HPI_Savage_RC

HPI "Bulletproof" Ring and Pinion Set

"This Machined Bulletproof Diff Bevel Gear Set is our toughest diff set-up ever for the Savage monster truck line. The ring gear and pinion gears are precision machined from high carbon steel and have stronger gear profiles for the ultimate in durability. The 29T gear is machined to use the included "oversized" ball bearing for extra durability and efficiency.

This diff gear set was developed for extremely high horsepower applications like the Savage Flux and Savage XL. It's so strong that it replaces the 86922 and 102246 Heavy Duty and Super Duty gear sets, both now discontinued. So if you're using big block nitro engines or high voltage brushless motors, get the new Machined Bulletproof gear set!

Each package upgrades one diff, we recommend getting a pair of them so you can upgrade the front and rear diffs. Fits all Savage trucks. Recommended for use with 102272 Composite Gear Box/Bulkhead Set."

My thoughts:

- 7 years later and the largest issue with the Savage diffs is still the tiny dimensions of the side bearings. Why won't they fix this? People are still going to break diffs due to failed cup-side bearings.
- Very expensive for a single R/P gear set and a bearing. Even if they end up being sold for $30/set, $60 to outfit a truck is almost double what I payed for 2 complete CEN diff assemblies.
- I hope they finally figured out how to heat treat the steel correctly. The pre-XL gears had some brittle spots, but the "machined" XL/Flux gears were a complete metallurgical disaster.

Discuss.

-SomeGuy-

Hmmm, well they sure worded it nicely but this has been a non issue for me since i got nova diff cups a few years ago. Except for normal wear and tear and apart from user error my diffs hold up fine. If the CEN diffs are so cheap and solid that would be the way to go IMO.

rclugnut10

My Feedback: (1)

i think once the cheapen up a bit. i'm betting they'll be $30-$35 once they hit stores, and they will be on the next savage stock, so i think you'll be able to find them cheaply enough

the lug

spiftacu1ar

WHAT!?!?! You got 2 CEN diffs for $30. I haven't seen them go that low on ebay in a while. Generally almost $40 a set on ebay (unless you get the matrix ones with the plastic diff cup, which are $18 bin)

HPI_Savage_RC

I bought them over a year ago, one for $15, the other for $19. Not sure what they go for now, as I haven't checked the eBay listings lately.

rcnitrohead

HPI has bombed time and again on this issue.... no patience for them, but I can't complain cause I've only killed 2 diffs after 11 gallons.

MGT

looks like the cen ring & pinion. I'll stick with my cen stuff.

jbooker82

My Feedback: (4)

it looks like the teeth are larger. I haven't ever broken a pinion gear. The 2 diff failurs thar I have had were due to the bearing going bad on the ring gear. I got the standard flux gears with the large bearing, running boca bearings and haven't had a problem since. If you shim the diff properly you don't have near the problems as you do with an unshimed diff.

MGT

The shims are a myth lol, at least for me. I've broken the HD bones, HD cups tore in 1/2, even broke the steel case on one of my CEN diffs, with 6S. Now with 4S I just broke a center HD bone and tore a stock drive cup in 1/2. The stock flux diffs shimmed lasted me less than 2 min. I've also broken 3 bearings. Now since I've upgraded my bearings and I have the CEN diff covered in automotive grade grease they are staying together. Could also be due to running 4S. Though I'm running a way more intense tune with only 50% punch control and med. start power lol.

If you're running Nitro and not having problems I can understand..but brushless and 6S I dont know how you keep it together.

HPI_Savage_RC

Shims are not a myth, they do help, but only with low powered engines.

You have to realize that the Savage drivetrain was originally designed for a sport grade .21 engine, and the materials and geometry of the parts hasn't changed much since then. Even with HPI's attempts to upgrade it, this is a truck built for relatively moderate power, not 5hp brushless motors. If you want to run that much power in a Savage, you'll never stop the constant drivetrain breakage.

MGT

True but it's funny how they say you can run 6S. I know the shims arent a myth but shimming them futher than what hpi did from the factory didnt help me. I have my CEN diffs shimmed within .02mm. I do have the tools to measure within .001" so it's not like I'm guessing here.

Also the problem I see with the flux is the weight, it's about 1lb. heavier than my nitro. Add weight and a ton of power to the same platform..not good. With the instant torque of the brushless and the extra weight it snaps the teeth off the pinions like they are made out of wood. At the very least it will twist the diff inside the plastic bulks or destroy your bearings.

I think what HPI did here will stop most of the teeth breaking, but it wont slove the bearings busting. I still think the CEN stuff is better because the case is steel and allows a larger bearing. It all depends on what you run, but for the brushless guys I still think CEN is the ONLY way. For nitro, these and better bearings might last a lifetime. I still think spending the extra cash to use the CEN stuff is well worth it. It cost me under $90 for a complete CEN set up

Just some food for thought.

HPI_Savage_RC

Agreed.

yamasledhead

Since HPI came up with different styles, maybe their awesome customer service will send us power hungry flux owners 2 sets for free. Heck I have actually had good luck lately after shiming the heck out of diffs so no side play at all. Triple and almost quad backflips off trees and playground equipment.