Just finished my mod and I am happy with the way things turned out.
Started out with reading Mistercrash's thread, who supplied a boatload of info on swapping diffs. So I started out with taking the diffs apart to change the cups to traxxas shafts. As described in other threads I simply cut off the threaded area of the original traxxas axles that I kept in my box of spare parts. I cut approximately 1mm past the threaded area, and it resulted in a perfect fit. While I had everything open, I changed the diff oil to 60K front and rear.
I then took my time using a dremmel to grind out material from the bulkheads. After an hour of test fitting and adjusting I finally got them in.
I was a bit worried about lost material from grinding out the bulkheads, so I'm experimenting with a method of adding material to the outside area of the bulkhead that was affected the most. I used a urethane adhesive, and hopefully it will strengthen that area.
I decided to use my traxxas CVD center drive shaft, and connect it to the Losi diffs using this Losi diff drive yoke:
The ball end of the traxxas CVD is slightly smaller than the Losi version, so I added a 2.5mm spacer on each side of it to eliminate free play. In the pic below the red arrows show where each spacer was added. I had to slightly bend each spacer to fit the area since the area was curved. The blue arrow shows where I added adhesive to help keep the pins in place.
Final pic shows the center drive shaft installed. Took it for a test bash this morning and I am very pleased.
I forgot to count the teeth in the diff and compare it to the original diff gears to calculate my new ratio. I am currently running 65/21 with a ratio of 3.1 using the original traxxas diffs. Can anyone help me figure out what my new ratio is? Thanks in advance. My temps did not cross 150 this morning from 15 min of consistent high speed runs through grass, and a few jumps
Last edited by Revoroller; 07-31-2012 at 01:16 PM.
Did you do this because:
a) you destroyed the original diffs?
b) the factory diffs have a strong history of getting destroyed and these are proven stronger?
c) you just felt like doing it?
Oooohhhh. I was just worried because I just upgraded to the diffs you replaced. I have an original Revo that I put the 3.3 chassis on and E-Revo diffs in. I'm only running 4S an honestly really couldn't imagine running more than that, at least in the high CG, big-tire, monster truck form I have it in.
Go any video of your truck running on more than 4S?
Last edited by metoo2; 07-31-2012 at 03:05 PM.
revoroller, this thread and mistercrashes thread are awesome. i will be doing this conversion this weekend hopefully. where you tried strenghthening your bulkheads did you sand or scuff thenm in any way? ive tried this on my pede and when the chassis flexed a little it would break off of the chassis. anyway great job and im saving this in my favorites
You should be fine with 4S. I started in 4S, along with a good friend. When I upgraded to 6S I started having problems with diffs. My friend still runs on 4S with no diff problems.
This is the only good video that I have. No high speed runs, but the 6S is what's getting us to the top of that hill in the video. Tried to make the same jump on spare 4S batteries and couldn't do it.
Last edited by Revoroller; 07-31-2012 at 04:01 PM.
I cleaned the area well before applying the Urethane. Seems super solid!
I forgot to mention this. I used a longer pin to attach the Losi yolk to my CVD shaft. The part num for the pin is in the diagram.
I like your work mate...looks good. In time I might end up doing this conversion.
I've never tried 21/65 gearing...I've never gone over a 20 pinion. Do you get faster top end and less torque with that gearing?
Rock n Rolla !
Feels like I have more torque with my current gear set up. I also have 22T pinion which I love using, but my motor gets hot too fast when I'm running it through grass, which is what I do mostly. I run Robinson racing metal spurs, and they only come in 60 and 65 tooth.
Last edited by Revoroller; 07-31-2012 at 07:00 PM.
jmho pass on the metal spurs.
The LST is a lower gearing than the stock diff. 21/65 is kind of low gearing for 2/3s. about 45 mph is what I come up with.
21/54 is 55 mph.... little better gearing....
I just finished this up last week. Not all my work just getting it together.
Diff ratio LST2
4s = 40 mph
5s = 50 mph
6s = 60 mph
change the motor kv, cell count, spur & pinion count, & tire size.
BrianG speed chart:
Differential Ratio: 3.3076923076923075
Transmission Ratio: 1.8333333333333333
Other Ratio: 1
Spur Tooth Count: 68
Pinion Tooth Count: 24
Total Voltage: 22.2
Motor KV: 1800
Tire Diameter (inches): 5.9
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0.006
Spur/Pinion Ratio: 2.83 : 1
Total Ratio: 17.18162 : 1
Tire Circumference (inches): 18.54 inches (470.8 mm)
Total Motor Speed: 39960 RPM
Vehicle Speed: 40.82 mph (65.57 km/h)
Effective KV Value: 1800
KT constant: 0.75 oz-in/A
Would you go flip my truck back over??
Looks like you guys had a great time bashing. I wish we had something around here like that to bash.
^ PM coming........
Would you go flip my truck back over??
Nice work revoroller.....I did the lst2, xxl driveshaft, kershaw centers mod about a year ago and it is all still working flawlessly for me. I like your mod allowing you to use the traxxas center shafts....I think I would much prefer the double ended cvd's from traxxas to the kershaw dogbones I used.
