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Old 07-16-2007, 10:09 PM   #1
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Default Associated t4 diff won't stay tight!

Hey guys!

We are trying hard to avoid locking my brothers diff on his new T4. He assembled everything according to what he interpreted from the directions which are admittedly lacking somewhat.

He's using the mambamax 7700 combo, orion 3200 lipo and a 20 tooth pinion with the stock spur. The spur isn't slipping and he's being easy on the throttle but the damn diff system keeps loosening up on us. Are we missing something here? If it helps, it loosens more and more as he turns (differential action). We bottom out the spring and back it off 1/8" turn as instructed, and this time we even shot lock tight into the threads. It just won't stay tight. I know something must be wrong here as he's pampering the throttle. I didn't oversee the assembly, so he could be doing something wrong here. Anyone else have this problem? Make the mistake he may have made?

Thanks!

- Matt
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Old 07-16-2007, 10:52 PM   #2
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How old is the truck? Might need a new T-nut.
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Old 07-16-2007, 10:55 PM   #3
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I suggest rebuilding it again, with new parts.

my issue was different, but believe it or not I have broken 3 of those diff screws. not while tightening them either. all 3 broke at the end of a race while slowing down to exit the track. crazy huh?

finally I changed the entire diff to all new parts, no problem since.
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Old 07-16-2007, 11:17 PM   #4
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make sure that the nut itself isn't broken either.
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Old 07-16-2007, 11:20 PM   #5
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Quote:
Originally Posted by TechWun View Post
Hey guys!

We are trying hard to avoid locking my brothers diff on his new T4. He assembled everything according to what he interpreted from the directions which are admittedly lacking somewhat.

He's using the mambamax 7700 combo, orion 3200 lipo and a 20 tooth pinion with the stock spur. The spur isn't slipping and he's being easy on the throttle but the damn diff system keeps loosening up on us. Are we missing something here? If it helps, it loosens more and more as he turns (differential action). We bottom out the spring and back it off 1/8" turn as instructed, and this time we even shot lock tight into the threads. It just won't stay tight. I know something must be wrong here as he's pampering the throttle. I didn't oversee the assembly, so he could be doing something wrong here. Anyone else have this problem? Make the mistake he may have made?

Thanks!

- Matt
the thurst washers have to be seated flat inside the outdrive cup , make sure there is no dirt ,ect causing the washer to be tilted...


If this still does not cure the problem....

replace the thrust out drive cup ...

Its very rare , but once & a while a defected one can slip though inspection..
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Old 07-17-2007, 09:38 AM   #6
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Thanks for the replies guys.

I should have clarified though that this is a brand new build. He finished it sunday, and the screw actually snapped off in the t-nut about 2 minutes into testing. Last night he made a trip to the hobby shop for a new screw, washers, spring, and T-nut and rebuilt it again. This time he used the locktight and let that setup before he tried it.

He gave me a call to stop up and witness the run and it did exactly as I described. Last night I took a look at the directions online, and the only thing I can't seem to remember is him removing the CAP he was supposed to install OVER the screw head upon reassembly when he poped the dogbone out to retighten it. So one thought I had was if he didn't install the cap, the end of the dogbone may be making contact with the head of the hex screw and it might have enough friction to grab it and start turning it.

Purely speculation though. I need to drop by tonight and try and apply some wisdom. Anything else I should look at? thanks again for your help!

- Matt
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Old 07-17-2007, 10:03 AM   #7
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Because you have mention the screw breaking off, I`m now convince you have issue`s just as I describe....
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Old 07-17-2007, 10:09 AM   #8
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Just a thought, are you putting the diff in the right way? The nut is susposed to face a certain way and if not, it can spin and open up. My first T3 I had that problem.
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Old 07-17-2007, 10:28 AM   #9
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Make sure the head of the bolt is on the right rear side. The T-Nut should be on the left rear. Locking fluid should not be required.

Make sure to precompress the spring with a pair of pliers before inserting it.

When you are screwing the Diff Tight, don't overtighten it, otherwise you can strip the T-Nut out. It doesn't take a lot of pressure to tighten a bolt in the car. It should just feel snug.

