• 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 TCC solenoid, revisited

gmctd said:
Any of you guys out there with the '92-'93 mech injected 6.5TD and 4L80E: does the TCC unlock when you ease up on the go pedal, at some speed above 45mph?

Watch the tachometer, where available:

- if engine rpm remains steady, dropping slowly as vehicle slows, you have lockup

- if engine rpm drops rapidly to some lower rpm, then dropping slowly as vehicle slows, you have unlock, just like the EFI versions
Click to expand...


Yes they unlock when you let most of the way up on the go pedal, I have an LED on my TCC solenoid wire so I can see when the TCM or me has it locked.

I thought all the solenoids remained the same in the 4L80 except the pressure control solenoid that they change in 94 combined with the different valve body.

Let me ohm some of the new GM 4L80's we put in HMMWV's, they use the same TCM as the mechanical 94up van did, with the same 94up trans/valvebody. I'll also see what the Tech-II shows on modulation percent/frequency of the TCC solenoid.
 
My '93 also unlocks when the pedal is "released". But if i keep any amount of pedal down it will stay locked even when the truck is deaccelerating. I've been working out of town a lot and haven't had a chance to get my original '93 tranny out of my storage area and ohm the TCC solinoid out, my apologies.
Don
 
JD~ I am one of those 3500HD wreckers that you speak of.....in layman's (Wreckerman's) terms.....should I run out 4th gear (reasonably of course) or should I let the pcm do the work for TCC lockup?

Thanks,
 
preachermic said:
Where is the TCC Sol. and how would one go about changing it?
Click to expand...

There is a small clip get a small scew driver or something pointed to pull it down, the just pull the TCC Sol out, be sure when replacing to push it in well in so the clip sits and put some ATF on the O-Ring.

Edit. having problem with the pix but Im sure you can open it..
 

Attachments

  • breakdown.jpg
    breakdown.jpg
    46.6 KB · Views: 54
  • OPEN%20CASE1.jpg
    OPEN%20CASE1.jpg
    31.9 KB · Views: 58
Last edited:
Basically, Louis, that will depend on your acquired load, always keeping in mind the problem with that hollow input shaft in the 3500 dump and tow vehicles - main thing is you don't want a bunch of harsh torque\reverse-torque incidents as you repeatedly apply and release the go-pedal, particularly if running locked in 2nd or 3rd - the lower the gear the greater the reverse-torque - even worse in the heavier 3500HD, with it's available 4.56, 5.13 and 5.38 rear gears
 
gmctd said:
Basically, Louis, that will depend on your acquired load, always keeping in mind the problem with that hollow input shaft in the 3500 dump and tow vehicles - main thing is you don't want a bunch of harsh torque\reverse-torque incidents as you repeatedly apply and release the go-pedal, particularly if running locked in 2nd or 3rd - the lower the gear the greater the reverse-torque - even worse in the heavier 3500HD, with it's available 4.56, 5.13 and 5.38 rear gears
Click to expand...

She doesn't lock and unlock much....basically when she locks up she stays locked untill there is a signifigant change in speed (decrease).
Even when I push the pedal down she won't unlock untill i'm close to the floor, which results in a very slow but steady increase in MPH....not a lot of flip floppin back and forth, i'm assuming this is good?
 
thedole said:
Approximately what duty cycle would the pcm use under unloaded cruise conditions? I'm thinking this would be a place where it could be a great project to use a little programmable chip that took the pcm signal as input and modifyed it according to some switches and/or pots as inputs. But I have very limited understanding of this whole system so my ideas may be based on erroneous assumptions!
Click to expand...

For us OBD2 guys there is a product on the market that does what you and JD are talking about. I put a BD TorqLoc in my '96 truck to try and get some engine braking. It sort of works but you really have to manage it in order to not piss off the ECM and get the transmision into limp mode. Sometimes the ECM doesn't mind you locking up the TC and other times it does. This would be much more useful with an exhaust brake. Also, when you're towing at 19k combined and the mountain pass is all 15 mph curves a TC lockup doesn't help much anyway. I'm down to first gear at that point.
Mike
 
HELP - 4L80-E won't lockup, then looses 4th gear entirely.

Wow, you guys seem to really know your stuff. I did a google search for "4l80 tcc pwm" and stumbled upon this thread. After reading a few posts in this thread it seems the members here reallly know their stuff.

Here's my problem:
It's a 99' GMC K-3500, pushed by a stock 5.7 Vortec, and rarely tows anything at all.

I've run Mobil1 or Amsoil ATF in it since it was new, installed the largest cooler B&M made in 99', a B&M deep aluminum pan, and an external spin-on filter with a Magnafilter on the side. I've also used a Hypertech programmer to firm up the shifting. All this before it had 10,000 miles on it.

Mine just started having hiccups a few days ago. While driving on the interstate, I totally lost overdrive. When I got home, I noticed the cooling lines were much warmer than normal.

Typically, I can place my bare hand on the cooler lines, and leave them there, when it's at operating temp. Not so now, it would burn you real quick. I assume the higher temp came from not having Torq-Conv lockup.

I allowed it to cool for a few hours, than took it for another spin. It seems the T-Converter never goes to lockup. Then after about 5 miles, I lose overdrive again. Once I lose overdrive, it shifts far firmer than it ever has before, almost barking the tires at times. I understand this may be a "fail safe" mode when things get overheated or otherwise out of whack.

If I stop, kill the ignition, then restart, it goes back to normal shifting. Once I loose 4th, the hard shifting starts.

I've got the OEM service manual set, and it lists one potential cause as "no signal to the solenoid". It says check the VCM/PCM. I have a scan tool and there are no DTC's, or pending codes.

The fluid looks new (was serviced <10,000 miles ago), it's still bright red and doesn't smell burned. The fluid level is normal and there are no signs of a leak, and no odd vibrations. It also shows no signs of lost power. Shifting 1-2-3-4 is fine until I lose 4th altogether.

I'm leaning towards an electrical problem, not a mechanical or hydraulic one.

Any help from the forum members is appreciated.
 
gmctd said:
Should have a CEL - what are the associated DTC's???
Click to expand...
There were no DTC's using OBDII. I took it to my local GM dealer so he could use a Tech2 device to scan the PCM, which revealed P1870, which translates to "Transmission Component Slipping" in the Service Manual. That was something I already knew, I just didn't know why.

They dropped the pan and valve body and said my Torq-Conv was shot.

I've ordered a replacement from Hughes Performance (part# 25LFuel), and a Premium Overhaul kit (part# HP2589K).

Also, the salesman at Hughes recommended Castrol Type F fluid, rather than Dexron. He also recommended not using any synthetic at all. I'm still on the fence about that one.
 
Gentlemen,
My mechanic has completely rebuilt my 4L80-E, including replacement of all the shift solenoids, the torque converter, the internal wiring harness, the PCM computer, and the brake switch.

The torque converter will still not lockup.

My mechanic removed the tranny, disassembled it to insure he put it together correctly. Reassembled and reinstalled it, and it still does the same thing.

Pretty much every component in the transmission has been replaced or rebuilt.

Does anyone else have a suggestion on what to check?
 
You must log in or register to reply here.
Back
Top