The dreaded Transmission Flush

[mrrsm]

If you ZOOM in Deep on this Attached Image and Examine the Data closely, perhaps this ATF Compatibility Chart will reassure you that doing things your way to Flush and Replace the Old Dexron ATF will be Okay:


If your intent is to actually FLUSH out anything... it should be ONLY THE COOLER AND LINES by first isolating them away from the 4L60E Transmission and using a Can of Transmission Cooler Flush along with Compressed Air. This Method will NOT Introduce the Hidden, Clogged, Impacted or trapped Dirt, Metal or Old Friction Discs Material right back inside of your Transmission. This Video shows one of the Best Ways to do this:

 

[Mooseman]

I would recommend this instead:

Transmission Fluid Exchange (Flush)

 

[Stuntmanmike77]

I'll probably do a flush on it soon. Lot of fluid and money. Just wanted to replace that filter since it was rebuilt about 40,000 miles ago or so.

 

[Stuntmanmike77]

I know some things on these trucks are weird but, no sealer on the rubber gasket? Goes on dry I'm assuming.

 

[mrrsm]

At around 5:40 into this 20:05 Minute "Trailblazer/Envoy How to Change the Fluid and Filter in a 4L60E Transmission"... Eric "O" from South Main Auto demonstrates using some Amazing Permatex Non-Hardening, Super-Sticky Sealant Called "HIGH-TACK".

After spraying that Stuff around Only One Side of a pre-aligned OEM Rubber Gasket laying on some Sacrificial Cardboard (NOT on or inside of the Pan itself), he allows the Gasket to sit long enough until it slightly dries out.

Once it becomes "tacky", he carefully lays the Gasket around the perimeter of and matching Bolt Holes on this Spotlessly Clean ATF Tin Pan for added Leak-Proofing Insurance:

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Then, after Correctly Orienting the Pan, avoiding the snag that the presence of the Shift Cable Bracket will cause during its replacement, he gradually and evenly tightens down the myriad small Pan Fasteners by NOT using MAX Torque all at once against any One of the Fasteners.

By doing it this way, he prevents Crushing in or Dimpling the Metal Pan areas around each Bolt Hole. This also stops the Rubber Gasket Material from squashing down excessively and moving away from around each compressing Bolt.

Such aggressive over-pressure only serves to defeat the purpose and seal of the Gasket. This is one task where the expression, "Do NOT Over-Tighten the Fasteners..." really DOES mean something. Using a "Speed Wrench" can make this job EZR and more controllable and is a Very Handy Tool to have around:

 

[Stuntmanmike77]

So this is needed to do the job and won't damage the clutches like he says in the video?

 

[mrrsm]

Yes... replacing the Old Gasket with a Brand New one should be part of "Best Practices" regardless of which type of gasket gets used. Some people prefer using the Room Temperature Vulcanizing Silicone Rubber Gasket - In - A - Tube instead of following what they may believe are procedures using regular Solid Gaskets that are "Just TOO Laborious".

Nonetheless, ALL of these procedures will require having Clean, Dry Flange Mating Surfaces and there will always be some amount of "Elbow Grease" necessary to do this job right. Since Eric "O" NEVER sprays any of the Permatex High-Tack either onto or into the ATF Pan... nothing will settle in the bottom that can get picked up to clog up the Filter. Allowing for the proper "Cure Time" for ANY Specialty Adhesive during these applications is the Key to Success.

 

[Stuntmanmike77]

I'm using the rubber gasket that came with the AC Delco kit I bought. What I want to know is it absolutely necessary to use the spray tack or can I Install it dry?

 

[Mooseman]

Dry is fine. I never used anything. The tack is just handy to keep the gasket from moving. I use a few bolts that help keep it in place which the holes are just a little smaller.

 

[gmcman]

I know some things on these trucks are weird but, no sealer on the rubber gasket? Goes on dry I'm assuming.

Never had a leak with the OE rubber gasket.

Torque bolts to about half their spec at about 50 inch pounds, going around the pan. Then final torque to 108 INCH POUNDS.

I go around the pan about 3 times allowing the gasket to compress. 3 times at 108 INCH POUNDS and I've never had a leak.

 

[JayArr]

I don't know what that can of aerosol flush costs but an alternative is to get a refillable flush cylinder. They sell on eBay as "AC Flush Cylinder"

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You unscrew it fill it with whatever you want to flush with (I often use mineral spirits) and then you attach your air hose and flush. It's great for all kinds of lines and for shooting cleaning solution into corners and tight spaces. (reservoir tanks etc).

 

[Mooseman]

Here's a cheaper alternative, at least in Canada:

MR CARTOOL AC Flush Kit, Car Air Conditioner System Clean Canister Flushing Gun Tool Set with Spray Head Hook 3.5ft Hose Fitting for Air Conditioner Pipe, Condenser, Evaporator, Fuel Pipe, Air Conditioning Line Repair Tools - Amazon Canada

MR CARTOOL AC Flush Kit, Car Air Conditioner System Clean Canister Flushing Gun Tool Set with Spray Head Hook 3.5ft Hose Fitting for Air Conditioner Pipe, Condenser, Evaporator, Fuel Pipe in Air Conditioning Line Repair Tools.

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eBay is mostly US sellers and shipping charges are usually horrendous to Canada.

 

[Stuntmanmike77]

Dry it is. Thanks guys.

 

[Mektek]

Use the May03LT method for flushing out the old fluid you'll find on youtube - I do it everytime I'm changing the filter.
No need to dread the flush - it's not that hard. For a high mileage vehicle it's very worthwhile.

 

[JayArr]

Good video, it's basically a manual adaptation of what the professional machines do. New fluid goes into the pan, old fluid comes out the tube. Add new fluid until the output runs clear.

In the video he talks about the filter seal and how it's a pain to change so he doesn't. I saw a youtube video with a great hint that worked for me. Take a 6" 3/8 inch threaded iron pipe and it will thread into the seal, then take an elbow and another 4" of pipe. Wiggle the pipe around and/or tap on the 4" piece with a heavy pair of pliers and eventually the seal will come out. Took five minutes.