Can I Use DOT 5 Brake Fluid Or Stick To DOT 3 Or DOT 4 On Demco Brake Actuators?

Question

Question:

Can I use this with DOT 5 brake fluid? thx, Lee

asked by: Lee

0

Expert Reply:

Good question Lee. Most people don't think about fluid compatibility, but it's important.

Demco actuators like the DA75 Trailer Brake Actuator - Zinc - Disc # DM33CV are technically compatible with DOT 5 fluid, but only when it's new. It CANNOT be mixed with other fluids since it's a silicone-based fluid.

It's best to stick with standard DOT 3 or DOT 4, both of which are compatible with the internal seals and materials and can be mixed together. These can be found at any auto parts store and most gas stations.

What trailer are you putting this on?

expert reply by: Andrew N

0

Demco DOT
(click to enlarge)

Andrew N.

8/15/2025

Hey Lee, did you decide to go with DOT 3 or DOT 4 fluid for your trailer? I'm curious to know how it worked out for you since it helps me assist others in similar situations.

Answer 1

In order to determine the torque rating for the lug nuts on your trailer you will need to know check out the chart I attached that shows all of the torque specs for all the trailer lugs available based on stud size, wheel material and wheel size.

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Answer 2

The #84 spindle is just a common way to identify the spindle dimensions typically used for 3,500 lb axles. So instead of listing out the parts, people can just say they have #84 spindles and it's easier to know what fits it. The CE Smith Trailer…

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Answer 3

It sounds like you are speaking of the wires for the brake magnets. If this is correct, you will need to connect one of the wires to the brake controller output wire on your trailer connector and the other wire will need to be grounded to a clean…

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Answer 4

Even though I cannot comment specifically on the grease you used because I am not familiar with it, I can tell you the best grease for trailer bearings is a a grease with a rating of GC-LB, which just means it is made to withstand very high…

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Answer 5

Trailer wheel bearings are specific to the spindle that is installed on the axle that is on your trailer. You will need to safely support the trailer, remove the wheel and tire, remove the grease cap, remove the cotter pin and washer that secures the…

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Answer 6

To determine the size of the brake assemblies you need you have to measure the depth and width of the hub drum on the axle like what you see in the picture I attached. The most common size is 2-1/4 inch wide like the #T4071600-500 that you…

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Answer 7

That's a very good question, we tend to be extra cautious and say to use 10 gauge wire because that would be more than enough. When you get into longer trailers that will end up using a lot of wire the heavier gauge wire becomes more necessary.…

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Answer 8

There typically aren't any part numbers stamped onto the trailer spindle that can be used for identification. There are however numbers stamped onto the hub most times which can be used for identification. The TDE46210 tells me you have a 3,500…

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Answer 9

The Easy Grease Trailer Idler Hub Assembly for 3.5K Axles part #AKIHUB-545-35-G-EZ-K is a direct replacement for a UFP H-1377.

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Answer 10

The BTR and BT8 denotations refer to the spindle, not the trailer hub. The difference between a BTR and BT8 spindle is that the BTR spindle uses a 1.063" diameter L44649 bearing and the BT8 spindle uses a 0.99" diameter L44643 bearing. In…

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Answer 11

You will need to measure the diameter of the spindles where the seal and bearings ride. Check out the picture I attached that shows where this is. You will need an exact measurement so either a digital or dial caliper will be needed. To pick out the…

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Can I Use DOT 5 Brake Fluid Or Stick To DOT 3 Or DOT 4 On Demco Brake Actuators?

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