TMaxx .15 transmissions problem?? any help would be appreciated

[O123456789]

(Resolved?) TMaxx .15 transmissions problem?? any help would be appreciated

Hi,

I am trying to troubleshoot an issue with my TMaxx and would appreciate any help / suggestions. I am somewhere between a novice and a noob so if some of my terminology is wrong please don't hold it against me.

What I have:
Original Tmaxx .15 with forward/reverse transmission

Issue:
The Tmaxx does not move when I give it gas.

When I give the tmaxx gas I see bell clutch thing on the motor spin, which spins the spur gear. I believe the slipper clutch is fine since I see the drive shaft attached to the spur gear spinning. I have taken apart the clutch and inspected the shoes which appear to be fine. I took apart the transmission to see if anything looked wrong, like stripped gears. Everything appears to be fine, so I am not sure what else to look at or look for.

I tried to talk with an employee at my local hobby shop but he didn't seem to want to waste his time talking to me. He just said bring it in and he will look at it. Since I would like to understand how the truck works, and more importantly how to fix it myself, I don't want to become dependent on someone else fixing it when it breaks.

For reference in the exploded diagram from traxxas my transmission has the "old style" primary shaft assembly.
http://www.traxxas.com/PDF-Library/4910_pro15_tranny.pdf


More Info:
It "seems" to me that the rotation from the motor and spur gear is not getting transferred to the axles. I looked at the output gear assembly (item 4997 + 4998) and they "seem" ok. The little metal thing (black pawl/ shiny pawl) on the gears swings out when I push on the one side of them. It looks like that is how the 4990 (transmission clutch bell) gets engaged to spin the axel. How does one know if the output gear assembly is behaving correctly?

Thinking outloud:
I guess I really don't know that the clutch bell on the engine is engaging correctly. It is possible that even though it is spinning it could still be slipping and not giving enough rotation to the transmission (spur gear) for it to engage. How does one verify the engines clutch bell is being properly engaged?


Any suggestions or ideas would be much appreciated.

Note: I have a similar thread at another forum but I figure the more people I can get suggestions from, the better off I will be.

 

[pondy]

i had the same problem, the spur was spinning the input staft, but when you hold the spur it stopped, the clutch was melted

 

[olds97_lss]

You could try what pondy suggests. Get it running, then hold the spur gear and give it gas. If you feel a decent amount of force, then your clutch is engaging.

What does it do if you lift the truck off teh ground, then apply gas gently? Do you hear the transmission "click"?

In the older t-maxx with reverse trans, they had a horrible lurching problem until the gear was fully engaged with enough RPM's. Most people remove reverse and put in a FOC (forward only conversion), which removes this lurching problem.

If you do the spur test and are getting a decent amount of force, then it may just be that your forward/reverse servo is holding the shifter between gears and not engaging either. Maybe try pulling out/pushing in the shaft by hand that the reverse servo connects to and see if the shaft moves further in either direction than what the servo is moving it.

 

[O123456789]

You could try what pondy suggests. Get it running, then hold the spur gear and give it gas. If you feel a decent amount of force, then your clutch is engaging.

What does it do if you lift the truck off teh ground, then apply gas gently? Do you hear the transmission "click"?

In the older t-maxx with reverse trans, they had a horrible lurching problem until the gear was fully engaged with enough RPM's. Most people remove reverse and put in a FOC (forward only conversion), which removes this lurching problem.

If you do the spur test and are getting a decent amount of force, then it may just be that your forward/reverse servo is holding the shifter between gears and not engaging either. Maybe try pulling out/pushing in the shaft by hand that the reverse servo connects to and see if the shaft moves further in either direction than what the servo is moving it.

Hi (pondy,olds97)

I tried some of the suggestions and here are the results.

Note: After taking apart and putting back together the transmission a couple times it seems to be acting a little different then it was originally.

Action: Hold spur gear while I giving the car gas.
Result: I had to give the car a fair amount of gas to get the spur gear to spin (while holding the gear), but it was able to spin the gear. I would say I was using more then slight but less then vice like pressure on the spur gear. I did get a little cherry burn on my figure.

