• 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 driving me crazy

Richard Grant

Active Member
Messages
102
Likes
86
Location
Williamson Ga
Thread starter #1
Hello to all ,I have a 1996 K2500HD that needs a lot of love. I bought the truck at a steal. The man told me the trannie had been rebuilt which gave me many concerns. I was right. I purchased a used trannie from a dismantler, supposedly out of a 98 K2500. The old trannie has 2 vss plus the one in the transfer case. The purchased trannie only has the front sensor with the boss on the rear plugged. I inquired about the wiring harness and e.c.m. from the donor truck but it had been crushed. Everything I read contradicts each other. My truck is the H.D.version with the 5.7 and 8 lug wheels. Is it possible to reconfigure my harness ?
I really need some help, I'm a body in white guy and not the make it go guy. I appreciate any help I can get. Richard
 

1994ch

Active Member
Messages
460
Likes
248
Location
South Carolina
#2
THEFERMANATOR knows a lot about these things. I assume you are trying to find out which years are compatible with which years? Until fermanator tunes in here you could search around other threads on here. From what I have read the 4l80e's are very comparable year to year...maybe one or two minor differences in the early years like 93 but even they can be modified to work. The smaller 4l60E's cause a lot of confusion because there are many differences year to year. Is there a chance the trans out of the donor truck was a 4l60e? Easiest way to tell is the oil pan on the 80e is rectangular with two trimmed corners and the 60e is square with no trimmed corners.
 

Richard Grant

Active Member
Messages
102
Likes
86
Location
Williamson Ga
Thread starter #3
You are very correct on all points. I have had some medical problems the past 5 years so I am limited somewhat in movement. The transmission is sitting on a creeper and kinda hard to check the pan. . I'll con somebody into helping me. My G.M. electronics book touches on the subject but then stops. That's where I learned about one VSS being eliminated. I removed the plug covering the aft boss and found there was no reluctor on the shaft. That's the reason for inquiring about the vss wiring harness and the e.c.my. This will hurt but I have got to check the pan bolts. I'll be back. Thanks.
 

Richard Grant

Active Member
Messages
102
Likes
86
Location
Williamson Ga
Thread starter #4
Well the advantages of having a good young man dating my granddaughter seem limitless. Yes the pan has 17 bolts with the right shape. It also has the number 9 cast into the bellhousing which I read denotes 4L80. If I can contribute any more information please tell me and I will jump thru hoops to get this thing figured out. That would be fun to watch anyway. Richard
 

Will L.

Well-Known Member
Messages
8,196
Likes
7,519
Location
Boulder City Nv
#5
While waiting on the real expert I'll wing a shot from the hip...
I am guessing you need that toss sensor working like your original transmission had. Hope you still have the old one. There is a tone ring inside the trans that tou need to have installed in the new trans for it to work.

The other style only reads the front input and the transfer case as the output. Your komputer wants that trans output sensor. Way better imo to just have the proper set up than modify all the electrical.
 

Richard Grant

Active Member
Messages
102
Likes
86
Location
Williamson Ga
Thread starter #6
Thanks Will, my transmission harnesses look ragged anyway. I counted 5 butt splices while cleaning up another mess under there. Under the dash is just as bad. The previous owner in his infinite wisdom spliced into the brake light switch for some reason. He even used one of the little blue splice crimps that people use on their little trailer. Thanks.
 

Richard Grant

Active Member
Messages
102
Likes
86
Location
Williamson Ga
Thread starter #7
Update, I checked my crimper and it is for Deutch pins only and will not work on Amps pins. Will, you have the best idea I have heard. That's the reason I'm here, to ask all the smart guys. I still need to go thru the electrical system to undo bad craftsmanship.
On my last post I said some things I should've concerning the previous owner. I do apologize for those S.A. remarks!! The young man had some issues that I sincerely hope he has delt with.
If anyone else can contribute I am certainly open to all ideas. Thanks to you all, Richard
 

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
Messages
9,192
Likes
2,680
Location
ZEPHYRHILLS FL
Staff #8
Your 96 has a dummy plug in the rear. It lookslike an output speed sensor, somebody may have even put one in it at some point, but a 96 trans has no reluctor to read. GM used the same cases for 2 and 4 wheel drives, 2 wheel drives need it, 4x4's don't, so they just plug it. Now if you had a 91-93 4l80e 4x4, they did use the output speed sensor in the trans, hence why the 91-93 is rare, and brings a pretty penny. As to swapping in a 98 trans, it's doable, but your going to have to make an adapters for the cooler lines to hook up. I believe GM used only quick connect hookups on the 97+ trans, so you're going to have to source fittings to hook up your lines. Up to 96 they used 5/16" hard lines, and many hooked up with a flared line(not quick connects). Starting in 97 they moved the cooler return to the rear of the transmission, enlarged the cooler lines to 3/8", greatly increased cooler flow, pretty sure they switched to a quick connect with a spring retaining clip, and use a special long fitting in the rear return port(put the wrong fitting in and your trans will lunch itself in 20 miles from no lube flow). The trans plug will be the same, shift cable should hook right up, nsbu is the same, the only real difference is the cooler lines.
 

