Slip from lock up

[Truckie117]

Hi All
I recently noticed that while hwy driving around 60 the tranny slips. Rpm goes up and then down and seems to lock up again any thoughts?

[Robyn]

I will assume its the rig in your signature ???

How many miles on the tranny??

Pull the diptick on the tranny and have a look at the fluid.
If fluid is dark brown and or smells burnt there is likely serious issues.

Possibly a fluid and filter change may remedy the problem.
The lockup solenoid my be failing?

Any DTC codes popping up (Check engine light)

If there are no codes then a look into the pan is in order. The tranny may be on its last legs.

A failing converter clutch will slip at times or shudder when engaging.
Dropping out or slipping under a load when hot is also an indication of a failing converter clutch.

With the pan off you can look at the contents in the bottom of the pan.

A failing converter clutch will show flakes of burnt clutch lining and other crap in the pan.

You can also get the rig to a traany shop and have them place a scanner on the rig and drive it to make sure the electronics are doing what they are supposed to.

Hope this helps.

Robyn

[Truckie117]

Thanks Robyn
Rig has 175K the fluid is clear and bright red. I change it Reguler I will pull the pan and change the filter and fluid. No Codes I have a reader Is there any additive that has to be added to the tranny ? Is the solenoid easy to replace?
Thanks
Mike

[Robyn]

The solenoid is not hard to replace.
Having clean fluid is a good thing.

Scanning is nice if you can do "real time" and see if the computer is actually calling for the clutch to be engaged.

There is a possibility that the switch on the brake pedal is giving up or has become misadjusted.

This condition will cause the lockup to drop out.

If while scanning under running conditions the clutch fall out but the ECM is still calling for engagement then its either a solenoid problem or the clutch is worn out.

Do a real time scan if you can and see whats up.

If nothing shows then drop the pan and have a peek.

Keep us posted.

Robyn

[Truckie117]

Hi Robyn
How can I check the brake pedal switch is it part of the stop light switch cruise control switch?
Thanks
Mike

[JohnC]

"Yes, same switch assembly for all three functions. does it drop out of cruise control? the brake pedal return spring can cause this, too.

[Truckie117]

No John it does not drop out of cruise control. The pedal feels a little funny while driving from a stand still it accelerates ok but in street traffic it seem a little hard to keep it at a steady pace. could pedal be going? Also thinking about getting a new PMD what seems to be the best bet out there?
Thanks
Mike

[Robyn]

This almost sounds like an injector pump issue.

Any other symptoms??

RC

[Truckie117]

No Other symptoms when I was on Hwy the other day with cruise control on and tranny was dropping in and out of lockup. Took it off Cruise and drove it manual same thing it never really locked up. When driving at 60 I hardly have any pressure on the pedal and when I let up truck seems to drop speed fast kind of hard to keep it steady. There is no problem on side streets. Could this be a pedal problem I hate this fly by wire. I also replaced pmd recently with one I had a spare because of faliure of one that is remote mounted. I now have the new model PMD and a # 9 resistor. Maybe I should put the new pmd on and resistor to see what happens?
where can I get the lockup solenoid .
Thanks
Mike

[Truckie117]

Hi
I replaced the pmd with the new beefier model with a #9 resistor. while traveling on the hwy I hardly have to put my foot on pedal and I'm doing 65 when I try to back off to go to 60 there is not enough pedal and the truck seems to have a hard time finding a steady pace.
Is the pedal prone to failure or is it another problem? I am going to try to change the fluid is that a good time to replace the selenoid that you mention and where can I get that part?
I am having a hard time very sick wife and sick truck but the wife really needs me now so the truck is a second thought.
Thanks
Mike

[Robyn]

With all thats going on, has the check engine light come on???
If so you are going to need to see what codes are stored.

Also with the dropping in and out of lockup, you need to get this thing scanned while its going down the road to find out whats going on.

The tranny is electronically controled and a scan will tell a lot about whats happening.

With a scan tool, you can tell if the ECM is calling for lockup and not getting it or if there are other issues.

Keep us posted

Robyn

[Truckie117]

Well I used obdII scanner and there are no codes. Is that the type of scanner you are referring to? Next step is to change filter and fluid and you mentioned some selinoid that might need changing is that internal or on the case?
Taking care of a sick wife and sick truck at the same time is no fun.
Thanks
Mike

[convert2diesel]

Mike:

I noticed you are using veggie. While many have been successful using the straight stuff, the temps required do have an adverse efect on these pumps. Does your problem happen even when running on #2 (no veggie) or is it a universal problem?

I run bio-diesel in my vehicles in the summer with no problems, but in my opinion, these pumps don't really like the straight vegetable oil as you have to get the fuel temp too high to get it to work. The DS4 and the older DB2 pumps don't like heat and can give some wonky problems if they are not cooled properly. They depend entirely on the fuel for cooling and if the fuel is hot coming in then it can only get worse.

Bill

[JohnC]

If there are no codes then the PCM is not seeing it drop out of lockup unexpectedly. So, if it is dropping out, it is expected. Look for a flaky brake pedal switch or a flaky coolant temperature sensor.

My experience is that the #9 resistor can make the throttle on some trucks touchy. Whether or not it could be the cause of the trans issues is a good question...

[Truckie117]

Hi
I think I may have stated my problem wrong. What I thought was the OD dropping out is in fact a throttle problem. Tranny shifts fine but when I travel on side streets everything is fine.
When I go about 45 thats when the trouble starts truck accelerates but when I get to 60 I am hardly touching the pedal but when I try to back off the pedal truck bucks and its hard to keep steady without going faster. That is when the tranny drops out of OD like you are pressing the accelerator to pass. Going to check all the grounds and connections I have 2 new batteries and good battery connections.
Thanks
Mike

[Truckie117]

Could you tell me where the coolant temp sensor is located and what kind of reading it should have?
Thanks in Advance
Mike

[Truckie117]

I found the 2 temp sensors and replaced them the dash gauge seems to be working better more in line with the odb reader for live data. Still truck runs great from Idle to 45 good throttle response can ease off and go slower no problem, When I get to 45 or better when I ease off throttle its like it just wants to drop to idle.
Still no Codes but on hard acceleration a lot of black smoke even when I drop out of od to passing gear. Truck shifts fine through all gears.
Waiting for my manual to arrive so i have the proper books.

[JohnC]

The 4L80E has an over-running clutch when in OD. If you let off the throttle the RPM's will drop down close to idle. (A little higher for emissions purposes.) The electronic throttle is very difficult to hold at a specific RPM when there is no load on the engine, so if you are trying to hold the RPM at road speed when you are overrunning the trans, it will go back and forth from "too slow" to "to fast" and this could be what you are experiencing. It may be normal operation.

[Truckie117]

OK Folks
I changed the filter and fluid on tranny in pan there was the little magnet with gunk on it.
Fluid was red not burnt.
No leaks when I reinstalled everything.
Used mobil-1 synthetic
Truck still runs great from 0 to 40 after 40 -45 you have no middle throttle truck wants to keep going only if you have pressure on pedal.
Once you try to ease off it will drop back to an idle you cannot get a partial throttle.
I also have a carcode scanner and app voltages are all good.
There are no codes set.n
NewDTech PMD and #9 resistor remote mounted on heat sink behind bumper ground to pump J Kennedy extension
So What can it be? Is the pump going south?
Thanks for any thoughts on this.
Truckie117

[JohnC]

There is no engine braking in OD. The #9 resistor can make the throttle touchy, so the difference between idle and enough throttle to drive is difficult to detect. My guess is this is "normal" behavior. Try the same test in "3" instead of OD and see if it is more as you expect.