HPI Savage TCS Flux 5T (Differential Cup Sleeve)

Click here to view my gallery!

The CEN CVD is great but the diff cups are not holding up. Today the diff cup in the front of my savage gave out. I still want to run CEN CVDs in the front of the savage, so I will need to find a way to make the diff cups stronger.

I tried a few differential cups that are made by different companies and/or car models. Each of them had their own weakness.

Here in the picture below is a Diff cup from a Losi 8ight / LST. Like in the past in my brushless LST XXL the diff cup always snapped where the pins goes through.
HPI Savage 5T  Super Flux-   Broken LST Diff Cut

Next up I have the Hot Bodies D8T diff cups. These lasted a few minutes longer but not much more. Instead of breaking where the pin hole is, it looks like the actual diff cups just ripped right off.
HPI Savage 5T  Super Flux-   Broken Hot Bodies Diff Cup

In the front of the Savage I used a older model diff cup that used a smaller dog bone. But the inner hole was still 1mm larger than what is suppose to be. These diff cup are the non heat treated version (HPI part number 86064) that I heat treated myself. I got about an month of use out of it until it broke too. It is hard to say if this cup is an better than the rest because the 2 diff cups I used above was in the rear end of the savage. We all know that the all the weight shifts to the rear of the car when accelerating and that it is a lot more stress in the rear drive train.
HPI Savage 5T  Super Flux-   Broken HPI Savage 9mm diff cup

 

Here is a picture comparison to the different HPI diff cups. Starting from the left: HB D8T with a 8mm inner hole, HPI Savage with a 9mm inner hole, HPI Savage Flux with a 11mm inner hole.
HPI Savage 5T  Super Flux-   Different DIff Cups
HPI Savage 5T  Super Flux-   Diff Cups

My first attempt to create a stronger HPI diff cup is to make a sleeve that goes over the diff cup. If you even owned a HPI Baja 5B/5T/5SC you would have heard of a company called Dark Soul. They make a hopup part called toobz. It is a steel sleeve that is pressed over the diff cups to reinforce the outer edge. From the looks how the diff cups break on my savage it think this might help.

Unlike Dark Soul I will be using aluminum instead because I hate working with steel. Here I have a 7075 Aluminum rod that is about 16mm in diameter that I will make the sleeve with.
HPI Savage 5T  Super Flux-   Diff Cup Sleeve 7075 Aluminum

 

In this picture you will see the aluminum rod on the lathe after I finish making the inside of the rod a press on fit for the diff cup.
HPI Savage 5T  Super Flux-   Diff Cup Sleeve on the lathe

 

This is the diff cup sleeve before I installed it.
HPI Savage 5T  Super Flux-   Diff Cup nest to the sleeve
HPI Savage 5T  Super Flux-   Different view of the aluminum sleeve

 

On the right is the sleeve pressed on the diff cup and right next to it is same cup without the sleeve.
HPI Savage 5T  Super Flux-    Aluminum Diff Cup Sleeve pressed on the D8T cups

 

Here is a view from the back.
HPI Savage 5T  Super Flux-   Aluminum sleeve from the rear

 

 

Once again all three different diff cups right next to each other. Starting from the left: HB D8T with a 8mm inner hole, HPI Savage with a 9mm inner hole, HPI Savage Flux with a 11mm inner hole.
HPI Savage 5T  Super Flux-    Diff cups next to the d8T cup with the aluminum sleeve

 

 

After my first test fit I found out a made the sleeve too wide and it will rub against the plastic bulkhead. In the picture below you will see the modified sleeve on the left, with the edge trimmed off. And in the middle is the non modified sleeve. On the far right is the stock diff cup.
HPI Savage 5T  Super Flux-   Top View

 

 

Here is the diff with the sleeves over the diff cups. If this works out I might knurl the edge of the sleeve and but a rubber boot on it too seal in the grease inside the diff cups.
HPI Savage 5T  Super Flux-   Savage Bullet Proof diff with D8T diff cups w/ aluminum sleeve

 

 

Test fitting the diff in the bulkhead, making sure it does not rub against anything.
HPI Savage 5T  Super Flux-    Modded BP Diff mounted
HPI Savage 5T  Super Flux-    Test fitting the CEN GST/nemesis CVD with the BP Diff mod

Leave a Reply

Your email address will not be published. Required fields are marked *