Richard Grant

Active Member
Messages
102
Likes
86
Location
Williamson Ga
Thread starter #9
Thank you sir. Here comes the confusion, my truck is a 1996 K2500HD. The coolant lines are exactly as you described for the later years. My lines are located front and rear, contradicting everything I have researched. Line size are the same as the 98 year model. My 96 trannie does have the reluctor towards the rear of the case. The reason I know is I changed the sensor hoping to solve the problem. I looked inside with a light and saw the reluctor. The newer 98 trannie is plugged with no ring behind it. With the coolant lines being the same as the 98 model, what do I need to do with the middle vss signal plug? The signal wire will remain the same for the front and the transfere case sensors. I will gladly post pictures if that is allowed. I haven't seen other pictures so I wanted to be sure first.
I'm sure you see my state of insanity by now. Thank you for joining in for I need all the help I can get. Thanks again, Richard
 

Husker6.5

135' diagonal 16:9HD, 25KW sound!
Messages
1,808
Likes
1,299
Location
Lincoln, NE
#10
Picture posting is not just allowed, it is HIGHLY encouraged here on the forum, as one picture IS worth a thousand words! Just use the Upload File button at the bottom of the reply box and choose from uploading from a memory file or a photo directly.

IMHO it sounds like somebody has updated/converted your 96 4L80E to 97+ cooling specs to increase cooling capacity (perhaps for towing?) Converting a 4L80E from 2 to 4WD or the other way from 4 to 2WD is not just swapping the correct extension on to mate with the transfer case or the other way to the driveshaft, it also necessitates pulling the guts out of the tranny and putting in the correct output shaft for the application.
 

Richard Grant

Active Member
Messages
102
Likes
86
Location
Williamson Ga
Thread starter #11
GREAT, I like to ask first so I don't get run off. I'll post pic's tomorrow due to mounting pain in my back. Thanks to everyone that has contributed in this effort. Richard
 

JayTheCPA

Well-Known Member
Messages
1,684
Likes
1,037
Location
Annapolis, MD
#12
The previous owner in his infinite wisdom spliced into the brake light switch for some reason.
Somebody probably installed a brake controller. If you are not towing, just make sure the extra wire does not ground to anything. Alternatively, consider checking to make sure the extra wire is not actually doing anything, and if it is now a dead wire, clean-up the wiring by removing it and the blue crimp and wrap the former junction to prevent shorting from that point.

If the truck has towing in its future and installation of a new brake controller is necessary, IIRC, in a 96 there is a cleaner way to get the brake signal by way of a pin on one of the circuit boards on the firewall (to the left of the brake pedal).
 

Richard Grant

Active Member
Messages
102
Likes
86
Location
Williamson Ga
Thread starter #13
Excellent point and one I had not considered. I saw in the history of the truck that it was on the west coast for a number of years and came back south. I think you just nailed it. Thank you sir. Richard
 

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
Messages
9,192
Likes
2,680
Location
ZEPHYRHILLS FL
Staff #14
I would have to see pics, but GM never built a 4l80e 4x4 after the 93 model year with a reluctor wheel installed in the tail end. They only did this for 91-93 because the ecm's used in those years were not capable of correcting the output speed sensor reading by 2.72:1 for low range operation. A 96 black box has no problems performing that operation.
 

Richard Grant

Active Member
Messages
102
Likes
86
Location
Williamson Ga
Thread starter #15
I'm trying to find the pictures now of the underneath so we'll be on the same page. I'm going now to get new pictures in the mud. Be back shortly, and many thanks for sharing your knowledge.
 

Husker6.5

135' diagonal 16:9HD, 25KW sound!
Messages
1,808
Likes
1,299
Location
Lincoln, NE
#16
Without pictures, it sounds like somebody in the past put a 91-93 4L80E 4x4 into his K2500, upgraded the cooling lines to 97+ and plugged in the rear connector from the x-fer case reluctor into the output shaft reluctor sensor.
 

Richard Grant

Active Member
Messages
102
Likes
86
Location
Williamson Ga
Thread starter #17
Gentlemen, thank you for jumping in and sharing your knowledge. I did get some pictures but can't upload at this time, the pain is just too great. I'll try a little later this evening. Richard
 

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
Messages
9,192
Likes
2,680
Location
ZEPHYRHILLS FL
Staff #18
Without pictures, it sounds like somebody in the past put a 91-93 4L80E 4x4 into his K2500, upgraded the cooling lines to 97+ and plugged in the rear connector from the x-fer case reluctor into the output shaft reluctor sensor.
Doesn't work that way. The 91-93 trans has both trans cooler lines hooked up at the bell housing. Sounds to me like somebody cobbled together a 4l80e using a 91-93 output shaft which iirc will not oil correctly due to the case lube changes when they moved the return line.
 

Husker6.5

135' diagonal 16:9HD, 25KW sound!
Messages
1,808
Likes
1,299
Location
Lincoln, NE
#19
Doesn't work that way. The 91-93 trans has both trans cooler lines hooked up at the bell housing. Sounds to me like somebody cobbled together a 4l80e using a 91-93 output shaft which iirc will not oil correctly due to the case lube changes when they moved the return line.
That could very well be, makes sense to me, @THEFERMANATOR . Bottom line is that something isn't totally kosher with his current set up. Can't wait for some pictures so we can see what he's trying to describe.
 

Will L.

Well-Known Member
Messages
8,196
Likes
7,519
Location
Boulder City Nv
#20
My only other thought is maybe if hummer transmissions used it. I know all 3 are there and in use on my 95. There were n/a hummers made as late as 97 so still just tcm- they had rear reluctor, so I understand anyways- but ive been fed misinfo before- haha.
Anyways, with the hummers getting converted to duramax or cummins, a lot of 4l80e setups have been being sold. Possibly somebody picked up one of those.
 
Top