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Old 10-06-2007, 01:57 PM   #1
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Default rebuilding diff, how important is it?

i know many parts of rc cars need to be rebuilt to keep them running at there top performance. i rebuild my shocks quite often now because i do feel a difference with the car having fresh shocks. i mainly rebuild alot of parts on my cars but i never really feel like doing the diffs as often as i probably should. i know they will run better rebuilt fresh but will i actually see this equate to better lap times? i do feel a fresh diff in the car a bit if the diff was in poor shape before hand. really i am just asking how ofter should i rebuild it compared to say my shocks. mainly i dont like doing the diff sue to the cost of new balls and washers all the time. any insight s welcome. thanks for your time.
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Old 10-06-2007, 02:14 PM   #2
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Personally, I only like to rebuild my diff if it starts to feel gritty. If the diff is still operating smoothly, there's really no reason to rebuild. It's still doing its job.

If a diff gets too gritty, however, it stops being effective and you'll notice the car won't handle very consistantly. And you can feel a gritty diff very easily just by turning one wheel. It should turn smoothly and the opposite wheel should turn the opposite direction. If you feel any grittiness, it's time for a rebuild. Or, at the very least, a good cleaning and regreasing.
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Old 10-06-2007, 02:46 PM   #3
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I got the same problem with fjm9898. What do you guys use to clean diff ? any tips ? What causing the gritty feel ,is it dirt or the ball just not as round anymore ?
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Old 10-06-2007, 04:16 PM   #4
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so your take is that the car will handle inconsistently. so it may not directly affect the speed of the car, just how your going to be forced to dirve it... which will then change the lap times. basicallyi am just trying to figure out how much my laziness is hurting me.

b_budianto - if your not going to replace the balls and washers here is what you should do to clean it.

take it apart and spray everything down with motor spray in a shop towel and wipe everything 100% clean and i use a q-tip to get the extra grease off the pulley/gear. if you havent already u can flip the washers over so you have a fresh side (you wont see the ring on the washer that the ball has worn into it). once you got it all clean rebuild it with fresh grease. after that your diff should feel better then it once did, it will probably no be 100% smooth as the balls may need to be replaced.
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Old 10-06-2007, 04:35 PM   #5
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One of the thing's that separates the pro's from the casual racers is their attention to detail. How many times have you heard someone say "oh man I couldn't drive Hodge's setup; Man Dumas's setup was not for me; I tried Teemu's setup and couldn't drive it. Then you go back and look at their car and yes it has the right shocks and springs and oil and camber...etc, but you'll see a bent turnbuckle, tweak in the car, droop off left to right.....

True there are some who can just wheel any car to victory.

Always make sure you pay attention to the basics. I can honestly say that if I had payed more attention to these things, I would have been a better driver. Yes I was guilty of it too.

ride height
camber
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diffs smooth
shocks rebuilt when needed
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Old 10-06-2007, 05:15 PM   #6
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The condition of the diff is 20% of the cars handling, it is very important to have a smooth diff....Making sure your diff is run-in after a rebuild is an important part of a consistent diff build too.....This is even more important in modified where the diff is put under very high stress....
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Old 10-06-2007, 07:09 PM   #7
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the smooth the diff is...the great cornering handling&speed you will get...is it true?
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Old 10-06-2007, 09:32 PM   #8
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How tight is a good diff ?
Is it true the front diff ia set a bit tighter than the back ?
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Old 10-07-2007, 08:22 AM   #9
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Rear diff is very important to keep smooth as if it is too tight or notchy you will get some pretty inconsistent handling as you put the power down out of corners. It should rotate smoothly but not spin freely.

Ideally you want to combine this smoothness with a diff that doesn't slip... not always that easy to acheive and depends on the components you are using, for example I find that diff halves made of a harder material (alloy, steel) are easier to keep smooth without slipping. Same should apply with harder balls, they will stay rounder and thus smoother under greater pressure. Shame that nobody has started to make hardened diff rings yet...

Also don't forget the importance of the thrust bearing, this should be well packed with grease to run as smoothly as possible, it has to handle loads similar to the main balls.

If diff is still rough after being thoroughly cleaned, visually checked and rebuilt, then it is time for new internals.

Front diff is not so critical, if it is a bit rough you will be less likely to notice any handling problems, but it should be built to the same standards as the rear and will normally be set a little tighter, this adds a little stability on power.
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Old 10-08-2007, 05:20 AM   #10
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COOL
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Old 10-08-2007, 05:48 AM   #11
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Anyone see the plus point of running a spool upfront? Can you tell that I hate rebuilding diff's?
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Old 10-08-2007, 09:08 AM   #12
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Is there a clear advantage of ball diffs over gear diffs? Im asking this because, Ive been told to keep the rear diff as loose as possible without slipping. Isnt that pretty much an open diff? Gear diffs are open but they never slip by design. Maintenance is not much of a problem on my newer cars, but some of my older cars are a pain to get to.
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Old 10-08-2007, 10:31 AM   #13
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Ball diffs advantages are lighter weight and quicker adjustment.

However the loads on ball diffs are so great now in touring cars (due to monster power and grip) that I think there may be an argument for a high quality gear diff to be used instead.
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Old 10-08-2007, 11:07 AM   #14
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thanks for clearing that up. I'll probably keep the ball diffs in my race chassis, but I dont really wanna deal with diff maintenance on my bashers. I still enjoy drving my ta03 and tb01.
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