1999 f350 dually CC 7.3 with 200k

so for about 2 months my transmission was shifting hard as hell quite frequently. Both from 1 to 2 and 2 to 3. It would shift hard and or hang awhile before shifting up.

I was resigned to the fact that my tranny (often abused) was dying. I was within weeks of taking it in for a rebuild.

I also have had for over a year, a bad cps like symptom of the engine dying for a second while running (just boom dead for a second and then running again) but only when it was raining When it happened while stopped it would dye completely but always start right back up. I had put in a new cps to solve this but it made no difference and decided it was a worn wire in the harness somewhere. Code would always indicate the CPS but if that's the wire that's shorting then that makes sense.

Last week the bad cps symptom went nuts and it wasn't raining. It was dying as described at least 3 times a minute and no power under any load, like going up a slight hill.

To cap it all off its been -10f to -24f for a couple of weeks so starting the damn thing in general was getting to be a problem because the plug for the headbolt heater was broken. I would run 20 minutes at 2 am and 6 am just so I could start it each day.

When the engine dying started going hyper with no moisture I sucked it up and dove in on some maintenance. With half the truck as far in the garage as I could get it, and a tarp draped off the back end to hold in some heat (what a treat) I did the following.

Changed the oil and filter. switched from rotella dino to rotella t6 synthetic. Wished I had done this a long time ago, man what a difference. It will actually start with out headbolt heat sitting for 12 hours at -15f.

changed the cps. another gray one from carquest, old one was gray from O'Reillys. Old cps was sloppy loose so I know that was what was causing the increased dying.

Put a new plug on the headbolt heater.

cleaned the fuel bowl and replaced the filter

replaced the air filter

New cps fixed the dying. Don't think it will fix the stalls from moisture but the hyper dying is gone, not one hiccup since.

What surprised me is the tranny is shifting perfectly. Not just better but it feels brand new. If I had taken it in and they had only replaced the CPS but told me they rebuilt the tranny I would have believed them 100% its that much better.

All the maintenance was way past due and the CPS bolt was so loose its a miracle I made it home the last day I drove it. The transmission fluid had been boiled twice in the last two years before I drained and flushed it last summer along with a new filter as it was sporadically shifting hard and showing an increase of about 40 degrees temp at idle back then. The drain and flush really didn't change the temp and sporadic hard shift last summer but it made me feel better and the temp wasn't in the danger zone just more than it has ever read before. i figured I was buying some time.

Soooooo, could the cps been affecting my transmission shift even when the engine wasn't dying or running rough? Does the computer use data from the CPS to tell the transmission when and how to shift?

 

Moved to the 1999 - 2003 7.3L Power Stroke Diesel forum.

 

The CPS lets the PCM know what RPM the engine is at. It is nothing more than a on/off signal that is seen by the PCM. If the signal was noisy or being interrupted the RPM signal could be the cause of the hard shifting.

I would highly recommend not using aftermarket CPS's as they are not any cheaper than the OEM ones and I think they can be less reliable. I know Bosch makes a CPS and it appears to be a well made unit, I have not tried it myself. The OEM gray CPS can be bought for under $20 at Parts Guy Ed's site and will fit perfectly.

 

Hmmmmm, makes me want to go tis direction for my luck. I've been guessing for about 2 years but chocked my hard shifting up to bad trans. I too have had the stalling issue and hard cold starts. Mine seems to get worse when temp dips below freezing. No real codes though. Have done CPS, APP, IAT, ICP and harness, IPR, etc. UVCH will go down this weekend I hope.