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How does 2nd gear lock-up shift?


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I have browsed ever post on 2nd gear lock up. I am still confused! I didn't have the mod done when I recently had my trans overhauled because I wasn't sure what I could expect from the mod. Just read a post where the person said the truck would continue on into 3rd when in lockup. Will it do this if I have the selector in 2nd? I have a triple disc converter and a stock input shaft. I can't afford any surprise hard shifts when in lockup under a hard pull (13,000# load). I want to use 2nd lockup only to use it with selector in 2nd, then unlock before shifting to higher gear at the top of the grade. Will it do this? It would be most helpful if someone with the mod could explain EXACTLY how it shifts and is used. Thank You

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You must manually shift the gear selector to 2nd gear, allow the truck to shift into 2nd gear, and then throw the lock up switch. You are right in saying you must first disengage the lockup BEFORE allowing the transmission to upshift to prevent lock to lock shifts.

The lock up switch will lock the TC in whatever gear you have selected regardless of speed and which gear the transmission is currently in so you must make sure you are in the gear you want to be in and you have means of holding the transmission in that gear before you throw the switch.

 

For 2nd lockup, gear shift selector in "2", allow the trans to shift into 2nd and then hit the lock up switch 

 

For 3rd lock up, gear selector in "D" with the OD button on the shifter pressed in, allow the trans to shift into 3rd and then hit the lock up switch

 

For lock up in 4th (OD), gear selector in "D", allow the trans to shift into OD and then throw the lock up switch.

 

ALWAYS disengage the lock up switch BEFORE allowing the trans to upshift.

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Ok. Now I know exactly how it will work. Another question! Some other forums seem to indicate all that is needed is a switch that supplies a ground to the lock up solenoid and locks the converter. I have tried this switch and it does nothing. Our forum indicates that a valve body JB weld mod is needed. Why do the other forums other than cummins diesel forum not mention the valve body mod? Am I missing something?

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The jb weld is to enable 2nd gear lock up only. Once you do the jb weld you will be able to acheive lock up with the switch. You can install the switch without modifying your valve body and you will be able to hold lock up in third and OD but not second.

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OK, I have a question. It was reported that for the JB Weld all you needed was a enough to equal the size of a grain of rice. Are you completely blocking the passage or just part of it?

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