Transmission flush

**Restlessone** · 08-18-2009, 03:08 PM

I would like to hear opinions on when and if you should flush out the transmission and put in new fluid. This my first auto so I have no experience with auto transmissions.
I just purchased an 07 sliverado 4x4 with 72,000 km (45,000 miles). I'm being told by "people" that it is overdue for a flush. Is this true, what fluid is favoured?
Thanks
Gordon

**99'HEARTBEAT** · 08-18-2009, 03:20 PM

For my ride,I do a Flush every 30K,or there about.I tow a boat during the Summer.I just feel better knowing that I have done all I can to keep My Trans Running Strong.With 72K miles on your trans I would said it is Due for a Flush and new Filter.

**Jimmiee** · 08-18-2009, 03:34 PM

The word "flush" is a misnomer and should not be taken in the literal sense. A true flush where chemicals are used should never be done as it can cause problems by swelling seals and dislodging debris which can doom a perfectly working transmission.

What transmissions need is servicing. If servicing is done on schedule there is no need to flush or change all the fluid. The average transmission holds 10 - 14 quarts. A service only replaces 4 or 5 quarts along with the filter.

If your transmission has been neglected and the fluid is turning dark brown then a "flush" or fluid exchange is in order. This can be performed at home with a length of rubber hose and a 5 gallon bucket. This method although messy at times replaces all the fluid just as a fancy machine does at a repair shop or quickie lube.

Always drop the pan and change the filter before flushing the system. Once the filter is changed and the pan replaced the procedure is as follows:

Remove the return line from the trans at the radiator. Ususlly but not always the top line.
Attach a rubber hose to the outlet and into a bucket.
Fill the trans with 6 quarts of fluid.
Start the vehicle and as the old oil comes out add oil to the transmission a quart at a time.
Note that the new oil is picked up into the filter and displaced into the torque converter. So the oil you remove is a 50/50 mix of old and new oil. A dirty transmission may take 15 or more quarts of oil to get the oil clean and red looking.

**99'HEARTBEAT** · 08-18-2009, 03:37 PM

Very Good Infor!!!!....... Jimmiee

**Jimmiee** · 08-18-2009, 03:51 PM

Originally Posted by 99'HEARTBEAT

Very Good Infor!!!!....... Jimmiee

Awww shucks!!!!!

Thanks!

**99'HEARTBEAT** · 08-18-2009, 03:53 PM

Originally Posted by Jimmiee

Awww shucks!!!!!

Thanks!

Well All I know is that if I have a Problem with my Trans,I'm talking to you 1st.

**Restlessone** · 08-18-2009, 10:10 PM

I don't think the transmission has been neglected. The manual calls for servicing at 80,000 KM and I'm only at 73,000 KM. I just wondered what conventional wisdom was.
Thanks for the input.
Gord

**2COR517** · 08-18-2009, 10:34 PM

As usual, Jimmiee is right on the nose. If you have enough hands, you fill through the dipstick you pump out the old.

**nos351wcm** · 08-27-2009, 10:24 PM

what fluid should be used? i have 105,xxx miles on my 2000 1500. the trans could use a "flush." also how many quarts should i get? thanks
Cheers from NJ

**Jimmiee** · 08-28-2009, 07:51 AM

Originally Posted by nos351wcm

what fluid should be used? i have 105,xxx miles on my 2000 1500. the trans could use a "flush." also how many quarts should i get? thanks
Cheers from NJ

Use a good Synthetic that's Dextron compatible. To get brown / amber looking fluid red again you will need about 15 quarts. You can stop at 10 or 12, whenever the fluid turns red. The darker brown the fluid is the more clean fluid you will need. I have seen a bad 4L80E use 22 quarts to get it clean!