2nd Gen Non-Engine/Transmission Now to TDR, with a question

[JoshPeters]

Ladies and Gentlemen,

I'm new on here, but I've got a question that kinda baffles me. Back in October I bought a 1996 1-ton Dodge, with the Cummins 12valve in it. At the time it had 181,000 miles. I installed a 270hp fuel control plate, upgraded the turbo so I'm pushing approx 33-34lbs max boost and these trans upgrades. I purchased a new torque converter from Suncoast Converters, valve body and a torque converter lock up switch. I haven't gotten the torque converter in yet due to the size of the job, but the other items are in and functional.

The problem I have is this: When the torque converter lock up switch is on, the transmission will, under a light load go into OD(4th gear) at as low as 35mph, effectivly lugging the engine. If I get on it a bit it'll downshift like it should, but I don't want OD to come in till about 45-47 if possible. Anyone have any ideas? I've checked my wheel speed sensor up to the trans control unit, the

wiring is all good. Am I looking at a TPS issue or is this just an issue due to the switch?

I'm a Mercedes-Benz Technician in Minnesota, so the only exposure to these issues is with my own truck. Any and all ideas are appreciated. (I hope I can find my way back to this post to hear your replies!!)

Thanx

 

[Pit Bull]

Welcome Josh. I have a 02 6 speed so I am not up on your questions. You might also post this question in the 2nd generation drivetrain section and title it transmission mod question. You will get more feed back.

 

[Amianthus]

Lockup switch? Is that a Mystery switch? Or do you mean the OD lockout? Anyway, if you are in lockup (forced) the truck will go into OD and you will get the situation you described. The only way around that (outside of software change) is to not force lockup at those low speeds. Lockup will occur normally at around 40-45 MPH if the TPS is right and speed and RPM, etc. If you would like to rule out the TPS, you can remove it from the truck, disassemble it and clean it out. Or just spray it and smack it around a few times. But I doubt that is the problem. At least not as I understand you describing it.



If you want more info. first hand, swing down to LaCrosse this weekend. There will be a few guys there with way more expertese than I, that can probably answer all your questions. Good luck.

 

[JoshPeters]

Thanx for the reply,

It sounds like a software thing. I can turn the "mystery switch" or lock up switch off, and it will engage at 47 like it's supposed to. Being this truck is my daily driver I have to run in rush-hour traffic. I guess I'll just have to continue doing what I've been doing... . Trying to wear out my OD-lock out button! How far is LaCrosse from MPLS/St Paul? I don't have much going on, I might be able to swing that.....

 

[Mark_Kendrick]

The lock-up does force the 4th gear shift unless the valve body is modified to allow 2,3 gear lockup.



I dunno enough about the suncoast to tell but adjusting the lockup speed higher should fix it.



Later,

Mark

 

[Joe G.]

Josh,



The lockup (mystery) switch works by applying a ground to the lockup solenoid. This happens as soon as you turn on the switch. In fact it will lock up in 2nd. The computer applies a ground to the lockup solenoid according to how it is programmed. Then, regardless of how the qround is applied, the torque convertor clutch engages when the hydraulic conditions are correct. This is why your TCC locks up when it does. So don't turn the switch on until you get to the speed you want the lockup to occur. NO software involved with the switch. Your valve body probably has modifications to change the hydraulic conditions to allow kick down in spite of the lockup switch.

 

[Amianthus]

It's about 2. 5 hours from the 'Cities. From where you are, it's probably close to three. Stop down if you want to.



https://www.turbodieselregister.com/forums/showthread.php?s=&postid=629861#post629861

 

[illflem]

Josh, the dealer can flash your PCM to engage OD lock up wherever you want. I had mine set to 52 mph, stock it would lock at around 42 mph.

 

[JoshPeters]

When I installed that controller/mystery switch I was hoping to use the torque converter as more of a clutch than a "fan" as it's designed. The converter does a good job of robbing power. I was hoping that the transmission would continue to operate normally even with the lock-up engaged. Right now I have the controller set up as "late" as it will engage. Which seems to be 36 mph or so. I like being able to supprise people light to light when I'm driving to and from work. It's probably pretty hard on parts leaving that switch locked in. Has anyone suffered ill effects by leaving this switch on? Anyone modified the valve body so I don't have this problem? As much as I'd like to drop a manual trans in this truck, I don't have the time, money, or hoist to handle the truck. I appreciate all the feed back on this. You people have probably seen this a thousand times by now.....



thanx again

 

[Joe G.]

A "mystery" switch is a simple toggle switch used to ground the control wire to the TCC solenoid. A "controller" is a different kind of gadget. There are some different variations of controllers available. We don't know what you have. Your best bet is to get hold of the manufacturer for your questions about it.

 

[Steve St.Laurent]

I'm moving this to the 2nd gen forum for more exposure.