Time to bring up a often covered topic, 4T60 wiring options to make the TCC work properly. I've read a bunch of threads on it with lots of great ideas. It seems as though there are a number of ways to make this work. I really don't want to have to take the cover off if I don't have to so looking for solutions that don't require it. Will if I have to to make sure it works correctly.
seems as though the TCC lock up will work by using the stock 2.8 TH125 wiring that goes to the trans just by switching around the wires to match the 5 plug recepticle already on the 4T60 (using only two wires). There is a posting that covers which colors etc match up. If a person does that will the TCC work or does something else still need to be done? Is it that simple? Can a person buy the 5 plug male side (harness side) off the shelf at a parts store or does that need to come off a junkyard car?
I've read about replacing the pressure switch inside the cover and doing a little re-wiring and that seems to be a fix that works but then does one still need to do the wiring described above on the outside? Remember I'm trying to avoid removing the cover.
Lastly I came across the following that looks like the pressure switch can be added to the outside where there is currently a bolt screwed into the transmission shown at #119. Has anyone tried this method? It's the only posting I found on this so I question how well it works.
Below is the conversation about hooking this up. This is in an archived article started by Fierosound. I guess main question is how most folks wire or set up the TCC in order to make sure they get it to lock up?
Yep. That looks like it. Pics are not showing up for some reason on this trend. The port is right under the governor and by the r/s axle. It's a 1/8 pipe plug. The original plug for the tcc on the th125 trans has a purple wire and a tan and black. The purple wire has power to it when the key is on and when you step on the brake the power is interrupted (off ) and the tcc disengages. The tan and black wire gets cut and you splice it into the switch. So you cut the wire about 3 inches away from the plug and run one section from the plug down to the switch and then run another wire from the other side of the switch back up to the tan and black wire you cut. When the pressure at the switch reach 55 psi it grounds the circut and engages the tcc since theres power to it all the time from the purple wire. At the port under the governor 55 psi is approximately 55 mph. And if you step on the brake the power goes off and the tcc disengages.
4T6x is wired inside very different then TH125c/3T40. To make more confusing, 4T6x uses 3-4 wire setup depending on year/model is cars. It uses 2 switch and solenoid. 1 3rd gear, 1 4th gear. Switches have ground like Light/gauge on dash uses ground sensor in engine.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
The only downside to running the pressure switch at the differential is that once you pass the MPH that engages the TCC, it will remain locked until you drop below that speed. It will never disengage if you want to pass someone on the highway. If I were to do it again, I would just remove the cover and rewire the TCC circuit to be just like the 125C circuit (and some of the early 4T60's came this way from the factory).
I've got a 4T60 out of a 1991 so probably not very likely I've got internal wiring like the TH125. Really appreciate your experience and what you'd do if doing again.
Any production 4T60 you find can have its TCC solenoid activated by stock Fiero ECM control by just hooking up 2 wires. The purple TCC brake switch wire and the ECM-controlled TCC solenoid activation wire (tan/blk).
There were many different versions of 440T4/4T60's produced that had different numbers of pressure switches and such in the valve bodies. GM also changed the shape and number of terminals the electrical connectors they used on these transmissions had. In some cases, you may need to know what year/make/model of car the transmission you have came out of so you can consult wiring diagrams. But most of the time, if you have the electrical connector for the transmission and some length of wiring still attached, you should be able to match up wire colors. GM used standard wire colors for certain circuits for many years so it shouldn't be difficult to wire it up.
If you are going to let an ECM control the TCC directly, you don't need any sort of pressure switch which you don't want anyway for the reasons fieroguru mentioned.
-ryan
------------------ OVERKILL IS UNDERRATED Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com
[This message has been edited by Darth Fiero (edited 03-16-2013).]
Ryan That's the answer I'm really hoping for. switch a couple wires and let the ecm do it's thing. I'm attaching an article I found a while back that makes it seem pretty simple to wire in the stock harness (changing the connection to a 5 pin to match the 4T60) and away you go. no changing pressure switches etc, but really was hoping someone would be able to speak to it that it works. I know what the tranny came out of, a 1991 Olds 88 with the 3.8 motor and according to the GM dealer the gearing is 2.84 which is what I wanted. I am putting in a 1994 3.4L PR with some moderate upgrades (ported Y pipe, ported logs, enlarged intake manifold with 56MM TB, 260 cam) to give it a bit more umph but still wanted decent mpg when cruising. I had contacted you about burning a chip and see how close we can get. Plan to get with you on that in the next few weeks to give you whatever info you need to do that. I imagine the 4T60 also plays a factor in burning a chip? Anyway, thanks for your input on this, I'm really hoping I might be able to match up wires at the connector attached to the transmission without going inside. Somehow that seems too easy.
I just wired my 4T60 by removing the side cover and installing a 125C N.O switch in the 3rd gear pressure switch port. Was real easy to do. Then you do not have to worry about the Fiero ECM commanding the TCC to engage while you are not ready for it to work. You can not remove the 4T60 side case after it is installed into the car. Fix it right only once. I have a spare 5 prong plug I can send you if you will take me a good picture of your transmission case half of the connector. Just want to make sure it will fit for you before I mail it off for you.
