8 Speed Transmission Missed Shifts

[Rod Powell]

Hello.

I have an early 2017 Ram 1500 4WD with the hemi and 8 speed transmission with about 70000 miles on the clock.

Haven’t really had any problems with the truck, EXCEPT it has recently, over the last 10000 miles or so, and only upon cold starts, begun hard shift or missing the 3-4 shift. Only once, when leaving the driveway.

Strangely, if I shift into reverse, then back into drive and pull off, the effect is minimized. I can still feel it kinda slip just a little, and only between the third - fourth gear shift, but it drives normally until the next morning’s first start. Every morning. Seems to be worse in the winter than summer, too.

When I try to drive it without first shifting to reverse then back to drive, it usually will not shift into 4th, and I get a CEL, with a P0733 code.
I can pull over, restart the truck, clear the code, and everything is normal, until the next morning.

Anybody have any ideas? Thanks for any advice.

 

[Jeepwalker]

The following (below) was on a site I went to. Have you changed the fluid or filter recently? I would probably remove and wiggle the large connector on the transmission, check for corrosion or wire issues on the pins and socket. See if that makes a difference. Then check the fluid level (watch a video to see how that's *exactly* done), and/or consult with a transmission shop who knows these tranny's. I repeat, "..knows these transmissions". Maybe even the [gulp] dealer (get their best sleuth on it, not the new guy). There might be a relatively easy fix: new speed sensor (if bad), Solenoid pack or something even unrelated.

I'd probably also quadruple-check battery connections, major and minor grounds and re-seat fuses, ...just because I've seen these trucks act 'funny' in odd ways, when the electrical path is not super-good. Is the engine running fine, otherwise? I've seen where a bad throttle position sensor or temp sensor, and even faulty PCV/Vacuum piping, can spoof tranny shifting issues. Codes aren't always concrete. Keep us up to speed.

• DTC P0733 stands for “Gear 3 Incorrect Ratio.” It’s triggered when the PCM detects that the RPM of your input speed sensor and output speed sensor are different from what the PCM expects.
• Common causes of code P0733 include low transmission fluid levels, dirty transmission fluid, or malfunctioning shift solenoids.
• Typical symptoms of a P0733 include a lit check engine light, incorrect transmission shifting, and even performance problems.

,

 

[Rod Powell]

Thanks, Jeepwalker. Good info. Checking around now for quality transmission mechanics (if any) in the Huntsville AL area.

 

[cammed]

My battery was at around 70% so I bought new battery that helped out with the speed sensor and hard down shift that would put it into limp mode then after a while check engine light would come on with no chime alert and would be in limp mode
Went to my transmission guy and put my truck on his lift let temp get to 100* deg checked level it was good
Then he cleared everything and reflashed my trans I had drive easy so trans could relearn so far everything is going good

 

[Jeepwalker]

Note....rear wheels have to be lifted in the rear because the bottom of the transmission pan must be LEVEL with the ground ...in order to get a proper trans fluid level check. Can't do it as accurately on a lift b/c the the trans doesn't sit level in the vehicle.

That's ZF Trans 101. If a trans tech doesn't know that, stop right there and move on.

 

[Redfisher1974]

This is where my tranny sits level. Pretty much top of my big jack.

 

[Rod Powell]

Again, great info. Thanks, guys.

 

[Shawn Burns]

did you ever change trans fluid? I would start there. My truck drove so much smoother after a fluid change. There's tons of info on trans fluid changes and some videos on youtube of others changing it.

Some highlights that I've gathered.

1. OEM pan is plastic and thrown away after a fluid change because the filter is not replaceable. There are aftermarket plastic pans that have replaceable filters (dorman). There are also metal pans that cost much more that also have replaceable pans (I used a PPE and I can speak to it's quality).
2. Fluid: many people have had success using valvoline maxlife ATF instead of the uber expensive and so-so quality OEM fluid. Others have used amsoil with varying results and redline if you don't mind spending some money on a top notch fluid.

 

[EdGs]

Have you had the truck since new? Any towing or heavy hauling?

Chrysler will tell you the trans is "sealed for life", but ZF recommends a service at approx 80k miles, sooner if heavy use (might even be sooner, maybe 100k km?).

Please keep us posted on your progress.

 

[Rod Powell]

Got it in 2019, with 20000 on the clock. Never changed the fluid nor have I ever towed anything.

If I do change the fluid, I’ll go with the PPE pan and Maxlife.

Thanks for the advice.

 

[Wild one]

Got it in 2019, with 20000 on the clock. Never changed the fluid nor have I ever towed anything.

If I do change the fluid, I’ll go with the PPE pan and Maxlife.

Thanks for the advice.

Here's the procedure for checking the fluid level after you change the pan,the first high lighted paragraph is kind of important,you need the rear tires about 9 inches in the air,to get the transmission level.

 

[Jeepwalker]

"The 8HP fluid is luminous under a black light"

....hmmm I never picked up on that before.

 

[Curmudgeon]

I used to have a really nice black light in my garage
but shortly after acquiring it the damned thing ran
off with my 10mm socket.
Last I heard they are back-packing through South America,
whereabouts unknown.

 

[cammed]

Note....rear wheels have to be lifted in the rear because the bottom of the transmission pan must be LEVEL with the ground ...in order to get a proper trans fluid level check. Can't do it as accurately on a lift b/c the the trans doesn't sit level in the vehicle.

That's ZF Trans 101. If a trans tech doesn't know that, stop right there and move on.

That's why you use 2 post car lift so it will be level in the air