Opinions on Transmission Fluid Changes
 

The fluid in my 84 K/10's trans is dark and recently I've noticed a weak shift from 1st to 2nd under light throttle. I've been hearing some conflicting opinions on whether or not changing the fluid is good or bad. I have heard fluid FLUSHES are to be avoided, but I'm talking about a new pan gasket, new filter, and letting as much of the fluid that wants to drain out to drain out. Then replacing what came out with fresh fluid. Should I go ahead and do the trans service or is it best to be left alone to not ruin any existing seals inside the trans?

Re: Opinions on Transmission Fluid Changes
 

I have always gotten different opinions also.

I would do what your planning on changing. Its sounds like its in need of something anyways. Do it and start looking for a replacement t350? or tranny shop, just incase.

Re: Opinions on Transmission Fluid Changes
 

Drain it, put in full synthetic ATF, and add a bottle of this stuff.
http://www.summitracing.com/parts/atp-at205

Re: Opinions on Transmission Fluid Changes
 

The reason you hear conflicting opinions is what happens when you change the fluid you take away the friction particles from the fluid that it is using the keep the clutches from slipping.The clutches are wore out. If you change the fluid it removes what it is using to keep the clutches from slipping. Thats why you hear of people changing the fluid and the trans no longer will shift or work. I would not change the fluid until you decide to get another or time your rebuild. Its only a matter of time. New fluid will not fix your problem. It will most likely make it worse.

Re: Opinions on Transmission Fluid Changes
 

I tend to agree with Homemade87.. if you regularly change the fluids since you put in a new trans every 24-30K you would be ok but once you start experiencing weak shifts or the fluid is burnt, you will only hasten the death of the trans

Re: Opinions on Transmission Fluid Changes
 

If it's a TH350, Drop the pan (Save the Fluid), If the pan is full of Mud, Clean the pan out, Replace Filter. Strain old ATF with a rag & refill...Top off with fresh fluid. Save up for a rebuild. No sense in leaving a filter in that is most likely clogged.

Let us know if you have a 700R4, Several things can cause a soft 1-2, 90% of them can be fixed without pulling the trans.

Re: Opinions on Transmission Fluid Changes
 

I'm pretty sure it's a 700R4, it's a 4-speed w/ overdrive. My 76 Cadillac had a THM350 and I remember it being a 3-speed.

Re: Opinions on Transmission Fluid Changes
 

I would plan on changing the fluid and filter. My guess is most failures that are blamed on fluid changes are due to the transmission finally failing due to neglect or just plain being wore out. On the other hand, not changing the fluid just continues the neglect problem.

Before doing anything, research the fixes clinebarger mentions as they may require dropping the pan anyway.

Re: Opinions on Transmission Fluid Changes
 

^This. Speaking from experience, save your money for the rebuild. Changing the fluid will only compound your problems.

Re: Opinions on Transmission Fluid Changes
 

I've used auto paint filters to filter ATF used in my plow pistons.
hadn't thought of the tranny but I've replaced burnt fluid and filter that i could get out before,
but then no go.(got it rebuilt)
BTW (paint filters) work on cooled deep fryer grease too lol

Re: Opinions on Transmission Fluid Changes
 

Drop the pan, If there is a lot of Clutch debris or Metal, Time for a rebuild!
Unlike TH350/TH400....700R4's run clean until they are ready to fail.

If the pan is fairly clean, Check you TV cable adjustment (I have posted on this several times in the Engine & Drivetrain section).

If TV adjustment is OK, Remove the 1-2 Accumulator Housing, Check for a Broken Accumulator Spring, & Holes in the Separator Plate, Yes, The Spring can wear a hole right through the plate.

Re: Opinions on Transmission Fluid Changes
 

Fluid flushes are great if they are performed correctly and if you are using good product. Find a BG certified shop http://www.bgfindashop.com/locator/index.php

Re: Opinions on Transmission Fluid Changes
 

All right, I appreciate all the advice and opinions given here. I think I'm gonna go with what Clinebarger recommended and check for metal in the pan. I'll change the filter/pan gasket for fun and go from there. If it looks beat then I'll put the old fluid back in and just ride it out. What do you guys think, good plan?

