Transmission Fluid Recommendations

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Old November 3rd, 2018, 06:28 PM
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Transmission Fluid Recommendations

Getting a 1970 Cutlass Supreme project car with automatic transmission. One of my first task will be to change the transmission fluid and filter.

Any recommendation for the brand/type of fluid to be used in this 1970 transmission?

Are the fluids, such as Castro High Mileage fluid good for this older transmission?

Should the fluid in the torque converter also be changed?

Any other advice on servicing this transmission?

thanks,

Pat

Last edited by jpatfarrell; November 3rd, 2018 at 06:47 PM.
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Old November 3rd, 2018, 06:52 PM
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Use a Wix filter or NAPA Gold. They are one in the same and are the best.
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Old November 3rd, 2018, 07:13 PM
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thanks redoldsman!
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Old November 3rd, 2018, 08:27 PM
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The only way to get the fluid out of the converter without removing the trans is to disconnect the return line from the trans. Use some rubber hose to catch the fluid in a 5 gallon bucket. Start the car, once the bucket has a gallon of fluid,dump another gallon in. Repeat the procedure until the fluid comes out clean. Replace the filter, refill with fluid, call it good

if that’s too much expense in fluid, remove the pan, let the trans drain for a while. Replace the filter, refill, and don’t worry about it. If the tens was working ok you shouldn’t have any issues.
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Old November 3rd, 2018, 11:06 PM
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Agreed. Typical trans service is drop pan, drain fluid, replace filter, fill with ~5 quarts (system holds ~11 quarts? total). If the fluid is totally burned (dark color) then complete fluid replacement is warranted, per above procedure.

Any brand Dexron II compatible fluid will work, These days, it's Dexron 4 or 5, I forget what number it is these days.
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Old November 4th, 2018, 04:30 AM
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Originally Posted by matt69olds
The only way to get the fluid out of the converter without removing the trans is to disconnect the return line from the trans. Use some rubber hose to catch the fluid in a 5 gallon bucket. Start the car, once the bucket has a gallon of fluid,dump another gallon in. Repeat the procedure until the fluid comes out clean. Replace the filter, refill with fluid, call it good

if that’s too much expense in fluid, remove the pan, let the trans drain for a while. Replace the filter, refill, and don’t worry about it. If the tens was working ok you shouldn’t have any issues.
I took a transmission class years ago at a community college. The old guy instructor used to drill a hole in the torque converter and drain all the fluid. Then he tapped it and installed a brass plug. We did it to at least one car in class. That was what he did at his transmission shop when a car came in for a transmission service. I personally think that isn't necessary. It always seemed to me if a transmission is having internal problems it's too late for a fluid change to help. I have always just used the cheapest atf I could find that meets the requirements of the manufacturer.
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Old November 4th, 2018, 04:44 AM
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This is all good and helpful info. Didn't think changing the torque converter fluid was really a necessity if the trany is working ok.

thanks,

Pat
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Old November 4th, 2018, 05:52 AM
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[QUOTE=Greg Rogers;1134762]I took a transmission class years ago at a community college. The old guy instructor used to drill a hole in the torque converter and drain all the fluid. Then he tapped it and installed a brass plug. Unless my memory is worse than I thought......Back in the day, didn't Ford's have a drain plug in the converter?
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Old November 4th, 2018, 07:00 AM
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Originally Posted by Dave26
Back in the day, didn't Ford's have a drain plug in the converter?
Yes they did.

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Old November 4th, 2018, 07:10 AM
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The converter in my 70S had a drain plug but I could not get it out, check for one, mine had a square head plug.
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Old November 4th, 2018, 10:29 AM
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I wouldn’t want to drill holes in a converter!!! Nothing good can come from the small amount of shavings a drill and tap will leave behind. And if you have ever seen the inside of a torque converter, there isn’t any room to spare. If you tap that hole too deep, that plug screws in too deep and contact the turbine, the converter AND trans will need replaced or overhauled. Or the drill bit hitting one of the blades, once again hitting the turbine, posdible balance issues, all the aforementioned concerns with the turbine also apply to the converter pump, all around bad idea.

Seriously, if the fluid is cooked enough that a total replacement is needed, the trans is pretty tired and soon will need more work than a fluid and filter change can fix. Either use the method I described earlier, or just change the filter and what fluid you can until further service is needed. TH350 are pretty durable.
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Old November 4th, 2018, 01:38 PM
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Be sure you know if you have the 350 or 400 transmission.
If it has a filter, change it. If it has a strainer (screen), change it or clean it.
If the converter has a drain plug, drain it also. Every Hydramatic and Fordomatic I worked on had one. If it doesn't have one, leave it as is.
Use Dexron fluid from a reputable manufacturer.
Use a new pan gasket and straighten out the pan's bolt holes if they are distorted.
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Old November 4th, 2018, 08:32 PM
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I think you're going to find that most of the transmission fluids these days suitable for our old cars are labeled "DEX/MERC" like these.















Read the back side, and it will tell you this.



As long as the car is 2005 model year or earlier, Ford or GM, you should be fine. I've been using fluids labeled this way for several years now as that's all I can find at the local auto parts store. I've had no problems. There's no more bottles labeled simply "Dexron II" or "Dexron III" like there might have been 10 or 15 years ago that I can find.
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Old November 6th, 2018, 04:19 PM
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I currently have a tractor trans hydraulic fluid with just enough Type F to colour it. One of the reasons I switched is it a 5W30 weight in synthetic, 10w30 in conventional. I have had endless issues with transmission's leaking somewhere no matter how many seals I replace, I haven't added a drop to this TH350 with this fluid. I have had to add some Dexron 3 to my 2004R, I topping it up Transhydraulic fluid from now on.
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Old November 24th, 2018, 02:04 PM
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i've been using this stuff. Mostly because it came recommended and it is less expensive than real trans fluid.
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Old November 24th, 2018, 03:30 PM
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A lot of people have been going with type F for a performance application.
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