convertor lockup and synth. diff juice?

I've been working some bugs out of the fuel economy end on my 1991 Z71. I've paid very close attention to transmission shifting on reasonable acceleration up to highway speeds, and it shifts 1-2-3-4 like it should,
when it feels like it should.
I know these units employ a lockup torque convertor. is there a way to know when the TC locks up? the tc locking up on the highway helps fuel economy, right? can I "feel" the tc locking? or is there another way to know?
Also, I've heard good things about full synthetic differential fluid, with many claiming they get a gain in MPG by changing out both diffs. How much truth to this? I'm looking for every easy MPG I can get!!!
thanks!
b
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
if it has a tach, you should see RPM drop by 2-300 when it locks
when locked, you should be able to 'crowd' the throttle a bit without the RPM's increasing, while crowding the throttle, tap the brake with your left foot, the RPM's should immediately jump up 3-400

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Gary, that is the best "off the cuff" description of a procedure almost any one can do to check the operation of the TCC.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
thanks
I try to make it short and to the point

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
no tach, but will be installing one to be sure of this. when does convertor lockup usually happen? particular speed? only highway speeds? cruising at a specific "load" on the engine?
the truck shifts cleanly in and out of each gear, and I'm sure I "feel" the convertor unlocking when accelerating from say 90 to 100 km/h on the highway...
once the tach is in, I'll double check as you say to...thanks for the advice!
b

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
depends on speed, load and of course throttle opening
on a 91, 4th and lock-up usually happen so close together that you can't separate the feel
the throttle-crowding / brake test once it's in 4th at about 60 is the best test

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

G already hit the TC question; I'll tackle the synthetic question. Switching to synthetics in ALL drive units (engine, tranny, TC, front and rear diffs) will net you a 5-10% increase in fuel ecomomy. I've seen this in all of my trucks. But you're still calculating your fuel economy incorrectly so you won't know the difference anyways.
Doc

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
you're killing me man!! I've got it down pat right now (so poop on you :) Resetting the odometer /right at/ half a tank will yeild around 150 or so KM on the nose. Same with 3/4 to half. can't tell full to 3/4 or 1/4 to E cause the gauge is not calibrated, and won't go right to full, and goes well past empty.
I would notice a difference now :)
b

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Exactly right. The longer between fillup's, the better.
<<snip>>

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Doc,
Your wasting your breath. Some people were not meant to calculate MPG and you have stubmled across one.
Without some sort of static measurement it is impossible to get relibable/reproducable MPGs. Unless you either fill the tank/refill the tank and measure how much gas was put back in divided by total miles driven OR run her completely dry on level ground, refill a specific amount of fuel and divide the fuel consumed buy the mileage driven, its' just not going to work. According to Stugat's method, I am getting 40+ MPGs on my first 1/10 tank. (300 miles to the F mark, then 100 to E). Oh yeah, "Poop on you" LMFAO.
Derek
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I used the second (run dry, fill with 5 Litres, run dry) method on both my vehicles. My 2L petrol sedan, (now stolen) got 11.5 litres per 100 Km. my 2.8L TD SUV gets 11.25 litres per 100Km.
the difference seems to be the SUV in top gear can rumble along at 3200 revs for 100KmH, but the petrol needs 3600 revs, thats 400 revs more for the same speed, and diesels are more economical anyway.
rhys

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
3200 RPM cruising on a diesel????? you *sure* about that? if your cruise RPM's are that high for 60 MPH (100kph) you need some seriously higher gears. my wife's isuzu turns about 2800 RPM doing 75 and it's got 4.30's in the axles. my pickup with 3.73's turns about 1800 RPM again at 70 MPH
-Bret
diesel's are more economical because there is simply more BTU's in a gallon of diesel than gasoline.
wrote

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I think mines 5. something (5.37?), that'd mean turning the engine 5 times for every 1 on the wheels, as opposed to 3.7 turns of the engine for every one of the wheel on your pickup. not sure exactly what mine is anymore have to go look again at the notes I made. If I can find them, since it's been a while since i looked everything up and worked out it's perfomance.
5 gear manual '88 Bighorn
rhys
wrote

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Final drive is 5.37? I doubt it.
You have to take into account the transmision gearing as well as the rearend gear.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I have a 1993 K1500 w/5.7 liter and I can definitely feel the converter lock. And, after adding that Flowmaster muffler, I can hear the difference. It seems like it kicks in after I've reached cruising speed, where I'm not putting a lot of strain on the engine to get up to speed. I noticed, just recently, that I can feel it kick in even when I'm not in overdrive. It will go through the first three gears and then I'll feel that kind of smooth kick, which drops the RPM's. It seems to lock about 2-3 seconds after reaching a steady cruising speed.
One thing that I've never been able to find out is what the life expectancy is on the lock. I had one go out in a previous truck and it gave the computer a brain-hemmorhage. It kept trying to lock and compensate for the decreased RPM's (which never decreased since the lock was dead) which made the engine radically fluctuate RPM's as I was driving. It was embarassing!
-Derek

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.