Traxxas T-Maxx big block build.

[RyanKeith78]

Ok, having a huge problem and need some advice from some of you experienced builders. I keep breaking the primary shaft in my Tmax big block. Not sure if I'm doing something wrong or not. I have the Robison Racing slandered ratio still gears, and an Integy aluminum transition case. Is there suppose to be some slop for the primary shaft to move back and forth, or shim it. I shimmer the last one I put in and it broke in 3 places on the 2nd run.

 

[D3MON]

does your rig have a FOC in it? if i remember right on mine it had a very small amount of wiggle back and forth but just so much that it wasn't binding. dont recall having to shim it, but mine was also plastic case. are the bearings in yours good? well lubed? if i recall correctly a company used to make stronger shafts for the transmissions but i don't remember who. are you running steel driveshafts to the diffs from trans?

 

[cbaker65]

Ok, having a huge problem and need some advice from some of you experienced builders. I keep breaking the primary shaft in my Tmax big block. Not sure if I'm doing something wrong or not. I have the Robison Racing slandered ratio still gears, and an Integy aluminum transition case. Is there suppose to be some slop for the primary shaft to move back and forth, or shim it. I shimmer the last one I put in and it broke in 3 places on the 2nd run.

It might be ,that you may not have the slipper set right for the running conditions!

Now ,you have bigger power ,so sense you have bigger power ,you might have your slipper set
too tight ,also ,if you are running your truck ,or even test running the truck out on the street ,
might have snapped the shaft.

The slipper clutch is there for a reason ,its to allow ease some of the torque off the internals of
the trans.
The street ,the truck will have a lot more traction ,which is too hard on the trans. shaft ,especially
with the off road tires!

So ,you need to adjust your slipper accordingly ,I loosen mine up a little when I go from field to street ,
however ,the slipper also needs to be adjusted for rough terrain & jumps as well!...

 

[D3MON]

I didn't even think of the slipper clutch, good call.

 

[cbaker65]

I didn't even think of the slipper clutch, good call.

REVERSE ,there will be a pause between forward an reverse motion ,there has to be ,otherwise ,the explosion will
start to happen!

Some folks like reverse capabilities ,some folks don't know why people want to cancel it out!

Reverse is bad when you hit it at thirty miles n hour ,intensualy or by mistake ,years ago ,the Traxxas E-max was bad about
that ,LOL......I called it smack down ,My B-law would be going full throttle an hit reverse an the truck would stop real quick
an slam down on its roof top on the street!...

Also ,reverse gears add heavy dead weight!....I got rid of a half of pound by getting rid of reverse ,an saved wear & tear on my trans.!

 

[D3MON]

+1 to the FOC, first thing i did on my maxx and mgt, my little brother was runnin the maxx and saw the button and before i could answer or see what button it was it was already pressed... was funny because the FOC was in the mail at the time anyway and the only parts that broke were what was in the FOC kit, got way too lucky.

 

[RyanKeith78]

does your rig have a FOC in it? if i remember right on mine it had a very small amount of wiggle back and forth but just so much that it wasn't binding. dont recall having to shim it, but mine was also plastic case. are the bearings in yours good? well lubed? if i recall correctly a company used to make stronger shafts for the transmissions but i don't remember who. are you running steel driveshafts to the diffs from trans?

Yes, its forward only. My gear box is aluminum, Integy, and there is quite a bit of slop with the primary shaft. From this last break it looks like I shimmed it too much causing the bearings to fail. I have an all steel drive train, nothing is plastic. Running the Big Red .28. Thinking about having a machine shop make me a better shaft out of tool steel, its getting very frustratig. I have 2 grand in this thing already going to a true big block, now the shaft keeps breaking.

 

[olds97_lss]

I ran into that back in the day, but that was with the old style transmission. And that was after a year or so of abuse, but only with an OS21RG, which I'm guessing isn't putting out near the power of your 28. I snapped the two speed shaft in twain.

If the new style trans is anything like the revo transmission, I haven't busted anything in my BB revo other than gears. I went RRP for the main input and 2-speed gears, except for the two main output gears. My BB revo started as a slayer, which was geared different using different output gears. I never shredded those, but I fried the input and two speed a couple times, then went with RRP. I'm still running the plastic trans case and plastic center/outer axles on that revo too. When I did run it, I ran it a lot and would need to replace the centers at least once a season and the rears almost as frequently, but I liked having cheap axles to absorb my stupidity vs the transmission/diffs absorbing it.

I have an LRP28 in my BB revo and I honestly can't recall every snapping a shaft in it.

With my other revo, I put an OS21TM in it. It's not nearly as torquey as the LRP28, but it's enough to make the truck a lot more fun than the 3.3 ever did. That one was a revo 3.3 when I got it used. I made it to about tank 8 of break in before shearing pins in the trans. I fixed it, then shelled the gears the next weekend. I wasn't about to go through that constantly... Then I went with RRP fully in that transmission, then had a pin fall out, but once I replaced it, it's held up ok.

Anyway, long winded way to say, either your getting really bad luck, or something in your alloy case is aligned badly, or your getting crappy shafts, or your slipper is way too tight.

 

[RyanKeith78]

I ran into that back in the day, but that was with the old style transmission. And that was after a year or so of abuse, but only with an OS21RG, which I'm guessing isn't putting out near the power of your 28. I snapped the two speed shaft in twain.

If the new style trans is anything like the revo transmission, I haven't busted anything in my BB revo other than gears. I went RRP for the main input and 2-speed gears, except for the two main output gears. My BB revo started as a slayer, which was geared different using different output gears. I never shredded those, but I fried the input and two speed a couple times, then went with RRP. I'm still running the plastic trans case and plastic center/outer axles on that revo too. When I did run it, I ran it a lot and would need to replace the centers at least once a season and the rears almost as frequently, but I liked having cheap axles to absorb my stupidity vs the transmission/diffs absorbing it.

I have an LRP28 in my BB revo and I honestly can't recall every snapping a shaft in it.

With my other revo, I put an OS21TM in it. It's not nearly as torquey as the LRP28, but it's enough to make the truck a lot more fun than the 3.3 ever did. That one was a revo 3.3 when I got it used. I made it to about tank 8 of break in before shearing pins in the trans. I fixed it, then shelled the gears the next weekend. I wasn't about to go through that constantly... Then I went with RRP fully in that transmission, then had a pin fall out, but once I replaced it, it's held up ok.

Anyway, long winded way to say, either your getting really bad luck, or something in your alloy case is aligned badly, or your getting crappy shafts, or your slipper is way too tight.

Yes, its forward only. My gear box is aluminum, Integy, and there is quite a bit of slop with the primary shaft. From this last break it looks like I shimmed it too much causing the bearings to fail. I have an all steel drive train, nothing is plastic. Running the Big Red .28. Thinking about having a machine shop make me a better shaft out of tool steel, its getting very frustratig. I have 2 grand in this thing already going to a true big block, now the shaft keeps breaking.

You know, I kinda had a thought that the aluminum trans case just may be cheap or defected, cause from the get go I didn't think it should have had that much slop in the primary shaft. I ordered all knew parts and a new bearing kit, going to try oversized bearings, 5×11×5 instead of the 5×11×4's. If it breaks again think I may have to get a better quality aluminum case. I have all rrp gears as well, and have my slipper lose enough to absorb some of the take off power. I know the LRP.28 must have more power than the Dynamite .28 I have, if its not breaking that shaft then neither should mine. I've seen Tmax's with LRP.32's and 8 port Novarossi .28's and hold together.