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.

[DmaxMaverick]

I suggest trying a #5 resistor (including a PCM reset). If no joy, then you are probably looking at a failed IP.

[Truckie117]

Will do that to day I have a 5 & 4 resistor from previous pmd'
Ok replaced resistor.
Now to relearn is that foot to the floor turn on ignition hold down for 45 seconds and still holding peddel down shut off ignition?

[Truckie117]

OK I have tried the #5 resistor and still have the problem.
No Codes I ran on Hwy with computer connected and there were no codes.

[JohnC]

Did you do a TDC Offset learn after installing the resistor? If not, th ePCM doesn't know it has been changed.

Have you tried locking OD out by putting the gear selector in "3"?

Monitor the solenoid closure time while it is acting up and let us know what it reads and if it is steady.

[Truckie117]

Hi Guys
Well I think I did is that where you put the pedal to the floor turn on the key and while holding 45seconds the pedal to the floor turn off the key. Take your foot off the pedal and start the truck?
If that is it then I did it.
Here is a link to my web site : http://mysite.verizon.net/vze7ye05/
I have the xls file there if you have excel or a program that opens xls files you can look at it Thanks
Merry Christmas to all
We Have a lot of snow on Long Island to night

[JohnC]

Have you tried locking OD out by putting the gear selector in "3"?

I looked at the spread sheet. As far as I can tell, everything looks normal. Exactly what does the file cover? If it covers the "behavior", what timeframe?

[Truckie117]

Hi
The spread sheet covers about a half hour of driving from streets to hwy It is from carcode program l asked for all systems check. If all things seem normal then maybe the IP is going the symtoms are worse when the truck is cold but they get a little better as the truck get up to operating temp. The Ip has about 100K on it can I ask for more?
Thanks for looking
Merry Christmas
Truckie117

[JohnC]

If the file covers 1/2 hour then it is not much help. That much data should cover about 20 seconds...

One last time: Did you try driving with the shifter in "3" instead of OD? Does it do the same thing?

Do you have EGR? Faulty EGR can cause surging around 45-50 mph.

[GMC Hauler]

Can you drive and look at what your computer is calling engine temperature? I had a problem where the temperature sensor appeared bad (the one on the crossover)

I replaced my engine coolant temperature sensor, but that did not fix the problem. Turns out it was the wiring at the sensor. It was also included in the box that the new sensor came with.

DO what John says. Put the trans in 3 and drive, see if it does the same thing.

[Truckie117]

Hi
Yes John I did drive in just 3rd and still had the same problem. Now that it is below 30 here I seem to have more surging till the truck really warms up. I did change both coolant sensors. One in lower block and the cross over. Just had my wife's car inspected and mechanic at the shop said it sounds like a bad Throttle positioning sensor. Is there a replaceable one on the pump. I was wondering if the injection pump advance solenoid could have anything to do with this and where is it located?
The truck starts up like a champ glow light goes out turn the key and bang she is running.
Once warmed up she idles smooth as silk. runs great warmed up untill 45mph.
I have gm online service manual but that is a lot of information to wade through.
Hard to work on broken truck and take care sick wife.
Thanks Guys

[JohnC]

Does it have EGR?

Do the symptoms in "3" occur at the same engine speed or the same road speed?

Problems with the throttle and with the advance solenoid will set codes. Also, you can watch the actual vs. desired injection timing and the throttle position with your scan software. The throttle position sensor is on the end of the shaft attached to the accelerator pedal.

Have you confirmed the fuel pressure to the injection pump? Have you changed the filter and tried straight Diesel fuel? Any chance the veggie oil has deteriorated the fuel lines? The symptoms sound more like a fuel problem than an electronics problem.

Can you get a 10-20 second snapshot including every data frame from a time when it is surging?

[Truckie117]

John
Does not have EGR which is located on the top of the intake I do not have the plastic cover on the engine I do not run veg and have not for a while. The lines are new and I do a regular fuel filter change. I have a fuel pressure gauge in cab and that is how I knew the lift pump was gone that is now changed. To me it doesent seem like a fuel problem because I can go as fast as i want it is just when I let off the accelerator that the engine seems to not be able to find a happy medium it just seems to drop off. To controll it I just take my foot off accelerator and coast till I reach 55 and then try to touch the pedal to keep a steady speed. I should video this. Also only laptop with xp took a dump and now I cant find xp disk to fix they are at my job so it will be a while.
Thanks
Truckie

[Truckie117]

Hi
Does anyone know how to check if the pmd id good? I have a new pmd DTECh and my mechanic says that the pmd needs to be changed because he is getting reading on scanner that there is something wrong. I had to bring the truck in because I do not have the time while caring for my wife. Does the resistors ever go bad? I replaced the #9 with a 5 because someone said the #9 might give the problems I am having.
At the end of my rope thanks