1993 Caravan Trans question

Greetings all! I wanted to know if there was any way to drain ALL the
fluid from the transmission, not just what's in the pan but all of it.
It had started slipping so I: drained what was in the pan, changed the
filter, and replaced about 5 quarts with ATF +3. This fixed the
slipping, but I think I had put more fluid in than what came out (the
fluid is on the correct mark on the dipstick now, it was probably low
before). This vehicle is a fleet vehicle for an auto parts store, and it
has served its purpose well with 267,000+ miles. The transmission has
never been replaced! My boss didn't want to have it power flushed if he
could help it since it is kinda pricey. I told him I would post this
question on this group and see what I could come up with.

If it helps, it is a 3.3L engine, and I believe an A-604 tranny.

Any thoughts?
Thanks for the help!

 

Disconnect tranny cooler return line, extend the end coming from the
cooler with rubber tubing as necessary and place end of tubing into
empty bucket. Start engine to allow the tranny's own pump to push old
fluid into the bucket. Add fresh makeup fluid as necessary to keep the
level within proper range as old fluid gets pumped out. Move shifter
through the shift settings a couple of times during the process.

You will never get 100% of the old fluid out because it's a dilution
process, but if you use about 50% more fluid than the total capacity as
given in the shop manual (counting the 5 qts. that you already did with
the filter change), you'll end up with well over 90% complete flush.

It's just as well not to do a high pressure flush. It is claimed by
some that this could jarr lose deposits that might better be left where
they are and create problems.

The above-described process is arguably the optimum combination of low
cost, thoroughness, and least risk of creating new problems.

ATF+3 is the right fluid, so continue with that since you already
started with it, although some dealers and informed individuals
apparently would have used ATF+4, considered to be a better fluid (with
267k on the existing tranny, is anyone going to argue that ATF+3 is a
problem?). (Before someone corrects me, the TSB on this - #21-006-01 -
says to use ATF+4 on everything except '99 and earlier minivans due to
wear-in issues in the torque converter clutches if ATF+4 is used. The
logic apparently being used by many dealers, probably correctly, is that
with a 5+ year-old minivan, wear-in is pretty much a done deal.
Therefore the prevailing wisdom is ATF+4 for everything.)

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

 

Bill,

I believe that you are correct that the TSB specifically exempted 1999 and
older 4-speed minivan transmission from using ATF+4. That said, and
supporting your statement about what dealers are actually using, I had my
1999 T&C trans fluid replaced at the dealer two years ago (then at 36K
miles) and when I asked they said they used only ATF+4. The receipt also
clearly stated that ATF+4 was used. I have not noticed any problems with
the newer ATF+4 synthetic fluid.

I purchased the re-usable silicone/metal trans pan gasket and plan to do the
next filter change myself shortly using ATF+4 again. If anyone knows any
reason why ATF+4 would not be a good idea, I'd appreciate knowing since I
could just as easily use the cheaper ATF+3 as well. Thanks.

Bob

 

Well, Bill, I'm finally going to argue about this one. I've seen this
solution bandied about here and there for some time now, and as a
recommendation to a newbie tech, I think it's really fraught with the
possibility for disaster. My recommendation would be: a standard pan drop,
filter change and refill ought to be good enough. If you're concerned about
a mess when dropping the pan, pump as much of the old fluid out as possible
through the dipstick tube.

I think my main concern with this flush idea is the possibility that the
trans will pump itself dry. I realize that you make the point to 'add fresh
makeup fluid' as necessary, but I know from experience in trying new things
like this, that the process often becomes much more chaotic than originally
planned. I don't know about yourself, but to me, the idea that the trans
pump would run dry is a little scary. Perhaps my concern is needless? Or
is there the chance that the pump will suck air for awhile, and cause all
sorts of resulting bad secondary effects? Has anyone considered this? I'd
like to know.

