Associated RC10 B74.1D Center Diff

[Jay123]

Thanks for the add. Finished my build but center diff has me stuck. Something does not make sense. AE instructions using scale are ring gear assembly, screws, cup assembly and diff fluid should weigh in at 44.5 with metal gears or 34.5 grams with plastic gears. If you try to fill to line its not happening and to get even close to 44.5 grams it's an ice cream cone. All I've been able to get it to is 42.1 grams of 200K oil. Either AE numbers are off, I missed something or part #5455 is the issue because 200K oil is a different part number and that part number really is 10,000 cSt silicone oil. These are the correct Part numbers for silicone diff fluid.
Part 5461 200,000wt 200k Silicone Diff Fluid 2oz ASC5461
Part 545510,000wt (10K) Silicone Diff Fluid 2oz ASC5455
Hope someone can help. Thanks in advance.

 

[Cheez ‘n’ Quackers]

Bleed all the air bubbles out?

 

[DavidB1126]

Idk. When I build or rebuild my diffs, I never weigh them. Currently in my center, I am running 500K for indoor carpet. I would only weigh stuff if there is tech, and I need to go through it, or if I am a pro / big race event. Me as a fun club racer, not my thing.
Your getting below what AE spec, so is that good or bad? 200K is a more on the thin / normal side.
Air bubbles are / can be a possibility.

 

[9x19]

Weight isn't as important as fill level. If you're at the correct level, close it up and move on.

 

[BarnFabRC]

I don’t see the ring (spur) gear on the scale in your picture. I just went through this exact build a few weeks ago and I was able to hit the target weight with no issue.

But realistically, you can just fill it, work the diff back and forth a few times to get the fluid into any hidden crevices, let the bubbles float out on their own (takes 5 or so minutes), then cap it and move on.

Enjoy the car when you do get finished! I’m loving mine so far!

 

[hood52]

I never weigh mine. But you weighed it with out the spur gear, put that on the scale.

 

[Lumikko]

Weight isn't as important as fill level. If you're at the correct level, close it up and move on.

This doesn’t make sense.

If the weight is off, the amount of fluid is wrong even if the level appears fine. There might be an air bubble trapped somewhere.

You don’t necessarily have to weigh the diff to get a good build but when the amount of diff fluid is correct, the weight will match the AE numbers.

 

[Jay123]

Idk. When I build or rebuild my diffs, I never weigh them. Currently in my center, I am running 500K for indoor carpet. I would only weigh stuff if there is tech, and I need to go through it, or if I am a pro / big race event. Me as a fun club racer, not my thing.
Your getting below what AE spec, so is that good or bad? 200K is a more on the thin / normal side.
Air bubbles are / can be a possibility.

AE makes it look like if you don't do it this way you run the chance of ruining your brand new center diff but then again their instructions are full of mistakes like part #5455 is 200K diff fluid but part #5455 in reality is 10,000cSt diff fluid if you Google it. So that's why I'm hoping input like yours and will help point me in the right direction. Thanks.

 

[Lumikko]

I don’t have a 78t spur gear but a 72t spur gear weighs 2.7 grams.

42.1 g without a spur gear means you have too much fluid in the diff. Don’t drive the car before you have fixed this; too little fluid is not a serious problem but too much can damage the seals.