Action: Pick car off ground and give gas
Gentle Gas:
Result: I don't hear clicking just the motor spinning, and the tires do not move.
More Gas (1/2 throttle maybe):
Result: I can't say I hear clicking but the tires did spin. With the car off the ground I kept giving it gas until the wheels finally spun. It was sort of a jerking spin, then after a sec or two the wheels spun at a consistent speed.

Since the wheels spun this time I figured I would try to put it on the ground and see if it would go. Again I had to give the car a fair amount of gas for it to go, it was slow/sluggish but did move. I tried both forward and reverse and both seem to function.

Note: It has been a long time since I last drove it so I don't recall how responsive it was when I first got it. Maybe it is behaving normally now and I just don't know it.

I really appreciate the suggestions and ideas and welcome any more people may have.

 

[olds97_lss]

Check your throttle alignment. With the engine off and electronics on, take off the air filter and look down inside the carb. Move the trigger to WOT and see if the carb is actually opening all the way. With linkages set wrong, it may not actually be opening your carb up, so 1/2 throttle on the trigger may be less on the carb.

Now that you have it moving... just sounds like an adjustment or something is sticking in the trans.

 

[O123456789]

Check your throttle alignment. With the engine off and electronics on, take off the air filter and look down inside the carb. Move the trigger to WOT and see if the carb is actually opening all the way. With linkages set wrong, it may not actually be opening your carb up, so 1/2 throttle on the trigger may be less on the carb.

Now that you have it moving... just sounds like an adjustment or something is sticking in the trans.

Hi olds97_lss,

I looked at my throttle linkage and it did look a little off. I played around with it to remove extra play. Now wide open on the throttle does up the carb all the way up.

I took the car out and it still exhibits the sluggish behavior. When my car initially broke (a long time ago) I am not sure that I got it totally broken in, so perhaps these are now symptoms of an untuned engine.

 

[olds97_lss]

Then I think you should run through a typical break-in process just so it is done. If after 6-8 tanks have been through and your not seeing an improvement, then you can look at other possible problems.

 

[O123456789]

Then I think you should run through a typical break-in process just so it is done. If after 6-8 tanks have been through and your not seeing an improvement, then you can look at other possible problems.

Thanks, I will run through a complete break in to be sure it is done. Originally something was unhappy in the transmission but after taking it apart and putting it back together (2 times) I think I made it happy. I will post back when the breakin is done.

Thanks again to all for suggestions and ideas

 

[O123456789]

Thanks, I will run through a complete break in to be sure it is done. Originally something was unhappy in the transmission but after taking it apart and putting it back together (2 times) I think I made it happy. I will post back when the breakin is done.

Thanks again to all for suggestions and ideas

I have a follow on question/scenario I was hoping to run by people.

I bought a used foc transmission with a torque control slipper clutch on eBay.

Before with my stock transmission (w/ forward and reverse) the engine bell gear and spur gear would spin under light throttle but I would have to give a lot of throttle for the car to go.

With the foc transmission I have to give a lot of throttle for the engine bell gear and spur gear to spin.

I understand that with forward and reverse the transmission needs to spin up for the transmission clutch to engage. With the foc transmission there is no spin up required.

Keeping in mind my engine may not be broken in (plan to do this over the weekend).

Is this normal for me to have to give a lot of throttle for the foc transmission to move? Or since my car may not be broken in this may be normal. If this is not normal, might this mean my issue is not in the transmission but with the engine/bell gear/clutch.

It has been a long time since I first drove the car but I don't recall having to give as much throttle as I am now to move.

Any input is welcomed.

 

[O123456789]

So I think I know what happened with my TMaxx.

When I took apart the transmission and clutch bell I fixed an issue with my transmission and induced an issue with my clutch bell. I think my transmission was probably stuck in between forward/reverse and taking it apart and putting it back together got everything back in sync. When I put my clutch shoes back on, I did so referencing my operations manual, which states to put the shoes with leading edge engagement. When I looked at the online manual it states to put the shoes with trailing edge engagement (step 28) (http://www.traxxas.com/support/index.php?action=artikel&cat=35&id=99&lang=en&suchbegriff=)

After switching my clutch shoes around the car seems more responsive to throttle. I drove it around a bit and broke a few teeth off my spur gear. I read around the forum and I am guessing my motor likely shifted. So I am off to buy some light thread lock.

Thanks for the help and suggestions.

 

[Rolex]

TRAILING edge with the clutch shoes.