95black2615

This problem usually happens after I drive it 15 miles or so. If I have cruise control on when it happens......the cruise kicks off and the rpm's raise by 250. Normally runs at 1500 rpms at 55 mph, but when it happens it runs at 1750 rpm at 55 mph.

When it happens, the cruise control doesn't work at all.

I am assuming the torque converter is unlocking, but what does this have to do with the cruise control?

Trans fluid and filter have been changed recently. Fluid still looks good and doesn't smell burnt.

NHDiesel

I think you may have the same problem that I suspect I have. Does it happen when going over a fairly large bump? My cruise doesn't work, so I can't tell you if my cruise is affected, but since both things are shutting down for you (cruise and TC unlocking) I think we have the same issue. I suspect that my TC is unlocking over bumps because my brake pedal return spring is weak, the pedal loose, or the switch is out of adjustment. I hit a bump and the brake light switch is pushed slightly, causing the TC to unlock (it unlocks when you are on the brakes), along with the TC unlocking.

If you have the problem at the same spot in the road, or if it happens frequently, try hooking a heavy rubber band on the brake pedal to take pressure off it (and not restrict the brakes of course!) and see if the problem goes away.

I haven't checked mine out since thinking of the brake switch being the problem because I haven't had the time, but maybe tomorrow I'll get the time to do a little diag. work and see if I'm right.

Jim

fschiola

OK, I know this thread is for 24V's but it couldn't hurt to check yours.

Click

kandgo

Do a search on cleaning your Throttle Position Sensor known as the TPS and also read about the wires running to the PCM from the switch which can be taken out of the wire loom and put in thier own to stop the interference also. One more thing clean your battery cables good and cover them with some good dielectric grease when done. The brake switch is a good start to see if it is falling down and engaging the switch. When you are cruising down the highway without the cruise on tap on your brake with your left foot and you will feel the t/c unlock and lock back up. Both the brake pedal and the TPS will cause this senerio. Goodluck,,Rick

infidel

Jim hit the nail on the head, the brake switch is the one item the TC lockup and cruise have in common. Try lifting up on the brake pedal with your foot and see if the cruise works.
Some people have luck fooling around with the switch, it is self adjusting.
I have better luck with just replacing them, $12 from Napa.

kandgo

https://www.dieseltruckresource.com/...light=pappyman Here is a good thread on cleaning the tps, I suggest to save this as even if it is not the tps now you will eventually need to clean yours, also pappyman has the photos of the tps opened up in his gallery. I hope it is your brake switch. Goodluck,,, Rick

gwhammy

My brother had the cruise working kind of like what you are saying. He ended up replacing the switch on the steering wheel, it would work for awhile and then quit.

NHDiesel

I checked my truck out today and the problem with mine is definately the brake light switch. I need to buy a switch Monday when part's stores are open up here. I held the pedal up with my toe and hit every bump I couold find, and the TC never unlocked. Once I released the pedal the TC unlocked on the next bump.

If you are having problems with both cruise and TC, its most likely the brake light switch. The TPS won't give the same symptoms (both of the problems at the same time) so you can rule that out.

Jim

kandgo

Jim [/B][/QUOTE] The TPS won't give the same symptoms (both of the problems at the same time) so you can rule that out. Trust me when the Throttle position sensor sends a false reading to the pcm the torque convertor will and does act the same way as your brake switch and it will shut the cruise off. Glad it was your brake switch but I reinterate you will eventually need to clean or replace the TPS and cleaning is a whole lot cheaper. Goodluck,,Rick

95black2615

Mine turned out to be with the brake light switch.

I guess the fix is to buy a new switch.

NHDiesel

Cool! Good to hear it! I'll be waiting a few more days to get my switch. I had a rear shackle break on me yesterday while hauling a half a pickup bed of firewood. Nice. Now I have to wait for the ******* to order it, and have it shipped up here, so my week's project will probably be dealing with that, and put off the brake light switch for late in the week.

Jim