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Discussion Starter #1
My 2002 truck has started binding when I attempt to back up. It only happens when the truck is pointing down hill. Never when level or facing up hill. Other than this one issue the transmission is flawless. It has just over 100,000 miles on it after a major rebuild. Could the be slack in a clutch pack which is allowing a disk to hang forward, out of its position when pointed down hill?
 

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No, it isn't a loose clutch plate.

How is the fluid level? Make sure to check the level with the trans warmed up, in park, and the engine idling.
 

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Discussion Starter #3 (Edited by Moderator)
No, it isn't a loose clutch plate.

How is the fluid level? Make sure to check the level with the trans warmed up, in park, and the engine idling.
Mark, thanks for responding. I checked the fluid as you instructed. Now I am embarrassed! The level was below the stick. No fluid on stick at all. But I suspect you knew that. Lol. As Paul Harvey would say, Now the rest of the story: I installed a transmission cooler a few years ago and I discovered one of the connections had an ever so slight leak. I would have fixed it but pulling the radiator to get to it killed my desire to do so. However, however replacing a burnt up tranny would a lot more work. I had a quart on me and added it. Which raised the level to touch the stick. I totally forgot that I needed to check the fluid with engine running. I will repair the leak at the cooler this weekend. New motivation. Thank you.
 

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Discussion Starter #4
Mark, thanks for responding. I checked the fluid as you instructed. Now I am embarrassed! The level was below the stick. No fluid on stick at all. But I suspect you knew that. Lol. As Paul Harvey would say, Now the rest of the story: I installed a transmission cooler a few years ago and I discovered one of the connections had an ever so slight leak. I would have fixed it but pulling the radiator to get to it killed my desire to do so. However, however replacing a burnt up tranny would a lot more work. I had a quart on me and added it. Which raised the level to touch the stick. I totally forgot that I needed to check the fluid with engine running. I will repair the leak at the cooler this weekend. New motivation. Thank you.
Mark,
I had to add 2 quarts to get to the full level mark. But the i still have the binding when shifting to reverse when pointed down hill. I changed the filter and checked for any debris in the pan. There was just a little fine metal powder on the magnet. I read the recommended reading post, "Slight reverse issue." I see it is a low pressure issue. I will run the pressure test as described soon.
About a year or so ago I noticed that if I didn't drive the truck for a few days, it doesn't want to move for a half a minute or so. I am of the opinion that the Torque Converter fluid is draining back into the transmission as it sits for a day or so. If I let the truck idle for a moment after sitting, before I shift to drive. There is no hesitation.
Seeing how I must have a low pressure issue and in light of the converter draining when parked. Is it possible for the converter to have a seal going bad which is beginning to bypass fluid, thus lowing the line pressure in the converter? Or is the drain back a check valve problem, if there is such a valve used in the transmission. Then why is the reverse issue only happening when shifting to Reverse when truck is pointed down hill?
Thanks,
 

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The problem with the converter draining is a check valve, not a seal. The check valve is in the pump body, not the converter.

Did you get a filter for a 4x2 or a 4x4? If you have a filter from a 4x2 it is the wrong one. All 4R100 transmissions (except the Lightning) use the 4x4 filter. If you have a 4x2 filter in the trans it will suck air when on a slope and cause issues, such as binding.
 

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Discussion Starter #6
The problem with the converter draining is a check valve, not a seal. The check valve is in the pump body, not the converter.

Did you get a filter for a 4x2 or a 4x4? If you have a filter from a 4x2 it is the wrong one. All 4R100 transmissions (except the Lightning) use the 4x4 filter. If you have a 4x2 filter in the trans it will suck air when on a slope and cause issues, such as binding.
Thanks Mark,
I replaced it with a 4x4 filter. I even compared the filters to confirm. The binding only starting happening a few months ago. The filters must be correct. Fluid level is correct, filter is correct. The pump should then be getting a continuous supply of fluid.
Assuming the check valve is not effecting pump output, then why would the binding only happen when pointed down hill? 2 thoughts.
1) I noticed the hot mark on the dip stick allows the fluid level to immerse the control valves in fluid. If there was a gasket on the suction side of the pump that broke, which is normally immersed in fluid when the transmission is in a level or inclined position, but when in a declining position the fluid moves forward allowing the broken area of the gasket to suck air. Something to that effect.
2) Or, the check valve ball is needed for pump output and is able to seat when level or incline but moves off its seat when pointed down hill, but when I feel binding and let off the fuel, then reapply the fuel, the ball is able to seat and send pressure to drive the clutches.
My transducer is arriving Wednesday and I will be able to monitor pressure real time and get away from all this guess work.
Thanks Mark!
 

