Can TPS cause eratic shift first to second?

[dodgedieselnewbie]

Hi guys.. I'm am having a problem with my truck shifting from first to second.. only on slow acceleration. It seems like it kicks in out of second very quickly a couple to few times. If I accelerate quicker.. no problem. Can TPS cause this or do I have another problem? Thanks in advance! All other gears are fine...

Edited September 23, 2018 by dodgedieselnewbie

[Mopar1973Man]

@Dynamic I know he would know the exact answer...

 

Myself I would check for error codes. Then hook up a live data tool like an OBDLink LX or similar and now with the key on and engine off. Watch the TPS display as you slowly squeeze the throttle if it does jump or drop suddenly or trip error codes the TPS is not the cause. As far as what I know 1st, 2nd and 3rd gear shifts are all hydraulic. 4th gear is electronic.

 

You might look at the fluid condition and check your throttle valve cable adjustment. If it too tight or too loose can change shift behavior.

[dodgedieselnewbie]

Okay.. a little more info. I do get a TPS code on my smarty. I went camping a few weeks ago. We took a day trip/ride to next town over.. when we turned around to go back to campground.. we were climbing an uphill grade and the truck hung in first gear way longer than it should have.. then kicked REALLY HARD into second. I pulled over to let the dog out to do his business and the truck wouldn't go into neutral, reverse or park. Long story short.. tranny guy up there took pan and valve body down.. the piece that holds a band in place fell off and lodged itself in the linkage. He put back together and seemed to shift fine. But on slow take off... Not so fine.

 

[Dynamic]

If you're getting a TPS code, you need to start there. While the 1st - 3rd gear shifts are hydraulic in nature, the PCM generates the governor signal electronically based on several inputs, with the TPS being one of them.

 

The other question that needs to be answered is why did the band anchor fall off? How worn out is your intermediate band?

[Tittle Diesel Performance]

On 9/22/2018 at 9:39 PM, dodgedieselnewbie said:

Okay.. a little more info. I do get a TPS code on my smarty. I went camping a few weeks ago. We took a day trip/ride to next town over.. when we turned around to go back to campground.. we were climbing an uphill grade and the truck hung in first gear way longer than it should have.. then kicked REALLY HARD into second. I pulled over to let the dog out to do his business and the truck wouldn't go into neutral, reverse or park. Long story short.. tranny guy up there took pan and valve body down.. the piece that holds a band in place fell off and lodged itself in the linkage. He put back together and seemed to shift fine. But on slow take off... Not so fine.

 

The band anchor coming off isn’t an abnormal thing. Most trans builders set them loose to start for a cleaner 2-3 shift so general wear gives enough room to fall out of place. It happens. I doubt TPS is the issue, the gov signal is on a time based algorithm that offsets for TPS input errors. Basically it’s got a smoothing function. Your more likely that the 1-2 shift valve is worn or the bore is worn, the gov plug maybe getting stuck or even the intermediate 2nd gear servo is sticking, they use a metal sealing ring that wears a groove in the bore and gets hung up then bangs into gear. Another one is the throttle valve getting stuck or even as simple as your TV cable is frayed and sticking. That cable is the #1 cause of trans failures in dodges because no one adjusts or takes care of them properly. Make sure that cable is moving smoothly, and there is a return spring for it on the trans itself. If that’s broken find another to replace it. Shift points should be around 12mph 1-2 and 26-30 for 2-3 normal driving. Some times you can’t get it that high but it depends on the VB calibration so get it as close as you can. You should feel the TV return spring in the pedal feel at all times

[Dynamic]

Haha... Not that loose... If you're setting the band loose enough that the band anchor falls off, you need to reevaluate your setup.

[Tittle Diesel Performance]

On 9/24/2018 at 2:04 PM, Dynamic said:

Haha... Not that loose... If you're setting the band loose enough that the band anchor falls off, you need to reevaluate your setup.

You need to re-read that. Wear causes it to loosen up more and more till it comes apart. No real way around it unless you readjust bands every 50k or so but each truck is different too. Good setting is 1/8” drill bit between the servo and apply lever while pulling the apply lever under tension with your finger. Gives nearly 1/4” under hydraulic load of travel for a clean 2-3

[Dynamic]

The band simply does not wear that much unless something is drastically wrong, and 1/8" would be WAY too tight, and you'd likely have a pretty good tie-up on the 2-3 shift. 5/16" is really what you're after there. With a 3.8:1 band lever, this is appx. 2-1/4 turns out. You'll never lose a band anchor at that setting, your pin will contact the lever nearly perfectly perpendicular eliminating side loading of the pin, and your 2-3 will be nice and clean, assuming the correct direct clutch clearance and servo return spring rate for the line pressure that you're running. You should be adjusting your bands every 30K miles.

 

Some guys like to cheat the band on the loose side to compensate for the fact that they don't have enough servo return spring rate for the line pressure they have. A loose band setting will preload that spring a greater amount for more spring rate to get the band off quicker. It's a bandaid for an improper setup, and you really need quite a bit more spring rate if you're running any real pressure. It also puts the apply pin contacting the lever at a pretty good angle, which will side load the pin and wear your servo cover egg-shaped, which will in turn exhaust direct oil. The other down side of running that loose is that the band anchor can fall off.