• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

4l80e hunting gears 6.5l

Messages
17
Likes
1
Location
Sweden
Thread starter #1
Hello!
I have a problem with my 4l80e behind my 6.5l td from 1995
I have a intermittent shifting issue between 3-4th gear it seems like it cannot decide which one to have. I got it on video but it only does it once between 40-50 km/h.
Oil is red and no burned smells, I changed it for aboute 6 month ago.
I have voltage tested the apps and it was ok

Best regards / Tobias from Sweden
 

WarWagon

Well it hits on 7 of 8...
Messages
8,585
Likes
3,235
Location
AZ
#2
Check codes. If the engine starts to stall it can unlock the TCC. Same for a slipping TCC.
 
Messages
17
Likes
1
Location
Sweden
Thread starter #3
I have no codes, it does not feel like its slipping, more like a fast up/down shift. and this is just happening at a light throttle, if i give it more gas it shifts fine
 
Messages
17
Likes
1
Location
Sweden
Thread starter #4
I can also mention that i have had missfire problem for aboute a year. Sometime i can hear a exhaust poof while ideling, and a quick buck in highway speeds
 
Messages
17
Likes
1
Location
Sweden
Thread starter #7
Sounds like a fuel supply issue or grounds as far as the engine goes
I have Checked for air, good fuelpressure before the ip and LP relay mod.
I have gone true all grounds i can find.
Soon i drive this truck into a lakeo_O
@Tobias Säfvelin
Please fill out your signature line with details on your rig so we know what you are driving to help with diagnostics. Gas engine or diesel? What year rig tells which components on engine, etc.
Sorry, now its done:rolleyes:
 

Will L.

Well-Known Member
Messages
8,296
Likes
7,688
Location
Boulder City Nv
#8
Cool, thanks. So you have ds4 ip. What fuel pressure donyou have and does it flutter when the engine mis occurs?

Clear line on ip show any air?

It seems to me like a tc not staying engaged. Is it having hard/ time doing it in all 4 gears?
 

WarWagon

Well it hits on 7 of 8...
Messages
8,585
Likes
3,235
Location
AZ
#9
You feel slipping when the engine is at redline and you are sitting still. :facepalm: Otherwise the computer sees it first (before you feel it to save the clutches) and unlocks the torque converter clutch. It can do this very fast like the trans can't pick a gear. When I experimented with lower lockup MPH the worn TCC couldn't take it and felt like a fast up down up down shift. I had to use a scanner to see what gear was commanded and TCC status. By engine RPM vs trans input RPM I was able to see the TCC slip.

If the engine has a lot of "misfires" the TCC also unlocks untill the condition clears up. This is why we suggest the engine has to run good before chasing the trans. Note a quick buck is called fishbite. IMO the computer runs a test now and then to buck. If its constant then you have problems on the engine side: air in fuel, PMD, IP...
 
Messages
17
Likes
1
Location
Sweden
Thread starter #10
Cool, thanks. So you have ds4 ip. What fuel pressure donyou have and does it flutter when the engine mis occurs?
Clear line on ip show any air?

It seems to me like a tc not staying engaged. Is it having hard/ time doing it in all 4 gears?
Fuel pressure is 7-8psi at idle and 1.4psi at WOT, no flutter when the miss occurs.
clear tube did not show any bubbles.
What i can remember its just 3rd or 4th gear, but its very intermittent i can drive home from town 20-30 miles and nothing happen, but next time i drive
To town it bucks.
You feel slipping when the engine is at redline and you are sitting still. :facepalm: Otherwise the computer sees it first (before you feel it to save the clutches) and unlocks the torque converter clutch. It can do this very fast like the trans can't pick a gear. When I experimented with lower lockup MPH the worn TCC couldn't take it and felt like a fast up down up down shift. I had to use a scanner to see what gear was commanded and TCC status. By engine RPM vs trans input RPM I was able to see the TCC slip.

If the engine has a lot of "misfires" the TCC also unlocks untill the condition clears up. This is why we suggest the engine has to run good before chasing the trans. Note a quick buck is called fishbite.IMO the computer runs a test now and then to buck . If its constant then you have problems on the engine side: air in fuel, PMD, IP...
Well thank you! No its not constant just one quick i can feel it the most when on highway. At low er speeds (below 20mph) i can hear a "bloouup" in The exhaust (no muffler) so you think it might be the ecm?
 

Will L.

Well-Known Member
Messages
8,296
Likes
7,688
Location
Boulder City Nv
#11
So assuming that since you said light throttle is when it happens you are somewhere in the 6psi range. And while ideally you would be at 9 -14 psi all the time (someone correct me if my memory is off) and 1.4 is lower than I would want to drive mine at even wot, I don’t think that is your current issue. Once this issue is solved I would suggest improvements in that arena in the future if you frequently hit below 5psi.

There was something about having ecm reprogramed to stop a searching rpm, but I can’t remember details. Iirc it was a more consistent issue, where as yours sounds more random than that, and more searching than a randome surge of power.

Some live data streaming ona scanner when happening would sure come in handy for this one.
 

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
Messages
9,248
Likes
2,754
Location
ZEPHYRHILLS FL
Staff #12
Fuel pressure should be at least 4-6 psi, and not drop below 3 at wot iirc. Db2 runs higher pressure than ds4, ds4 just needs enough to fully fill the pump whereas db2 uses internal pressure to vary timing. I would be checking grounds 1st. These trucks are infamous for ground issues, and a ground could easily cause this. You may also want to check your brake switch. They can cause issues with shifting and lockup. It doesn't look like you're going fadt enough for lockup to occur. With 4.10 gears and 245/75/16 tires lockup isn't until 45 mph. Looking at your video, the rpm drop you're seeing looks to be greater than that of a gear change, it looks more like a loss of power to me during a shift.
 
