Lockup converter or not?

[phishfud]

My 84 K10 came with a 700R4 in it, and now that I will be doing a TPI swap, I need to know if it is a lockup converter or not. I really don't have a clue what a lockup does, if I need it, or if I have it. All my project vehicles to date have either beed TH350's or 4 speeds. When I get my custom harness, one of the options is for the lockup converter, and I just don't know what to order. Now my truck has had all the factory computer stuff and emissions removed by the PO, and there are a few wires coming from the trans that were cut. Truck runs and shifts fine though as it is. Any info would be great. Thanks.

Terry

[magnethead]

I'd like to think it's lockup..i'm yet to see a non-lockup 700.

[Slonaker]

A regular torque converter has some slippage all the time. This is why you can stop in drive and the engine does not die like it would with a stickshift. A lockup torque converter stops slipping once you get up to speed. That allows your engine to turn fewer rpm, which bumps gas mileage up a little. That is probably oversimplified a little, but it should give you the idea...


AFAIK, 700R4s were all lockup from the factory. I think you can have one custom built without lockup, but any stock one would have it.

Hopefully someone with more knowledge will chime in...

Slonaker

[marvxyz1]

Great explanation of a lock up converter!!!!!

[84 400]

yeah great job simply explaning a lock up! if it is stock 700r4 then it is deffinatly a lock up.

[phishfud]

Makes alot more sense now, thanks for the info. I guess I'll ask for the lockup connections as well then.

[piecesparts]

A 700 R4 is a lock-up convertor style tranny. They CAN be changed over to a NON lock-up convertor, if that is what you need or desire. My 84 has a 700 R4 with the overdrive operational, but the lockup has been sacrificed for a 2400 stall convertor, so that my cam doesn't choke me down at a stop light. The change over to a TPI motor will probably be easier than you think. Your odds are in your favor that the motor and computer came from an automatic vehicle and that it was an overdrive tranny. If that is the case the wiring harness and computer should be ready for it. If not there are ways to set up a 700R4 for actuation without a computer to drive it. If you open Street and Performance's website, www.hotrodlane.cc they have a picture/info section that has the necessary steps to get a tranny to operate without a computer.

[phishfud]

Since I will be using a GM computer, I guess I'll just leave it as lockup. This will just be for haulin and wheelin, so a nice torque cam is all I'm after, so should be able to keep the stock converter. At I finally learned what a lockup is Thanks for the info.

Terry

[piecesparts]

What cam are you considering with theTPI unit? I am told that the GM TPIs are not easy to get the right performance out of with a torquey cam. The one that I am putting together for my 91 Silverado, still has the Vette roller cam in it, but I changed the heads to Vortec units with Comp Cams 1.6 roller rocker arms. Along with the upgrade on my injectors and the larger runners, I am hoping for a good solid 350+ HP.

[phishfud]

I dont have a number just yet, but the cam should be similar to the ZZ4 hot cam specs, which is about the biggest one you can run using a stock GM computer and not have to burn a new prom. There is also a Summit cam that would work well for me. The stock TPI unit is actually a great torque setup as it is with the stock long runners. I know my GTA has torque like mad, but gives up around 4800 because of the long runners, which is a pretty good setup for wheelin. Now if you want one that's fast with lots of HP, then the stock runners are useless. The motor in my truck now scoots pretty good, but I want the reliability and hopefully mileage from injection. Eventually I may build a 383 with TPI and get a prominator so I can tune it accordingly.

[crawdad]

Originally Posted by piecesparts

A 700 R4 is a lock-up convertor style tranny. They CAN be changed over to a NON lock-up convertor, if that is what you need or desire. My 84 has a 700 R4 with the overdrive operational, but the lockup has been sacrificed for a 2400 stall convertor, so that my cam doesn't choke me down at a stop light. The change over to a TPI motor will probably be easier than you think. Your odds are in your favor that the motor and computer came from an automatic vehicle and that it was an overdrive tranny. If that is the case the wiring harness and computer should be ready for it. If not there are ways to set up a 700R4 for actuation without a computer to drive it. If you open Street and Performance's website, www.hotrodlane.cc they have a picture/info section that has the necessary steps to get a tranny to operate without a computer.

Dang it! Just about the time I thought I understood the lock up converter and such, you had to go and confuse me. My truck is an 86 with 305, 4bbl, 700R4 tranny and lockup converter, however, I don't think there is a computer in my truck. Am I wrong about this, or does it all work by some other means? My other truck (an 85) was computerless too, but it had a TH350 with a lockup converter. Exactly what does a 700R4 with a lockup converter need to operate correctly? I ask because I have been contemplating removing all of the smog stuff, but I don't want to screw up the operation of the tranny or the converter.

