Hi, I know this thread is going to end up in an argument, but I have looked all over the internet, and all I get is conflicting information. Probably what I'm gonna get here, too, but here goes.

I have a 1980 'vette, would like to put a 700r4 in it. I don't want the lockup converter. My pickup truck has one and I absolutely hate it. Now, some folks say, if you don't use the lockup feature, your tranny will fry before you can even drive to the junkyard. Others say, it'll generate a little more heat, so use a tranny cooler and you'll be fine. Still others say, you must make certain mods to the tranny, and then you will be fine.
Are there any knowledgeable folks out there who can set me straight, or at least point me in the right direction to the info I need?


Scott

 

I have a switch for my lockup. I run most of the time with the lockup turned off. I occassionally lock up on the freeway. I run a large cooler, but you should do that either way. No problems.
Bee Jay

 

IF racing, just turn off the +12 volt to the solenoid.....or just leave it unplugged more or less permanently....but keep in mind that the Torque converter generated one hell of a lot of heat, much more than the tranny itself.....you need put a HUGE cooler in there after the rad cooler in the flow.....

why not use the feature?? I don't understand....

 

I told ya, my truck has one, and I hate it! Plus, it's just something else to go wrong. If my rpm at 70 mph goes from 3000 to 2300, Ill be a happy camper, I don't think the extra 200 rpm is gonna kill me.

Then again, the manual switch idea might not be too bad......just use it on trips. OK, but regarding the rest of my question, what's the real deal? So much conflicting opinion out there, I need some from people I trust.

Scott

 

Hey Scott..if you look at how the lockup works on a 700 its real simple..on the old cars like the 350 trans..the computer turns on the lock up once it saw 4 th gear oil pressure and low map volts..meaning cruise..its only there for gas mileage..yes it can be used to decrease heat but it wasn't designed for that..if you ever have one of these apart you will see that 4th gear only has 3 frictions and steels..and the diameter is maybe 3 inches..if a pre 90 700 trans is lugged with the converter locked it will burn up 4th real quick..that's why you don't see all that many mid to late 80's blazers around anymore..if you do a 700 trans using a radiator style cooler is best..they cost more than the tube style but are better at dissipating heat..one thing also is the 700 is longer and needs driveshaft mods and crossmember mode..a 200 is also a good trans and takes less mods to get it in there..just know the swap isn't all that cheap but if you want better mileage then it is the way to go..

 

I have a th700r4 out of an '88 IROC, and a friend has an '82 'vette driveshaft leftover from a car that he converted to a 5-speed. I'm planning on using the crossmember from Bowties. I have decided on the 700 as opposed to the 200 because I have a 3.07 rear-end gear, (the low first gear will give me a final drive in first gear of about 9.39:1) and a relatively mild 350 with a nice broad torque curve (for the widely spaced gears). If I had a little more rear gear, I'd probably go with the 200.

So, are ya saying that if I use a good tranny cooler, plumbed into the return line from the cooler in the radiator, I shouldn't have anything to worry about? I guess I could put a switch on the dashboard for long trips. I have a feeling that the people who say things like "I didn't hook up the lockup, and my tranny burned up after 5 miles!!!" are full of crap.


Scott

Scott

 

Yes they are full of poop..chances the trans was junk in the first place..now that being said..you got one out of an 88 Iroc..not so good..unless its been rebuilt by some one who knows what they are doing chances are it will burn up real quick also..when these came out in 85 they where junk from day one..there were so many updated parts that I couldn't mention them all..that's why I said 90 and up at least gives you a some what of a chance...I would hate to see you put in all this work and have a failure in a week..I hate let downs..that's why I really warn you from using that trans..you also need to change the shifter stuff also..that's the easy part..I may go to a GM dealer and ask for a rebuilt one from them??? Most people know someone at a GM dealer that would give you shop cost or maybe even employee cost..or one from any good rebuild place which there are many of..but I really would avoid that trans..88 Iroc had a 305 if I remember right..his much power was in that thing?? 150 hp in a tuned port one if your lucky..to say it funny..you will be changing that trans like your underwear after a weekend of eating hot wings from Hooters!..

 

The way the lock up torque converter is designed is simple, and the idea that if you don't use it, it'll create exessive heat is an internet myth. The lockup feature is simply a selonoid that directs fluid to the converter to engage a clutch disc to the front of the converter creating a mechanical rather than fluid connection with the engine and trans. If you don't want to use it, you can get a converter that doesn't have the lock up feature if you don't already have the trans or not connect it if your current trans has one.

This video shows how a lock up works.

http://www.youtube.com/watch?v=g7TUy6gz8HU

If you don't use this feature, how would it build more heat than normal?

 

If I could put the little dude up with the agree flag I would..mobile version a no go there!

 

The stock 700R4's are very weak and the TC is a monster 11 inch. Get rid of a heat producing stock TC and get a highley efficient 9.5 inch.

If you have any kind of power, the Vette cooling systems are already on the edge. So don't add more heat with a tranny running hot oil through it.

I used the biggest B&M tranny cooler with 1/2 ID lines. I also had a dash switched lockup. My lockup clutch failed when I applied 600 hp to it at 150 mph. So I drove it around with no lockup the last two years. another forum member has been running that tranny with my rebuilt TC for the past two years behind a solid roller 406 ci

 

That lockup function is strictly for fuel efficiency...not for heat reduction. The lockup control strategy is set to drop lockup whenever there is significant increase in load on the tranny because that lockup clutch is not designed to handle power, but only to bypass the torque converter to save some efficiency when you are at steady speed and not going up a significant slope.

If you decide not to use it, it will only cause you a small decrease in fuel economy. Since it is 'dropped' when under load anyway, you really won't have any significant increase in heating.

The issue of whether to use that vintage 700R4 [or not] is up to you and the other "diplomats" on this Forum. If you intend to put a lot more power through it than came from the factory, it should be rebuilt/upgraded to make it more solid. If you don't plan on 'pushing' it very hard, the 700R4 will be just fine. Now, the fact that it was already "used" is another issue; I would not install a "used" tranny into my car without having it rebuilt first. Just my .02....