94 Overdrive/Lockup Switch questions...

Cummins Driver

Cummins Driver

THE Cummins Driver
Joined
May 16, 2007
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Yesterday while driving my truck I was pulling a load in overdrive with the lockup switch on. I was coming to a stoplight so I hit the O/D off button to force it into 3rd gear to help me slow down a little, but nothing happened. I've had the lockup switch for many years now and never had this issue. So just for the sake of trying things I flipped my lockup switch down, and instantly it went into 3rd gear. It continued to do this for the rest of the drive to my dads house, however, if I have the overdrive off and converter locked, and then hit the button again to allow overdrive, it changed right into overdrive with no issues at all. The problem is only downgearing with the T/C locked.

The transmission is working perfectly other than this. Shifts are firm and lockup is normal while not using the lockup switch.

However, once I unhooked from the trailer I played with it some more and noticed that a couple times while downgearing with the TC lockup switch not on, it still didnt want to downgear. However, when i hit the switch again to allow it to go back to overdrive (that it never came out of), it unlocked the coverter then locked back up (like it normally would if going from 3rd to 4th).

It sounds like the switch may be going bad to me. I thought it could be internal, but the thing is working perfectly other than this. I havent driven the truck today to see if its still acting the same or not. Any suggestions or ideas? Thanks

Eric
 
most valve bodies will not downshift from OD to 3rd Locked....

I am surprised that my current one will, but my last two "upgraded" VB's have not
 
All of them I have messed with have. I have had my lockup switch in this truck for probably 9 years now and its always downgeared locked, so I know it is at least normal for my truck.
 
hmmmm interesting...

it might be worth rigging the OD switch full manual for a test... rig it just like a lock up switch, and you will at least be able to rule out the PCM if it downshifts with a manual switch.
 
I was thinking about doing that. If there is no clear answer soon I probably will just to see if I can figure out if its a switch or in the transmission itself. If its in the transmission I probably wont mess with it because it still works fine otherwise. lol

I am running a POT in place of the TPS on my truck, but that shouldnt make any difference with this issue because the overdrive switch works the same regardless of having a TPS or POT in place.
 
So you are talking about the over drive off button that comes stock in the cab when you buy an auto correct?

Mine has never allowed me to switch anything once the TC is locked up, even if I go from OD off, to OD on with it locked.
It also seems to adjust the line pressure slightly less (I am guessing) since the rpms just slightly higher with OD Off. It's been that way with two different OEM VB's too.
 
Yes, the original factory button on the dash. Mine has ALWAYS allowed me to shift while locked. I have come from o/d into 3rd locked hundreds of times with never an issue.
 
Cummins Driver said:
I have come from o/d into 3rd locked hundreds of times with never an issue.
Click to expand...

This is not normal. I'm running a Goerend VB that allows locked shifting and even it will not allow locked down-shifting out of OD. Once the tranny's in OD and the TC locked, it will stay in OD until you unlock the TC. I have not tried to manually downshift using the shifter while locked, but I still don't think it would downshift whe the TC's locked.
 
It is pretty nice...

Mine has a problem holding 3rd lock WOT at low rpm, it will downshift locked into 2nd... Not fun
 
It's a really simple mod to get them to do locked 4-3 shifts... can be done while you're doing the mod for 2nd gear lockup.
 
BigPapa said:
This is not normal. I'm running a Goerend VB that allows locked shifting and even it will not allow locked down-shifting out of OD. Once the tranny's in OD and the TC locked, it will stay in OD until you unlock the TC. I have not tried to manually downshift using the shifter while locked, but I still don't think it would downshift whe the TC's locked.
Click to expand...

So what is your point?
 
CorneliusRox said:
I think he is talking about valve body modification, not just splicing wires.
Click to expand...

Indeed

Cummins Driver said:
What is the mod? Might help me find my issue...
Click to expand...

There is a valve and spring in the lower VB that needs to be flipped in it's bore. I'll have to get a picture or two of this one yet, I've only taken pictures for second lockup and increasing lockup pressure/shift firmness.
 
CorneliusRox said:
I think he is talking about valve body modification, not just splicing wires.
Click to expand...

Thats what I mean. Possibly a clogged orifice in my valve body? My transmission has some miles on it and I was working it pretty hard. Im sure I was grossing around 24k lbs. I never really felt it slipping though and would downgear into 3rd on the bigger hills.
 
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BlackSkyRacing said:
Indeed



There is a valve and spring in the lower VB that needs to be flipped in it's bore. I'll have to get a picture or two of this one yet, I've only taken pictures for second lockup and increasing lockup pressure/shift firmness.
Click to expand...

I see. Sounds like that shouldnt be my problem? What would happen if the spring broke or clutch material got in there? Could that cause my symptoms? Thanks
 
Will the 47rh do 4-3 locked shift and the 47re won't? Could that be a difference cause I think everyone on this thread says there's will have a 94
 
01silver bullet said:
Will the 47rh do 4-3 locked shift and the 47re won't? Could that be a difference cause I think everyone on this thread says there's will have a 94
Click to expand...

Nope, a stock dodge VB of any year will not allow a locked 4-3 downshift.

Cummins Driver said:
I see. Sounds like that shouldnt be my problem? What would happen if the spring broke or clutch material got in there? Could that cause my symptoms? Thanks
Click to expand...

Something does seem amiss that you had it and lost it. You have a full Georend VB correct?
 
BlackSkyRacing said:
Something does seem amiss that you had it and lost it. You have a full Georend VB correct?
Click to expand...

Yes, full Goerend VB modified for first gear lockup. If I have it locked and hit the O/D off button, then flip the lockup switch off, it wont downgear. But if im just cruising along without the tc lockup switch on and hit the button, it downgears as it should. It used to downgear anytime i hit the o/d off button, wether i had the lockup switch flipped or not. It wont downgear out of O/D on its own with the lockup switch on without me hitting o/d off though, and never has.

Hope that isnt too confusing.
 
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