379 / c-15 cruise control shuts off

I believe it's under the driver's side kick panel on an air junction block....

 

check your trailer brake handle. I had a driver that hung his pick-up key ring on brake handle When he hit a bump it kicked cruise off.Spent quite a lot of $$$$$ figuring that one out.

 

ok so i replaced the brake switch already and nothing happening. i called the original owner and he said to mess with 2 of the speed sensors on the tranny. he said he did that a couple of times and solved this problem. and that all this happened when he put the 18 speed on it. My speedometer and tach are working fine. Any idea to check if theyre good before i replace them? Could this even be the problem?

 

Find someone w/ CAT ET. It tells you what the last thing to shut the cruise off is. As far as the speed sensors in the trans go. If there are 2 sensors, one is for the dash and the other is for the ECM. If the ECM is set up to turn off cruise when the speed fluctuates more then a set speed, it will knock your cruise out if it looses signal.. Check and make sure the yolk is tight on the output of the trans, and make sure the sensor gap is correct.

 

make sure your floormat isnt under your brake pedal & pedal isnt sticking

 

If you have an "Applied Brake Pressure" gauge in the dash (and you should,) follow its airline. It should go into an aluminum block - a manifold - and the brake light switch will or should be screwed into that same manifold.

 

Check wires from speed sensors to ecm an into cab if you have a short or bad speed sensor it or wire it can short sometimes and tell ecm truck is moving or slowing down you can check ohm on the sensors as well as the harness also checkout the out put shaft on your trans I've seen the yoke loose and when ideling will bounce and vibrate the pulse ring for the speed sensors

 

so i checked the wires running from the sensors to the ecm and cab, everything looks fine, i unplugged connections and cleaned them up real good with electrical cleaner...i checked the sensonr on the tranny by the flywheel since i was told that was my problem, i disconnect it tachometer rpm stops working, connect it again and tach works fine; so that sensor works correct? or should i replace it anyways?
Im really going nuts here, i dont wanna pay 120 bucks to just connect it to a scanner... im running out of options...

YES, i removed floor mat and not under brake pedal...

clutch switch working as i mentioned before, brake pressure switch changed...

 

so i checked the wires running from the sensors to the ecm and cab, everything looks fine, i unplugged connections and cleaned them up real good with electrical cleaner...i checked the sensonr on the tranny by the flywheel since i was told that was my problem, i disconnect it tachometer rpm stops working, connect it again and tach works fine; so that sensor works correct? or should i replace it anyways?
Im really going nuts here, i dont wanna pay 120 bucks to just connect it to a scanner... im running out of options...

YES, i removed floor mat and not under brake pedal...

clutch switch working as i mentioned before, brake pressure switch changed...