First off, What exactly does a shift kit do? anything to a built trans the ECM doesnt already do? Or is it more an upgrade to prolong the life and efficiency of a stock trans?
Second, we all know its foolish that your TC unlocks when turning overdrive off, (normally shooting your rpm's through the hood when pulling 5+k up a grade) until that gnarly second passes and it locks back up. Would a TC lock up switch take care of that? Just hit the switch before turning overdrive off keeping the TC locked and strong full of power?
TIA

 

hi
shift kit will firm up your shifts and extend the life of the trany !

if locked in od i dont believe it will unlock and downshift y hitting the od off button .
would have to also hit lock up button .

however you can use the button to lock up in 3rd gear and pull hard without downshifting .

 

Or if you have a built VB you can lock up 2nd gear which has come in handy pulling in the mountains. Just have to be careful with it and remeber to unlock it before shifting gears.

 

oldblues, You say a shift kit firms up shifts, mine is already rock hard from my built DTT so safe to say i prob dont have much use for a shift kit huh.

Maybe its differant between years, but mine totally unlocks. You can hear it and feel it... OD off, back to third and unlocked rpm's 2,300, a second passes and it re locks rpm's back to 1,900 and i have power again. Does a lock up switch basically give me some what manual control over the TC?

 

If youy have a DTT transmission you have a built VB to go along with it and you can not add a shift kit to it. Built VBs are set-up to the trans and its components and not a one size fits all approch used by the over the counter shift kit. Also, make sure your truck has had all transmission related TSB's done. Your 2002 should shift to 3rd and lock the TC. The OD off on your truck is just that....no 4th gear but it will lock up the TC. The od is very low in these trans (.69 if i remember right) so you will see a large reduction in cruising rpm.


As for the unlocking problem, do you have a DTT noise filter installed. You may have an apps problem with noise that has been documented many times before. Search and you will find all your answers.


Richard

 

Yea od off will still allow the tc to lock in third i know, but it unlocks for a few seconds when already in 4th when i turn od off and it shifts from 4th to 3rd. Then locks back up in third. But those few seconds still cause rpms to rise and the loss of tc locked power. Here's the sinerio... I'll be almost starting to lug in 4th, turn od off, immediately shifts to 3rd and unlocks at the same time, few seconds pass and it relocks. I want it to stay locked between shifts.
Its definantly not a noise thing, you can feel it and see through the rpm's that its unlocking for a few seconds. And i heard Rich at Gillett diesel, a local shop, talking about this happening and how its normal but still not the best way to run, tc unlock then relock when turning od off while in 4th but didnt have time to ask more.
So my question still stands, would a tc lock up switch keep the tc from unlocking when turning overdrive off while in 4th?

 

Yes it will IIRC. The only time I've switched locked was when I was manually going from 2nd (locked) to third and forgot to turn the switch off and it hit pretty hard.

I don't think those few seconds of unlocked will hurt anything...actually I know they don't. I've watched my trans temp gauge during the scenerio you described and it takes a good 30 seconds before my temps start to climb and at that point I lock her up (this was pulling my TT in mtns). You also get some engine braking with the switch on.

 

Yep...what you describe is normal. A switch will do what you want it to do or get a DTT smart comtroller. About the TC unlocking and locking again...you don't loose power, you loose the mechanical 1 to 1 lock between the tranny and the engine.

Are you towing or driving normal when driving out of OD. There is only so much you can do with the stock PCM. A full aftermarket controller is all you have left after that and I would talk to Bill at DTT before installing one.

Richard

 

Right, loosing that mechanical 1 to 1 is exactly what I want to stop from happening. Most of the time its when Im towing but once in a while its just while driving up a steep grade at speed that I'll hit OD off. My trans will make the engine lug pretty low, raising egt's quickly, before shifting on its own, especially while towing. So most the time in that situation I'll just turn OD off. But I hate loosing lock up.
I figured if I did get a lock up switch, Id flick it before turning OD off to keep it locked, then when back on level ground and ready for 4th, flick the lock up switch off so as not to get that hard shift, and turn OD back on to shift to 4th. Would that keep it locked while jumping between 4th OD on, 3rd OD off, and back to 4th OD on?? Or will turning lock switch off before OD back on, unlock tc in the top of 3rd before I let it shift to 4th?
Thanks alot guys by the way.

 

I have a lockup switch and when i want to downshift i leave the switch off, take it out of o/d and immediately hit the lockup switch. it still unlocks but it locks up way faster than waiting for the tranny to do it. for a $2 switch, its worth it to me.

 

I shift mine locked all the time. I do have a VB set up for doing that though.

 

I shift mine locked as well but only have a single disc converter so it will slip where a tripple disc converter would be prone to snapping the input under heavy acceleration locked shifts.

 

If you have the switch in lockup position and hit the OD button, it will shift from 4th to 3rd while still locked up. Same goes for the other way (3rd to 4th).

However, if you're towing heavy I would definitely not recommend shifting from 4th to 3rd while locked, or shifting locked to any gear. Something has to absorb the power and it's most likely going to be your input shaft breaking.

 

Well now that I know some extra info, I guess the next thing for me to do is call up Terry at Moonlight diesel (he built my DTT) and find out if it would be a good idea with my particular trans. Thanks for the info guys.

 

That's the best bet since he should know your tranny. Tony (Dunrite) has certain questions he will ask guys about how they use their rig and future plans before he makes a recommendation on what parts to use and how to use them.