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Old 05-25-2009, 10:26 AM   #1
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Default Xray Active Diff Issues...

The active diff is new to me, and this is the problem I am having.

When I use the active diff, car seems to handle well, however after things get warm some binding occurs. It is much the same as if a bearing were going out, however I have checked all in the drive train, and even replaced them although they all looked and felt good. Things are binding up enough that my motor is over heating. I thought I had a tuning problem at first, however after feeling 'stumped' in that arena I found that the front end was binding up under the appropriate load. It is very inconsistent, however noticeable by simply 'dragging' the front end. I have checked the shims (using 1 shim to open mesh) and everything seems actually ideal (ever so slight play). When the car cools, seems as if no binding is present. I will have to check my notes, however I believe I am running Losi, 5k-5k-3k (front to back).

I must admit, I am feeling a little disgruntled. With the difficulty of assembling this thing, (and immediately reassembling to replace bearings) and now the difficulties in running it, I feel that the $114 something that I spent was maybe wasted. Am I missing something? If so, please enlighten me.
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Old 05-25-2009, 10:41 AM   #2
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I have not had problems yet with my active diff. I run 3k oil and use 90 degree.
Are you using newer bulkheads. Could there be a bulkhead that is not seating the bearings right maybe not cut right. I would try to replace bulkhead and go from there. Hope that helps.
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Old 05-25-2009, 10:49 AM   #3
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I am using the bulkheads that came with the kit (I guess version 1). I can't seem to bring myself to replace a part that has had less then 5 tanks of fuel through it. If the bulkhead I have is the culprit, I will have a bone to pick with xray for not replacing defective parts. Since I have not read anything about that, I will not jump to that conclusion.

Thanks for the insight, however I think everything is seating properly. I can run the normal diff without any issues.
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Old 05-25-2009, 11:24 AM   #4
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Quote:
Originally Posted by Larks View Post
The active diff is new to me, and this is the problem I am having.

When I use the active diff, car seems to handle well, however after things get warm some binding occurs. It is much the same as if a bearing were going out, however I have checked all in the drive train, and even replaced them although they all looked and felt good. Things are binding up enough that my motor is over heating. I thought I had a tuning problem at first, however after feeling 'stumped' in that arena I found that the front end was binding up under the appropriate load. It is very inconsistent, however noticeable by simply 'dragging' the front end. I have checked the shims (using 1 shim to open mesh) and everything seems actually ideal (ever so slight play). When the car cools, seems as if no binding is present. I will have to check my notes, however I believe I am running Losi, 5k-5k-3k (front to back).

I must admit, I am feeling a little disgruntled. With the difficulty of assembling this thing, (and immediately reassembling to replace bearings) and now the difficulties in running it, I feel that the $114 something that I spent was maybe wasted. Am I missing something? If so, please enlighten me.
I've never heard of this issue, I would call RC America and ask them for help.
I run 4k Mugen oil in the front with 90 segment. 4K 6K 2K in diffs. I would also use the 09 spec bulkheads. Every car that has ever been released has had some issue, and good companies update those weak parts for a reason. Xray has updated its new bulkhead parts, bearings, & spacers, so i would get those parts.
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Old 05-25-2009, 11:25 AM   #5
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The Active diff needs to be shimmed differently than the standard diff..Whats happening is when it heats up it is binding with your pinion, just shim it a tick further away from your pinion, and all your problems will go away

James, Did you not find this to be true? This is what I am reading from most of the people who run them..I still have not installed mine, but The guy I bought it from said the shimming was different
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Old 05-25-2009, 11:33 AM   #6
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With further inspection, I have noticed that there is a bout .100" movement (100 thousandths) in the front cvd forward/backward direction. This allows the gear mesh on the front diff to fluctuate from approx .050" to .100". Is this normal and acceptable?
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Old 05-25-2009, 11:35 AM   #7
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Quote:
Originally Posted by Jaz240 View Post
The Active diff needs to be shimmed differently than the standard diff..Whats happening is when it heats up it is binding with your pinion, just shim it a tick further away from your pinion, and all your problems will go away

