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Transmission, transfer case, or torque converter?

6K views 16 replies 8 participants last post by  Dtoyne  
#1 · (Edited)
Hello all.

I finally got tires installed on my p38 a couple weeks ago. And it drove great until this afternoon.

I noticed it stalling around 30mph and if I give it gas, it revs to 3000ish rpm and just stays there but doesn’t accelerate. If I let off it feels like it grabs again. I had just finished changing the diff and transfer case fluid. Which makes me suspect the transfer case but the fluid as darker red, and I didn’t notice any metallic specks or anything. And had no signs of issues before.

The rear diff oil was very dark. I was planning on changing all the fluids again in a few weeks.

I also have everything to service the transmission and was planning to do that soon. Would fresh fluid and filter help?

I am also noticing it will die when the gas tank around 1/4 full and idling for a few minutes. Starts right back up though.

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#2 ·
When you say stalling at 30mph, does it happen while going up to that speed, coming down to that speed, or while cruising at 30mph? I suppose something like a stuck turbine within the torque converter may cause stalling issues, but typically such stalling is caused by sensor related issues like CPS.

I would also take a look at the color and smell of the transmission fluid, since it's easy to do.
 
#4 ·
When you say stalling at 30mph, does it happen while going up to that speed, coming down to that speed, or while cruising at 30mph? I suppose something like a stuck turbine within the torque converter may cause stalling issues, but typically such stalling is caused by sensor related issues like CPS.

I would also take a look at the color and smell of the transmission fluid, since it's easy to do.
Color and smell of the fluid was fine. I didn’t check the level.

The stalling is basically it stops accelerating. The motor revs up but acceleration stops. Let off the gas pedal and it “catches” again and will slowly accelerate. Very odd behavior. My first thought was torque converter but I am unsure of how to diagnose that.

I’m sure going up 4” on tire size didn’t help....

Does a nanocom give live reading of what the drivetrain is doing? I wanted to get one anyway but this may push me to finally get one.


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#3 ·
Obvious things I guess to start with. Auto trans fluid at the correct level? (Checked cold and running). It isn’t going to be a diff as that would make a lot of expensive noises and certainly won’t give you the symptoms you describe here. Neither will the transfer case.

As for the stalling at idle, time to check the fuel pump pressure. Worth removing the pump as over the years it migh have a lot of crud on the gauge screen on the pick up, which floats off with a full tank and concentrates as the level lowers. The pickup is in its own little “pen” so making it highly susceptible to getting clogged with low fuel. The reason it re-starts is that the crud falls away once it stalls.

A few thoughts for consideration.
 
#7 ·
That would be a great outcome. I’ll be out of town over the weekend I might try to tackle the trans service next week.

Thanks I’ll update you guys to what I figure out.

One more thing to add is I drove through flood waters a couple weeks ago, up to the front bumper at times, getting my kids from school when my town flooded. That is why I was checking and changing fluids but none were milky including the trans. Which is why I didn’t check the level because I was looking for water intrusion and it was driving perfectly.


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#8 ·
Up to the bumper is nothing, it's only when it is up to halfway up the headlights you need to worry. Everything has, or should have, breather hoses attached that have their ends high up by the bulkhead or by the sides of the radiator so unlikely that water got in anything. Only thing that could have been affected by water is the XYZ switch on the side of the gearbox. that has a breather so should be fine but the breather often comes off. If that has been affected the dash and gear lever will show a different gear to what you have selected and it will go into limp mode.
 
#9 ·
Check the fluid level first. If that's as it should be, you could try manually selecting a lower gear and see what happens then. If it's the torque converter, I expect it will top out (I wouldn't call it stalling) at a lower speed in lower gears, but at a higher rpm as there is less load.
 
#10 · (Edited)
Well the fluid was not very dirty or below the lowest dot on the dipstick.

I changed the fluid and filter and took it on about a 30 mile drive. Did perfect until the last 1/4 mile. Did the same thing again. Once it cools I’ll verify the level is correct again. About to drop the gas tank as it died on me once while idling again today.

Edit:
Dropped the gas tank and pulled the pump. No obvious trash in the tank. Or built up on the sock. I sprayed it down with carb cleaner and I didn’t see anything come off of it. I wiped out the tank the best I could and other than a couple specks, all was clean. Re installed and checked the trans level and it’s perfect.

Any other suggestions? Or tests to try to figure out what is going on?

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#11 ·
Well the fluid was not very dirty or below the lowest dot on the dipstick.

I changed the fluid and filter and took it on about a 30 mile drive. Did perfect until the last 1/4 mile. Did the same thing again. Once it cools I’ll verify the level is correct again. About to drop the gas tank as it died on me once while idling again today.

Edit:
Dropped the gas tank and pulled the pump. No obvious trash in the tank. Or built up on the sock. I sprayed it down with carb cleaner and I didn’t see anything come off of it. I wiped out the tank the best I could and other than a couple specks, all was clean. Re installed and checked the trans level and it’s perfect.

Any other suggestions? Or tests to try to figure out what is going on?

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My 2001 Vogue had been in storage for 10 years and it drove fine for a couple of years but when I came to regularly flooring it on the open road or hills here in NZ it would run out of puff --- rev properly but loose power, ease the accelerator and it would change up a gear and use the torque to quietly accelerate away.....problem turned out to be the fuel pump. It had been tested for pressure which was OK but hadn't been tested for flow. When it was tested for flow it wasn't sufficient to keep full power even though the engine would rev. New fuel pump last year and now it has full power whenever I want it.
Might pay to check your fuel flow as opposed to pressure :)
 
#13 ·
Figured it’s been a couple weeks now and an update would be good. Since I dropped the tank and added topped off the transfer case I have had zero issues with the truck over the last 2 weeks. I drove it almost every day and even towed my small trailer one afternoon with it. I guess I’ll call it good for now.


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#14 ·
Figured it’s been a couple weeks now and an update would be good. Since I dropped the tank and added topped off the transfer case I have had zero issues with the truck over the last 2 weeks. I drove it almost every day and even towed my small trailer one afternoon with it. I guess I’ll call it good for now.


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Those symptoms sound a lot like the Crank-Shaft-Position-Sensor to me as I've had 2 go out on a non Rover that produced the same exact attributes. You say you went thru high water. Water will destroy an aging CPS whose rubber grommet/gasket has been degraded either by heat or age and allows water to seep into the sensor. It will put the vehicle into Limp-Home Mode initially and then gets overwhelmed and stalls/shuts off after a thorough "Heat-Soak" of the engine. Then it will usually reset and allow the vehicle's engine to turn over again and start up and start the cycle over again.

I was in college and had a nightmare chasing down the CPS as the stalling, RPM revving, shutting off intermittently. In my case both times was a leaky water-pump that was allowing Anti-Freeze to drip down and onto the CPS. Thus corroding the sensor. Fixed just the sensor the first time... 2nd time the water-pump and CPS sensor was replaced to never have that problem again. Not say that is exactly your problem but the High-Water Crossing "Could" have introduced water into that sensor causing essentially the same problem.

The CPS is usually pretty easy to get to on the outside wall of the engine block near the bottom end where the internal Crank-Shaft rotates thus turning the rods/pistons. Hope this helps!
 
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#15 ·
That sensor under the water pump is the Camshaft Position Sensor. The Crankshaft Position Sensor is located at the back of the engine, bottom right corner, and is definitely not easy to replace. From what I have read that one typically fails to work when the engine is hot and then you have a spinning motor that will not start until it fully cools down.