After the diff is together, put the car up on a stand, hold the a rear tire, run some throttle on the car for 30 seconds. hold the other tire, and do it again.

Readjust the Nut and you should be ready to go.

Adjust the slipper as necessary.
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Old 07-17-2007, 10:35 AM   #10
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Quote:
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Just a thought, are you putting the diff in the right way? The nut is susposed to face a certain way and if not, it can spin and open up. My first T3 I had that problem.
Directions say the hex end faces passenger rear, and thats where he has it. Also confirmed by another poster. Thanks!

- Matt
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Old 07-17-2007, 10:40 AM   #11
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Quote:
Originally Posted by Tubaboy View Post
Make sure the head of the bolt is on the right rear side. The T-Nut should be on the left rear. Locking fluid should not be required.
Check!

Quote:
Originally Posted by Tubaboy View Post
Make sure to precompress the spring with a pair of pliers before inserting it.
Check! He was able to get this part and the screw on sunday, but had to wait till monday for the t-nut. So we compressed the spring in a c-clamp overnight. Should have been plenty relaxed. (you would think anyway)

Quote:
Originally Posted by Tubaboy View Post
When you are screwing the Diff Tight, don't overtighten it, otherwise you can strip the T-Nut out. It doesn't take a lot of pressure to tighten a bolt in the car. It should just feel snug.
Check! We have a good 'touch' for that sort of thing. To date strippage is the one thing we have not done. lol..

Quote:
Originally Posted by Tubaboy View Post
After the diff is together, put the car up on a stand, hold the a rear tire, run some throttle on the car for 30 seconds. hold the other tire, and do it again.

Readjust the Nut and you should be ready to go.

Adjust the slipper as necessary.
Check! I am gonna have another go at it tonight, see what happens.

Thanks for all the input guys! it's nice to have a supportive community to turn to!

- Matt
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Old 07-17-2007, 10:47 AM   #12
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After you done all that above before you install, look inside the drive cup and rotate the diff. If you see the head of the thrust screw is wobbling , you may have a defected out drive cup....
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Old 07-17-2007, 11:15 AM   #13
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Are you driving on dirt or pavement?
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Old 07-19-2007, 03:41 PM   #14
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Well I just wanted to follow up. I took matters into my own and capable hands (I went to my brothers house when he wasn't home!) and did my own work to it. After I retightened the diff, I took it for a spin. On launch I noticed no slippage from the spur. This is bad and as the torque grew out of control during accelleration the read end let out a hell of a noise. So apparently things are not setup right and the diff itself is slipping up a storm.

I retightened the diff, only this time I left the spring damn near bottomed out only backing off a CH after bottom. Then I loosened up the spur slipper nut until the nut was flush with the end of the threads (This is the time when I prepared the speech I was going to give my brother about how the spur is SUPPOSED to slip to give excellent launches!). Then I reprogramed the ESC from where I had it at medium starting power, to low. I also put a slight drop in the linear accelleration curve between 10% and 60% throttle.

Then I ran it again. over and over until I had the spur slipping just right. The end result was fantastic! On asphalt I was able to gun the throttle from the stop and launch into rocket mode without even bringing the front tires off the ground. Control was excellent and accelleration was grotesque until the tires turned into pinpoints (balloned out)

So far, so good!

I want to say thanks to everyone who offered advice! And if anyone from team associated happens across this thread please take my following statement into consideration ->

'The future is here. This are becoming grotesquely powerful and your rear ends need to be able to deal with it. It does you absolutely no good to design such a fabulous rear end and hold it all together with nylon and that inexcusably small piece of hardware. You can't keep a bridge together with one bolt. It would also be very decent of you to predrill two holes through the diff assembly at 6 and 12 o'clock, and kick a couple extra threaded bolts/nuts into the kit as an option for allowing users to properly lock the diff assembly. What good is all this power if I have to detune it? It's like the lotus espirit and the renault gearboxes all over again! '

And for anyone else whow as wondering we took the entire diff assy. back to the hobby shop and got a new assembly and rebuilt it. Same results. This thing just won't tolerate the power of that system without serious tuning. At least this is my experience.

- Matt
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Old 07-19-2007, 04:38 PM   #15
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geared to high already thats one problem
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