If you throw a rcsolutions roll cage into the mix you pretty much won't have to worry about breaking bulkheads (or the chassis) anymore even with some material removed.
i only have 1 thing to say, i have done what you did to the cups with the washers to keep the pin and it didnt last long. me too i wanted to keep my traxxas steel center shafts... i d buy the kershaw designs dogbones if i were you and install them on losi default drive cups while changing the transmission cups as well. its the best thing.
im running 24t on the motor and 54t in gbox
defenately transforms the car compared to 18t
i bought a 22t and 24t but just leave the 24t in there
theres plenty of torque so no need to gear it low
just dont press so hard on throttle hehehe
i really should get a speed reading one day
i have a tqi controller and sensors coming now so hope to set up speed and rpm accurately
I will keep the Kershaw shaft in mind if I have problems later on. From my observation, the main thing that can fail with what I did is the pin slipping out of place. The washers are not there to keep the pin in, but there to keep the ball end of the shaft centered, and without free play. I used a small amount of glue on each end to create a barrier for the pin. In addition I used the blue sleeve which covers each end of the pin. This is the same glue that I used to glue my telemetry magnet onto my metal spur gear, and it's still attached. The glue is basically covering the hole at each tip of that pin.
Remember the red metal sleeve that was attached to the end of the CVD shaft? That is what traxxas put in place to keep that pin in place. If I can find a metal sleeve to slip over the Losi part then I can simulate what was done by traxxas and add further protection for that pin.
BTW- I visited Greece and Rome last year! Had a blast!!!! Pompeii is a freaky town , lol! Loved Athens !! The dogs in the street followed us everywhere , lol!
Last edited by Revoroller; 08-01-2012 at 10:51 AM.
lol hey nice of you to visit ;P still the islands is the best thing greece has to offer.
to the point. i know exactly what you did with the washers i didnt say it correctly before sorry. my solution for the pin not slipping out is using/making some kinds of hard rings outside the cup just like the traxxas red thing that you say. they all eventually failed, the power is too much! even the dogbones slowly grind the steel cups. you say that you glued the pin to the cup eh.. i dont know i didnt try that. i hope it works for you but i wouldnt feel safe anymore like that
Great write up...soon I will be doing this.
ERBE,Losi 8ight,Slash 4X4
If there's room so it doesn't rub anything I think a ring (or two) of shrink tubing shrunk and glued on to capture the pin would set my mind at ease more than just the glue....There's just too much vibration and violent jarring on those pins for me to trust any kind of glue to stay put for long.
After taking candy76man's advice, I decided to take out the shafts to wrap shrink wrap around the pins. After inspecting the pins I am very pleased to see that they are still in place
This is great, since I drove the truck for 3 sessions after doing the mod.
After my inspection I added the shrink wrap, and it worked well. I definately feel better about the safety of these pins. Thank you for the suggestion candy76man.
The shrink wrap also gave the blue boot cover a tighter fit.
I ordered a new HPP motor brace, which was shipped from Germany with two bags of German gummy bears, lol! I installed it, along with another popular mod
Last edited by Revoroller; 08-03-2012 at 01:30 AM.
Ready for some action!!!
Looking good mate...looking good
Rock n Rolla !
Very cool truck. I'm also waiting for my HPP brace so i can do the rear toe link brace mod. I remark you got stiff Pink 5.4 springs, with a cranked-up preload setting. Happy with it? Doesn't it make your erbe too bouncy?
I ripped my HPP brace of my motor yesterday, the rear shock mount collapsed . It did do its job thou and save my spur. Motor didn't move either . There is a price to pay for bigger and badder bashing...that's what I'm about.
Revoroller I did a revised video of my clip I posted yesterday. I put some notes in then with some heights and distances.
Rock n Rolla !
Got an HR alu rear shock mount so hopefully it'll bear the add-on stress of the HPP brace...
I have it cranked because jumping high is what I do mostly, but it is bouncy at times. I had them cranked too high on my last session and kept breaking rod ends. I have blue in the front and pink in the rear.
Do these springs ever loose their strength over time ?
i dont like the rear brace motor mount. it reduces the chassis flex, and from what i see it also breaks stuff :P try double motor mount if you want (the blue one) since i put another one there bam no more spur stripping. the stock motor mount is just too thin and bends at jumps.
bit to much preload
push the chassis to the ground, if the springs fully compress before the chassis touches the ground, to much preload.
Would you go flip my truck back over??
For the double motor motor mount, which is 2x single motor plates stuck together:
- you mention in your post here to grind the spur holder. I guess they are the fins on the back on the slipper hub? How much grinding is needed?
- Screws...Are longer screws needed?
Here are the stock screws on the motor plate:
- Tranny: (4x) 3x12 BCS
- Motor mount hinge post: (1x) 4x12 BCS. This one is going to get the M4 bolt/washer/lock nut "87GN treatment" (Thanks Doc...). An M4 x20 should do (?)
- Finned Motor mount: (1x) 4x10 CS (mesh adjustment screw). looks short if you add 3mm from the motor plate.
Am i getting this right?...