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Thread: help with diffs

  1. #1
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    help with diffs

    could someone please give me the how to... on shimming diffs i have the FLM Ultimate front/Rear Hybrid Bulks with diffs

    any help is greatly appreciated... thanks
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  2. #2
    RC Turnbuckle Jr.
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    Look at this very good explained.

    http://traxxas.com/forums/showthread...Street-Machine

  3. #3
    RC Turnbuckle Jr.
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    that explains it for the stock diff but shim size is different for 1/8 scale hybrid diffs but you get the idea
    which diffs are you using ?

    some have 8mm bearings on both ends and some have one 8mm and one 10mm and a 8mm pinion bearing
    i used kyosho shims- 8mm pinion 8x16mm 096046 if you have one 10mm bearing 10x15mm 096647
    Last edited by 50togo; 04-11-2013 at 08:33 PM.

  4. #4
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    i have the diffs that come with the FLM Ultimate front/Rear Hybrid Bulk
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  5. #5
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    Look at the diff. One bearing is bigger then the other right?
    once you know what bearings you need put the pinion in and then the diff and put the bulkheads together and lightly tighten up the 3 bolts to hold the bulkhead together. check the side to side play -i usually shim the diff towards the pinion.keep adding shims until it binds when you turn the pinion then take one shim out.
    assemble it and check the side to side again. if there is still play add a shim to the other side to remove the play. once all the play is gone assemble and turn the pinion .now check the pinion -pull and push on the pinion checking for play-add a shim and assemble -turn the pinion should turn smooth .you get the idea
    shimming the spider gears the same way
    when shimming you have to add shims until it binds and then take a shim out and check for binding again
    Last edited by 50togo; 04-11-2013 at 08:54 PM.

  6. #6
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    okay thanks for the help
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  7. #7
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    Dann, heres a few notes on how i shimmed my flm uhb diffs.
    (1)Use the gaskets that came with the flm uhb to shim the diff first. Add or remove as needed untill the gears mesh together and turn smooth and theres no binding when the ring gear is tightened down. You should be able to hold the output shafts with your fingers and turn in oppisite directions and have a nice smooth feel. A very slight notchy feel in one small spot is ok, they will wear in. But only very small! Once you have it shimmed take it apart one more time and add your diff oil of choice and reassemble.
    (2) I shim the pinion so the teeth line it up with the ring gear. You want to make shore the pinion teeth make good full contact with the ring gear.
    (3) Then Just like 50 says, Start adding shims to the ring gear side untill it meshes with the pinion. Keep in mind whitch side the ring gear is on. I think its driver side rear,pass side front. Either way the front and rear have to be oppisite so the tires all turn in same direction. Make shore when doing this that the bearings are fully seated in the housing. sometimes they can stick a little. Once you get that shimmed so the gears mesh as close as possible with no notchy feeling or binding, take it back apart and add shims to the other side of the diff to remove the diff side to side play in the bulk. Then reassemble tighten screws a little and see how it feels. The pinion should have a nice smooth feel when you turn it. and little to no backlash. And again here if theres one small spot thats a tiny bit tight and a notchy spot its ok. BUT ONLY SLIGHT you dont want them actually binding up. It is my expieriance that they usally will have one spot that will hit and start to bind first. Thats what you want to find and shim so you just barely feel it.
    And a few more little notes that might save you some headaches
    To get an acurate feel of the gears, like 50 says you really should tighten the three screws that hold it togtether just a little each time you make a shim change. You will probably put it together and take it apart quite a few times untill you get it to feel right. You also need to to rotate the pinion around a few times when checking so it goes all the way around the ring gear.
    After you get the diff shimmed in between the bulk so there is no side to side play and the pinion feels good with just a tiny bit to no backlash. Put a little grease on the ring gear and hopfully put it together for the last time. Till you break it in. LOL Then you can do it all over again. After its been used for a while its a good idea to take apart and check for play and gear mesh. They will wear in over time and abuse.
    A lot of people also put a small rubber oring or shim behind the drive cup on the pinion shaft to keep the pinion from moving in towards the ring gear. This is a good to do and loctite the the cup on there good and tight
    Well i cant type worth beans and this has taken me forever. LOL But glad to help another E-maxx guy.
    Did the best i could to explain it. Hope this helps you out. If you search you can find some pretty good vids on this too.
    Last edited by EMAXXBRUSHLESS; 04-12-2013 at 09:32 AM.

  8. #8
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    Thanks a lot I greatly appreciate it ill be posting soon the story of my emaxx for everyone to see
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  9. #9
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    hey EMAXXBRUSHLESS... did you also shim the the inside of the diff or just outside one the ring and pinion gear
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  10. #10
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    I shimmed the inner diff using one blue gasket that came with it behind the ring gear. Then some 8mm shims on the pinion to line it up with the ring gear. Then shim both sides of the diff to get the gears to mesh properly and remove the side to side play.

  11. #11
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    Okay so I don't really have to shim on the inside of the differential like I don't have to take it apart put shims on it put it back together and put shims on the outside and put it back in the case
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  12. #12
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    Thats corect, you shouldnt have to put any shim washers inside the diff. Did it come with a bunch of paper type gaskets with 4 holes in them? These should be all you need for the diff itself. Mine came with one thicker blue gasket witch is what i used.

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