My second concern with this is that it wastes fluid! This ATF+4 stuff is
expensive, and even though you might make the claim that the net cost is
lower than replacing/rebuilding the transmission, I question how much more
effective this method is than just dropping the pan and replacing what fluid
comes out at regular intervals. Pissing away expensive fluid for a
maintenance process seems like overkill to me, not to mention a waste of
resources. Certainly there will be some older fluid still in the
transmission if you forego the flush, but if you're maintaining a regular
maintenance interval, how much does it really matter? I think little. If
there's a study that indicates that the benefits of throwing away good fluid
in a flush are really high, I'd like to see it.

Thirdly, I think that this is a potentially dangerous process. Engaging a
vehicle's transmission with the engine running while it's being worked on is
inherently dangerous. Not to mention that typically it will be supported on
jack stands during the process; I'm always particularly concerned about
entering a vehicle that's supported on jack stands, as would be necessary to
operate the shift lever. It seems to me that you're creating an additional
opportunity to knock the thing off the stands; perhaps not a real easy thing
to do, but to be honest, claustrophobic as I sometimes get when lying under
a vehicle, I don't like taking chances.

So I'm interested in seeing a debate on this topic. I'll freely admit that
I'm going to be tough to convince that this flush idea is a good one, but
I'll try to keep an open mind. Whatcha got?

--Geoff

 

I appreciate an honest debate.

I can't back up anything that I said with anything other than gut feel
and a little (more than none, less than a lot) experience in doing the
procedure I described.

You are right - for me, it did initially become more chaotic than I had
anticipated. However, within less than a minute of starting it, my
over-optimism became obvious, and I stopped and had my wife come out to
assist. She sat in the driver's seat to periodically start the engine,
move the shifter, stop the engine, etc. at my command. With a helper it
was very manageable. It will be easy going the next time I do it. I
even spliced the line for easy disconnect and re-connect for future
flushes.

Once I got my bearings, it was very simple to periodically check the
fluid - it wasn't like it was going to empty iteslf out in a minute or
less - there was a comforable amount of time to check fluid during the
process, and when it started getting low, stop the engine and add more
fluid, then proceed. Never came close to sucking air.

Re: the wasted fluid, my reasoning is this: If one believes that the
fluid deteriorates at a certain rate (due to temperature and shearing),
then over the life of the vehicle, one would need to put (approximately)
the same amount of fresh fluid thru the vehicle whether in a
partial-change fashion, or thru sudden 100% changes - the former being
closer to your one pan-full at a time, the latter being closer to my
90+% transfusion at a time. Since any time any procedure is done, there
is a certain fixed amount of overhead involved (in getting tools, out,
cleaning up, etc.), I figure I will do my 90+% procedure less often than
you would have to do your less-than-50% change to get the same benefits
(in tranny life and performance), and due to the "overhead effect", will
save time overall. But yes - I probably do waste more fluid. But for
less total money than if I paid a shop to do it, I get a *lot* more
fluid to do with what I want, and get the benefit of a more thorough
change.

As far as the danger, I would not be under the vehicle during any of
this - I make the rubber hose long enough to do it all standing up
(except for the initial hookup).

That's it for me. We each look at the facts at hand and make our
decisions, and get the results good or bad. I am not saying your
philosophy is wrong. I'm just saying what feels right for me as one who
is arguably an obsessive-compulsive (as in "Hmmm - in the above post,
did I spell "shearing" right? Is it "procede" and "preceed", or is it
"proceed" and "precede", but I know it's "procedure"), but getting less
so as I get older.

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

 

Thanks Bill for your quick reply! I have heard of this procedure before,
but couldn't remember the exact steps to be performed; so thank you for
clearing them up for me

I will let my boss know and see what he wants to do. So far he is
keeping the van in town for a couple days to see how the tranny is
acting before he "re-assigns" it to "out of town duty." He may want me
to do it on a saturday, which is our oil change day for the vehicles.

I will post back if I perform this procedure. Thanks again!

 

This is the initial feeling I got when I read this procedure. After
thinking it over I will perform this on the van if I can get a helper. I
would rather not do it alone. I don't think he will want to put ATF +4
in it, but just keep the +3 stuff since we carry that in our store.

Thanks for your opinions and comments