[Gmecm] Now Long <sigh> Geting rid of electronic transmission.

Fri Mar 3 13:28:44 UTC 2006

> >> Where did this idea come from that the cooler only work in tcc
> >> mode?
> From a GM trans class, based on observed fluid flow.

Ask for a refund. :)
Ouch!

Hey, have you ever heard the old fable about the blind men trying to 
describe an elephant?  One described it by the texture of it's skin, 
another by the surface of a tusk, and another by the length of the 
trunk.  Each had a different interpretation of what the elephant was.  
And although each one was correct in what he perceived, none could 
accept that the others were right.  After all, each man had complete 
faith that what he percieved was the correct answer.

So I have to ask, did you decide on your own what this phrase from my 
original post means?
"Stock configuration 700 does not cool when TCC is unlocked in
4th."  Or did someone else's reply turn your thinking without your even 
realizing it?

It's good that there are people here willing to correct misinformation. 
  I like that.  But I haven't supplied any.  Let's see what happens 
after this post.

I'll answer your first question.  No, I didn't ask for a refund for 
that class.  It was GM sponsored and paid for, and was a damn good 
class.  As I said, my claim is from watching the volume of fluid 
flowing through a cooler while the trans is in 4th and the tcc is not 
applied.

Here are answers to your other questions.

"With this in mind, and remembering that "heat kills transmissions", do
you think maybe it's more likely that the transmissions died due to
excess heat build up from the slipping convertor"
Absolutely!  And you can look through my first post and confirm that.

"beyond the ability of the whimpy stock cooler to dissipate heat,"
No!  Absolutely not!  No matter how large the cooler is, with 
insufficient fluid flow through a cooler there is no possible way to 
remove enough heat to make a difference.

"or more likely that GM totally redesigned their transmissions on the 
advent of lockup-style
convertors such that fluid only flows through the cooler when the TCC
is locked and the tranny is generating a minimum of heat?"
Well, for this I'll answer a question with a question.  Do you think 
it's possible that Chevrolet, when trying to save costs by designing 
this transmission in house rather than give it over to Hydramatic 
division, failed to correctly model the requirements of the cooling 
system for a transmission that reduces available driving torque by more 
than 30% through the the combination of overdrive gearing and 
rotational mass while being installed in 3000lb+ vehicles?  Now be 
careful, Danny, because you have to consider that between the time the 
trans was introduced in 1982 and the final "major revision" by 
Hydramatic in about 1993 when it was re-introduced with electronic 
controls, there were 3 major "generations" of 4L60 (re)designs (82-85, 
86-91, and 92+) along with a huge number of smalerl production changes 
and in field fixes.  In fact, there were so many attempts to make this 
trans "right" that GM powertrain printed separate manuals just to cover 
the changes!  I've got one here that was in easy reach titled 
"Hydra-matic 4L60 Product Update" part no 17007.11-7, dated March 93, 
which is probably about 60 pages detailing just the product fixes from 
86 to 93!

Now Danny, you've put a lot of effort into your reply.  That's good.  
"You've got heart, kid."  So I'll give you a little more to stew on.  
The Caprice/ Impala manual you've got is for a vehicle which marks a 
departure in GM's thinking with regards to transmission cooling.  In 
all the years that GM installed auto trannies, in all the models, that 
car with the 4L60E is among the first with 3/8 trans cooler lines.  
It's almost standard now, but prior to 93 B cars, almost everything 
short of heavy trucks and some limo/ hearse packages had 5/16" cooler 
lines!  So why the switch?  And why on that family of transmissions 
first?  Surely the Impy's of the 60's and 70's were just as heavy.  
Gawd... the 73 Kingswood wagon we owned must have topped the 95 B car 
by half a ton if not more.  So if there was a problem with the "wimpy 
stock cooler" you'd have expected it to show up long before 1993.  But 
the old 350's and 400's generally seemed to live happy and long lives 
in those old war wagons.  And it can't be solely because of the 
overdrive transmission.  The number of 4L80E failures I've seen is far 
lower than the 4L60 family, and more of the 4L80E's are used in "severe 
duty" applications.  No, the change was specifically because of the 
need to improve cooling for that family of transmission, and using 
larger lines and fittings was one of the steps taken to increase the 
volume of fluid moved though the stock, wimpy cooler.

"Well, right now, on my lap, is the factory service manual for the 1995 
B platform, book 1 of 2.  On page 7A-14A-13 (about halfway through) the 
words "4L60-E Transmission fluid flow and circuit descriptions" appear 
in bold type, and on the pages that follow,"
That's real good that you're willing to look through a manual to back 
up your claim.  I think you're an ok guy!  But where in those diagrams 
do they relate the volume of fluid flowing through a passage to the 
marking which delineates the circuit the fluid is working in?  Oh, 
sure, when the volume is zero the circuit in question is shown with no 
fluid, but you know what I'm getting at.  You can't tell "more flow" 
from "less flow" by that diagram.

"The old-timer's Corvettes probably don't fail because 1) they're 
performance vehicles designed with extra heat in mind and 2) they 
usually have shorter gears, so they're revving more in town."
Well, no.  You have to look at the Vettes he was pulling the TCC on.  
He would have started with the 80 or 81 model with the 350C, continued 
through the last of the C3's in 82, then moved into the early C4's in 
84.  He probably didn't mess with the 87 and up models as much, unless 
there was a customer complaint.  So we're looking at 82-86 cars with 
700R4.  In '80 GM lightened the fiberglass bodied 'Vette by switching 
to aluminum rear differential supports and changing some of the rear 
suspension.  Vehicle weight was somewhere around 3200 lbs... not light, 
but not as heavy as a full size truck.  And GM had really done away 
with performance gearing in the Vettes around '78 or so.  In '82 the 
available rear gear ratios were a standard 2.72:1 or an optional 2.82:1 
if you had aluminum wheels.  With the release of the C4, rear gearing 
got a little taller.  3.07:1 standard and 3.31:1 optional, but with 
taller tires the engine rpm was still about the same as the trucks with 
3.42 or 3.73 gears.  And weight dropped to just a whisker over 3000 
lbs.  So what you've got is a lighter, more aerodynamic vehicle with 
numerically lower gearing.  There was an extra heavy duty cooling 
option in '82 which added an electric fan, but the 84+ vehicles used 
the plastic/aluminum radiator construction which is commonplace today.  
My 93 S10 blazer (which I bought for a song because the 4L60E was 
blown) has the same type of radiator as those Vettes.  The Vettes 
weren't really "high performance" vehicles in the traditional sense, 
they didn't have anything magic about the cooling system, and they 
didn't have numerically higher gears than other vehicles.  Here's the 
deal.

4L60 failures due to TCC being unplugged are likely to happen on the 
highway, not around town.  Long drives with heavy vehicles shaped like 
bricks combined with constant converter slippage, delayed downshifts, 
and ineffective cooling conspire to send the trans to an early grave.  
The Vette is different in that it is lighter, more aerodynamic, and 
calibrated to downshift under a lighter load.  In short, the engine and 
trans don't have to work as hard to keep the car moving, so it doesn't 
heat up anywhere near as much.  Could you imagine the Doug Nash 4 +3 
Vette transmission being used in a truck?  It would quickly experience 
catastrophic failure.  And there's one other consideration.  You're 
much more likely to find an SUV owner driving down the left lane at 
85-90 than a Vette owner.  The Vette guys are more likely to take it 
easy.  Vette guys belong to a whole different crowd.

So good job with the research, nice to see you're taking the time.  
Thanks for creating the opportunity to talk about trans issues on the 
ecm list.

Zaphod
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