C6 tranny partial fluid replacement

[pacem]

89 F250 "Heavy duty". Sometimes towes 9,000 lbs.

The last owner told me I had another 15K miles to go until transmission service, but I want to do one of these partial fluid replacements (vs. a full flush)

That is, drop the pan, replace the lost fluid and the filter.

I want to examine the pan. What's the absolutely best synthetic fluid to use for heavy-duty towing? Filter? I want to mix the synthetic with what's already there, as far as I understand, that won't cause any problems.

My second question is, where can I get a pan which is like the oil pan - loosen the bolt and the fluid comes out, instead of undoing 16 bolts with RTV.

 

[MolaKule]

Is the C6 speced for Mercon-V?

 

[heyjay]

I still have my 1984 Ford F-150 with 302 and C6 that I bought new.

My C6 has a tiny drain plug in the torque converter. Use a bump switch to bump over the motor until you see that bolt and take it off.

It takes forever to drain, but you get 99% of the ATF out. I wouldn't waste money on a "flush" like the MotorVac TransTech unless your C6 had a sealed torque converter. Or unless your C6 was really trashed up.

 

[therion]

quote:

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Originally posted by pacem:
89 F250 "Heavy duty". Sometimes towes 9,000 lbs.

The last owner told me I had another 15K miles to go until transmission service, but I want to do one of these partial fluid replacements (vs. a full flush)

That is, drop the pan, replace the lost fluid and the filter.

I want to examine the pan. What's the absolutely best synthetic fluid to use for heavy-duty towing? Filter? I want to mix the synthetic with what's already there, as far as I understand, that won't cause any problems.

My second question is, where can I get a pan which is like the oil pan - loosen the bolt and the fluid comes out, instead of undoing 16 bolts with RTV.

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Yes, most synthetic ATF's are 100% compatible with petrol fluids. The 2 best ATF's on the market are Amsoil Synthetic ATF & SynLube both are approved for your Mercon spec transmission. I just changed my ford truck to Amsoils ATF and it shifts much smoother, Althought i did mine on the TTech machine which got all of it out for just $40 + the ATF at the local mechanic.

 

[heyjay]

I would still check to see if your '89 C6 has a torque converter drain plug. There is a shield between the torque converter housing and the motor that is fairly easy to remove.

Use a bump switch from underneath to keep bumping the motor while watching the converter. If you see a little bolt that points forward towards the motor, that's the drain plug.

By dropping the pan and draining the torque converter, you'll get out +95% of the fluid. Just be patient with the torque converter, mine takes a good 5 minutes to drain.

Jerry