Competition '94-'95 Auto Trans T/C Lock-Up Question (Long)

[Extreme1]

I'm posting this here because it seems to be a problem with high HP trucks...



I need a way to make the T/C stay unlocked longer under normal acceleration. As it is it locks up at either 44 mph or 41 mph depending on which speedo gear I use. At that low a speed, the torque is way more than the TC clutch can take, probably due to the TV cable not being pulled far enough to increase the pressure. It's worse when pulling a trailer.



I already have the TPS slotted to the point it is barely held on by the screws. I also have the throttle linkage adjusted so there is barely enough travel to get WOT. Neither of these mods have affected the lock up point much.



I really don't want to hang something on the side of the trans to manipulate the TV or add an electronic control.



I think better placement of the linkage rod pivots would allow more travel on the bellcrank which would allow the TV and TPS signals to increase quicker before the pump lever was moved too far.



Has anyone tried changing the lever lengths on the linkage?



Is there a better way?

 

[HVAC]

Adjustment

I have heard of bending the bracket to get more pull/remove the slack. However, it's sounds like you have gone as far as you can if you can barely get to full throttle.



I control l/u with a push button switch for racing. After the rear tires get about one half a turn on them we LOCK THAT SUCKER!!!



But seriously, you don't need lock in town, just on the wide open highway. Would pushing a button be too much trouble? Kinda be like the O/D lock-out button.

 

[Extreme1]

I'd really like to get it to work kind of like it should without pushing buttons or flipping switches. As it is now, If I take off from a stop and it locks at a little over 40 mph, I have to back out of it to keep from slipping the clutch badly. It's worse when towing. When towing, I use the beloved O/D OFF button, I still have to back out of it when it locks in 3rd.



If I mash it, it won't lock until around 55 or so (too soon!) but it would slip really bad because the engine is making some real power. In this situation, a switch would be okey dokey but for normal driving I'd like to avoid it.

 

[BigYellowIron]

Have you tried the TSB 21-5-95, It is susposed to flash the pcm to make lockup occor around 55 mph opposed to 44.



My dealer told me that my truck was to old for them to hook up to because they did not have the right cable so I am still waiting on a chance to get it to another dealer.



Adam

 

[Extreme1]

Hi Adam,



Thanks for the tip. I looked at the TSB's and the one I think you're refering to is 21-04-95.



I printed it out but I haven't looked under the hood yet. By checking at the TSB repair options, it looks like I'll have to find a PCM from a '95 with the right part number and then get it reprogramed to do it cheap.

 

[phoekema]

another option

I know you said you didn't really want switches etc, but another very inexpensive solution might be to install a "mystery switch". By using a single pole, double throw with a separate position in the middle you can have 1)stock operation, 2)forced lockup and 3)no lockup. You could start out in position 3 (no lockup) and stay there until you wanted it to lockup, then go to either position 1 or 2. The only downside to position 2 is you have to remember to flip the swich again before stopping or it is like stopping with a manual trans and not pushing in the clutch.

I played around like this for a year and ended up investing in a ATS triple lock converter and valve body. You probably don't want to hear this, but the long term solution is an aftermarket converter. ATS, DTT Dave Goerend (forgive me, Dave, if I miss-spelled your name) and Suncoast are four very good alternatives to consider. I was constantly babying the truck and watching the tack vs speedometer, now it is truely a non-issue with better performance and fuel economy as an added benifit.



Paul H

 

[Extreme1]

I already have a mystery switch variant, Goerend single disk and vb mods. The trouble with the convertor slippage is that the throttle is barely open at 1,100 RPM when the TC locks so the TV (throttle valve) cable going to the trans that increases the trans pressure as the throttle is opened isn't being pulled far enough. With the power output I have now, it doesn't take nearly a much "gas pedal" to get down the road.



I do have a mystery switch but it is a stealth one. I installed a '98 shift lever and used the momentary switch to engage the TC lock up (No unlock option, I never needed it before), I also used a switch on the throttle pedal to disengage the lock when I let off.



If I don't have the right PCM to reprogram, my next option will be modding the linkage. I'm thinking that a progressive (non-linear) throttle linkage between the bellcrank (where the TPS and TV cable are) and the pump lever is looking like the easiest and most effective. The idea is for the first part of the throttle pedal travel to move the pump lever much less than the last part. Kind of like opening the secondaries on a spread bore carb.



This will take some tinkering and right now I'm up to my ears on sled set ups. Of course, when the racing season is over, this won't be as big an issue.



Thanks for the ideas - keep them coming!

 

[phoekema]

two other thoughts

Extreme1,



The only other things I can think of is 1)the gadget that BD sells. It fools the transmission into thinking you've got you foot into it even though you are at a very low throttle position. I believe it is called torque lock or something similar. or 2)ATS sells a controller that allows you to set a speed where the converter will lock. I don't know if it would work with your set-up, but it may be worth a call to them if you are interested.



I had the same problem you had before I upgraded my transmission. It's kind of a compound problem - you are putting out a lot more torque than stock and because of the low throttle position the transmission thinks you are just taking it real easy. I guess I was fortunate, as the ATS setup locks up rock solid. Is it possible that the single disk Goerend is not up to the kind of torque you are putting out now?

 

[Strick-9]

The original question was, "has anyone done this before. "



I have. I started playing with the TV lever about two years ago. It wasn't because my TC was slipping, but because I wanted more line pressure AND later light throttle shifts.



I've been all over the place with the bracket. I also designed my own throttle lever for the pump (more throttle travel, more kickdown travel, less pump rotation) to help with the problem.



I went so far as to cut my kickdown cable in two down by the transmission and insert a spring inline. That way, I could run my kickdown cable VERY aggressive and not limit my throttle travel at the pump any.



So yes, I've been there. It won't help with your situation though because lockup is commanded by the PCM. Making a different kickdown bracket will give you more kickdown lever rotation, but doesn't affect the PCM inputs any. So the PCM will still command lockup at the same time.



For your particular situation, I'd recommend a hobbs switch plumbed into a boost line that unlocks the converter. You said your converter will slip at high RPM too under extreme power. I think this is your best and cheapest bet. You could adjust it for 15-20 psi of boost or whatever boost the converter would handle. That way when accelerating at low boost, the converter will automatically kick out and stay out if you keep your foot in it. When you let off and begin crusing down the highway, the boost will fall and the converter will lockup allowing lower transmission temps and better fuel economy.



Hope this helps.



-Chris