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Old 01-18-2025, 02:43 PM   #1
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Checking differential fluid on Powerglide

Can someone tell me which plug is used to check the fluid level? I'm guessing the inset one on the bottom since that is what they look like on a car.
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Old 01-19-2025, 02:13 PM   #2
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Differential plug should be on the top third of the differential, not the bottom.
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Old 01-19-2025, 02:16 PM   #3
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Quote:
Originally Posted by Warhorse6 View Post
Differential plug should be on the top third of the differential, not the bottom.
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Old 01-19-2025, 04:03 PM   #4
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the lowest one is a drain plug
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Old 01-19-2025, 06:03 PM   #5
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No, the oil level should be about a third full to something less than half. The oil level will be just above the inside of the axle tubes, so it will reach each end, they're roughly 1/4-3/8" thick. The drain should be on the bottom of the differential, not the ones shown in the pic. This is probably a modified axle that has the original plug for installation with a front engine, and the new one added for a rear engine. The plug that is closest to the level of the bottom tubes is the correct oil level, the upper plug would be that level if the axle was flipped.
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Old 01-19-2025, 06:28 PM   #6
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One looks too high to me and one too low :-(. On my coach, I'm pretty sure the fill is the top one - with the square "nut" on the end. BuT - I don't think it's above the center of the rear axle tubes either.

Clean around both plugs, remove the top one and stick your finger in there and see if you end up in diff fluid.... Also a photo with the axle tubs in it for perspective would help.

Here you go - does this photo look like yours?
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Old 01-19-2025, 06:58 PM   #7
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Here the zoomed out pic. The inset one on the bottom is about 1/3 up and level with the axle. There is a drain plug on the very bottom, so I don't think the inset one is a drain.

Mine does look like the prior post.
This is a Powerglide chassis, so a modified Freightliner one.

The comment that one is for a FRED kind of makes sense. It would be about the same height up if you flipped the differential.

I guess it must be the square drive one slightly above the axle. I'll clean both up and stick my finger in the top one first.
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Old 01-19-2025, 07:38 PM   #8
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Here the zoomed out pic. The inset one on the bottom is about 1/3 up and level with the axle. There is a drain plug on the very bottom, so I don't think the inset one is a drain.

Mine does look like the prior post, so I guess it must be the square drive plug. I'll clean both up and stick a finger inside.

This is a Powerglide chassis, so a modified Freightliner one.

The comment that one is for a FRED kind of makes sense. It would be about the same level if you flipped the differential.

The Tiffin chassis manual is so good for chassis lube points. Surprised they only state to check it.
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Old 01-19-2025, 07:55 PM   #9
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That looks like the correct plug. The fluid level only has to be high enough to flow out to the wheel bearings on both sides.
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Old 01-19-2025, 08:58 PM   #10
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This is from the tiffin supplied docs on the flash drive:

Bus-Phaeton Chassis Manuals/Suspension/Drive Axle/23K Service Manual.pdf

Also this: Torque for fill and drain plug 40–60 lbs. ft
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Old 01-19-2025, 11:01 PM   #11
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Thank you, so it is the top one in the pic. Hard to judge the angle of the pictures I guess, a level would tell the difference.
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Old 01-20-2025, 09:33 AM   #12
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I just got confirmation from Tiffin. It is the top, square drive, plug.

Appreciate the torque specs. The manual for my year doesn't have that info, or the drawing.
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