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-   -   T-Maxx transmission problem (http://www.rcuniverse.com/forum/traxxas-monster-truck-forum-251/7288154-t-maxx-transmission-problem.html)

caylorray 03-26-2008 08:16 PM

T-Maxx transmission problem
A friend has an older T-Maxx with the .15 engine. His transmission is acting funny. It won't shift from fwd to reverse properly. It doesn't seem to engage right when trying to throttle fwd. Sometimes when sitting idle it seems to pulse, like it's trying to spin.

We've taken the transmission apart and everything appears to be good. All gear teeth look fine. There's no binding. The centrifugal clutches seem fine, although I wouldn't know for sure if they were failing. Went ahead and changed the one-way bearing just as a thought. That only made a slight improvement. There also is a high-pitched sound when it's trying to engage.

I don't have alot of experience with these transmissions. What could be the problem? Anything we could look at that might not be so obvious to the untrained eye?

ccity 03-26-2008 08:45 PM

RE: T-Maxx transmission problem
For starters the one way bearing is for the starter not the transmission. Have you checked the servo to make sure its working correctly? checked linkage? check connection to reciever? make sure nothing in the way and bindng it up? Is your idle to high causing it not to engage/disengage?

caylorray 03-26-2008 09:14 PM

RE: T-Maxx transmission problem
There's is a one-way bearing in the transmission. It's part number 4986. Different than the owb for the starting system.
Servo is working fine. Drives shift-linkage to full extremes. Receiver not an issue.
Nothing is binding. Idle is fine.
The fwd/reverse shifting issue is not the primary issue....it's just a side affect of what's really wrong.

When fwd is properly engaged, it drives fwd, just not performing at 100%. Again, there's a whine emitting from the xmsn; doesn't seem like it's fully engaged; sometimes pulses at idle as if trying to drive; will not shift to reverse very well; sometimes gets stuck in "neutral"; and everything visually looks fine inside.

ufdfireman 03-26-2008 09:29 PM

RE: T-Maxx transmission problem
Sounds like your idle is too high. Try putting the brakes on before you shift into reverse. If the idle dies down when the brakes are on, your idle is too high.

caylorray 03-26-2008 09:41 PM

RE: T-Maxx transmission problem
Idle is fine. The problem definitely lies somewhere between the clutch, pinion, and/or transmission, and right now I'm leaning heavily towards the transmission. Just can't figure out what it could be with the transmisison.

DaveG55 03-26-2008 10:34 PM

RE: T-Maxx transmission problem
The idle does sound high, that would definatly give you the pulsing at idle. It doesn't have to be very high to cause that. It's been a long time since I've been inside my Pro.15 transmission but I seem to remember some springs that return the forward/reverse pawls to their resting position. Maybe look there?????? Also be sure that eveything is moving smoothly and engaging fully in the f/r drum and that nothing is rubbing.
Has your friend considerd the "no buck/constant engagement" mod? It's one of the best mods I've made to my Maxx.

systemlord 03-26-2008 11:22 PM

RE: T-Maxx transmission problem
If your rpm's are too high, then it won't engage into reverse properly. It seems like your idle/rpm's are too high causing you clutch in trans to engage prematurely. Traxxas fix this in the Revo to where the Revo will not shift into reverse until your truck comes to a complete stop. I can recall my TRX 2.5 when running lean it to would want to hesitate, try lowering you idle.

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