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TO FLUSH OR NOT TO FLUSH?

dhalltoyo

dhalltoyo

Veteran Expediter
I have heard conflicting opinions about transmission flushing.

My local GM dealer offers this service.

Basically, they drain the fluid, flush it internally with a chemical solution, drop the pan and replace the filter and then add 11 quarts of Dextron IV.

One reply to this question on the Diesel page indicated that you are creating a reverse flow during flushing and therefore you pushing crud out of the filter only to send the junk back through the valve body.

What do you think?
 
rode2rouen

rode2rouen

Expert Expediter
>I have heard conflicting opinions about transmission
>flushing.
>
>My local GM dealer offers this service.
>
>>snip<<
>
>What do you think?


A more pertinent question would seem to be: What does Allison think?


Rex
 
dhalltoyo

dhalltoyo

Veteran Expediter
The tranny in the 2006 GM cargo vans with a Duramax Diesel is a GM Hydromatic 4L80E, so every dealer seems to recommend transmission flushes.

If you can get a hold of anyone at GM to ask them a question, be my guest.

I am open to suggestions that will help me make an informed decision.
 
Deville

Deville

Not a Member
NEVER EVER FLUSH A TRANSMISSON, DRAIN,REFILL & CHANGE THE FLITERS! THAT IS IT, THESE FLUSHES ARE USELESS AND CAUSE MORE PROLBEMS IN THE LONG RUN
 
rode2rouen

rode2rouen

Expert Expediter
>The tranny in the 2006 GM cargo vans with a Duramax Diesel
>is a GM Hydromatic 4L80E, so every dealer seems to recommend
>transmission flushes.
>


Oops, my bad!!! I assumed a truck with an Allison.
I'll go away quietly.


Rex
 
highway star

highway star

Veteran Expediter
Owner/Operator
I don't think you're going to end up with any kind of concensus on this one. I go with the filter change, I've never had it flushed. Some, including the much respected Dieseldoctor, say to just leave it alone.
 
dhalltoyo

dhalltoyo

Veteran Expediter
I guess flush is the wrong terminology.

The device cycles a chemical wash through the tranny system to loosen any debris, slug, varnish, etc.

Next, new fluid is added to remove all the chem wash out of the tranny system.

Then the pan is dropped, wiped clean and the filter replaced.

Finally, more new fuild is cycled until the outflow shows perfectly clean new fluid.

I have spoken with a Master Mechanic who has done an automotive radio talk show every Saturday morning for years here in Dayton and has his own Auto Repair Center. He changes his own tranny fluid with this method every 30,000 miles.

He said that if I were to only drop the pan to drain the fluid it would only loose 6 to 7 quarts. The torque converter would still be holding another 6 quarts of old fluid.

A GM Master Tech with 22 years of experience agreed with that statement and he also believes in using the above method to change the fluid.
 
U

unorthodoxneon

Expert Expediter
I know at my local dodge dealership they drop the pan and change the filter what they also do is take a hose and put it in the torque convertor and suck the rest of the fluid out of there. they fill the tranny back up, adjust all the bands and check the sensors and send you on your way $300 later

My question is when was the last time the tranny was serviced? If its got alot of miles on it and your want to do this all of a sudden i wouldnt and just let the tranny die out then replace it later then sooner cause if you put in new fluid and filter you are probably just going to blow out the seals and need a rebuild quick.
 
dhalltoyo

dhalltoyo

Veteran Expediter
Van just turned 65K.

GM manual says 100K on fluid changes unless towing or taxi type service with a lot of stop and go driving.

I drive like an elderly lady. Rarely over 62mph, very slow and even starts from a stop, no passing gear accelerations, complete stops and a pause before shifting into reverse; set parking brake, chock wheels, and leave in neutral when being loaded or unloaded, etc....

Fluid was very clear and odorless at 65K.
 
greg334

greg334

Veteran Expediter
David,
A bit of advice.

If the trans is not subjected to high load and high heat, 100K would be a minimal oil change cycle – you may be able to go as long as 150K. My Dodge had 200K on it before I changed the oil and the oil analysis came back clean before I changed it.