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Discussion Starter #7
Thanks Mark,
I replaced it with a 4x4 filter. I even compared the filters to confirm. The binding only starting happening a few months ago. The filters must be correct. Fluid level is correct, filter is correct. The pump should then be getting a continuous supply of fluid.
Assuming the check valve is not effecting pump output, then why would the binding only happen when pointed down hill? 2 thoughts.
1) I noticed the hot mark on the dip stick allows the fluid level to immerse the control valves in fluid. If there was a gasket on the suction side of the pump that broke, which is normally immersed in fluid when the transmission is in a level or inclined position, but when in a declining position the fluid moves forward allowing the broken area of the gasket to suck air. Something to that effect.
2) Or, the check valve ball is needed for pump output and is able to seat when level or incline but moves off its seat when pointed down hill, but when I feel binding and let off the fuel, then reapply the fuel, the ball is able to seat and send pressure to drive the clutches.
My transducer is arriving Wednesday and I will be able to monitor pressure real time and get away from all this guess work.
Thanks Mark!
Oh! I tightened the leaking fitting at the additional transmission cooler I installed. With two years of planning (LOL!) It only took a whole day draining fluids, removing the radiator, battery box, and intercooler. No more leak! Praise God!
 

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The check ball doesn't affect the pump. If it is off the seat when the engine is running it won't make a difference, it only affects engine off.

Nowhere in the valve bodies has suction. Suction is only present at the filter. Everywhere else has positive pressure.
 

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If your valve body has a worn manual valve bore this would be the way to fix it.
 

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Discussion Starter #12
Mark,
I have installed my pressure gauge and the results don't look good. The pressures on a warmed transmission at idle are:
P/N.....15.5
R.........21.5
OD/M2...15.3
M1.......15.3
Would it be reasonable to think that a worn valve body could be at fault or are the pressures more indicative of a pump issue?
Thanks
 

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I can't tell if you have a major leak or a worn pump. I really doubt that it is the valve body. A complete teardown is needed to find out what is causing the low pressures.
 

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Discussion Starter #14
I know it is hard to know if leak or pump? To bad cant monitor pump flow with pressure.

Thinking about a major leak possibility;
We do know that the Torque Converter is draining down when parked because the check valve is not working. If the check valve is actually working, can the converter drain down in another way? Is the flow to the converter just a flood process providing fluid for the fluid coupling and then draining back to the pan for cooling? Or is the converter actually pressurized and could be bypassing thru a bad seal thus reducing the available pressure by of the system?

Thanks,
 

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The converter is fed pressure regulated to 120 PSI. Fluid exiting the converter goes through the cooling system, then into the lube system, then is dumped into the pan. There are seals on the input shaft that could be leaking.
 

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Discussion Starter #16
The converter is fed pressure regulated to 120 PSI. Fluid exiting the converter goes through the cooling system, then into the lube system, then is dumped into the pan. There are seals on the input shaft that could be leaking.
Would low fed pressure to the converter affect the fluid coupling effect of the converter? The reason I ask is because my F350 truck has a welding bed on it and the truck total weight is 10,500 lbs. I run a tuner with modifications which I estimate are producing 380 hp. With the weight and the added horse power I have always had a problem with getting enough fluid coupling out of the converter to reach 45 mph where the converter will make the 3rd gear lock up point. I did some research which led me to believe the added weight and added hp changed the stall dynamics of the converter. I have all the power needed to accelerate but the converter just couldn't couple enough to transfer the power. I would just hold the engine RPMS at 2200 and wait on the converter to catch up. Some hills in the north east the converter never catches up until I reach the top of the hill. Which is a uneasy when traffic is speeding around you because you cant get going. Which led me to remove the stock triple disk and replace it with a 1200 stall, 1000 hp converter triple disk by Diamond D. It was my hope to gain more fluid coupling to carry me thru 3rd unlocked, but i saw very little improvement if any. Some attempted to argue with me that the truck would be un-drive-able with a 1200 stall. But it seems perfect. At a red light on a slight incline the truck will move forward on its own at idle if I don't hold it with the brake. I may have had low pressure after the rebuild and now some ware has caused the pressure to drop even lower.
 

