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Purpose of lockup switch


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I’ve been trying to do some research of what the purpose of a lock up switch is but can’t find a clear answer. I get that it’s used to lock up the convertor but what I can’t find a clear answer on is under what scenarios would you want to use a lock up switch? I know this is a newbie question but I just don’t know the answer to it ?

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Newbie questions are good around here.

 

Lockup switch is used for 3rd and 4th gears. Helps slowing on curves with engine braking. It will shift from 3rd to forth while locked up okay but won't go from 4th to 3rd till you unlock it and shut off overdrive switch. I really like mine since IBMobile set up mine with a relay that automatically unlocks when you hit the brakes. That is with one switch on the shift lever.

 

The other switch on the floor will leave it locked while using the brakes for mountain curves.

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One big variable is how much work has been done on the trans. This will dictate what gears it’ll lock in, and what gears the trans can shift to and from without causing damage. 

 

Most people use it to have a locked 3rd-4th shift which is nice. I have my trans setup so I can also downshift from 4th-3rd locked no problem. 

 

The other main reason/scenario people use the switch is for slower speed pulls up hills either in a steep grade that the truck just can’t pull in 3rd so you’d naturally drop into 2nd. Being able to lock in 2nd to keep your trans temp down when hauling can save you some headaches.

 

Last scenario is like @JAG1 mentioned and using the lockup switch as a sort of engine brake, which is does a surprisingly good job at.

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47 minutes ago, notlimah said:

One big variable is how much work has been done on the trans. This will dictate what gears it’ll lock in, and what gears the trans can shift to and from without causing damage. 

 

 

 

It’s built to 700hp and still under warranty so I’m not worried about hurting it at all. 

 

@IBMobile I’ve been looking at your write-up. Looks like a good option to go with. I also have been looking at Me’s write up on how he put it into the gear shifter like how you did. I really like that location. 

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5 hours ago, Youngblood24v said:

I get that it’s used to lock up the convertor but what I can’t find a clear answer on is under what scenarios would you want to use a lock up switch?

 

You have now read several posts for different scenarios for having the torque converter locked up, and they are good posts.  But, the really important reason hasn't been mentioned... and that is heat from normal torque converter slippage.   Serious heat if you are towing up a hill for any distance and the torque converter is not locked.   Heat takes out transmissions.

 

The moment the torque converter locks up (with a lockup switch that you control), the automatic transmission instantly behaves like an manual transmission and the only heat that is  generated is from moving parts, and that heat is minimal by comparison.

 

- John

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1 hour ago, Tractorman said:

 

You have now read several posts for different scenarios for having the torque converter locked up, and they are good posts.  But, the really important reason hasn't been mentioned... and that is heat from normal torque converter slippage.   Serious heat if you are towing up a hill for any distance and the torque converter is not locked.   Heat takes out transmissions.

 

The moment the torque converter locks up (with a lockup switch that you control), the automatic transmission instantly behaves like an manual transmission and the only heat that is  generated is from moving parts, and that heat is minimal by comparison.

 

- John

 

Heyyyy I mentioned it too!!

 

:sofa:

 

 

But seriously, that’s probably the most important reason. When I’m using my lockup switch and towing a travel trailer for instance, I can keep my trans temp below 145 pretty easily even in town. 

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1 hour ago, notlimah said:

 

Heyyyy I mentioned it too!!

 

But seriously, that’s probably the most important reason. When I’m using my lockup switch and towing a travel trailer for instance, I can keep my trans temp below 145 pretty easily even in town. 

 

Yes, you did mention it first - I missed that on my first read, so I apologize for that and thank you for letting me know.

 

I had a '99 with an automatic (with temp gauge) and an exhaust brake for 70,000 miles.  I controlled the exhaust brake and the lockup converter with a momentary floor switch and a throttle switch.  This way I could lock the converter with or without the exhaust brake.  Like you said, the transmission always runs cool.

 

I have had the '02 with the  six-speed manual for the last 16 years and 283,000 miles.  For me it is a better solution.

 

- John

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1 hour ago, Tractorman said:

 

Yes, you did mention it first - I missed that on my first read, so I apologize for that and thank you for letting me know.

 

I had a '99 with an automatic (with temp gauge) and an exhaust brake for 70,000 miles.  I controlled the exhaust brake and the lockup converter with a momentary floor switch and a throttle switch.  This way I could lock the converter with or without the exhaust brake.  Like you said, the transmission always runs cool.

 

I have had the '02 with the  six-speed manual for the last 16 years and 283,000 miles.  For me it is a better solution.

 

- John

 

No big deal man, just givin ya a hard time! :thumb1:

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6 hours ago, hex0rz said:

Okay, so would anybody be able to tell me whether or not i could safely do one in mine? Trans description in my Sig. No billet parts..

 

If I were you and I was gonna install a lockup switch, I’d only use it to hold 3rd or 4th locked, no shifting. Locked shifts are tough on the input shaft from what I understand so I’d want to avoid that without having a billet piece in there. Easy enough to make sure you stay in the right gear using the od button. That’s just my :2cents:! I’m sure plenty have done more with less then you have and gotten away with it forever.

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When I let mine shift from 3rd to 4th while locked up it doesn't feel hard on the trans. I smoothly goes into the next gear without grabbing and no clunk.

 

So I shouldn't do that anymore.?

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I agree @JAG1, locked 3-4 shifts way smoother then when I let the truck do it on its own. 

 

Ill just say this... from my many talks with Jon I remember him saying something along the lines of a lockup switch when used incorrectly can damage even a built trans but if used right can be fine for either. So I’d say just use good judgement for what your trans has and you’ll be fine. 

 

 

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