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Backwheels dont spin, any suggestions??

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Old 10-30-2011, 08:55 AM
  #1
Vinno
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Default Backwheels dont spin, any suggestions??

Hey guys,

Was bashing on the grass, no jumps for 2 hours today, got it to a perfect tune and then went to bash on the dirt few mins away.

Started it up again, wierd noise like it like strugglying/bog/lean noise. Then lifted up the car and notice the backwheels dont turn when giving it gas but front wheels do.

I turned off the truck then spun the left front wheel, right front wheels spins together. I spun back wheels indiviually, only one side spins instead of both. I checked the scrub screws on the center shaft from the front to the center brakes then then the shalft behind it down to the rear, seems like all grub screws were still there.

Does this sound like the back diff died? If the center shafts were lose and lost a grub screw holding it, then the back wheels shound still spin in sync together right?

Had truck maybe 4 days now. Maybe 6 hours run time.
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Old 10-30-2011, 09:09 AM
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Default RE: Backwheels dont spin, any suggestions??


Quote:
ORIGINAL: Vinno

Hey guys,

Was bashing on the grass, no jumps for 2 hours today, got it to a perfect tune and then went to bash on the dirt few mins away.

Started it up again, wierd noise like it like strugglying/bog/lean noise. Then lifted up the car and notice the backwheels dont turn when giving it gas but front wheels do.

I turned off the truck then spun the left front wheel, right front wheels spins together. I spun back wheels indiviually, only one side spins instead of both. I checked the scrub screws on the center shaft from the front to the center brakes then then the shalft behind it down to the rear, seems like all grub screws were still there.

Does this sound like the back diff died? If the center shafts were lose and lost a grub screw holding it, then the back wheels shound still spin in sync together right?

Had truck maybe 4 days now. Maybe 6 hours run time.
Just because the grub screws are still present doesnt mean its tight. Verify the grub screws in on the diff output yokes are tight. If they are tight, then spin the transmission (spur gear) to see if both front/rear driveshafts are turning. If they both turn and the back wheels do not turn at all, then I'd suspect something amiss in the rear diff.

I've lost power to the front or rear on my LST2's a couple times and it ended up just being a loose grub screw. If the Diffs are shimmed properly, they should last for a really really long time without needing service provided the bearings are in good shape.
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Old 10-30-2011, 11:38 AM
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Default RE: Backwheels dont spin, any suggestions??

Okay guys, i undid it all. Once i took the diff out from the back. Not sure how i snapped it :O

The diff cup drive on one side just pulled off with ease. Snapped.

Need a replacement:
Front/Rear Diff Outdrive Set Product ID LOSB3540

Here are the snapshots from the iphone:


Uploaded with ImageShack.us


Uploaded with ImageShack.us

I think i might need to refill with bit more grease now:


Uploaded with ImageShack.us


The replacement part looks like its in stock at my local place and can drive get it tomorrow but anyone know if any grease can do to fill the diff up?? or does it have to be the losi grease which i dont think anything local to me stocks losi grease maybe other branded rc grease though but not sure if its made for diffs? do grease have weight like diff silicon fluid?

Any input would be much appreciated. Thanks in advance.

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Old 10-30-2011, 02:57 PM
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Default RE: Backwheels dont spin, any suggestions??

you will be at your LHS for your drive cup, just buy a bottle of diff fluid(5$).
take one between 10wt and 40wt. your preference, the more the number is high, the more it will ''lock'' your diff.
the more the number is high, the more chance you have to break another cup...

personnally, i run 30wt. frton and rear.
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Old 10-30-2011, 04:34 PM
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Default RE: Backwheels dont spin, any suggestions??

I did the grease-delete function and used Silicone diff fluid as well. I tried 30k weight in the front and rear but I found the steering suffered some with the diff acting more locked. I now use 10k weight in the front and 30k in the back. Make sure the gasket mating surfaces are super clean so it seals good. No need to replace the gaskets if they aren't torn. Just clean them well.

I've never seen a drive cup break like that. Well, since the rear diff is out, its a good time to re-shim it anyway. if there's any amount of play in the diff bearings, I'd replace them.
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Old 10-30-2011, 05:35 PM
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Default RE: Backwheels dont spin, any suggestions??

If they don't have any silicone fluid, or any suitable diff grease, use automotive wheel bearing grease. I personally use synthetic in my old t-maxx diffs (non sealed type), but silicone fluid is really the best in my opinion. I like 10K F+R but want to stiffen up the front a bit more one of these days.
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Old 10-31-2011, 09:42 AM
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Default RE: Backwheels dont spin, any suggestions??

I ordered 3 types of losi grease, pick up tomorrow sometime with the replacement part. I will buy 2 bottles of 10k/30k just incase none of the losi grease i get tomorrow is for filling diffs.

Hmm, the manual doesnt say what losi grease is in it too.

If i were to put the 10k/30 fluids in, how did you guys clean out the grease from the diffs?
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Old 10-31-2011, 10:24 AM
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Default RE: Backwheels dont spin, any suggestions??

I hate doing diffs. I put all the bits in a cup or bowl of some sort, spray them down with brake cleaner,and just try to get as much grease off as possible. Then just fill up with diff oil.. One bottle of 10 or 30 is plenty...

I just did a diff this morning.. [:'(]
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Old 10-31-2011, 01:54 PM
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Default RE: Backwheels dont spin, any suggestions??

Don't forget the blue locktite on the grub screws!
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