Flush Transmission cooler??

The A670 3-speed transmission in my '88 Caravan finally died last week. I'm
replacing it with a reman but, before I do, I'm thinking I should flush the
transmission cooler and hoses in case the fluid still in it is contaminated
from the previous damaged tranny.

I'm not sure how to do this. First, does one just use new ATF-3 as the
flushing agent? or is there something else? Second, any ideas on how to
perform the flush, i.e., apply the pressure needed to push the old fluid
out?

TIA,
Dave

 

Subject: Flush Transmission cooler??

Dave : There are cooler flushers that come in an aerosol can you can use.
However, I simply use a Tru-cool cooler by itself and unhook the factory
one-since they are difficult at best to clean and may appear to be ok when
running compressed air through them-and when in use and at operating
temperature they go restrictive from occult crud lodged in them. This usually
after a trans has nuked. On the trans u have the cooler is usually crapped from
the torque convertor clutch coming apart.


Respectfully submitted,

Loren Knighton
Woodland, CA.

Under the hood since 1964
Member TRNI IATN
http://www.lubegard.com/automotive/trans_atf.html
http://www.longmfg.com/web/longwebframework.nsf/home/web.trucool

 

I'd definitely flush it.

As to HOW, I would blow it out with compressed air first, then use a
piece of hose and a funnel to run about a quart of new ATF through it,
and then blow it out again with compressed air.

If you don't have a compressor, rig up the hose/funnel trick and
gravity-flush it with 4-5 quarts of cheap ATF, then finish off with
whatever type ATF you intend to use in the new tranny.

 

I just installed a napa stand alone (in front of radiator) on my 89 GC and
it cost me 28 bucks. It came with the hoses and clamps.. Why not go that
route instead of hoping you'll get out all the garbage? It has some funky
install clips you have to use but it had good instructions too.

Ric

 

They make a flush gun that consists of a can that you fill with flush agent
(generally mineral spirits or something that is very lightweight, dissolves
oil, and evaporates quickly, some like to use lacquer thinner) and a hose
that goes to a gun with a rubber tip that seals the gun tip to one side of
the
cooler. On the can is a compressed air fitting, you hook this to a
compressor
and put as much shop air pressure as your compressor can deliver into it.

flush several times both directions with at least a gallon of flush agent
then
blow clean non-oiled shop air through the cooler for several minutes at
full pressure. Make sure to capture the flush agent don't dump it all over
the driveway.

I believe on yours the design puts the cooler on the fluid exit, so any
remaining metal particles should go into the pan and get caught in the
tranny filter.

Ted

 

I bought a NAPA cooler and noticed how much smaller it was than the OEM
cooler. I read the material and the size cooler they gave me was
recommended for my application when used in series with the OEM cooler. To
replace mine, I needed the cooler two sized larger. Well, I paid $55 for
the when I got, so I took it back and then took my OEM cooler down to the
local tranny shop and they flushed it for me.

The tranny R&R job finally ended today. Unfortunately, just before a road
test, my engine started acting up. It sounds like I'm running on 2
cylinders (3.0L V6). Not sure what that's about yet.

David

 

|
|> One good reason is that in cold weather the cooler may over cool the
|fluid. By
|> routing the cooled fluid back into the radiator it will regain some heat
|before
|> returning to the transmission.
|
|I did say a Stand Alone cooler. Not feeding back to the radiator. Placed as
|low to the radiator as you can (as per instructions) will ensure warm oil
|back to the tranny.

Perhaps if placed behind the radiator.
Put a standalone cooler in front of the radiator and you could be asking for
trouble this winter, unless you live in the sunbelt as opposed to the snowbelt.

Rex in Fort Worth

 

I've heard that unlike engines, you really can't run an automatic
transmission too cool. Is this not the case? I have to admit I'm
pretty slushbox-ignorant, I've been a stickshift snob all my life.

nate

 

The '92 Hyundai Elantra I previously owned would only drop into OD when
the trans fluid reached a certain temp. Verified as normal operation by
dealer, regional and national service managers.

It was nice to have the regional and national service reps located
locally, (Had direct numbers to their desks, so no run around with
underlings) but I still like my '00 2.7L Intrepid tons more. In fact,
the Intrepid get better mileage than the Elantra, and its at least twice
a big. 33 MPG on the last 200 mile trip with the AC on.

--

 

|Rex B wrote:
|>
|>
|> |
|> |> One good reason is that in cold weather the cooler may over cool the
|> |fluid. By
|> |> routing the cooled fluid back into the radiator it will regain some heat
|> |before
|> |> returning to the transmission.
|> |
|> |I did say a Stand Alone cooler. Not feeding back to the radiator. Placed as
|> |low to the radiator as you can (as per instructions) will ensure warm oil
|> |back to the tranny.
|>
|> Perhaps if placed behind the radiator.
|> Put a standalone cooler in front of the radiator and you could be asking for
|> trouble this winter, unless you live in the sunbelt as opposed to the
snowbelt.
|>
|> Rex in Fort Worth
|
|I've heard that unlike engines, you really can't run an automatic
|transmission too cool. Is this not the case? I have to admit I'm
|pretty slushbox-ignorant, I've been a stickshift snob all my life.
|
|nate

Nate
Truthfully, my information is dated and came originally from the Kool Klutch
reps some 20 years ago. It made sense and still does, although I admit every
rule probably has exceptions.
An auto trans is just a big oil pump working hydraulic rams. It's designed
to be most efficient in a given viscosity range, which is directly influenced by
temperature. It makes sense that the same fluid will not work the same at -20
degrees F as it does at 190 degrees. The water coolant is kept realatively
stable by the thermostat. By exchanging heat with the transmission oil in the
radiator, the transmission oil temp is stabilized to a certain extent and
transmission performance is more predictable.
A secondary issue may be that the coefficient of friction changes with
temperature. A cold fluid may affect shift quality and clutch wear.
Rex in Fort Worth

 

Apparently some late model Subarus are the same way. On a Subaru newsgroup
that I frequent, you will periodically see posts by owners wondering if
something is wrong with their transmission because on cold mornings, it
doesn't shift into overdrive until warmed up, and an explanation of a sensor
and intentional upshift lockout is usually quick to follow.

However, I don't think that necessarily has to do with the longevity or
operation of the transmission (although it might). More likely, it is a way
to provide lower lugging load for the engine when cold and get the engine
oil heated up to it's operating temperature faster (motor oil's primary
lubing properties don't turn on until around 160 or 170°F or so).

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my address
with "x")