2002 Dakota has only 1st gear and reverse

dodge
dakota

#1

I have to admit right off the bat that I know little about Transmissions.

This is a 2002 Dakota with 3.9 engine and 3 speed Automatic with OD. 282K miles.
Great runner and well maintained.
No DTC codes present, and checking Transmission codes showed no codes.
Tranny fluid and filter was changed 20K ago.
Tranny fluid is clean and does not smell burnt.
One shift solenoid was replaced about 100k ago. But I dont remember wich one.

This morning I got off the main highway and when I came to a stop and started away from the stop sign The truck stayed in 1st gear and would not up shift.
I was only a few miles from my shop so I nursed it to the shop.
It stayed in 1st gear until I started down a small hill and as I gained speed it shifted into 3rd gear. The reason I feel it was third was that I topped out at about 50 and the tach read 2300 RPM. If I was in overdrive it would have dropped to about 1700 RPM at that speed.

I tested the TPS to be sure it was sending the signal to the PCM.
Checking voltage across pins 1 & 3, I got 5.2 volts. This is within the range the book calls for.
Next with the connecter plugged back in I probed pin 2 and and got a range of .36 V with the throttle in the idle position and the reading climbed to .38v as I went to full throttle position. The book says .35v at idle and 4.5 V at full throttle.

I think I can eliminate the TPS as the problem.

I then put the truck up on the lift and found a broken wire at a 6 pin connector on the tranny. I think it was a black wire. The wiring schematic I have shows no black wire though.
There was just enough wire out of the connector for me to solder in a short lead and solder to the remaining wire.

I still have no upshifting.

Addition; I had work to do today and had to use the truck for work.

I drove about 25 miles and had to get to about 30mph…3500rpm and let off on the gas a bit and it would finally shift to third…skipping 2nd gear. I checked the tranny fluid 3 times on the trip and again when I got home. The fluid was clean and pink with no foul odor.

Any help would be appreciated.

Where are all those tranny experts!!!

Yosemite


#2

It might not be a transmission issue, anything that seriously hurts engine power and drops vacuum can stop your transmission from up shifting except downhill.


#3

I have no loss of engine power. Vacuum test was good.

Yosemite


#4

I have updated a few items. Look for> additions in my original post.

Thanks, Yosemite


#5

It could be one of the other wires to that same connector is broken too, just inside the wire insulation so you can’t see it. Suggest checking all those other connections in that connector you found w/the broken wire. hmmm … it’s a Dodge, right? does the tranny use a throttle cable input? i.e. A cable connected to something near the engine throttle valve area that goes back to a lever or knob on the side of the transmission? If so, that might have broken or be out of adjustment.

280 K on that transmission, could be most anything of course. I expect what a tranny shop would do first if there was nothing obviously wrong is do a transmission fluid pressure test. Do you know how to do that?


#6

@GeorgeSanJose

I do not know how to do a pressure test.

I did check all five wires from the female pins to as far up the wire loom I could get. The loom goes over the top of the tranny so I couldn’t reach more than about 8 inches from the connector. The wires were almost too short and a lot of stress were on them. I presume that is why one broke.
All five wires had continuity to that point, so I think the connections are ok. I have a new pigtail on order and will solder that in as soon as I get it.

There are a couple of trans fuses and a relay and all of those checked out good.

I did find some info on the trans cable and will be checking that tomorrow. I only checked that it was not broken , but will check the adjustment on that.


#7

The way an automatic transmission works — by way of a paper napkin explanation anyway – there’s several gear sets inside, each has one clutch input and one band input. If you had 4 gear sets, you’d have 2 x 4 = 8 total inputs to deal with. These hydraulic pressure inputs, but each are logically either on or off. Never in between. Each of these inputs actuate either a clutch, or a band on one of the gear sets.

So each gear-set can do one of 4 things. (0,0) might be neutral, (0,1) might be 1:1.5 gear ratio, (1,0) might be 1:1 gear ratio, (2,2) might be reverse say. So your problem is either one or more of those 8 inputs are not correct, or they are correct but they aren’t doing what they are supposed to do. The latter would be most likely caused b/c a piston/valve arrangement inside isn’t holding pressure due to leaky seal for example.

The 8 hydraulic inputs are determined in the valve body, using the vehicle speed (known from the governor pressure), the throttle position cable input, and any electronic selenoid inputs. From what I can tell only 4th gear has electronic input on yours, and the lock up TC has an electronic input too.