This type of switch will not work inside the 91 4T60 with out changing the connector ends of the two wires also. You need the type that has the two little 'nubs'.
I know you don't want to remove the side cover, BUT it is so easy, even a cave man could do it.
[This message has been edited by josef644 (edited 03-16-2013).]
not a great picture but does it show up well enough or should I try for a better picture? Now I'm interested in the pro's and con's doing it either way. Is one better than the other? LOL I'm a snow man not as much a cave man. I know I can do it, just trying not to mess with the tranny fluid. I'm also checking with the PO on the 4T60, see if he still has the harness with the connector he can cut off for me.
I see what you mean by nub and you can't see it in the picture. It's got 1 nub around the outside, assume that's how it fastens.
[This message has been edited by Grantman (edited 03-16-2013).]
I don't mean to be dumb about this but want to understand whether I do this or I have someone else. Is the switch you added at # 1 or # 2? Did you add a wire or extend a wire to reach it and was there a plug or something there that you took out to screw in the pressure switch? I think in your thread you mentioned soldering the wire. just trying to think through what it was you added. Plus as others have said the wiring from different years might be slightly different inside the case.
not a great picture but does it show up well enough or should I try for a better picture? Now I'm interested in the pro's and con's doing it either way. Is one better than the other? LOL I'm a snow man not as much a cave man. I know I can do it, just trying not to mess with the tranny fluid. I'm also checking with the PO on the 4T60, see if he still has the harness with the connector he can cut off for me.
I see what you mean by nub and you can't see it in the picture. It's got 1 nub around the outside, assume that's how it fastens.
G man I have editted my post above. Go back are re read it. The little 'nubs' I was speaking of were on the pressure switch. Pic stolen from the Fiero Store
Here is the case part of the harness on my 91 4T60
[This message has been edited by josef644 (edited 03-16-2013).]
oh. much better photo of the transmission side of the connector. yes that's what mine looks like. I'll pm you my address if you're willing to send it to me.
Ok I wired mine as fieroguru's diagrams were, almost, for the 85 4T60 in his posted diagram, bottom right hand corner. I just put the switch on the out side, instead of the before side of TCC. The I removed 2nd gear switch wires, and 4th gear switch wires. Leave these two old switches in place. If you want to remove them, you will need to plug them off. They will not be used. Wire 'A comes out of the connector and goes directly to the TCC solenoid. Leave it be. The wire 'D that was headed back the connector I cut, and added in the 125C into the 3rd gear port. So the switch is in the - part of 'D's' wiring. After the TCC solenoid.
I did this because I read where in the spacecoast Fiero install instructions, he had an occasional TCC lock up at traffic lights. Not supposed to happen, but it does on occasion. He installed a relay, I just used the N.O. switch.
Wanted to add there are two side pan gaskets required to do this switch install.
[This message has been edited by josef644 (edited 03-16-2013).]
Those I have. I was going to use a different 4T60 until I opened it up and there were a number of things that didn't look right so I found another that I knew had been rebuilt and was working correctly when pulled. You are correct I better do it right before it goes into the car. Thanks! You've been most helpful.
I just put the switch on the out side, instead of the before side of TCC.
I did this because I read where in the spacecoast Fiero install instructions, he had an occasional TCC lock up at traffic lights. Not supposed to happen, but it does on occasion. He installed a relay, I just used the N.O. switch.
I wanted to note that the "occasional TCC lock-up at traffic lights" that causes the engine to stall out was a common problem with the stock 3-speed automatic 125-C transmission. The problem was due to a defective TCC solenoid design which was corrected with an updated replacement TCC solenoid.
As far as I am aware, the 440-T4/4T60 transmissions NEVER had this issue. I also think it is not hydraulically possible to lock the TCC up in 1st gear on the 440T4/4T60 transmissions - it should only be allowed (hydraulically) to lock up in 2nd, 3rd, or 4th gears regardless of the state of the TCC solenoid itself.
Furthermore, if you have the TCC solenoid under ECM control, the ECM should NEVER be trying to lock the TCC up while sitting at a traffic light. Even if it did, with your foot on the brake, 12v + power would be cut to the TCC solenoid (purple wire) anyway - preventing the solenoid for energizing thus preventing lockup.
The pressure switch you guys are talking about installing is absolutely UNNECESSARY if you are going to hook the TCC solenoid up under ECM control. The only reason why you would ever want such a switch is if you were running a carb and had no ECM or no other electronic way of activating the TCC solenoid.
I wanted to note that the "occasional TCC lock-up at traffic lights" that causes the engine to stall out was a common problem with the stock 3-speed automatic 125-C transmission. The problem was due to a defective TCC solenoid design which was corrected with an updated replacement TCC solenoid.