Messages
17
Likes
1
Location
Sweden
Thread starter #13
So assuming that since you said light throttle is when it happens you are somewhere in the 6psi range. And while ideally you would be at 9 -14 psi all the time (someone correct me if my memory is off) and 1.4 is lower than I would want to drive mine at even wot, I don’t think that is your current issue. Once this issue is solved I would suggest improvements in that arena in the future if you frequently hit below 5psi.

There was something about having ecm reprogramed to stop a searching rpm, but I can’t remember details. Iirc it was a more consistent issue, where as yours sounds more random than that, and more searching than a randome surge of power.

Some live data streaming ona scanner when happening would sure come in handy for this one.
I Will try to get my hands on a scanner
Fuel pressure should be at least 4-6 psi, and not drop below 3 at wot iirc. Db2 runs higher pressure than ds4, ds4 just needs enough to fully fill the pump whereas db2 uses internal pressure to vary timing. I would be checking grounds 1st. These trucks are infamous for ground issues, and a ground could easily cause this. You may also want to check your brake switch. They can cause issues with shifting and lockup. It doesn't look like you're going fadt enough for lockup to occur. With 4.10 gears and 245/75/16 tires lockup isn't until 45 mph. Looking at your video, the rpm drop you're seeing looks to be greater than that of a gear change, it looks more like a loss of power to me during a shift.
I have heard that if fuelpressure is positive the ds4 Will make it pretty good, vacuum is not good.
Yes i also think that is to low speed for the lockup to have something to do with it. It usaly lock at 80km/h(50mph) on 275/55r20.
Maybe your right with the power loss. I maybe get a big fish just at the shift moment, wich cause the transmission to down/upshift. Beacuse if i try to remake it i shifts good
 
Messages
17
Likes
1
Location
Sweden
Thread starter #14
Today it set dtc 58, wich is Transmission Fluid Temperature Sensor Low (High Temp). How do i diagnose this? Maybe measure with a pyrometer? What temp should it be?
 
Messages
17
Likes
1
Location
Sweden
Thread starter #15
And o also get a better video

Normaly the Tcc locks at 4th gear but today i noticed it did it in 3rd, Will it lock in 3rd to if the ecm think oil is to hot?
 
Messages
17
Likes
1
Location
Sweden
Thread starter #17
Bought gmtdscan and took a test drive. The trans temp was around 70c(158f) and then for s millisec jumped up to around 149c(298f).seems to me that i have found a problem. But how will i now what to change? Internal harness with the temp sensor? I think it maybe be some kind of intermittent short to ground, but how can i see if the wires are damaged other then with my eyes? Maybe its best to change the internal and external harness?
 

WarWagon

Well it hits on 7 of 8...
Messages
8,585
Likes
3,235
Location
AZ
#18
Today it set dtc 58, wich is Transmission Fluid Temperature Sensor Low (High Temp). How do i diagnose this? Maybe measure with a pyrometer? What temp should it be?
This has a wiring problem written all over it. Maybe it's time to take it to an auto electrical shop. You can have a helper watch the scanner while you wiggle the wires and wireing harness. You are looking for a short or broken wire. Throwing parts at it is just expensive and may not solve the problem. Again it may be cheaper to hire experience than throw a bunch of (rare, obsolete, and hard to get) parts at it. Likely you will not get lucky by throwing parts at it. If you do buy a lotto ticket and avoid lightning prone areas...

With the engine misfire we are back to grounds, positive voltage supply including ignition switch, wiring, random short, and ECM.

Adding to @ak diesel driver If you are towing a grade with you foot on the floor in 3rd gear at some point around 90 seconds the TCC will lock up to stop heat build up from a unlocked converter.
 

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
Messages
9,248
Likes
2,754
Location
ZEPHYRHILLS FL
Staff #19
Normal driving I never seen lockup in 3rd, only in 4th gear. Yes, if trans temp goes to high, it will lockout 4th and lockup the converter in 3rd to help reduce trans temps. I would start by unplugging the trans plug and looking for oil in the plug. Over time oil leaking in the plug can break down the insulation on the wires, and eventually let them short out. The trans temp sensor on mid 93's and up(or any with the new style plug) is built into the internal trans harness. I know here in the states the internal harness is readily available, and not very much money. I would check all the harnesses closely though for signs of oil intrusion. I had a 93 once where it was a farm truck. The combination of manure, mud, and oil had literally melted all the insulation off of the wires going to the transmission. It was giving randomn shifting and high line pressure issues. I had to cut the harness open, remove the tape, and then try seperating the wires to find the problem.
 
Messages
17
Likes
1
Location
Sweden
Thread starter #20
This has a wiring problem written all over it. Maybe it's time to take it to an auto electrical shop. You can have a helper watch the scanner while you wiggle the wires and wireing harness. You are looking for a short or broken wire. Throwing parts at it is just expensive and may not solve the problem. Again it may be cheaper to hire experience than throw a bunch of (rare, obsolete, and hard to get) parts at it. Likely you will not get lucky by throwing parts at it. If you do buy a lotto ticket and avoid lightning prone areas...

With the engine misfire we are back to grounds, positive voltage supply including ignition switch, wiring, random short, and ECM.

Adding to @ak diesel driver If you are towing a grade with you foot on the floor in 3rd gear at some point around 90 seconds the TCC will lock up to stop heat build up from a unlocked converter.
Thank for the advice! wiggle the wires i Will try that. I havent thrown any parts yet, just my time and labor haha :)
i have changed the ignition switch beacuse when i put in a new starter, it did just click, i turned the key multiple times when i did so i fried the barrel inside the switch, but still no change with the fishbite with the new switch. What do you mean with the Ecm?
 
Top