I’ve never had occasion to do that test either. I expect it is a fairly simple one to do tho, but might require special equipment since the pressures are pretty high in a transmission. But checking the pressure when you have a tranny symptom is a basic thing, sort of like checking the battery voltage with an electrical fault. If the pressure isn’t correct, the transmission will never work correctly. Here’s the pressures from what I can see for the 42RE. I think the most common one to test is the “line pressure”.

overdrive clutch: 70 psi, closed throttle, 110 psi, 1/2 to 3/4 throttle
line pressure at accumulator: 58 psi
rear servo: in 1st, within 3 psi of line pressure; in R 160 - 270 psi, varies w/rpm
governor: less than 1.5 psi at stand still, increasing smoothly with vehicle speed

Here’s a quick summary of how the inputs are set up

Reverse: Front clutch/rear band
1st: Rear clutch/kickdown band
2nd: Front clutch/rear clutch/front band
3rd: Front clutch/rear clutch/front band (released)
4th: Electronic controlled & hydraulically activated


Here’s a couple of wild guesses … first guess, if the 4th gear electronic control were activating in other than 4th, that might confuse the transmission and cause your symptom. There’s diagnostic codes for the transmission that can be read out I think, but might need a special scan tool. second guess, the rear servo seems to be involved with 1st and R only, so might have something to do with that.

Edit: Just out of curiosity, did some more looking reveals the governor pressure isn’t hydraulically controlled, it is electronically controlled. The pressure spec is roughly 1 psi per mph. there’s governor pressure solenoid, and a governor pressure sensor, separate parts. The fluid temperature sensor and throttle position sensor and transmission speed sensor and pcm are all involved with setting the governor pressure.

Complicated? That’s why we have professionals working at transmission shops!!!


#8

Thanks for the detailed explanation @GeorgeSanJose. I did some research myself and that helped me understand the Automatic’s workings a little better. I also watched how to do a pressure test, but would need to get the gauge set. Right now that is out of the question because of money. If I had the money, I’d just take it to a trasnny guy and let him fix it.

I thought that I had no 2nd gear, but yesterday I did notice that on flat ground 2nd gear was keeping me rolling with little gas. But as soon as I gave it much gas it tranny would just slip in that gear.

I talked to two other mechanics and both tended to think it was the “Governor Pressure Sensor”. So that is what I am going with. I have it ready to order but am wondering if I should replace the “Governor Valve” as I’m in there. The part is cheap. I’ll do a filter and fluid change and tighten the bands while I’m under there too.

Shouldn’t I have gotten an engine light or… at least set a code because of the Trans fluid pressure .

Yosemite


#9

Those two mechanics helping may be on to something. The governor’s job is to create a fluid pressure proportional to the vehicle speed. That’s the primary input to the maze of valves and hydraulic lines used in the valve body to decide what gear to shift to. The faster you go, the higher the gear you want, and there’s only a slight deviation to that formula, for things like going uphill, accelerating, so the valve body knowing the vehicle speed accurately is critical to the shift decision. And that information is exactly the governor fluid pressure. If the governor fluid pressure is lower than the true vehicle speed, the transmission thinks the vehicle is going slow all the time, and shifts to gears coinciding with slow speeds, reverse and 1st.

Which part to replace? Me, I’d probably measure the governor fluid pressure before replacing parts. But parts replacement and crossing fingers is a reasonable thing to do for this problem I think. I’d be inclined to replace one of the two, then test to see if that fixes it. If not, I’d replace the other.

Re: Shouldn’t I have gotten an engine light because of the Trans fluid pressure .

I’d think so. Perhaps all it is doing is storing a diagnostic code. You probably need a special scan tool to read transmission codes. But there may be a way to read them out yourself, using the blinking light method. On some vehicles that feature is built in, there’s a light on the dashboard or in the engine compartment that blinks out the code if you tell it to, usually something to do with the ignition switch.


#10

I dropped the drain pan from the tranny, and it was an easy fix to replace the “Governor Pressure Sensor”.

Test drove the truck and I had all the gears back and the shift ranges were smooth and at the appropriate speeds.

It took longer to clean up all the tranny fluid that I spilled on the floor than it took to replace the sensor.
I was doing great until the pan slipped out of my hand.

Yosemite