[magnethead]

there is indeed a computer. It's location changes, but it's there somewhere, i think the more common place was near the fuse block and behind the radio i think???????

[piecesparts]

Take a look behind the glove box (on top of the heater. The computer is there. The wiring goes through the firewall just above and behind the motor. The lock up portion of a convertor can be bypassed and it be used as a standard tranny, just by unplugging it. That is not the right way to do it, though. My truck (84 GMC) and my son's truck (86 silverado) both came with the 350C trannies (350 with a lockup convertor) and we removed them for the overdrive trannies. The best thing that I ever did. I purchased the trannies from what used to Premier Performance (now known as JET Performance trannies) and they came without the lockup feature. Since that purchase we have had the trannies built up to a stronger combination tha what JET supplies. The smog stuff is unecessary for a lockup to work. I had my smog stuff gone long before I changed out my 350C tranny. You need to look at a power source that is triggered off of a speed or tranny pressure to set the lockup around 45 MPH and keep it applied until you get below that speed. As I stated above, go to Speed and Performance's website and open their page http://www.hotrodlane.cc/ONLINETECH/translockup.html to see that the lockup can be connected up for use anywhere.


The TPI is a good idea, the top end can be moved by getting rid of the heads that comes with the original setup. The Scoggin Dickey Vortec conversion will allow for the power curve to move up another 1000 RPMs and give you another 100 to 125 HP in the boot. There was an article in Chevy High Performance on this install and the review was good. Just don't loose that vacuum signal that the TPI needs for it's operation, the cam is the important part of this.

[phishfud]

No doubt the Vortec heads are the way to go. The downside is you need the Vortec TPI base which is like $300. I have one of the Accel Superram bases on my GTA which can be used on Vortec or standard L98 heads, and if I could find another one used at a decent price, I would definately use the Vortecs on my truck.

[magnethead]

Originally Posted by piecesparts

Take a look behind the glove box (on top of the heater. The computer is there. The wiring goes through the firewall just above and behind the motor. The lock up portion of a convertor can be bypassed and it be used as a standard tranny, just by unplugging it. That is not the right way to do it, though. My truck (84 GMC) and my son's truck (86 silverado) both came with the 350C trannies (350 with a lockup convertor) and we removed them for the overdrive trannies. The best thing that I ever did. I purchased the trannies from what used to Premier Performance (now known as JET Performance trannies) and they came without the lockup feature. Since that purchase we have had the trannies built up to a stronger combination tha what JET supplies. The smog stuff is unecessary for a lockup to work. I had my smog stuff gone long before I changed out my 350C tranny. You need to look at a power source that is triggered off of a speed or tranny pressure to set the lockup around 45 MPH and keep it applied until you get below that speed. As I stated above, go to Speed and Performance's website and open their page http://www.hotrodlane.cc/ONLINETECH/translockup.html to see that the lockup can be connected up for use anywhere.


The TPI is a good idea, the top end can be moved by getting rid of the heads that comes with the original setup. The Scoggin Dickey Vortec conversion will allow for the power curve to move up another 1000 RPMs and give you another 100 to 125 HP in the boot. There was an article in Chevy High Performance on this install and the review was good. Just don't loose that vacuum signal that the TPI needs for it's operation, the cam is the important part of this.

Also, from my off-road knowledge, you can just run a switch to those wires and lock up the convertor anytime you want, or unlock it anytime you want.

[Slonaker]

Originally Posted by piecesparts

Take a look behind the glove box (on top of the heater. The computer is there.

'86 and earlier does not have a computer.

Slonaker

[89 crew]

My Dad has an 85 c10 305 and it DOES have a ecm. (It is useless on his cause it was changed to the old hei) The ECM is on the passenger side right by the heater like Magnethead said. I won't be foolish enough to say all of the 85's have them but I would look and see if yours does.

[73stepside]

my 86 has the electronic spark controller. although it's not technically an ecm it does somewhat control the spark advance for ping. i think only the 305 trucks had the esc module. it's behind the glove box just above the heater box. 82-86 700r4's run better if you run the lock up feature. they burn up the 3/4 clutch pack if you don't. if you want to run lock up with out a computer, look at the trucks that had the 350c. you can get all the parts to run a lock up tranny from them. my truck has the 350c. it's not a bad tranny but it's not a 700 which will go in sometime soon.

[piecesparts]

You can call it what you want---The dang thing is behind the glove box and is tied to the stupid distributor and it is absolutely worthless. Get the HEI and throw the computer thingy away. The tranny is tied to the TCC valve on the intake for switching.