The key to longevity of the trans is keeping the heat down which prevents the oil from burning. Burnt oil indicates a lot of problems and will cause a lot more.

If you check your trans fluid every oil change and it does not smell burnt (remember it will look dirty after a while), than you are safe but if it smells burnt, change it with a filter ASAP. You will always get particles on the bottom of the pan but as long as they are not a lot of good size aluminum particles, this may be normal.

As for flushing, I have a friend at GM who puts these transmissions through all kinds of h*ll and he says he will never have the trans flushed because it can crude up things that you can not get to unless you rip the trans down.

Now if you ever have you trans rebuilt, get a new torque converter and have all the cooler lines flushed.

The way you describe how you drive, I would not worry about it. I would guess that you will do no harm as a granny driver because these transmissions are build to take the torque of the Duramax.
 
B

Broompilot

Veteran Expediter
I have had this done to my personal PU a Silverado Transmission has never given me a bit of problem and I used this vehile for Towing a trailer around for Joe Gibbs Racing for years.

Also check on this special that GM offered me. Any Fluid they changed which was Oil, Trnamssion, and Coolant covered every working part these chemicals touched for an extneded warranty as long as they did a schedule maint to the vehicle. So if the Radiator sprung a leak, it was covered under this extneded warranty for replacement.

It was a little pricey, but got to admitt I never have seen with this truck a single breakdown. Its not a commercail vehicle but they did know its work history at the Dealer.

Ask and see if they still offer this special.
 
U

unorthodoxneon

Expert Expediter
Best thing to do is to have the fluid changed. I always feel preventative maintance is better then hind sight, also when they do the change they will be able to see if there is any problems with the tranny that you cant smell or see on the dip stick.
 
Moot

Moot

Veteran Expediter
Owner/Operator
There is an old Northern Minnesota (where the frost line can exceed 10') saying among home owners with septic tanks. If it's brown flush it down, if it's yellow let it mellow.

How that helps.
 
B

bryan

Veteran Expediter
HI

I agree with flushing the system, the problem is the machine they use really does send all the band shavings through the valve body.You can flush the system without having this problem by draining the pan, putting it back on then remove the return line from the cooler.then start the truck and add fluid untill you get clean fluid out of the return line.You will use 2 to 3 more guarts of fluid this way, but its alot cheaper than rebuilding the tranny a week after it was chemically flushed.

I don't know about Chevy's, but you can get a Ford torque convertor that has a drain plug. When I had my tranny rebuild in Feb. I had them install this torque convertor.Its a little pricey but I feel its worth it. This way I just remove the pan and then take off the inspection cover and have someone bump the key untill the tc plug is at it's lowest point, remove the plug and remove and clean the tranny cooler.This way I know that I have replaced all the old fluid.
 
cheri1122

cheri1122

Veteran Expediter
Driver
What a timely topic - guess whose Dodge van is getting a transmission rebuild at this very moment, just a few weeks after having a flush? What bothers me most, (besides the bill, of course), is the wondering: did the flush create the problem? The mechanic said he's had to rebuild Dodge trannies at half the mileage on mine, (167k), and I really want to have confidence in his integrity, but I didn't have any transmission issues before the flush, and I drive pretty much like DHalltoyo, except I set my cruise 5mph higher, so is there any way for me to determine the truth? Or, do I just have to have faith?
 
B

bryan

Veteran Expediter
Hi
Cheri ask to see the torque convertor and the valve body.The inside of a transmission is exceptionally clean.Like polished chrome.So seeing band shaving is really pretty easy.Also check out thedeiselstop.com do a search on tranny flushes.When you look at the torque convertor you are actually looking at the fluid that comes out of it.By the way ask your mechanic if they are putting in a plastic torque convertor or a steel one.The plastic ones do not hold up to 10 to 14 hours of constant heat.They are great for most vehicles but can't handle what we do.
 
cheri1122

cheri1122

Veteran Expediter
Driver
Neither was Moot, apparently - but I heard the severe cold in Minnesota can do strange things to your brain...:p
 
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