As far as I am aware, the 440-T4/4T60 transmissions NEVER had this issue. I also think it is not hydraulically possible to lock the TCC up in 1st gear on the 440T4/4T60 transmissions - it should only be allowed (hydraulically) to lock up in 2nd, 3rd, or 4th gears regardless of the state of the TCC solenoid itself.
Furthermore, if you have the TCC solenoid under ECM control, the ECM should NEVER be trying to lock the TCC up while sitting at a traffic light. Even if it did, with your foot on the brake, 12v + power would be cut to the TCC solenoid (purple wire) anyway - preventing the solenoid for energizing thus preventing lockup.
The pressure switch you guys are talking about installing is absolutely UNNECESSARY if you are going to hook the TCC solenoid up under ECM control. The only reason why you would ever want such a switch is if you were running a carb and had no ECM or no other electronic way of activating the TCC solenoid.
Ryan, I'm not saying you are wrong. Here is Karl Hamiltons quote out of the spacecoast article about the problems he had after his 4T60 install. Almost at the bottom of the page. http://spacecoastfieros.com.../440-4T60/index.html
"The transmission did seem to work without the switch. Lockup occurred in both 3d and 4th gears at steady speeds and shifting seemed normal but occasionally while at a stop the engine would stumble or die as I released the brakes (but before I touched the gas pedal). My only explanation for this annoying feature was that the ECM was sometimes calling for TCC lockup at zero speed and was only prevented from accomplishing this by the open brake switch. When the brake was released and the switch closed the TCC tried to lockup which stalled the engine. Most of the time the drop in engine rpm causes the ECM to open the TCC circuit fast enough to prevent a complete stall. This problem seems to occur only at random intervals. It was several months before it had happened enough times that I was able to figure out what the problem was. Cars that suddenly stall (even occasionally) can be very dangerous to drive in heavy traffic."
I am just trying to avoid this condition. Houston, Tx traffic is the wrong place for this to happen. Even once.
[This message has been edited by josef644 (edited 03-17-2013).]
Ryan, I'm not saying you are wrong. Here is Karl Hamiltons quote out of the spacecoast article about the problems he had after his 4T60 install. Lockup occurred in both 3d and 4th gears at steady speeds and shifting seemed normal but occasionally while at a stop the engine would stumble or die as I released the brakes (but before I touched the gas pedal).
No worries. I'm not discounting what Karl said either but there are so many variables in play here. First off, the ECM should NEVER command the TCC on below a set vehicle speed (in most Fiero applications, the minimum is going to be above 30mph). Certainly not as low as what Karl said it was kicking on. If his ECM was indeed trying to activate the TCC at very low speeds, he would have encountered the same problem with his stock 125-C transmission.
Another variable is what year / make / model of car did Karl get his 440T4/4T60 out of? There are many different revisions to the internal electrical system and hydraulic system GM applied to these transmission over the years. There were also many updates and fixes to common problems these transmissions developed that were discovered before production ended. Also, versions of these transmissions that were used in Cadillac applications could be much different than those used in other cars - especially pertaining to the lockup converter clutch.
MY POINT is the pressure switch you guys are talking about "adding on" is completely unnecessary in a 100% working TCC control system. If you are installing the pressure switch to "Band-Aid" another problem (like Karl did), then that isn't truly fixing the problem - rather it is just putting a Band-Aid on it.
I just wired my 4T60 by removing the side cover and installing a 125C N.O. switch in the 3rd gear pressure switch port. Was real easy to do. Then you do not have to worry about the Fiero ECM commanding the TCC to engage while you are not ready for it to work. You can not remove the 4T60 side case after it is installed into the car. Fix it right only once.
I have someone quizzing me about the 4T60 swap. We will be removing the side cover and valve body to change the chain gears.
The swap diagrams show the addition of a relay to control the TCC solenoid of the 4T60. I believe the relay is only needed because the 4T60's 3rd gear switch is N.C. (normally closed)?
So replacing it with the N.O. (normally open) 3rd gear switch from the Fiero's TH125 would have 4T60 functioning as the original TH125 without additional external wiring or relays?
What exactly do we need to do? What about the 4T60's 4th gear switch? Leave that as N.C. ?
While the valve body will be out, has anyone installed a "shift kit"? Is it worth it? If you were happy, what BRAND of shift kit did you use and with what convertor?
Switches are so later ECM/PCM know gear and allow TC lockup or not. Might cause other things to charge depending on ECM/PCM programing.
2 switches because in "city" driving or hill county you can use 3 gear as Drive and still get lockup to work. Is why 4txx have many shifter are labeled as 1 2 D and OD. Example from 1995 Pontiac trans-sport owners manual (Page 2-29): (Get many Pontiac OM here... http://www.pontiac.com/owne...sources/manuals.html )
Why? Depending on total trans ratio and driving contitions, OD in city etc can and often will cause driveablility problems. 5 speed stick often can't use 5th gear, even 4 gear in the city. I had 3 speed stick and often only use 1 and 2 driving thru downtown.
If you really want to use 125 switch then use it in 4th gear and ignore 3rd, Or use two 125 switches and wire in parallel.
