Finally did the TCC switch

[Skandocious]

I've been meaning to put a switch on my torque converter clutch for quite some time and by gawd I finally did it. For those of you that don't know... The torque converter clutch is an electronically activated clutch that will LOCK the transmission to engine so there is a 1:1 spin ratio between the two. This happens at about 43mph. Up until that point, the torque converter is allowed to slip so that the engine can build more rpm's to multiply the torque output (no I'm not kidding... cool huh?)

So at ~43mph the computer grounds the purple/yellow wire on the tranny harness which locks the TCC and no longer allows the TC to slip, which gives you better gas mileage.

What I did: I installed a 3-position switch INLINE on the purple/yellow wire. The top position will make the TCC behave normally (just completes the circuit). The middle position BREAKS the circuit so the TCC is not able to lock at all. And the bottom position will force the TCC to lock up, no matter what speed. Must be careful with this --- I've heard the engine will stall if you leave the TCC locked when you come to a stop (makes sense right?)

Haven't gotten a chance to test drive it yet but I did stick my head under the bellhousing while flipping the switch and I can hear it click I'm excited. I'll keep ya'll updated with my findings.

 

[surewhynot]

That sounds like it would also be a useful mod to gain compression braking.

 

[TheRoadVirus]

Yet another reason I love my manual..

 

[flareside_thunder]

whoa...did someone say JAKE BRAKE????????

 

[Skandocious]

That sounds like it would also be a useful mod to gain compression braking.

Absolutely my friend, that's one of the reasons I did it. I did it for the compression breaking and also for diagnostic purposes (trying to narrow down some vibrations in my drivetrain). I'll post some pics of the switch and wiring later. I really had a hard time figuring out where I wanted to put it.

 

[Skandocious]

UPDATE: Took it out for a spin and wow! What a neat mod.

So far the most useful thing I see about it is merging onto the freeway. Locking the TCC robs power (as I mentioned above) and I've always had trouble merging onto the freeway cuz my TCC locks really early (around 30-35mph). I'd start to merge and have good acceleration then the TCC would lockup and my RPMs would drop and the truck wouldn't go anywhere. When I merged onto the freeway today I put the switch on UNLOCKED and the RPMs stayed revved all the way to 65!! It was really awesome.

I also tried engine breaking when I got off the freeway. Worked pretty well actually, not nearly as much as a manual transmission though. Still a nice feature

I mostly did the mod for towing. Slipping TC + pulling a lot of weight = HOT fluid. If I can lock the TC while cruising through town and around the slowing streets then I won't heat up the TC as much. And if I UNLOCK when getting on the freeway it'll give me that much more torque to bring the trailer up to speed.

I absolutely recommend this mod just for the fact that it's so freakin easy.

 

[Skandocious]

Also... Left the TCC unlocked up to about 45mph (bottom of Overdrive) and then locked it in and the RPMs dropped from about 2000 to 1600. WOW! That's a pretty substantial drop and you can imagine that it's robbing power, especially if your TCC is lock way too early like in my truck. Anyone know why my TCC would be locking up too soon? I've heard it's supposed to lock up at 43-45mph, and mine DEFINITELY ain't lockin' up that late.

 

[Skandocious]

Here's some pics of the switch and wiring. I used quick disconnects so that I could remove the switch and connect it back to stock if I need to for any reason.

And here's the e-fan switch, I think I forgot to post pics a while back...

 

[Mr. Stroker]

NICE!

Ok let me get this straight, you wont get your truck dirty, but youll cut into a harness that controls a pretty important part..... Yikes. lol jk man. Good deal. Definatly would consider doing it to my truck, but i think im done doing anything to it lmao.

 

[flareside_thunder]

Oh pish posh......come on down here to florida and me n Tony will straighten that truck up for ya...you'd be leavin here with longtubes a staight axle and some bigger tires....hack off a bit of the fenders cut the edges of that purdy bumper throwin in an np205 and maybe even a carbed big block...don't that sound nice?

 

[andym]

What kind of switch did you get? And where did you get it? Radio shack? We need more details... and a tech article section while we're at it.

 

[Skandocious]

Switch is just a generic 3-position (On-Off-On) switch that I bought at the auto parts store for a few bucks. I'll give more details about the install later (or tomorrow).