TC lock-up

[SlyBones]

OK, So I am an idiot. I read lots of posts about tc lockup converters locking and un-locking, sometimes when they should not be. Or others want to control this manually, etc.

I am familiar with the effect, especially in OD, when you back off the pedal, and the lockup clutch dis-enagages and the truck coasts. ( correct terminology ?? ). I understand the reason for keeping this engaged in this scenario, especially when using an exhaust brake. I see how an AutoLoc from BD, for example, does this for you.

Here is what I dont get. I am now holding it to the floor, smoking down the freeway on ramp. -- Or I am pulling my RV up a big mountain pass -- How can you tell if the lockup clutch is enaged or dis-engaged? When/how is the clutch used in acceleration? Why would you want to control this manually when gassing it ( er uh I mean fuelling ).

Thanks for the education.


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1997 2500 4x4, CC, Auto, 3. 54 LSD, Everything inc Leather, K&N, 4" BD cat-back, otherwise stock, Isspro Gauges(3), 285/75/16 on Alcola's, Canopy, BedLiner, and tons more.

 

[Red Rocket]

Sly, I have about the same size tires and axle ratio, and I have installed the lockup switch. what I can tell you is that it will make your transmission shift like a manual in 2nd thru 4th. This means your engine will rev high in first, hit second and drag down to about 1600, and so on for the rest of the gears. The other advantage is once you've hit 3rd or 4th, it will not downshift! Not really a big deal, you just have to pull it into second or shut off the switch. This helps you stay in gear and use the torque.

 

[John]

..... and after you smoke your TCC lining from forcing lockup while under heavy acceleration or under heavy tow (or God forbid, both) you will understand why this is NOT a good idea.

Read some of Bill Kondolay's past posts regarding this very topic... search the archives.

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John Treibel
'98. 5 2500 QC 4x4 Sport, Glasstite Vision II, 285 BFG A/Ts on M/T Challengers, Warn 4X Boards, Mopar fender flares & tow hooks, NW Custom s/s-rubber mud flaps and accs. , Mag-Hytec diff. cover & trans. pan, Edelbrock IAS shocks, Reese Titan V hitch, SPA gauges (3), Dynamat, '00 Sport grille and headlights/PIAA Super White bulbs, PIAA Dual Sport 900 aux. lights, BD exh. brake, Amsoil Dual Remote Bypass, Optima Yellow Tops, DD3s and DD TTPM, Aeroquip AQP braided s/s fuel hoses, Banks High-Ram intake manifold and 14 cm2 turbine housing w/Big Head wastegate actuator, ATS 3-piece exh. man. , Banks 4" dia. s/s exh. sys. , DTT 93% TC, DTT custom tuned VB, BD modified trans. front pump (enhanced by DTT), Air Bulldog induction hood (with NACA ducts), plus MANY other trick modifications

NRA Life (Patron) member

 

[Dak - BD Power]

SlyBones, the idea of keeping the lockup clutch engaged is normally for use with engine braking ONLY.

There are times when it can be advantages to keep lockup when travelling on a windy or hilly road where you are on and off the throttle lightly (and I repeat LIGHTLY).

The lockup clutch is not designed for heavy acceleration and as such should be disengaged, either manually or automatically, once the throttle pedal goes beyond 60-70% applied, this then allows the torque convertor to do its stuff (torque multiplication up to fluid coupling) until the vehicle speed catches up to engine speed.



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Real BOMBers never get speeding tickets. . just a lot of warnings!

 

[JConley]

RedRocket
That $5. 00 lockup switch will end up destroying your $3000. 00 transmission. If you want firm shifts, get a $375. 00 valve body from Bill K, and beef up that transmission, rather than destroy it.

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98 QC 2500 2WD 12 Valve Automatic, 3. 54 Mag-Hytec transmission pan. DTT Valve Body. Wrap around black Grill Guard (BIG solid steel one. AFC controller adjusted, Mopar mud flaps, Camper package, 2001 Tow mirrors, Cat ran away, No Muff
My Mustang
My Ram
The Wrecking Crew web site for Junkyard Wars
Go Aggies!!!

 

[SlyBones]

So here is where I am at so far, after reading and searching some archives,

- Can keep locked whe decelerating with your ebrake, but dont for get to switch off.

- Many manually unlock under hard acceleration, especially with heavly BOMBed engines to keep from destroying the clutch face.

- Use aftermarket TC and VB to improve shifting and transmission performance. Dont abuse the lockup clutch to gain performance.

- When towing or passing, there are times when you want to get the clutch to unlock for the extra boost your get from the fluid coupling. Keep your eye on the temp gauge. transmission will get too hot, the reason the DC computer did not do it in the first place.

- Not sure I got the one about keeping in it locked, when traveling on windy roads where you are on/off the throttle. Is this just because it will keep locking and unlocking, back and forth. Manually locking it keeps the wear and tear down from all the engaging and disengaging. However must be light throttle situations.

 

[Red Rocket]

You have the idea. Just for the record, I only use mine when cruising under very light throttle, for the reasons the other guys specified. I also plan to remove the switch as soon as I find the money for the trans/VB/TC upgrades. Im just going for mileage with the switch.

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1998 2500, auto, 3. 54, 285/75-16, TST 230/605, t/c switch, DiPricol EGT/boost guages,K&N,camper special, 65,000 miles,
12 ton goosneck!

 

[Dak - BD Power]

SlyBones, your bang on with all statements, and you hit it on the head with keeping it locked up for windy roads, etc... #ad



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Real BOMBers never get speeding tickets. . just a lot of warnings!

 

[Bill Kondolay]

#ad


[This message has been edited by Bill Kondolay (edited 03-03-2001). ]

 

[John]

Hey Bill, can you put the one on the left in my TC? #ad

 

[KB0OU]

So how do you wire up a switch to keep the TCC from locking up?

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96 CC 4X4 2500 SLT AUTO transmission, PrimeLoc, ISSPRO EGT Boost transmission Temp, GUTTED CAT, 155,000+ Miles still goin' strong, Lots of Ham Radio gear, NO IGNITION NOISE!!! Love my diesel!!! # 8 TST Fuel Plate.

 

[SlyBones]

OK, so now I have learned what this thing does, a little on how it works, mostly when to or not to use it, if you installed manual switches. ( I have not ).

I read an archive where Bill K. talked about TC efficiency. My RPM's drop 100-150 RPMs in third, when I us O/D lockout button.

So my last question for this lession, is how can you tell when the lockup clutch is engaged or disengaged? Or maybe a point to a place where we learn more about when and how this thing works. Then I can figure it out.