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If line pressure in the trans is low the main regulator valve will cut the supply to the torque converter. That's because the converter will function with zero feed pressure. As long as the converter is full of fluid it's function will be normal. The only problem is that with no feed there is no flow to the coolers, so things get hot. But it doesn't affect the fluid coupling or the torque multiplication.
 

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Discussion Starter #18
If line pressure in the trans is low the main regulator valve will cut the supply to the torque converter. That's because the converter will function with zero feed pressure. As long as the converter is full of fluid it's function will be normal. The only problem is that with no feed there is no flow to the coolers, so things get hot. But it doesn't affect the fluid coupling or the torque multiplication.
 

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Discussion Starter #19
Ah!
Then the main regulator is a spring operated valve which will dump off any pressure over 120 psi and prioritizes fluid to the shift solenoids?
Fluid flows to converter, thru coolers, and then the cooled fluid i used to lube the bearings draining back into the pan?
The converter lockup is controlled by a PWM solenoid on it own pressurized supply?
Is that close to how it works?

As you stated, with the low line pressures I have, the flow to the cooler should be small. I haven't had any heating issues but the reverse issue didn't show up until a couple of months after I pulled my 16 K camper 1400 miles. It would be nice to get back home when this job ends to pull the transmission, but a break down on the road along the way would be a disaster! I have noticed that the line pressure gets up to about 40-ish psi while cruising at 60 mph. I typically pull my camper at and above that speed. If I keep engine RPM's 2000+ and monitor my line pressure gauge. I may be able to get back home.

Do you have a flow rate spec for the amount of out flow to the cooler in idle? Which line is the out flow? Front of engine or the rear line? I could take loose a hose from the cooler and time out a minute worth into a bucket. Not sure that would prove anything other than what we already know??? Low line pressure.

I have to talk with my transmission builder. I know that he enlarges the valve bores to get more pressure on the clutches while maintaining the pump's factory pressure settings. Which may be allowing me to have more pressure on the clutches than I would normally have with such low pressure?

Thank you for sharing your years of experience! It's a great help!
 

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Ah!
Then the main regulator is a spring operated valve which will dump off any pressure over 120 psi and prioritizes fluid to the shift solenoids?
No.

The main regulator creates line pressure. It is controlled by the EPC (Electronic Pressure Control) solenoid. Line pressure is used to actuate the clutches, but not through the shift solenoids. The shift solenoids use a pressure tapped off of line, but also limited. All the shift solenoids do is move the shift valves in the valve body. The shift valves send line pressure to the clutches.
Fluid flows to converter, thru coolers, and then the cooled fluid i used to lube the bearings draining back into the pan?
The converter lockup is controlled by a PWM solenoid on it own pressurized supply?
Is that close to how it works?
Yes, that's how it works.

As you stated, with the low line pressures I have, the flow to the cooler should be small.
Not necessarily. The converter doesn't see line pressure, it sees a pressure that is limited to 120 PSI. Line pressure can exceed 300 PSI.

Do you have a flow rate spec for the amount of out flow to the cooler in idle? Which line is the out flow? Front of engine or the rear line? I could take loose a hose from the cooler and time out a minute worth into a bucket. Not sure that would prove anything other than what we already know??? Low line pressure.
One gallon per minute is the spec. I like to measure one quart in 15 seconds. That way you won't run the pan out of fluid.

I have to talk with my transmission builder. I know that he enlarges the valve bores to get more pressure on the clutches while maintaining the pump's factory pressure settings. Which may be allowing me to have more pressure on the clutches than I would normally have with such low pressure?
Maybe that will help while the clutch is applying. Maybe.
 
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