Results 1 to 18 of 18
  1. #1
    RC Enthusiast
    Join Date
    May 2020
    Location
    Earth
    Posts
    38

    Question T Maxx classic transmission problems

    seems like my transmission is slipping a crazy amount it will barely move the engine gets to high rpms but the cars barely moving. The slipper clutch is very tight but it still slips. Sometimes the car will stall also(I made sure it’s not to lean). I checked the clutch shoes and they seem perfectly fine I was going to replace it to be safe but none of the hobby shops near me sell Traxxas nitro parts anymore except fuel. What else could cause it to do this? I’m not terribly knowledgeable when it comes to nitro vehicles as it’s my first one I have owned. Any advice on what I should check next?
    Last edited by NurturantQuasar; 05-29-2020 at 12:17 AM.
    Slash 4x4 brushless>everything else

  2. #2
    RC Qualifier nebulous.cow's Avatar
    Join Date
    Feb 2012
    Location
    Seattle by summer, AZ by Winter
    Posts
    327
    Check the one way bearing inside the transmission that engages for first gear. My classic Maxx does the same thing.

    The slipper clutch should be able to be tightened enough to the point where it should stop slipping. If the slipper is slipping even tightened a bunch (but never all the way) then it has a mechanical problem.

    My and my buddy's classic maxx has this issue with the OWB, and it is shown as lurching sometimes.

    The shaft and OWB should be replaced together.

    Bearing is 4986
    Shaft it mates to is 4993

    Here is the exploded view of the maxx transmission.
    https://traxxas.com/explodedviews/T-...ssion-Assembly

    I know it looks like a looooot of parts, but being careful and sorting the parts you take out, anyone can learn to break it down and inspect. The shaft will appear polished, grooved, or notched when worn out. If you can make the OWB slip by hand on the shaft, then both parts are shot.

    That would be my recommendation to inspect if the slipper and clutch truly are in good shape.

    -Mike

  3. #3
    RC Enthusiast
    Join Date
    May 2020
    Location
    Earth
    Posts
    38
    Quote Originally Posted by nebulous.cow View Post
    Check the one way bearing inside the transmission that engages for first gear. My classic Maxx does the same thing.

    The slipper clutch should be able to be tightened enough to the point where it should stop slipping. If the slipper is slipping even tightened a bunch (but never all the way) then it has a mechanical problem.

    My and my buddy's classic maxx has this issue with the OWB, and it is shown as lurching sometimes.

    The shaft and OWB should be replaced together.

    Bearing is 4986
    Shaft it mates to is 4993

    Here is the exploded view of the maxx transmission.
    https://traxxas.com/explodedviews/T-...ssion-Assembly

    I know it looks like a looooot of parts, but being careful and sorting the parts you take out, anyone can learn to break it down and inspect. The shaft will appear polished, grooved, or notched when worn out. If you can make the OWB slip by hand on the shaft, then both parts are shot.

    That would be my recommendation to inspect if the slipper and clutch truly are in good shape.

    -Mike
    Alright thanks Iíll give that a shot tomorrow my Maxx does lurch so it very well might be the OWB.
    Slash 4x4 brushless>everything else

  4. #4
    RC Champion grizzly03's Avatar
    Join Date
    Dec 2014
    Location
    Adirondacks
    Posts
    1,415
    It could also be the friction pegs in the spur gear. They could be worn down. They should stick out past the spur gear slightly.

    Here is a link of what I'm talking about. https://traxxas.com/support/Spur-Gea...t-Instructions

  5. #5
    Marshal Double G's Avatar
    Join Date
    May 2008
    Posts
    13,951
    For the most part the only difference between a nitro and electric is how the truck moves. There may be a few more areas to check but the “checklist” is still the same.
    The Super Derecho

  6. #6
    RC Enthusiast
    Join Date
    Feb 2020
    Posts
    38
    My classic has always lurched on idle since the day I broke it in. I thought it was normal. Does it mean something's wrong?

    Also, I had the same issue except my truck would just rev up and not move at all. Turned out a pin was broken in the transmission. If your truck still won't move you might have the same issue. Here's the thread:

    https://forums.traxxas.com/showthrea...-and-spur-gear
    Last edited by len- tmaxx 2.5; 05-30-2020 at 05:31 PM.

  7. #7
    RC Champion grizzly03's Avatar
    Join Date
    Dec 2014
    Location
    Adirondacks
    Posts
    1,415
    Quote Originally Posted by len- tmaxx 2.5 View Post
    My classic has always lurched on idle since the day I broke it in. I thought it was normal. Does it mean something's wrong?...
    What do you mean by yours lurches?
    If you have reverse installed, and at idle your truck seems to rock. That can be normal. Lowering the idle helps.
    If you don't have reverse it shouldn't move at all at idle.

  8. #8
    RC Qualifier nebulous.cow's Avatar
    Join Date
    Feb 2012
    Location
    Seattle by summer, AZ by Winter
    Posts
    327
    Grizzly, its the one way slipping and grabbing suddenly inside the transmission. the truck literally kicks a couple times when you roll away from a stop every time, and then finally grabs and rolls away. Weird to watch kinda, lol.

    -Mike

  9. #9
    RC Champion grizzly03's Avatar
    Join Date
    Dec 2014
    Location
    Adirondacks
    Posts
    1,415
    Quote Originally Posted by nebulous.cow View Post
    Grizzly, its the one way slipping and grabbing suddenly inside the transmission. the truck literally kicks a couple times when you roll away from a stop every time, and then finally grabs and rolls away. Weird to watch kinda, lol
    I've only experience the vehicle jerking at idle. I could watch the spur spin up and then something internal would grab for a split second and the truck would jerk and spur would stop spinning. And then do it over and over and over again at idle.

