeth which agreed with my memory That bumps it up to ~121,500 pulses per mile...

 

[Kevin Means]

I'll then I'll go with 36. That helps a lot. Clearly I'll want to install the Eco Hubs before trying to get a cruise control to play nicely with the transmission's output. Thanks Ronmar. BIG help.
Kevin