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  1. #1
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    Trx 3.3 connecting rod defect?

    This is the connecting rod out of my slayer pro 4x4 3.3. It sure looks like a defect in material to me! What's your opinions? Traxxas support said I over heated the engine or over-reved it


  2. #2
    Marshal Double G's Avatar
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    There have been multiple reports of it happening with the 3.3 since it is the same rod as the 2.5. You could make arguments/complaints about this happening, but honestly it has already been said. Consensus here is that a lean tune and overrevving it will cause the rod to split. We need to see photos of the piston top too--which is straight from the engine and has not been cleaned off.
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  3. #3
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    The dark colored spots say it all. Over-heated and over-stressed. Defective tune.
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  4. #4
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    Quote Originally Posted by lubecakes View Post
    The dark colored spots say it all. Over-heated and over-stressed. Defective tune.
    Or possibly a leak causing leaning out at high rpms and irratic idle....

    I bet there's a couple of pieces of the piston skirt broken off as well. Usually is what breaks first causing debris to be flying around the engine, then it gets caght up on the internals creating a lot of stress and then the weakest part then breaks, which is the conrod at the wristpin area.

    THis is not a defect if the engine is tuned properly and having no leaks....

    It can also happen by running too rich and high rpms, this makes a lot of fuel in the casing for the conrod now swimming through causing the added stress and of coarse it would break at the weakest point...

    Now, say you've had this problem with tuning, then figured out your tune or fixed whatever leak there could be. The damge to the internals could already have been started and just regular running to finish off the job...

    You can pick up a new 3.3 online at ebay for around $105.00 or rebuild yours. Ebay conrod, piston and sleeve for $65.00 and a new set of engine bearings for around $20.00 ..
    Founder of H.U.A.
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  5. #5
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    Been there done that. No doubt it was overheated. It got so hot it started turning blue. When you find your best tune richen it up by 1/4 turn. Also try running with higher oil content.

  6. #6
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    Quote Originally Posted by Powerman View Post
    Been there done that. No doubt it was overheated. It got so hot it started turning blue. When you find your best tune richen it up by 1/4 turn. Also try running with higher oil content.
    Richening a little is good, more oil is BAD!
    erbe emaxx 26maxx s27revo 18tmrevo XXL platinum

  7. #7
    RC Turnbuckle Jr. Nitronaught's Avatar
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    Quote Originally Posted by lubecakes View Post
    Richening a little is good, more oil is BAD!
    Oil content is going to be baased on how the fuel has the oil blended, they don't just use one type of oil but a mixture of oils. It also has a lot to do with the type of oils used and their overall viscosity of the oil blend used ib the fuel. A lighter viscosity might use a higher % of overall content compared to a blend of oils having a higher viscosity.
    I'm pretty sure that's why there's as much as 11%-18% of overall oil content in various fuels.....

    I do agree that some fuels have a lot more oil content for what they are and it affects performance big time. I find a lot of the RTR fuels are like this.

    I found what I like. I'm sticking to it as long is it is still around.
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  8. #8
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    Yeah I'm staying with Byron's.
    You have a point in regards to mixture. I believe it all revolves around how much castor they use in a given fuel....if any at all. I know there are synthetics too, but castor works great at high temps.

    There's actually a range from 7.5-18% oil in car fuels. I don't know exactly why, but a noob should always use 12% or more, since noobs often lean their engines way too much.
    erbe emaxx 26maxx s27revo 18tmrevo XXL platinum

  9. #9
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    It normally takes some form of abuse to split like that, either overheating the crap out of it, preignition, or over-revving can break it quick, or running hot and shifting late can shorten it's life. I tend to tune a bit warm, practice and race at the local track, and bash around in between. Normally I get about 5-8 gallons out of a piston and liner, and about 2 rebuilds to a rod and bearings, although some have failed earlier, and I usually just get a new engine if it needs more than a rod/liner/piston set. I have had a couple rods split just ike the OP pic, one recently was a result of a cracked carb, running very lean, and temps got above 300. Fixed the carb, and got another 1/2 gallon through it before the rod split. That is why split rods seem to be a "defect", high temps weaken the steel gradually, and permanently, you can even have massive overheating a couple times, and think you dodged the bullet, but the rod is damaged, and will break before it would have worn out. I usually keep a few piston/liner/rods, a couple bearing sets, a couple carb bodies, and a spare crank on hand, so I can keep the truck running, and don't have to miss a race waiting on parts, they can be had relatively cheap, especially if you get a few sets at a time, it is really helpful if you plan to run the truck/s a lot, or run them regularly, and will keep them long term, i lucked out and got 6 liner/rod/piston sets for $200(removed from new engines). You can even make use of the replacement plan, after a few $40-$60 piston/liner/rod rebuilds, or replacing one bad part or another, just assemble a "trade-in" engine with all the bad parts you don't want, and trade it in locally, or just buy a swapped new engine off of ebay for about the same $100.

  10. #10
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    +1, but they are aluminum LOL
    erbe emaxx 26maxx s27revo 18tmrevo XXL platinum

  11. #11
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    Traxxas should make a iron engine, heavy, but durable.





    God answers prayer,pray,believe,NEVER GIVE UP!!!

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    LOL, yes aluminum. OOPS

  13. #13
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    Hello, new here and new to Nitro R/C - bought a T-Maxx and after breakin , mine split the rod , talked to a friend of mine and got a used rod from him and reassembled , there was no damage other than the , piston and liner was still good , running O.K. now , is Traxxas replacing rods that split down the middle?

  14. #14
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    Seems that all the pics I have seen, most of them that are split down the middle are split at the groove in them. I have a machine shop here that is looking at making some for me with a bronze bushing at each end. To me it looks like from all the running of the motor the wrist pin will wear the end of the rod quick and then sent it down the center of the rod and it splits. The one I am running now does not have that grove through the center but it is still not bushed at the piston pin. Hoping the machine shop here will be able to handle what I am looking for. Will let you all know as we progress.

  15. #15
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    Mine did the same thing. I broke the motor in just as the instructions said to do. After break-in I even ran it with the body off for my first few passes on the blacktop. My onboard temp gauge never even reached 190 close 188 and then it locked up ? Thinking it was something i did wrong to the 3.3 I traded it in on the upgrade plan for $ 110.00 and got a new one. But now I'am not sure after seeing the problem that other people have had with that motor that I had with mine. I've broke the 2nd motor in the same way and no problems. Did they change the connecting rod. If so how do I get my refund for my $110

  16. #16
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    Quote Originally Posted by tcbigair View Post
    Mine did the same thing. I broke the motor in just as the instructions said to do. After break-in I even ran it with the body off for my first few passes on the blacktop. My onboard temp gauge never even reached 190 close 188 and then it locked up ?
    And there is the problem...
    Running a 3.3 under 200 degrees F is a split rod waiting to happen among other things.
    No slipper/tall gearing/power = broken parts.

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