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Thread: LST2 diff mod

  1. #1
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    LST2 diff mod

    I decided to do this mod so that I can enjoy a little more durability on 6s.

    Here's a shot of all the parts needed to build one front or rear assembly. This includes new bulkheads.



    This will be a slow build but I hope to have the assemblies ready to install by this spring.
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  2. #2
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    Looks good man! I know wesley is in the works of finishing the other bulkhead to fit the 1/8 diffs

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    Here's a shot of all the parts out of their baggies.



    Doesn't look to bad! It quite surprising to see just how much bigger the bearings are in comparison to the stock revo bearings. Traxxas really fell short on that part.

    You can see the traxxas hub shafts that I will cut the threads off and I am going to use stock tmaxx pins to lock them to the side gears. I am also going to summit drive shafts as well.
    Last edited by rock-rod; 01-07-2014 at 09:21 PM.
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    This shows how the traxxas hub shafts fit into the losi side gears with the tmaxx pin and also the threaded portion that needs to be cut off.



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    Quote Originally Posted by brushlessemaxx View Post
    Looks good man! I know wesley is in the works of finishing the other bulkhead to fit the 1/8 diffs

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    Yeah I would like to see those finished. Sure would make it easier!
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    Mike from rc monster is tweaking his too!

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    Looking good,,,subscribed this might be my next mod.

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    Wesley K does not plan to produce and sell them, they are for him and him only.
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    Found some time to assemble one of the diff housings this morning.

    I started by trimming the threaded portion from the traxxas axle stubs and installing them into the case halves.







    Then I installed the spiders into the cup and added 50k silicon oil.







    Diff assembled with oil. You can see the traxxas stubs fit perfectly so kudos to whoever figured that out.



    Next I dropped the diff and pinion into the polished aluminum housings for a test fit.



    Some shimming was needed. I ended up with .3 on the non-ring gear side and .1 on the ring gear side to get a good snap fit into the housing and to allow for a little bit of gear play to allow for expansion of the parts as they heat up from operation.





    Greased up the teeth and assembled the diff housing.
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    I did find that the pinion needed about .4 on the outer bearing so that the yoke would snug things up. I also found that the pinion bearings were a little sloppy inside their races in the housing so I tightened them up by placing flattened out staples to cause the case halves to be a force fit when the bolts were snugged down. Otherwise the pinion would wallow around and risk stripping the teeth. It spins nice and smooth with zero slop. This is the rear. The front is going to get 100k oil.

    More soon!
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  11. #11
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    looking good,
    Would you go flip my truck back over??

  12. #12
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    Nice dont forget unless you want to have to trim alot from the bulkheads you going to have to modify the cases also did you pop the seals in rhe bearing to see if they were greased well my first set I got wasnt and I determined that was the source of failure
    Last edited by littleman152008; 01-12-2014 at 12:16 AM.

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    That's good advice. I started working on the bulk head and ruined it by removing too much plastic. I cant quite get the halves to close all the way. I will get another one from the lhs today and start again and this time remove some material from the diff case.


    I did pop the seals and add a little machine oil to each one. I have tried grease in the past and found the bearings tend to lock up pretty quick. It seems that to use grease it needs to be really light weight for it to work well and I have not been able to find anything that would work. I just use oil.
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    Hi can u list what parts u bought exactly if that's not to much to ask ??? thank u


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    The parts list is in your other thread.
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    Cheers mate ! Much appreciated


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  17. #17
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    Finally got this project done. Installed the diffs with 50k fluid in the rear and 100k in the front. Short test run on 4s was successful with no funny noises. The diffs are really right and are going to need a few runs to loosen up.
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    Went to the Littleton track today and had a pretty good time. The LST2 diffs worked out great. First run was on 4s to give them a chance to break in and loosen up a little, and then the second run was on full power 6s. Everything worked great until a bad crash broke a rear summit cvd. The pin broke through the plastic end and ended up breaking the bulkhead in the process. The lst2 diff is cocked a little in the bulkhead. I will pull it a part over the next day or so and post some pics of the damage. I want to pull both diffs and change out the diff fluid. I put 50k in the rear and 100k in the front. Both are way to stiff. I am going to put 30k front and rear and fix the damage. The diffs themselves held up great though.
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  19. #19
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    If a big traxxas supplier was to step up and do this mod and sell the front and backs already shimmed, trimmed, and just ready to drop in they would make an absolute killing!

    A lot of people want/need this mod but either don't have the time or they're intimidated by it (myself included) whoever stepped up could essentially name their own price!!