    I install forward only kits and all those jerking, slipping issues go away. Along with those one way bearings and reverse gears. Now the spur gear only spins when the tires are moving.
    Last edited by grizzly03; 05-30-2020 at 08:40 PM.

  10. #10
    RC Qualifier nebulous.cow's Avatar
    Join Date
    Feb 2012
    Location
    Seattle by summer, AZ by Winter
    Posts
    327
    The forward only conversion does not remove the OWB that engages for first gear, it cannot. The OWB engages when you hit the throttle in first gear, and then when second gear kicks in due to the centrifugal clutch, it 'overspeeds' the first gear set of gears, and thus spins the OWB in the direction it can spin freely. My nitro touring cars with 2 speeds still have this OWB, as do all 2-speed nitro models, with or without reverse.

    Interesting you say installing the FOC has reduced the kicking at idle, that should not technically matter, if this is the actual issue. Nothing changes about the 2-speed transmission for forward driving, with or without the reverse gears, so long as no gears or parts are damaged.

    For clarity, if your OWB for first gear was in perfect shape, like it should be, there will be no kicking or lurching whatsoever. Instead, it would be manifested as the truck trying to pull away gently, smoothly, just as if the idle was set too high (which it probably is, but it could also be loose/worn out clutch springs allowing too early engagement).

    -Mike

  11. #11
    Marshal Double G's Avatar
    Join Date
    May 2008
    Posts
    13,951
    If your truck has reverse there are clutches built into the transmission that cause it to buck at low speeds. Search for the "no-buck mod" to eliminate the jerking.
    The Super Derecho

  12. #12
    RC Champion grizzly03's Avatar
    Join Date
    Dec 2014
    Location
    Adirondacks
    Posts
    1,415
    Quote Originally Posted by grizzly03 View Post
    I install forward only kits and all those jerking, slipping issues go away. Along with those one way bearings and reverse gears. Now the spur gear only spins when the tires are moving.
    Ooops my bad. Meant clutches and the reverse gears.


    Quote Originally Posted by nebulous.cow View Post
    ...Interesting you say installing the FOC has reduced the kicking at idle, that should not technically matter, if this is the actual issue. Nothing changes about the 2-speed transmission for forward driving, with or without the reverse gears, so long as no gears or parts are damaged.

    For clarity, if your OWB for first gear was in perfect shape, like it should be, there will be no kicking or lurching whatsoever. Instead, it would be manifested as the truck trying to pull away gently, smoothly, just as if the idle was set too high (which it probably is, but it could also be loose/worn out clutch springs allowing too early engagement).
    Without reverse the transmission is always engaged. There is nothing inside that needs to speed up in order to take off. The OWB only locks in second gear, it freewheels in first. It isn't involved on take-off, if it locks up you would be taking off in second gear.

    Check out the exploded views.
    With reverse there is a total of 3 clutches in the tranny. Without reverse there is only one (the second gear clutch).
    Reverse Transmission:https://traxxas.com/explodedviews/T-...ssion-Assembly
    Forward only Transmission:https://traxxas.com/explodedviews/T-...-Exploded-View

  13. #13
    RC Champion grizzly03's Avatar
    Join Date
    Dec 2014
    Location
    Adirondacks
    Posts
    1,415
    Quote Originally Posted by Double G View Post
    If your truck has reverse there are clutches built into the transmission that cause it to buck at low speeds. Search for the "no-buck mod" to eliminate the jerking.
    Many good reviews for the "no-buck mod". I would have given it a try at the time but already had FOC installed. If I ever decide on having reverse I will try this modification. As I never did care for the bucking.

    IMO I think the bucking made the fwd/rev shifting act up.

  14. #14
    RC Qualifier nebulous.cow's Avatar
    Join Date
    Feb 2012
    Location
    Seattle by summer, AZ by Winter
    Posts
    327
    Huh interesting.... I stand corrected, thanks! My classic maxx is FOC from a previous owner, and it bucks, but drive like a dream still. I would assume the Revo trans is different though, but interesting it doesn't do that. So that raises the question, does the 2 speed work in reverse too? Lol. Havent tried on my revo... haha.

    Seems way overcomplicated for what it should be, lol. No wonder people have so many issues, so many parts to cause issues...

    -Mike

  15. #15
    RC Champion grizzly03's Avatar
    Join Date
    Dec 2014
    Location
    Adirondacks
    Posts
    1,415
    The classic tranny is different from either the Tmaxx 3.3 and the Revo or Slayer tranny's. It has too many internal clutches! Traxxas did away with them in the 3.3 Tmaxx and Revo. A much simpler design.

    I could never control my truck well enough in reverse to hit the speed needed to shift into 2nd.

  16. #16
    Marshal Double G's Avatar
    Join Date
    May 2008
    Posts
    13,951
    Starting with the 4908 T-Maxx and newer, Traxxas installed the Revo-spec gears so they are interchangeable between the Revo and T-Maxx. Just need a different case.
    The Super Derecho

  17. #17
    RC Champion grizzly03's Avatar
    Join Date
    Dec 2014
    Location
    Adirondacks
    Posts
    1,415
    Does the Revo-spec transmissions with Fwd/Rev gears that have the one-way bearings instead of the clutches work better? I guess I'm trying to ask does the bucking stop? Does the spur gear free-wheel like the "classic" setup?

    I have never tried newer design Fwd/Rev transmissions except for the "classic" style.

  18. #18
    Marshal Double G's Avatar
    Join Date
    May 2008
    Posts
    13,951
    I don't know. I've ran FOC since I bought my 4908 T-Maxx and built my 5308 Revo.
    The Super Derecho

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •