I just installed a mystery switch. Just had a couple questions:

1) Is it ok to engage lock-up when coasting downhill in 3rd or 4th? Or should I bring the rpm's up to speed before engaging lock-up?

2) Can I use it in "2" going downhill? In "2" accelerating?

 

1) Once the computer locks the convertor, flipping the switch will keep it locked. If you are coasting and you flip the switch, nothing will happen.
2) The convertor won't lock with the shift lever in 2nd. But if you flip the switch at a stop, and accelerate, the convertor will lock right after the 1st to 2nd shift, and stay locked thru 3rd and 4th.
NOTE-- My rig is a '99. Don't know if there is a difference. Mike

 

Thanks Mike. For #1 you said nothing will happen if I flip the switch when I'm coasting... But on a downhill stretch if I'm coasting, the TC isn't locked up right? So the rpm's are lower than what they should be. Then if I flip the switch, won't it lock up and cause the rpm's to go up? Just wondering if that's bad...

 

hi
what happens if you have the switch in the lock position and you slow to a stop ?
does it unlock for 1 st gear ? or

does it stay locked till you unlock it ?

would it stall the engine at a stop ?

thank you !

 

if u pull the gear selector down to 1st then the converter will unlock, but if u just leave it in drive then it will stay locked in overdrive and will stall the motor.

 

Yes it will stall the engine if you stop with it locked. You have to be real careful with the mystery switch. I'm mainly just going to use it on declines in final gear. It's not good to have the tranny shift while it's locked either.

 

the lock-up switch only works in drive...if u put the gear selector in 1st or 2nd it doesnt work...if start fromt a dead stop and have the switch on then u will shift into 2nd and it will lock-up and u will make locked shifts untill OD or until 3rd if od is off...if u engage the switch during coasting...the TC will stay locked untill the motor is killed...u will feel a violent shudder/shaking...will start to smoke and will kill the motor unless u unlock it...i have it on the truck a sa "just in case" tool now if the TC lock-up starts to be problematic ....some guys have been driving around having it locked and using it as an exhaust brake type of thing to slow the truck down...but i personally think it is far too stressfule for a stock tranny...billet shafts and increased line-pressures are a must...but once u get a better tranny and TC u won't need the lock-up switch

 

the trouble with that is that line pressure for TC lock-up and clutches in ur tranny is largely dependent on a combination of rpms and throttle pressure..so as u coast down a hill ur barely putting any pressure through the go pedal and ur creatign heat because the TC cluth linings may be slipping creatign heat...etc etc heat= adios tranny at some point

 

Dang, so maybe I should just un-install the lock-up switch. Guess that's why it wasn't like that from the factory. I could see how it would be stressful on a stock tranny. Mr T, you have a 47RH, doesn't that normally not have lock-up?

 

wcbcruzer - Using the lock up for an engine brake will not do any harm, IMO.
But I would wait till you are in 3rd...or OD...or the gear of your choice, and till you have cruise rpm before throwing the switch! This will be the least harmful IMO. It will just hold the engine where it is and work as a engine brake.

For steep hills I accerate till third gear and than throw the switch before backing off the throttle! Works great....but don't forget to disengage it before rpm's get too low.

MrT - I have asked DTT and been told there was no damage done using the 'lockup switch' the way I do... as long as rpm's stay up! Maybe it's different with the stock 47RE but have never heard what you talk about??

RJ

 

Once you release throttle pressure, the convertor unlocks. The lockup switch won't lockup the convertor from an un-locked state. I wouldn't worry about causing tranny problems with a lockup sw. and no exhaust brake. Yes, the line pressure is lowest when the throttle is closed, but a diesel has so little hold-back that I don't think you'll slip your conv. clutch. But it does help keep downhill speed in check! (on mild hills)
The 47RH does have lockup, it's just a hyd. controlled tranny.

 

That's cool... Well I guess I'll just try it out a little and see how it goes. I did such a clean job on the install I'd hate to abandon it. On the other hand, I'd hate to shorten the life of the tranny (even if I may not see any immediate effects) for something stupid.

With the shifter in "2," won't it lock up by default on a downhill? I think that's what someone once told me.

 

I once tried shifting into 2nd while my sw. was on and locked in 3rd. it was like I simply flipped the switch off while I downshifted.
I have read that some aftermarket valve bodies will allow lockup in 2nd.
Mike

 

My Trans from Goerands will lockup in 2nd gear, its something most of the good rebuilders do. As for the 96 wbcruzer if its an early 96,, I think the ones from Sept 95 to Feb 96 have to have the computer reflashed in order for the switch to work right, if its not flashed it wont unlock after you flipped the switch from on to off,,, just something I found out.