Put 4l80e tcc on a switch, and lost OD?

[letitsnow]

On my 1998 s10 (4l60e/4.3) I have been using it with a switch hooked up to the tcc so that I can lock it manually. It has been this way for a while and has been working great.

I tried hooking the same style switch to manually lock the tcc in my 1999 k2500 (4l80e/5.7) and it worked in 3rd gear, but OD would slip - like the gear was nearly non-existent. It did this whether locked or not. When I remove the switch, OD works normally (and is strong) again.

Both trucks have Blackbear tunes, with the k2500 tune shifting at high rpms (I asked them to do this) for towing.

Transmission smart people - any ideas why the difference between the two trucks?

 

[L31MaxExpress]

Are you sure you hooked the ground to the correct wire. Then again, personally I do not understand forcing lockup with a switch vs properly tuning the lockup tables. I can lock in any gear above 1st at any throttle or speed with the PCM. Under about 55 mph at heavy load you want the torque converter unlocked for torque multiplication. I have dyno tested both unlocked and locked. With a factory B82 small block converter and 3.73s with 30.5" tall tires, the cross-over is about 60 mph. In 2nd gear under 60 mph you will put down more torque to the tires unlocked. Above 60 mph it puts down more locked. It is super easy to make the PCM do this for you. My stock diameter ~2,800 is about the same as far as torque multiplication vs efficiency. WOT I have lockup enabled at 60 mph and unlock below 57 mph. The stock 4L80E converter only has 200-300 rpm slip above 60 mph so it is not gaining much either. Locking below 60 mph costs you 10-15 ft/lbs. Keeping it unlocked above 60 mph cost about 5-10 hp. With 4.10 gears the difference is close to 10% in speed. The cross-over point would thus be about 54 mph. Lockup at 55 mph and unlock at 52 mph would work well.

 

[letitsnow]

Everything that I have read told me that the brown wire coming off of the trans was the tcc wire - running it to ground to get tcc lock. That is what I did, and being it worked in 3rd makes me think that it was the correct wire, but I could be wrong.

My only real reason for doing this is after being used to driving a 5 speed/cummins delivery van for years, the on/off tcc (when on/off the gas) of the 4l80e drives me nuts. Every person on the road now needs to drive at a slightly different speed, so you can no longer just cruise along. There seems to be no real way around this (tcc unlock/lock each time) on the 4l80e, as not allowing the tcc clutch to unlock when off the throttle seems to be what wrecks stuff - it's only real weak point from what i've read.

I may end up nv4500 swapping in the end. Part of what keeps me from doing this is that it isn't unheard of for me to be driving the truck (pulling camper) 6-10 hours with a newly broken arm/leg from race accidents.

 

[L31MaxExpress]

Everything that I have read told me that the brown wire coming off of the trans was the tcc wire - running it to ground to get tcc lock. That is what I did, and being it worked in 3rd makes me think that it was the correct wire, but I could be wrong.

My only real reason for doing this is after being used to driving a 5 speed/cummins delivery van for years, the on/off tcc (when on/off the gas) of the 4l80e drives me nuts. Every person on the road now needs to drive at a slightly different speed, so you can no longer just cruise along. There seems to be no real way around this (tcc unlock/lock each time) on the 4l80e, as not allowing the tcc clutch to unlock when off the throttle seems to be what wrecks stuff - it's only real weak point from what i've read.

I may end up nv4500 swapping in the end. Part of what keeps me from doing this is that it isn't unheard of for me to be driving the truck (pulling camper) 6-10 hours with a newly broken arm/leg from race accidents.

As long as I am doing 45+ mph my converter stay locked on or off throttle. It has since I put the 4L85E into the van. I already had an 0411 in it though.

 

[yevgenievich]

Ecu will go in fail safe mode if it applies tcc and does not see it actually apply. Which can disable 4th gear depending on exact ecu

 

[letitsnow]

As long as I am doing 45+ mph my converter stay locked on or off throttle. It has since I put the 4L85E into the van. I already had an 0411 in it though.

I tried to relay what I wanted (to the tuner) but maybe didn't really know what I wanted at the time. I am not the best communicator, and they have room for improvement in that area also. Not sure if we (bb & I) speak close enough to the same language to warrant sending ecm back and forth any more.

 

[letitsnow]

Looking at my notes - the last time that I sent the ecm back for a change, I would lose 8 mph (while towing the camper up a hill etc) before the trans would downshift. I asked for that to be cut in half so that it would downshift sooner. They accomplished this, and the shift points are good, but now the tcc acts more like it did with the stock tune as far as the locking/unlocking when on/off the throttle.

Each time you send it back the shipping is $40, and I have asked for things that they can't accomplish in the past - seemed like they would just make a change and send it back instead of contacting me to tell me that I am asking for something that they can't accomplish. That makes me not want to send it back...

 

[letitsnow]

Ecu will go in fail safe mode if it applies tcc and does not see it actually apply. Which can disable 4th gear depending on exact ecu

Any idea how to get around this? Thanks.

 

[1998_K1500_Sub]

Any idea how to get around this? Thanks.

The quickest route to satisfaction IMHO is to get a tuning set-up and tune it yourself.

There are a variety of products out there. I use JET's DST but I won't claim it's the most versatile, cheapest, or best / worse in any regard.

The only reason I went with JET's DST is because of its kinship with TunerCat's product, which I had been using for years prior on OBD I vehicles.

 

[letitsnow]

The quickest route to satisfaction IMHO is to get a tuning set-up and tune it yourself.

There are a variety of products out there. I use JET's DST but I won't claim it's the most versatile, cheapest, or best / worse in any regard.

The only reason I went with JET's DST is because of its kinship with TunerCat's product, which I had been using for years prior on OBD I vehicles.

Thanks.

It probably isn't possible but I prefer to only spend $$$ on maintenance, or items that make this truck more analog in the future.

If there is no simple fix I will just leave it as is.