  20. #20
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    The problem is that the lst2 diffs are not an endless supply. The stock will run out and then what? What we need is someone to make a replacement bulkhead that will house an 1/8 scale diff just like the fast lane machine Maxx bulkheads. Also, the clearanced revo bulkhead is quite a bit weaker.
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  21. #21
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    I am just wondering is this the same as what you are building or the internal components are different.
    Thanks you
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    That's just the diff. There is no pinion included so you then have to buy a ring/pinion set just for a pinion gear. It's cheaper to piece everything together.
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  23. #23
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    Quote Originally Posted by rock-rod View Post
    That's just the diff. There is no pinion included so you then have to buy a ring/pinion set just for a pinion gear. It's cheaper to piece everything together.
    Thanks, can't wait to see your videos.
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    Quote Originally Posted by Jezza View Post
    I am just wondering is this the same as what you are building or the internal components are different.
    Thanks you
    What you linked is the regular LST diff, what the OP is using is the HD diff from the LST XXL. Some people doing this LST conversion need to look up the original thread about it where there is no need for the Traxxas stub axles since the LST XXL drive shafts are used for a real 8th scale drive train.
    It's been fun. See ya.

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    the XXL drive axles are my next step.

    FWIW, i just broke the rear LST2 diff this am when I stopped for a quick run at the wheelpark track in Aurora. It's probably a result of the earlier issue that took out the summit shaft. I didn't take the diff apart to inspect but I think some damage was done to it. 6s=destruction.
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  26. #26
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    Quote Originally Posted by mistercrash View Post
    What you linked is the regular LST diff, what the OP is using is the HD diff from the LST XXL. Some people doing this LST conversion need to look up the original thread about it where there is no need for the Traxxas stub axles since the LST XXL drive shafts are used for a real 8th scale drive train.
    Thanks I am checking out the other threads too, that of 87 Gn and others who has done it, the reason I asked is I got 2 sets of all the traxxas diff parts, and trying to see if I return them and go ahead right away with the Lst2 diffs, both the lst2 and original lst diff uses the same case I think, but different beavel gears, and carriers, cannot find the XXL drive shaft number.....
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  27. #27
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    Quote Originally Posted by rock-rod View Post
    the XXL drive axles are my next step.

    FWIW, i just broke the rear LST2 diff this am when I stopped for a quick run at the wheelpark track in Aurora. It's probably a result of the earlier issue that took out the summit shaft. I didn't take the diff apart to inspect but I think some damage was done to it. 6s=destruction.
    OK so the diff was fine. The set screw for the rear pinion cup fell out. I found it rolling around in the skid pan. I reinstaled it with better lock tight this time.
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  28. #28
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    Sounds like an easy fix,,,was wondering because those diffs are bulletproof.

  29. #29
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    Quote Originally Posted by rock-rod View Post
    OK so the diff was fine. The set screw for the rear pinion cup fell out. I found it rolling around in the skid pan. I reinstaled it with better lock tight this time.
    What do you mean by the rear pinion set screw? Also what did you end up going with for diff fluid in the front and rear and do you like it? I'm in the process of building the diffs so I'd like to know what weight fluid people find to be the best for both the front and rear.

  30. #30
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    Should I do this if I run 4s only? Will it be worth it?

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    Quote Originally Posted by E-Revo32 View Post
    Should I do this if I run 4s only? Will it be worth it?
    It is a worthy upgrade if for anything else piece of mind. The weight of the truck with the combination of power makes quick work out of the stock parts. Had there been a hardened ring and pinion installed the gears might have lasted longer. For the original nitro version they were fine as they did not see the shock associated with the instant brushless power.
    If it didn't break you can do it again.

  32. #32
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    Ok thanks. How hard is it yo dremel the bulk?

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    It is pretty easy to dremel the the bulk as it is plastic. Best advice though is to dremel your cases down first then test fit it it and remove just enough of the bulks to make it fit. The less plastic you remove in certain places the better. Don't worry about being able to slide them in from the top like the stock, just mold the bulk around the case. Then when done don't forget to modify the chassis tab above where the diff goes. Personally I use hot glue when done to fill in any gaps and to prevent movement of the diff but that is a personal preference.

    Above all else take your time.
    If it didn't break you can do it again.

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    it is worth it,,,I stripped my diffs on 4s, the hot glue trick is great.

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    yep it's worth it. the only thing I need to go back and do is to hot glue the diff into the bulkhead. I keep having an issue where the rear diff will shift out of position. Other than that, the car has been very reliable even under 6s.
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  36. #36
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    So rock-rod, what did you end up trimming, the outer can or the bulkhead.
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    mostly the bulkhead. i may end up doing another rear bulkhead if the hot glue doesn't hold. the front is holding up great.
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  38. #38
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    Quote Originally Posted by rock-rod View Post
    mostly the bulkhead. i may end up doing another rear bulkhead if the hot glue doesn't hold. the front is holding up great.
    Thanks, as for the traxxas part 5454, after you cut it off (threaded part), how is it attached to the spider gear , (by the pin or welded on), I saw the pics above but I wanted to confirm, what drive shafts did you end up using. I am planing to use the traxxas ones and go to MIP later, which ever comes first at the lhs.
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  39. #39
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    The pin holds it in there.
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  40. #40
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    What about the diff fluid ? Did you end up going with 30 in the front and rear? And if so how do you like it. I'm in the process of building the losi diffs now but I'm not sure which oil weight is the best to go with

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