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Gear diffs in Touring Cars.

Gear diffs in Touring Cars.

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Old 10-27-2011, 09:28 AM
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It just occurred to me why I am so happy with my ball diff that I've never considered the gear diff. I run 17.5 "blinky" (non-boost). The slower speed of the spec class along with smooth driving = not a lot of load on the rear diff. Hence with the covered diff on my XRay using carbon diff balls and properly lubed and built results in a diff that I hardly have to maintain for the class I am running.

However, the strong point of the gear diff is that it is more durable than a ball diff. If I were to run in the hotter mod class with boost, I would be putting a significantly more load on the diff. I suppose that in this case the gear diff is more appropriate.

We have a guy at our track who got the Ta-06 which had the gear diffs run 17.5 non-boosted and had to switch to the ball diff. He was much faster with the ball diff. Same as it is in 1/12 with the smaller and lighter cars, the ball diff works better. It really depends on the load of the intended application.

Not everyone runs mod and not everyone runs "blinky". Decide for yourself what is best. Also the premium kit manufacturers almost always package their kits for the intent in running mod because that is what Volker, Rheinhart and Hara, etc... runs. If the new kits are coming with gear diffs, its not that its the new way to run for all classes, its just the new way to run mod.
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Old 10-27-2011, 10:51 AM
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Most of the top guys in 17.5 blinky ARE running gear diffs on carpet.

I've been running a gear diff in blinky for the past year and prefer it over a ball diff. You're able to get on throttle much sooner with a gear diff.
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Old 10-27-2011, 11:29 AM
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Originally Posted by malkiy View Post
Most of the top guys in 17.5 blinky ARE running gear diffs on carpet.

I've been running a gear diff in blinky for the past year and prefer it over a ball diff. You're able to get on throttle much sooner with a gear diff.
Are you running foams or rubber? I don't run carpet but carpet has a lot more bite than outdoor asphalt parking lot. So I can see how you're able to get on throttle sooner because of the lack of slip on a gear diff.

Honestly, TCs on carpet with foams, I wouldn't be surprised if someone were to get around the track with oneways up front with a solid axle in the rear.
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Old 10-27-2011, 12:24 PM
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Originally Posted by YR4Dude View Post
Are you running foams or rubber? I don't run carpet but carpet has a lot more bite than outdoor asphalt parking lot. So I can see how you're able to get on throttle sooner because of the lack of slip on a gear diff.

Honestly, TCs on carpet with foams, I wouldn't be surprised if someone were to get around the track with oneways up front with a solid axle in the rear.
No foam. Rubber tires on carpet and yes the traction is very high. Most common setup is a spool upfront and a gear diff in back.
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Old 01-17-2012, 05:25 PM
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Question?

In reading this thread guys mentioned running putty in the front gear diff. Who makes it and how much do you put in?

Also with the gear diff oil do you just fill it up and make it level with the top or do you leave some air gap in it?

Had usually been a diff/spool person but some friends have been telling me I CAN be faster with the gear diffs, so figure it was worth trying.

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Old 01-17-2012, 08:31 PM
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Check this out

http://www.rctech.net/forum/electric...s-explain.html

Also search for " diff putty" there are several on the market.

As far as oil goes it's thick as grease, I pack it and let it set for an hour, to let it seep into the planetarys, then add as needed, repeat, then close it up.
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Old 01-18-2012, 02:37 AM
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Xray T3 diff uses composite gears, NT1 diff (which many people convert for EP) uses steel, with composite as an option. Kyosho also use steel with a fine pitch. Composite is just fine for EP even mod, you only run into troubles when they are shimmed wrong or when your shims collapse - spec R, tamiya I'm looking at you.

Gear diffs are where it's at. Lap times are better in every situation provided you get the oil right - which isn't hard - and the low maintenance is a plus. Ball diffs need to be rebuilt every run to perform at their best (it might feel smooth but it's not the same!), and even then they aren't as good. Chuck them out, put a gear diff in the back and have the option of spool or gear diff with heavy oil or putty for the front and you'll have the fastest car for every track.

