Controlling lock up in a 4L80E

[1bad383]

Hi, I need to get rid of my 4.56 gear and install something smaller, so I can go at least the speed limit, without spinning 3000 RPM in OD (74 MPH). So I was thinking of a 3.73. Only problem is I tow a 6000 #ish load regulary on some hilly roads and I don't want the torque converter lock up to burn out. Is ther a way I can wire up a 'tow/haul' switch to manually unlock the converter like the newer trucks? Thanks!

[qwomack]

http://blog.heathdiesel.com/2005/11/manual-operation-of-torque-converter.html

[ronniejoe]

BD TorqLoc

[Dale S]

http://blog.heathdiesel.com/2005/11/...converter.html

As suggested above, I have done this on my 98 cab and chassis that runs 4.63 gears and 19.5 tires. The only difference is that I located the wire right at the computer and added a relay to do the work. I used a "lighted" handle switch so I do not forget and leave it on. This truck pulls 14,000 of its rated 15 GVW and a 4,000 pound camper as well.
This lockup is sweeeeeet in third gear

[rjwest]

You may be better running in a lower gear and forcing the
TC 'Locked' Trans runs much cooler,

[MTTwister]

Evidently the DOES work on the 96 and later models? ( EDIT - per Dale S it should, he did it on his '98. but always cautious, ya know.)

Also - Do you have the ECM Pin out handy?

I did the GMC Hauler TCC lockup - via the High Trans temp over-ride, but I don't think it stays locked up on Deceleration.

[Shikaroka]

So, does this work on a 96?

[rjwest]

My experience, forcing the TCC locked with a 'gnd' on the
tcc wire will cause problems on 96 and newer ( obd2)

The " resister" switched in parallel with the trans temp sensor will not set any 'bad' codes, but will cause
full pressure shifts, Therefore, manual shifting like a std shift
is required to unload trans clutches...

Yes, the TCC will unlock when coasting...

[Dale S]

I have not had a problem to date with the lockup modification that I did on the 98, however, I am not reccommending that others do as I did just because I have not had problems. I did it because I knew it worked fine on OBDI and others had tried it with OBDII with limited success. I do use it sparingly and only when I feel necessary (ie: 3rd gear on a grade) . I feel I would rather blow the tranny than the engine. I pull 19,000 pounds total weight and am tired of doing 40 at the top of a grade with the engine roaring. 3rd gear in lockup makes ll the difference.
Sorry if I mislead anyone that my conversion is a foolproof mod for a 98. I was only trying to state the advantages to me, and I think it's a great modification.
BD Autoloc or Torqueloc is made for the 1993 to 1998 trucks (according to them) for about $250. This is probably the best route to go. Just do a serach for Torqueloc or PM me.
Like medications: Use as directed!

[rjwest]

BD torque loc will set codes on OBD2,( my experience)
BD would not admit to this until I really pressed one of there Tech's, The phone reps will keep telling you that you screwed up the wiring, If it were not for a Scan tool I
would have 'almost' believed them,
The PCM compares front and rear speed sensors, if not
as expected it will set a code and cause Hard shifting,

The only means I have found to Loc the TC with an OBD2
truck was to use the resister on the temp sensor,
The PCM is fooled into a HOT condition and
will Lock the tc sooner in 3rd(40mphvs50), loc it in 2nd ( above28mph)
and Hold TC locked in 4th(no change to lock up speed.

It also boosts Line pressure( hard shifts), That is why I shift manually when using the TCC

[atom_c]

I want to set up a 3 pole toggle switch to force my torque converter to lock up by tapping into the brown wire from ECM to tranny. All my wires out of the tranny looked brown from dirt and grime. I thought it might be easier to find it on the ECM end. Does anyone know which one it is on the ECM or give me a few hints on how to find it on the tranny?

Thanks
Adam

[bcbigfoot]

Atom C try this link it might help you it helped me http://www.atraonline.com/manuals/general/tetdv/tetdv-c3i.htm

The wire your looking for is the S wire to tap into. I've done the heath mod and it works great on OBD1 and earlier trans. My truck is a 93 with 3.42 gears.

[jspringator]

Will any of the aftermarket reflashes cause lower look up speed in 3rd and lockup in second?

[rjwest]

I asked that question a few years back, no positive responces from any of the PCM reprogrammers..

[atom_c]

Thanks BcBigfoot,

That might get me pointed in the right direction.

Adam