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More Hyper 8 diff questions

Old 01-13-2008, 05:24 AM
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mrbonk
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Default More Hyper 8 diff questions

Hey all,
After my recent strip down and rebuild (including re-oiling my diffs with 5,7,1 (F,C,R)), my car is virtually impossible to drive. It's unbelievably 'taily' and very hard to keep in a straight line. I'm thinking that the 1K oil in the rear is just too thin? I also returned the suspension settings all back to stock when I did the rebuild, so it's quite soft overall compared to how it was when I got the car. When I first got it, it had massive amounts of understeer. Now, it's almost the opposite.

So, what to try first? Thicker oil in the rear diff? I've got some 3K oil.....I was thinking about trying it with that. Would the softer suspension settings have anything to do with the rear end feeling so loose now?
Old 01-13-2008, 03:29 PM
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jonnymac
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Default RE: More Hyper 8 diff questions

I use 3K rear but before you do anything be sure you are getting drive to the front wheels. It sounds like you may just be running rear wheels only. Make sure all your grub screws are tight on the drivetrain
Old 01-13-2008, 03:39 PM
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mrbonk
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Default RE: More Hyper 8 diff questions

Nah, it's definitely turning all 4 wheels. As evidenced by the rapidly diminishing tread around the centre of the fronts

I'll pull the rear diff out (again....*sigh*) and put some 3K oil in and see what happens then.
Old 01-13-2008, 06:13 PM
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Da Smak
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Default RE: More Hyper 8 diff questions

When you filled the diffs, did you put them back in the right ends?
Old 01-13-2008, 06:40 PM
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mrbonk
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Default RE: More Hyper 8 diff questions


ORIGINAL: Da Smak

When you filled the diffs, did you put them back in the right ends?
Yeah....I did them one at a time as I dismantled and slowly cleaned the entire car up.

The oil in the centre diff was basically non-existent. Just a dark coloured 'paste' that didn't even drip out of the casing when I tipped the planetary gears etc out. Consequently, the bevel gears have some obvious wear now [:'(] The front and rears weren't much better, but the gears are all still fine.

The alterations to the car have definitely improved the turn-in and the on-power steering, but it's just too loose in the rear end now. Uncontrollably fishtailing down the straight at full noise is funny to watch, but not much good for respectable lap times . Once it's up to speed it's fine, but if I have to make steering adjustments while it's still not getting full traction, it starts fishtailing much too easily.

Before I did the rebuild, I could hammer the throttle out of a corner and it would push the front badly, but basically be very easy to steer/control, even while it was spinning all 4 wheels. Something between that and what I've got now would be ideal
Old 01-13-2008, 08:09 PM
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Default RE: More Hyper 8 diff questions

Going from almost non existent oil in the center to 7k would probably be a major part in what you're feeling now.
A lot of power goes to the rear compared to before.
Old 01-13-2008, 08:14 PM
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Default RE: More Hyper 8 diff questions

how much the diff should be filled ? full or half only ?
Old 01-13-2008, 08:20 PM
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Default RE: More Hyper 8 diff questions

I always fill mine ~75%. (I don't run a Hyper 8)
Old 01-13-2008, 09:23 PM
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vulpina
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Default RE: More Hyper 8 diff questions

allright , filling to the max is bad ?
Old 01-13-2008, 10:50 PM
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Default RE: More Hyper 8 diff questions

No, by using less fluid it will act like a lighter weight oil in the same diff. For the 8.5s with spyder center diffs you could use less fluid of the same weight and get (in theory) the same out come as a standard diff with the same oil fully filled. I hope I didn't make that sound too confusing.

Anyways this is because the spyder diff have more surface area (gears) so the oil does more 'slowing down' of the diff action so if you wanted the same action as 7k in a standard diff you would want to try 5-6k in your spyder diff. This is the diffs being filled all the way.
Old 01-15-2008, 01:59 AM
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Default RE: More Hyper 8 diff questions

I have a hyper 8 and ive also realized with most buggys a good staring point is 5fr 7cr 3r if you need to go a bit stiffer on shocks id try 40 front and 35 rear and id also recomend some proline tires i have the crime fighters makes a difference and stering servo will be next upgrade but i put most my money into hyper st
Old 01-15-2008, 06:14 AM
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Default RE: More Hyper 8 diff questions

That's the diff setup I'll have now. Just changed the rear diff oil for some 3K stuff. Not sure if I need to go stiffer oil in the shocks yet, but maybe. The front seems to be a little fast on the rebound, but I haven't had a decent enough drive with it at these standard settings to decide yet. As for tyres, I've got some Proline Bowties on at the moment but they're too soft for my track. I've got a set of the standard Hobao rims and tyres (FIRE ones) to see if that's any better. The tread blocks are definitely more solid than on the Proline ones, so we'll see.
Old 01-15-2008, 12:36 PM
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Default RE: More Hyper 8 diff questions

i run the pre mounted crime fighters there doin prety good
Old 01-15-2008, 05:58 PM
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Default RE: More Hyper 8 diff questions

Check your brakes aren't binding.
Old 01-15-2008, 06:22 PM
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mrbonk
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Default RE: More Hyper 8 diff questions

Nope. No binding. Went over the entire setup with a fine toothed comb when I rebuilt the car. Reset everything properly (steering rods, suspension arms and pushrods were all incorrect lengths) and made sure I had everything running smoothly and no brake at idle.
Old 01-15-2008, 06:33 PM
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Default RE: More Hyper 8 diff questions

actually try 5 in the center bf you do anything
it will make the car diff out a little and be easier to drive
Old 01-15-2008, 06:59 PM
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mrbonk
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Default RE: More Hyper 8 diff questions

As it stands now, I'll have 5,7,3 (F,C,R). I'll give it a quick test like this first, before I go to the trouble of pulling the centre diff out again. I'm gonna be pushed for time before the club open day on Saturday, so if it's drivable like this, I'll just leave it.
Old 01-16-2008, 01:27 AM
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Default RE: More Hyper 8 diff questions

let me know what you think of the difference
Old 01-17-2008, 09:37 AM
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Default RE: More Hyper 8 diff questions

I prefer 5/3/1 on the hyper 8 and hyper 8.5.
Old 01-17-2008, 09:53 AM
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Default RE: More Hyper 8 diff questions

I run 5,7,2
Old 01-17-2008, 09:06 PM
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Default RE: More Hyper 8 diff questions

Hi Bro, its Andrew here from the bundy track. I found 7/5/2 is the best diff setup for the types of surfaces we run on or 5/5/2, and i also found that any diff setup that feels good on the hyper always torches the fronts, keep rotating your tyres. Fill your diffs to the top of the cross pins. And k2's med soft seemd to last longer than any other tyre i used on the h8.

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