The only downside is with no give you snap rear belts more often.
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Old 01-18-2012, 11:33 AM
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Well...... Can someone suggest a gear diff setup? I am currently running ball/ball and have two gear diffs in my box. Have tried them with 500k in front and a slipper spool. I am not used to them and keep going back to my ball diffs for the feel. Anything else seems out of control to me and twitchy....... Am I doing something wrong? Is there a better oil for the gear diff?
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Old 01-18-2012, 07:27 PM
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Originally Posted by bjanzen View Post
Well...... Can someone suggest a gear diff setup? I am currently running ball/ball and have two gear diffs in my box. Have tried them with 500k in front and a slipper spool. I am not used to them and keep going back to my ball diffs for the feel. Anything else seems out of control to me and twitchy....... Am I doing something wrong? Is there a better oil for the gear diff?
There are a couple things to think about when using the gear diffs. The weight oil you are putting in and the amount of oil you are putting in. Comparing 500k from one car to another or from one build to another only helps if you know how much oil was put in the diff. If you've been driving dual ball diffs, start with a lighter oil in the front until you get used to the handling differences. I've been running the spec-r gear diff in the rear with 40wt shock oil filled to the top of the gears. The lighter the oil, the more rotation you'll get from the car. The heavier you go in the front, the closer you'll get to a spool with similar results.
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Old 01-19-2012, 11:28 AM
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Okay..... Thanks for the help. I don't have a collection of gear oils so I built one of my gear diffs with Lucas oil stabilizer. Not sure where it falls in the range of fluids...... Feels tighter than my ball diff but certainly free compared to 500k silicone. Hoping to try it before I leave for the 'birds.......
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Old 01-19-2012, 11:43 AM
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Okay..... Thanks for the help. I don't have a collection of gear oils so I built one of my gear diffs with Lucas oil stabilizer. Not sure where it falls in the range of fluids...... Feels tighter than my ball diff but certainly free compared to 500k silicone. Hoping to try it before I leave for the 'birds.......
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Old 01-19-2012, 11:50 AM
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Originally Posted by bjanzen View Post
Okay..... Thanks for the help. I don't have a collection of gear oils so I built one of my gear diffs with Lucas oil stabilizer. Not sure where it falls in the range of fluids...... Feels tighter than my ball diff but certainly free compared to 500k silicone. Hoping to try it before I leave for the 'birds.......
Be careful when using automotive stuff in RC. Some of that stuff is not designed to run with plastic components and will eat plastic. Stick with fluids that are made for RC use to avoid trouble.
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Old 01-20-2012, 12:58 AM
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I cant help but wondering if "adjusting the diff" really is a tuning option? I mean, I've heard about 1:1 4WD which can lock the diffs, but thats for the purpose not getting stuck in the mud. I dont recall having heard about a 1:1 Rally car or Touring car, which used the diffs as a tuning option? Also, several tuning guides for RC cars dont mention this as a option?

I dont say it dont work in RC TC's, I can feel the effect, but I cant help but thinking of this as a shortcut, because it's easier than to tune the other settings?
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Old 01-20-2012, 02:06 AM
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To answer my own question: Several 1:1 cars uses various kind of differentials, often it's LSD (Limited Slip Diffs) or even active differentials, which can be changed by the driver. Mitsubishi Lancer Eco, Ford Focus WRC and Mercedes 190 are some of those cars.

Anyway, about 10 years ago, one of the arguments to upgrade the HPI Sport2 gear diffs to ball diffs, were that they were lighter. The lower rotating mass should be good for acceleration. Are modern gear diffs still heavier than ball diffs?
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Old 01-20-2012, 03:06 AM
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Originally Posted by Cole Trickle View Post
....The lower rotating mass should be good for acceleration. Are modern gear diffs still heavier than ball diffs?
Xray's T3 gear diff is 10g lighter than the standard ball diff!

Ahh, the benefits of modern composite components and manufacturing techniques
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