Re: Opinions on Transmission Fluid Changes
 

Sounds good to me , Clinebarger helped me get a700r4 installed and all setup correctly in my 77 P10 with a 292 6 . He's not going to steer you in the wrong direction with what to do

Re: Opinions on Transmission Fluid Changes
 

Everyone on here gave great opinions and insight to what my problem could be and how to deal with it. Clinebarger's info happened to encompass the best of both anti-fluid change and pro-fluid change specific to what trans I have so I liked what he said. I'm all too familiar with TV cable maladjustment having dealt with that on my Fleetwood Brougham's 307+200R4 combo.....

Re: Opinions on Transmission Fluid Changes
 

I have a Summit Th350 with very little miles I bought from another. I dropped the pan to install a Lokar Dipstick. The fluid is nice fresh and clean. The only problem is I don't know what kind of fluid to put back in it.
It still has fluid in the Torque Converter, so I guess my concern is if it matters that whatever is in it needs to be the same or not?

Re: Opinions on Transmission Fluid Changes
 

Anything Dexron III certified will be fine.

Re: Opinions on Transmission Fluid Changes
 

I see there is different Types such as Type F.
What Type should I use?

Re: Opinions on Transmission Fluid Changes
 

For the TH700R4 TH400 TH350 4L60 4L80 3L60 or 3L80 in good condition fill with Dexron VI.
There is no such thing as Dexron III certified anymore. In 2006 GM stopped buying and licensing it so there's no guarantee it's Dexron III anymore because the fox is watching the henhouse.

Here's GM Tech Service Bulletin 04-07-30-037D on the "new" Dexron VI transmission fluid. Our trucks fall into the "2008 and Prior GM Passenger Cars and Light Duty Trucks" category...
It's worth reading the recommendation to not use Dexron VI in Power Steering, Manual Transmissions, and Transfer cases that originally called for Dexron III. It obviously doesn't apply to the SM465 or the NP203 & NP205 transfer cases that had other fluid recommendations.
The GM recommended juice is noticeably less expensive than the Exxon Mobil product I would trust.

"The content of this bulletin does not apply to manual transmissions or transfer cases. Any
vehicle that previously required DEXRON®-III for a manual transmission or transfer case
should now use P/N 88861800. This fluid is labeled Manual Transmission and Transfer Case
Fluid. Power Steering Systems should now use P/N 9985010 labeled Power Steering Fluid."

Re: Opinions on Transmission Fluid Changes
 

Dexron VI is expensive, and in my opinion, a complete waste to run in a 700R4 or an TH350/TH400.

Something that says it's suitable to use in a transmission that called for Dexron III originally will be perfectly fine and acceptable, even Wal-Mart Supertech. Heck, even a lot of the big name trans guys have no qualms with Supertech. There is no need to spend the big bucks on Dexron VI unless you are running a late model trans, in my book. You can get a gallon of Dexron III compatible Supertech for $15 or so. I've been running it in my GM autos for years without a single problem.

Re: Opinions on Transmission Fluid Changes
 

My transmission guy said the fluid type doesn't really matter, the main difference he said was some fluids grip differently. He always ran Ford fluid in his GMs to make them shift harder. The GM fluid allows some slippage for smoother shifts.

That being said I just run Dexron whatever from AutoZone.

Re: Opinions on Transmission Fluid Changes
 

UMMM... NO. Not more expensive. Exactly the same price.
http://www.walmart.com/browse/auto-t...d:Super%20Tech
The WalMart Supertech Dexron VI is licensed just like everything labeled Dexron VI. It's the same $4.27/qt as the Multi-Vehicle Dexron Mercon. Super expensive stuff there.:lol::lol::lol:

Fair enough, it's been a few years since I looked at dex vi. Used to be a lot more expensive.
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Re: Opinions on Transmission Fluid Changes
 

A lot more GM rigs on the road that came with Dexron VI now. Demand is up so supply is up and price is down. The inverse is true of Dexron III.
Dexron III compatible price isn't likely to stay even with Dexron VI for much longer.

Re: Opinions on Transmission Fluid Changes
 

I have always changed/flushed auto trans oil in my own shop. I pull the pan, change filter and reinstall. Pour in a gallon of new ATF, and remove the lower trans line from radiator. I than slide a short piece of rubber hose on line , and put into drain pail. Start the truck, and let fluid pump from line into pail until clean , red fluid appears. Reinstall line on rad, and refill trans to correct level. Maybe not quite as effective as a professional flush, but works and saves you a few bucks.