700R4. Love it or hate it?

[Mixup]

Love it. It's been in my truck almost 7 years.

[charlie diaz]

I may be reading it wrong, but I think that there is some confusion on what the lock up does. The electric lock up locks up the converter electronically once the tranny is in OD, or in 3rd if you just have it in D. The locking mechanism is designed to reduce slippage of the tranny for lower RPMs which will in turn give you better MPG. with the lock up set up on a switch, then you can lock it up when you are in 3rd for when you are towing. You're obviously not going to tow in OD. You can still go into OD without the lockup, but you will have slippage and eventual failure. I'm not trying to steal the thread, I just thought that this was pertinent information.

[sweet70beast]

Originally Posted by charlie diaz

I may be reading it wrong, but I think that there is some confusion on what the lock up does. The electric lock up locks up the converter electronically once the tranny is in OD, or in 3rd if you just have it in D. The locking mechanism is designed to reduce slippage of the tranny for lower RPMs which will in turn give you better MPG.

Accually the lock up of the torque converter reduces heat. When a torque converter "slips" it creates alot of heat in the tranny fluid, heat will break down the fluid. More heat faster the break down of the fluid. By locking the torque converter it acts like a presher plate/clutch assembly for a manuel trans, buy physically locking the output of the engine and the input of the trans so they are spinningv the same speed. If the tranny fluid breaks down because of the heat it will sooner or later toast the trans. That's another reason the TV cable set up is so important, if it's set wrong the internals of the trans slip causing the same heat then failier.
Locking the torque converter does get you little better milage it is not the reason for it. A slipping converter can spin anywhere from 200 rpm to 700 rpm slower than the engine, by locking them together they spin at the same rate causing the effecientcy (milage) to go up slightly.
I personaly love the 700r4, I am going to put one in my 71 K20 this summer. I had one in my 70 Nova for a while and hated it. My Nova has 3.08 rear and I was using more gas with the 700 than I was with the th350 that was in it before. I am switching to a 3.73 rear when I put a T5 in it. I wouldn't go any higher than a 3.73 unless the engine is fuel injected. Some cars run 3.08 or 3.42(from the factory) with 700r4 but they are usually fuel injected.

[67ChevyRedneck]

I may be wrong, but I believe in "stock" form the 700R only locks in 3rd and OD.

[68shortstep]

Originally Posted by 67ChevyRedneck

I may be wrong, but I believe in "stock" form the 700R only locks in 3rd and OD.

That's right, I'm pretty sure. No overdrive in 1st or second if a stock trans.

I had a nasty-colored (yellow/tan/yellow/tan) '85 Silverado when it was brand new, that I absolutely-hated, because it was always see-sawing in & out of gears between overdrive & third, going up long gentle-slope hills. Got lotsa those in this part of Arkansas.

Then somebody told me: Hey dumb*ss, just set the transmission gear selector pointer on the "D" marker, & not the D with the "O" around it, unless you're out on flat highway/freeway....... you'll burn the trans up with all that pointless shifting, & it won't go into the overdrive at all unless you use the "O" marked drive pointer.

All was better then.

I guess that would be the purpose of a manual lockout / engage switch after a trans swap.

Sure made a big difference to me in how much I liked the truck.

Maybe I should have read the owners manual, or something, too ??????

We later had a '92 Buick Roadmonster (that's the color I used for my pickup) with the same 350 engine & 700 OD trans in it, that my wife drove most of the time, and we hardly ever used the overdrive, unless out on the road on long trips. Same "see-sawing" in & out of overdrive, otherwise.

[Critter]

A little off subject, but I remember something about the 200r not being able to mate with a transfercase, aka, a 4x4 application. Am I making this up or IS it possible using GM parts?

[67ChevyRedneck]

^700R's are NOTORIOUS for wanting to shift in OD early. With light acceleration mine will shift into OD at about 40-45mph. Way too slow of a speed. That's one of the reason's I love my Lokar floor shift. I drop it into 3rd and leave it there until the truck hits about 50mph or so, then I bump it up into 4th. If I do city driving where I almost never hit much over 40-45mph I just leave it in 3rd.

[6772owner]

I have my trans set up with the Jet Performance vacuum switch kit and have no problems what-so-ever with the locking/unlocking of the torque convertor, seems to operate as it should to me, basically seemless til you hear the RPM's drop.

[tekno62]

I searched but didnt fond anything meanful

you have a link for the Jet Performance vacuum switch kit

Originally Posted by 6772owner

I have my trans set up with the Jet Performance vacuum switch kit and have no problems what-so-ever with the locking/unlocking of the torque convertor, seems to operate as it should to me, basically seemless til you hear the RPM's drop.