Swingline76

i am fixing up my nephews tmaxx 2.5 and when i start the engine the truck jerks a few times unless i give it gas but when i come back to idle it starts jerking again. does anyone know what would cause the jerking. clutch bell is spinning freely. spur gear seems fine but has slight wobble to it. could this be causing the jerking in the truck or is it something else? any info would be great

fabrimacator21

100% normal... that's your centrifical clutch inside the bellhousing. The clutch has a spring on it that lets the shoes catch the clutchbell at a certain rpm, which moves the truck. Basically your idle is right on the edge of too high. Try turning the idle down a little.

Swingline76

thanks for the info i will try that tonight after work and let you know what is going on

DaveG55

Well, fab is right about it being normal for the 2.5 T-maxx and about the soultion to the problem, turn the idle down.

But the cause of the jerking is in the transmission, not the engine clutch bell. There are centrifical pawls in the forward/reverse portion of the transmissionthat only allows the truck to move forward (or backward) after a certain rpm with-in the transmissionhas been reached. When the idle is slightly high the pawls willengage causingthe truck to jerk forward. But the engaging and jerking brings the internal rpm back down and the pawls disengage. The reduced load then lets the internal rpm build back up, causing the cycle to repeat.