This is just an FYI:

You see that thin cork material that surrounds the outer half of the convertor? When the lock up solenoid is activated it causes pressure for an inner plate to push up against that cork which in turn removes the fluid coupling of the convertor to end and a "direct lock up" between engine and driveshaft.

if you ever wonder why our transmission (700r4) quickly disengages its because our motors will quickly wipe that thin material right off the wall.


By scotiapilot at 2012-01-09

 

Kinds makes sense to drive in the city in D rather than OD

 

Your only in OD when your car hits between 35 and 40mph.Any thing slower than that and its between 1,2,and drive.Even if your selector is in OD.

 

CORRECT! Thats why its easier on your tranny to stay in D in the city when some driving can keep you bouncing around in and out of OD.
In dallas most our roads are 35-45mph and your tranny can keep kicking in and out of OD with the variable speeds you do when in traffic.

 

OK, I can see that.As a mater of fact I "used" to do just that because I liked keeping my car in the higher rpms so it would be more responsive especially with the new 3.42s. I no longer do that,but was not aware that I was hurting my trans driving with the selector in OD around town .Our roads here are the same as yours and between the 35 and 45mph. so If that's the case I'm always open to learning exactly what is best for our cars.

 

I drive in OD, that's the way I have driven all my cars. Are you saying its better to drive on D in the heavy town driving? Would like to know how many people agree with this. Can we get some of the older guys in here that might know more about this> for feedback. Thx

 

I've always heard it is better to keep it in drive for city (slower driving) and try to do it. never realy knew the theory behind it till this.

 

WOW. Way ta go GM.

 

Does going in and out of OD on these trans really cause that much wear? It's not exactly slamming in and out at city speeds. If it was the kind of OD that affected all gears then it would make sense not to use it for city driving as it would keep the revs up some for better response. Our OD is really just a 4th gear so why not use it if it's appropriate for the driving conditions?

 

You answered your own question, use it in appropriate conditions.

Ill pull my owners manual. it is very specific about when to use D and OD

Never an issue until things break and in most transmissions its usually heat that causes issues.

Shifting in an out of OD/lock up causes heat. Valves, line pressures etc all have to meet certain high and low pressures which cause the shift to happen. Clutchs engage etc. imagine driving your car in traffic or at low air speeds like 35-45 mph and your fluid starts to build up heat which get transfered to your radiator.

During the summer I think you will find your cooling system works better along with your A/C system.

I am not saying the OD/lock up is a bad thing. Matter of fact if we could use lock-up in all our gears it would actually reduce heat!
What I am sayin is that when your driving around town where speeds causes your transmission to hunt for 4 and or lock up its a bad thing. That hunting causes heat in your tranny.

The picture is to show what actually LOCKS UP in your transmission. Nothing more.

As for fuel mileage, in city driving this is what I get driving in Dallas in D

By scotiapilot at 2011-12-16

 

I have the opposite cooling issue. I'm thinking of restricting air flow! It seems to me though that the amount of heat, wear etc. at light loads is not significant when going in/out of OD. But I'm not a trans expert.

 

Me either. I was hoping that a few pics of what connects our motor to transmission in LOCK UP would be eye-opening. LOL

 

What brand of torque converter is that?

Im curious what other companies use.

 

That is a GM convertor according to Transtar

 

that is not the lock-up set-up for a 700r4 and it is not made of cork. it is a clutch material similar to the other clutches inside the tranny. in a torque converter for a 700r4, the clutch material is on the apply plate, not the cover. same principal though. also, depending on how the tranny is wired, the converter can lock-up in drive as well as overdrive. so, the lock-up plate has nothing to do with overdrive. the lock-up plate just happens to apply about the same time the factory tranny goes into overdrive.

 

i may sound dumb but what is lock-up

 

Have any pics? The opposing side of the convertor had nothing on it. I asked them and they said that it was a gm TQ convertor.

Its when your transmission uses the torque convertor locks up the dive system so it doesnt have any slip.



A good video to watch:
http://blogs.howstuffworks.com/2009/...onverter-work/

http://www.youtube.com/watch?v=s613GPE8bS4

video of a lock up converter
http://www.youtube.com/watch?v=x-OFiTUne_M

 

Just an fyi, your 700R4 also locks up in 3rd gear from the factory not just in OD.

 

YUP!

 

Reid posted this in one of my recent threads on here

http://www.ls1tech.com/forums/automa...education.html

It contains some pictures of 700r4 lock-up clutches.

 

Awesome!

 

Thanks for the great read. In the long run it is never better to go cheap. Like the article stated, can't afford quality, wait a while, save up the pennies, and then buy the good stuff.

 

The idea of needing to drive in town in D instead of OD doesn't make much sense to me. The TCC locks up in 3rd and 4th if I remember right, so what's the point of keeping it in D? Just worsens your fuel mileage.