Other than it looks neat, is there a reason to use an aluminum differential case? I have seen some which have a greater liquid volume, but would not not also increase rotating mass on the drivetrain?

Thanks.

s.

I think the primary claim is that they improve heat dissipation so that oil viscosity doesn't tend to decrease over the course of a run.

Which car? Some kits have pretty low quality, leaky, plastic diffs that the aluminum diffs help with.

large volume will not increase rotating mass..its larger volume is to keep diff oil cooler than a smaller volume 1..

I suspect what he means by increase rotating mass he means by a alloy diff case will weigh more than a plastic diff case

It's likely they can hold tighter tolerances with machined aluminum then molded plastic. Could possibly wind up smoother rotation and quieter running. Also less deflection under load is a possibility

More oil is more weight. High volume diffs absolutely increase the rotating mass. The trade off is worth it though.

Thanks guys,

Yes, I was thinking the increased weight would be there, but I'm not sure if the change would be measurable, so I figured I would ask. I have seen these for Tekno and Team Associated platforms. Was curious about them.
Out here we do longer, sustained runs at 80% power, and I was curious as to if there would be a benefit. I might give it a try; they are not too expensive.

Thanks.!

s

I have seen these used mostly by bashers who are overloading their diffs with excessive power on 6S and failing to properly service their diffs which leads to "cooking" the diff where the plastic melts. Instead of doing proper maintenance and proper setup, then upgrade the diff case to aluminum for an otherwise unnecessary upgrade.

I found in my B6.1 the plastic diff housing was not flat and so the oil came out of the gear diff as it sat on the side before I even put it into the car, so I put the aluminium side on the diff and it was fixed. I did not have to do this with the diff in the B6.2. We do 5 minute races here in the UK and do not run stock motors so weight and rotating mass is not a concern, but I have never tested the difference between the two but would think that the aluminium side on the diff will keep the oil cooler and hence more consistant over a single run, but then again I am not sure I am good enough to notice the difference.

Electric power can stand to use a little more flywheel.

Shimming a new diff wrong can ruin it in one minuet of run time. On some rc’s Proper shimming keeps the sides from too much pre load pushing the outdrive into the case, to much shimming is just as bad as not enough.

Glass filled nylon66 can continuously operate at 180 degrees F and silicone oil has remarkable stability upto 250degree C or 480F.

Thanks.!

Is there a thread which gets into the proper shimming techniques. I keep mine regularly serviced and replace shims as they wear, but I just copy the factory setup. I'm curious to learn more about this. I'm referring to the inside of the differential. I have seen some good videos for shimming the diff on the outside.

Thanks.
s

Really shimming the gears inside the diff is just a case of putting together and check mesh for minimal backlash on gears by hold one outdrive and turn the outdrive on the other side and see how much it moves anticlockwise and clockwise. You must also twist each outdrive through a complete turn checking for binding. If you feel too much backlash then add shims but always check for tight spots on a full revolution, If you feel any tight spots then you need to remove shims. So it is a case of trying to reach a happy medium of the minimum amount of backlash without and tight spots. Also as the diff gets older then you may be able to add more shims due to wear on the gears but you just keep doing the same process over and over again when you rebuild the diff. Also make sure that when you are tightening down the screws on the diff to make sure that you get the screw head to meet the plastic and then only tighten it up maybe 1/4 of a turn to make sure that you are not deforming the plastic which could mean you end up with a tight spot in your diff. This goes for any screw head that meets plastic especially in and around the gearbox as the screw head should just meet the plastic and then be tightened up a small amount. A typical example of this going wrong are usually the screws that go through the rear gearbox and into the motor mount where I have see people over tighten and then wonder why the motor has overheated. You can tell as there are many hard spots as you turn the spur gear because everything is now a bit deformed and the bearings are being crushed again the layshaft, idler gear and or diff case causing binding.

On a non belt drive 4wd you can shim the diffs left and right of the bearings on the outdrive of the diff as well as adding or removing shims just behind the pinion gear which meshes with the ring gear as well. In a 4wd diff the bearings that hold the diff and especially the bearings the are holding the pinion must be in very good condition otherwise under load the mesh can change with disastrous effects.

A lot of this is trial and error.

If you are referencing the b74 alu f/r diffs, I noticed they help prevent the diff cup side outdrive from leaking as much or at all. The alu center diff will reduce spur gear damage due to the AE spur and diff sometimes being a little off true. The plastic center cases do not seem to have a leak issue in my experience.

I'm just adding these benefits to the list of already mentioned oil cooling. They might have just a smidge more oil capacity due to the slightly different inner design but it looks really close.

Thanks guys. I'm looking to get the most out of my Nomad(s) and getting them tuned as well as possible. Many thanks for the info. Will put these tips to use next diff service.

s.