James, Did you not find this to be true? This is what I am reading from most of the people who run them..I still have not installed mine, but The guy I bought it from said the shimming was different
Yes as mentioned, I have shimmed the active diff to what I see as acceptable tolerances. If those are not acceptable please advise. The normal diff required no shimming.
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Old 05-25-2009, 12:01 PM   #8
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Yes as mentioned, I have shimmed the active diff to what I see as acceptable tolerances. If those are not acceptable please advise. The normal diff required no shimming.
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Old 05-25-2009, 12:03 PM   #9
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Quote:
Originally Posted by Jaz240 View Post
The Active diff needs to be shimmed differently than the standard diff..Whats happening is when it heats up it is binding with your pinion, just shim it a tick further away from your pinion, and all your problems will go away

James, Did you not find this to be true? This is what I am reading from most of the people who run them..I still have not installed mine, but The guy I bought it from said the shimming was different
wrong.................
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Old 05-25-2009, 12:16 PM   #10
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Not that this is causing your problem but 5K seems a little heavy for the active diff. You are not going to get the full benifit of it by running that heavy. Most guys here are running 600-1k weight oil. I have 700 shock oil in mine and it turns great and pulls hard.

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Old 05-25-2009, 12:54 PM   #11
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wrong.................

Did yours require no shimming? My stock diffs just dropped in with no shims, but Lots of peeps are saying the Active needs to be further away from the Pinion?
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Old 05-25-2009, 01:12 PM   #12
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I have not shimmed mine and had zero problems.
Active diff needs 1000-3000 diff oil otherwise it is defeating the purpose of what it does. I tried 1000-2000-3000 at the Nitro Pit where tight corners are not there so I use 3000.
The bulkheads are a known issue so I recommend the V2's. I believe Rcamerica does not even stock the older bulkheads so ordering them is easy to do.
No offense Jaz but your giving Lark help without even running the Diff....
Just a thought
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Old 05-25-2009, 01:51 PM   #13
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From what I understand, by reading, and simply engineering intuition, the active diff simply releases off power, and locks on. While on power, it should act as a normal differential and the oil viscosity should affect its 'action' in much the same way as it does the normal. While off power, it should release, somewhat 'freewheeling' and the viscosity of fluid should be of a much lesser affect because at this time the gears should not be engaged. I don't see how running thicker fluid should affect 'what it does' anymore then it does in a normal differential. Although a thicker fluid would provide less 'freewheeling' it is still not engaged like the normal differential is 100% of the time.

Again, I claim to be no expert, and I could be missing the whole point. This is the way I see it. Again, in response to shimming, weather you 'should' or 'should not' shim the active or normal diff, I believe that an appropriate gear mesh is required in whichever diff you have installed. The normal diff did not require shimming in my assembly, however the active did. This determination was based solely on the amount of play present (or not present) when the diff was installed in my assembly. I am sure with the tolerances of these things, everyone has similar yet different enough experience, i.e. some will require massive shimming, others a little, and perhaps for others, none at all.

Back to the question. Am I off base on the mesh tolerances? Or am I missing something else that could cause excessive load to heat my motor? (Let's assume my tuning is correct, for I think I have that one in the bag.) It is definetely in the front end, and seems to only happen when things are hot.

BTW, note taken on using lighter fluid to 'increase' the effect of the diff. This is understandable. Obviously when disengaged the lighter fluid will allow a more noticeable freewheel. I went for a thicker oil simply to try to mimic my normal diff action on power for I am on it more then I am off =).
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Old 05-25-2009, 02:03 PM   #14
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Quote:
Originally Posted by diamondracing View Post
I have not shimmed mine and had zero problems.
Active diff needs 1000-3000 diff oil otherwise it is defeating the purpose of what it does. I tried 1000-2000-3000 at the Nitro Pit where tight corners are not there so I use 3000.
The bulkheads are a known issue so I recommend the V2's. I believe Rcamerica does not even stock the older bulkheads so ordering them is easy to do.
No offense Jaz but your giving Lark help without even running the Diff....
Just a thought
Sure flame on me for trying to help a fello
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Old 05-25-2009, 02:33 PM   #15
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Jaz, don't sweat it. All comments (well nearly all :P) are helpful. Thanks for your input.
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