Adding / Changing Transmission fluid on FluidDrive

The owners manual calls for SAE-10W engine oil. Is there any problem with using the new "synthetic" oils for either adding of replacing the transmission fluid? How hard is it to access the port? It looks like the car needs to be on a lift to get reasonable access.

This subject has been covered extensively. If you do a search for Fluid Drive you will find much information including a couple of long threads from 2008.

To answer your question, ordinary 10W motor oil is recommended but many of us use TDH Tractor fluid, ISO 22 or 32 grade. This is available at Walmart, auto parts stores and farm supply stores. TDH stands for Transmission Differential and Hydraulic fluid. ISO22 is better but ISO32 is easier to get. There is not much diff between the 2.

There is a removable plate in the floor boards for Fluid Drive access. It is below the dash board, on the right side of the transmission tunnel. Roll back the carpet and you will see it. Remove the plate and you will see the bellhousing, with a round steel plug. Pry out the plug and you will see the Fluid Drive unit. "Bump" the starter using the key until the plug comes into view. Before you unscrew it, stuff a rag around the hole so the plug can't fall inside the bellhousing.

Get a funnel and pour in oil until it is full. There must be an air space for expansion, the hole is located so the oil will be at the correct level.

The transmission itself is serviced separately. It is easiest to get at from under the car, although there is another access plate in the floor, farther back than the first one.

On the side of the trans are 2 pipe plugs. The one on the bottom is for draining the oil. The one about half way up is the fill plug. Remove the plug and stick your finger in the hole, if you touch oil you are done. If not, pour or pump oil in until it drips out.

I don't know anyone who has used synthetic oil but some Fluid Drive units have gone for 70 years on straight mineral oil.

Thank you. I was informed by an mechanic that that the synthetic oils do not hold up as long.

Thank you. I was informed by an mechanic that that the synthetic oils do not hold up as long.

Alot of debate on synthetic lubricants.

If the manufacturer suggests changing the filter between engine synthetic oil changes because it doesn't break down like dinosaur oil it would contradict your mechanic.

One disadvantage to synthetics in old cars is that it is thin and tends to seep through any opening, which means any leaky seals or gaskets will leak worse, and you will get leaks where you never had any before.

In the Fluid Drive there is one critical seal that is very long lived, but very difficult and expensive to replace. For this reason alone I would not use synthetics.

Plus, the Fluid Drive only had one moving part and the friction involved is minute. So the main advantage of synthetics, reducing friction, becomes meaningless.

The second advantage, standing up to higher temps, is also meaningless. The Fluid Drive gets hot but nowhere near as hot as a modern engine. Chrysler had NO recommendation for ever changing the oil in a Fluid Drive. Since it never gets too hot the oil never breaks down, and since it is a sealed unit it never gets dirty. So you never need to change the fluid, just top it up every 25 or 30 years, if necessary.