I have looked everywhere and called multiple places and came up empty. Here is a pic of the id tag on the passenger side near the tailshaft as well as tailshaft casting # just trying to find out the year and what it actually was removed from if that's possible. Any help is greatly appreciated. Thanks in advance, Steve
THFxxxxxx T=GMC truck H=1987 F=Flint This is the partial VIN. I would confirm by looking for circular casting dates, they should say 86 or 87 in the center.
Perfect. I seen that site but apparently I was confused. Next question how can I tell if it was from a diesel or not? I have the pan off and can take some pics of the valve body later on this evening. Thanks for the info , Steve
Here's a half assed pic. Just needed a new tcc and they seem to have multiple styles. What I found was I needed a type 2.
torque converter clutch lockup.... I don't know which it applied to, perhaps just earlier ones? but sometimes the diesels had a few tack welds on the lugs, and sometimes they had different fin angles. Shift points would be wrong for a gas engine, too.
Thanks, that's what I was curious about. I know the govener and converter can be changed out if a dieael. Just didnt know any visual differences on the valve body or not. To determine whether it was diesel or gas Thanks
If you had the tag, instead of just the partial VIN, then you could tell what it is. I don't know much about these things, only played with a couple of them. Kind of too new....
The diesel 700R4 is made from the torque converter, and governor. I have found no unique parts inside. On the TCC topic, I have see four distinct arrangements from the factory, including ones that can lock up in both 3rd, and 4th. One type of switch has two poles, and allows 12V+ through to the TCC, which has its other wire grounded. The other has one pole, and provides ground to the TCC, which you supply with 12V+. In every case, I set them up to lock up in 4th only, automatically. I only ever install a switch to disable that function, via switch, on vehicles that are used for towing, as the lockup clutch is suitable only for the weight of the vehicle itself, and not the towed load, additionally. Some folks here are lazy, reckless, or don't understand physics. They just put a toggle switch in, for the TCC. This leaves the responsibility to unlock it up to them. Forget to unlock once, and you could be explaining to a cop, lawyer, insurance company forensic investigator, and judge, why you built a dangerous car.
Before computers got involved, GM used a brake switch wired in to some of the TCC circuits...might be a good idea to add one, if you're the toggle switch kind of guy.
While this would work, I disagree that it is a good idea. If you have the TCC switch on, and you let off of the brakes, you have a locked torque converter. This brings two physics issues into play. One, you have defeated the torque multiplication function of a torque converter, which is handy in getting the car off of the line. And, you are placing a load on a mechanism which it is not designed to accommodate. This is the same reason that I put a TCC lockup override switch in tow vehicles. It is a common practice for those who build high performance 2004Rs to build them without the lockup feature included. This is for two reasons. It makes for a stronger input shaft, and, it prevents the lockup clutch from exploding on engagement. Instantly locking one, on a vehicle that is stationary, at the very least would make it short-lived, if not outright break it.
Again thanks for all the info. I bought an American auto wire lock up kit. Which is through a brake/pressure switch. I dont or didn't plan on running a toggle switch for override since I dont see a need for it.
I had one running with no computer that would do everything (lockup) as if computer controlled. Not easy to acheive, but it can be done. Needs a stand alone wiring system built which incorporates a rev switch, speed sensor, manifold vacuum switch, brake switch, temperature switch, and multiple relays. Probably overkill, but hey, I like a challenge. Worked great. I have the wiring diagram filed away somewhere (sold the vehicle, transmission still going strong).
Well they call it a brake switch . Goes into the pressure port that is on the side of the transmission. Only ground and 12v ignition. Works off pressure only.
How can you tell if it locks up in 3rd and 4th vs just 4th? Besides driving it. Here is a pic of my tcc and the many plugs if that helps. Thanks, Steve
Can you post the part number for that? That is a 3rd and 4th harness. A 4th only harness has fewer wires.
If it is this one: https://www.americanautowire.com/shop/torque-converter-lockup-kit This provides 12V+ to an existing harness, with a pressure switch for the 4th gear port. It can be used in conjunction with this (if it fits), which would interrupt the TCC circuit and cause an unlock, when you put the brakes on: https://www.americanautowire.com/shop/brake-light-switch-4422
There is a 2-wire valve, which controls fluid flow to the lockup clutch, which is like a large single clutch found in an automatic clutch pack, but it is in the torque converter. It takes a 12V+ and GND to run it. The 12V+ comes from an ignition controlled circuit, run through a pressure switch, triggered by 4th (and also sometimes 3rd too) gear. Some kits include an unlock option via brake application, and/or high vacuum, and/or a manual override, or any combination therof. I, most often just wire the basic setup, which is converter locked when in 4th.
Gimpy, just so I have this straight, (I have a 700 for a future project), 12 volt ignition feed through a normally open pressure switch in the forth gear pressure port to the TCC solenoid? Is the forth gear pressure port external? 1/8” NPT? Finally, how much pressure should close the switch? I love the idea of your set up. Thanks for the help. Sent from my iPhone using The H.A.M.B. mobile app
Yes that is the kit I am using. I dont plan to have it ran to a brake light switch. I read that in hard braking it may can a bad extremely low rpm and may stall. At this point I am just running to 12v ign and will see if I need to add a brake light switch to disengage when braking.
There are some 700r4s that do not not have this external port. It is located on the passenger side near transmission lines. I dont have a pic at the moment. They sell a bunch of different kits.
Anyhow shall we talk about auxiliary vs non auxiliary 700r4's now? Just kidding. Thanks for all the Information fellas.
Hey @demon452 , @gimpyshotrods and others. The stalling problem can be caused by not using a brake switch system. When the brakes are applied, the electrical signal is interupted to the transmission to unlock the torque converter clutch by de-activating the solenoid. Think of it like jumping on the brakes with a manual box without using the clutch.....SHUDDER, SHUDDER, STALL. And possibly plough straight through the intersection, or whatever else is in front of you (soccer moms loaded with kids included). Get the lockup right, it really is important. Converter lockup and brakes can never be allowed to operate at the same time!!! In the earlier 700r4, the converter lockup is the only thing that requires electrical wiring. There will be a 4 pin socket on the transmission for this purpose. You don't need to do anything with the fluid system/line pressures to get the lockup working. It is all electrical solenoid controlled. Be especially aware of torque converter lockup and throttle valve cable setup with the 700r4. They cook themselves very quickly if not right. Don't be put off though. A well setup 700r4 and the rearend gearing to suit will make you wish you had done it years ago. The later 4L60-E transmission is essentially the same as the 700r4 except that the box is a whole lot more computer controlled (the E at the end means "electronic"). The shift points/line pressures are determined by the computer and initiated in the transmission by electronic signals to the shift solenoids. The torque converter lockup, however, is still controlled the same as a 700r4, though with a few more parameters determined by the computer. 4L60-E transmissions can be used without a computer, but usually with a full manual valve body. Kits to get the 700r4 locking up properly are not really needed. It is a simple thing to do yourself. For a basic system it requires dropping the trans pan and making very simple wiring modifications, then incorporating a brake switch and a lockup "kill switch". I am happy to do a step by step if people want it, but be aware, only do this yourself if you have the skills and understanding. Be honest with yourself. Transmission rebuilds are costly, and I take no responsibility for any damage to any transmissions. If you are even the slightest bit unsure, get a professional to do this job for you.
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