Differential Maitenance

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Boriqua935

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Hey everyone. Just wanted to know how similar or different the diffs are on the rampage pro MT compared to the HPI 5T. I want to go in and check the fluid in my rampage diff but the manual is not very good. I have done it on my 5T and its pretty easy. How is it on the Rampage. Pics anyone? Thanks
 
The Rampage is setup similar to an 1/8 scale truggy/buggy in that you can remove the outward part of the diff housing to remove the diff without taking the front or rear out of the car. The HPI is totally different in that you have to remove alot of crap just to get the tranny out. The difference is night and day. It's one of the very nice things about owning a Rampage. I used to break/replace alot of driv cups on my HPI due to shear torque. Diff maintenance was one of the many things I just hated about that car. Turtle Racing makes a quick diff housing for the HPI which makes it easier to work on but it's still a PITA compared to the Rampage/MCD.


As far as the build of the actual diff, there really isn't any major difference. They are built diffference but you would maintain them the same way.
 
Its easy open the diff just make sure you open it with the bolts facing up so when you crack it the diff oil don't pour out.
 
Ok so do I have to take anything apart on the truck besides the wheels to get to the diff?
 
No the box that the shock towers bolt to open that up then theirs a box with a gear bolted to it that box has the diff fluid and gears in it.
 
I changed out the rear one. Wow it was like tar. Black and not much in there. Cleaned out diff with engine degreaser and filled up with OFNA 5000k. Also cleaned main gear and bearing and greased them. Pretty easy job compared to hpi. Gonna do the front tonight. You guys running the same weight oil in front and back? Does it matter?
 
boriqua935 said:
I changed out the rear one. Wow it was like tar. Black and not much in there. Cleaned out diff with engine degreaser and filled up with OFNA 5000k. Also cleaned main gear and bearing and greased them. Pretty easy job compared to hpi. Gonna do the front tonight. You guys running the same weight oil in front and back? Does it matter?
Click to expand...
I run OFNA 7k front and 3k rear.


If you get to heavy in the rear you will lose alot of turning capability, however, it gives you the ability to drift the rear end by staying on power in a turn. This is something you probably don't want if you are trying to stay consistant. It's fun as hell to drift it though. I would make sure to keep the front the same or heavier than the rear cause if the front diff is too "loose" you will end up spinning out like the HPI knuckleheads.


Front diff tuning is the most important in how your car handles in turns. A loose front diff give you more steering when turning off power, however, you will get more push and understeer when turning on power. The reason for that is because when you turn under power, the car leans to the outside tire and it has more traction than the inside tire. Since the inside tire has less traction now, the diff moves the power to the inside tire. This counteracts the direction you are trying to turn and thus you car ends up trying to go straight. Think of it like you are trying to turn left but only you left tire has power and your right side doesn't which pushes the car to the right and counteracts the tires pointed left. A loose front diff allows you to enter a corner much faster than you could with a stiffer front diff. The reason is because you have more off power steering to make it through the corner. You exit speed will be slower though.


A heavier oil in the front diff keeps more power to the tire that has lost traction (inside tire when turning). This gives you much more on power steering. The counter side to that is that you lose off power steering. What that will end up doing is force you to slow down you corner entry speed but you can get back on the throttle much quicker when coming through a corner (exit speed).


I'm sure all of you guys notice how racers blip their throttle through a corner right? Why do you think that is? Because no racer goes so heavy in the front that they can just drift the corner. Typically a 1/8 scale racer has their buggy/truggy setup where there is a "somewhat" of a balance between the two. So they can't just stay on throttle in a corner cause the "push" would force em into the wall. So they blip their throttle to keep momentum through the turn and the time between the blips is considered off-power steering which is what they use to actually make it through the turn.
 
so DEMON would you recommend 5000 up front also or 1000 up front. i don't race, mostly just run on open grass field and asphalt.
 
Try 7k front 5k rear. That would be a good starting point. I like the 7k 3k combo in my car but I have to navigate a track. This is also in my XT. I think I ran 7k/5k and 7k/3k in my TT when I had it.
 
It comes with some sludge that they scraped off the bottom of some barrell somewhere. The stuff is very sticky and would be the equivelent of heavy weight silicon. I'd guess when the stuff is brand new it's similar to 7k-10k weight silicon.
 
The manual states 10,000, but don't know what rating. I opened my diffs when they were new and clean. It seemed more like 30k to me comparing to to the 30k Associated oil I had on hand.


I think you would want thicker if just doin circle track like 10k in the rear and maybe a little heavier in the front. Just a guess tho.
 
We ran an oval for a long time over here. You'll want to stay on power in any long gradual corner so heavier is a must.


Also, I popped my diffs after a few weeks of running and it seemed like 10k. I believe you when you say your seemed like 30k brand new. That's just scary.
 
Why is that scary? I only bash and have been running 30K front and rear since I got my truck (about 3.5 gallons). It gives a limited slip type differntial for powering up, down, and around....or am I just reading wrong how I think my truck handles and should try lower weight when I (eventually) rebuild them?
 
Oh I was just saying that the goo in my diffs that was aready broken down was a mess and that removing it when it was brand new and even tackier would be a scary thought.


Also, it does have it's own drive characteristics which are really good for power drifting around corners. Fun as hell for bashing but can be a headache at a track where consistancy is king.
 
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