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Silverado & Fullsize Pick-ups The Silverado has been one of the best selling trucks in the US for decades, and is truly proven to be "like a rock".

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Old 07-12-2010, 09:16 AM
CF Junior Member
1997 Chevrolet C/K 1500
Join Date: Jul 2010
Posts: 55
Default Transmission Fluid change. Drain/Fill or Flush? What type of oil?

I have heard so many bad things about flushing transmissions. This truck has over 261,000 miles on it and not sure about flushing... I think I would rather them drop the pan to clean it out.

So should I just have it drained and filled? Has anyone had issues with flushing? I have no idea when the transmission was serviced last.

Sounds easy to do myself by loosening up the bolts on the pan and having it drain out...?

What is a good transmission fluid I should use?

Thanks for the help guys.
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Old 07-12-2010, 09:46 AM
CF Beginner
Join Date: Jul 2010
Posts: 19


In early 2005, General Motors released a newly developed automatic transmission fluid (ATF) for the factory fill of all GM Powertrain stepped-gear automatic transmissions. The new fluid provides significantly improved performance in terms of friction durability, viscosity stability, aeration and foam control and oxidation resistance. In addition, the fluid has the potential to enable improved fuel economy and extended drain intervals. Because the performance of the new fluid far exceeded that of the DEXRON-III service-fill fluids available at the time, it became necessary to upgrade the DEXRON service-fill specification in order to ensure that similar fluids were available in the market for service situations. This latest upgrade to the service- fill specification is designated DEXRON-VI (fig. 1).

Since General Motors introduced the first ATF service-fill specification in 1949, it has been necessary to upgrade the specification periodically.

The upgrading process ensures that available service-fill fluids are of an appropriate quality for use in transmissions that have been designed around the factory-fill fluid performance.

TIP: As with previous upgrades, DEXRON-VI fluids are designed to be backward compatible with earlier transmission hardware. More importantly, earlier type fluids are not forward compatible with transmission hardware that was designed to use DEXRON-VI fluid.

DEXRON-III is not compatible with the most recently designed transmissions, and the use of these earlier type fluids could result in transmission damage. All current calibrations and certification tests are now conducted with DEXRON-VI ATF. DEXRON-III fluids should not be used for those applications where the owner manual recommends the use of DEXRON-VI.

TIP: GM does not license or support obsolete ATF specifications or the use of fluids that are being marketed against cancelled specifications.

All DEXRON-III licenses expired at the end of 2006 and will not be renewed. Beyond that date, GM will support only DEXRON-VI fluids for use in Hydra-Matic transmissions. Avoid fluids sold in the market after that date bearing claims such as “suitable for use in
DEXRON-III applications” or similar wording. DEXRON-VI licensed fluids are fully backward compatible and can be used in all applications covered by earlier GM ATF specifications.

The use of unlicensed fluids and/or non-GM approved aftermarket additives may prove detrimental to transmission performance and void warranty coverage.

- Thanks to (Name Removed)

Precaution: DEXRON-VI in Manual Transmissions

When DEXRON-III is indicated as the fluid fill for manual transmissions and transfer cases, DO NOT use DEXRON-VI. Instead, use GM Manual Transmission Fluid p/n 88861800 in these components.

TIP: Refer to PIP3836B (Feb. 2007).

If the manual transmission or transfer case indicates use of DEXRON-VI, then, of course, it should be used.

Purging Equipment

Before filling your bulk fluid equipment with DEXRON-VI, be sure to purge the old oil from it.

Also, be sure to purge your J-45096 Transflow machine before using it with DEXRON-VI.
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Old 07-12-2010, 07:36 PM
CF Active Member
Join Date: Feb 2008
Posts: 121

with that many miles i would just drain and replace filter and refill with std trans oil for the vehicle. Then repeat this procedure in 10K, do this twice and you wil have most of the oil changed.
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Old 07-12-2010, 08:22 PM
MDTAHOE's Avatar
Super Moderator
Professional Mechanic
Join Date: Nov 2008
Location: Bowie, MD
Posts: 2,955

As long as you are having no problems with the trans and the fluid does not smell burnt the Flush, Flush, Flush. Dropping the pan only changes a small % of fluid. I have flushed hundreds of transmissions without a problem.

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Old 07-12-2010, 08:22 PM

2005, 99, atf, change, chev, drain, fill, fluid, flush, hd, malibu, montecarlo, oil, trans, transmission, type

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