another newbie question on transmission

encantotom · 06-19-2007, 05:58 AM

hi, i have the allison 740 tranny. coach drives and rides great. the question is this.....when driving there is a howling that varies with rpm's coming from the tranny shift stick. no real loud but noticible. what in the world is that from? today we just went over the rockies at 11,000 feet. what a ride!

thanks

tom

fulltiming · 06-19-2007, 06:08 AM

Tom, are you referring to a shift lever next to the driver? If so, I would suspect something is loose and vibrating. Mine has the momentary contact toggle switch to shift gears with the digital display on the instrument panel. Mine controls an electric solenoid on the side of the transmission. Some models had a mechanical linkage to the transmission.

encantotom · 06-19-2007, 06:12 AM

yes the shift lever next to the driver. it is clearly tied to engine speed so i would guess if i traced it out it must have a mechanical linkage back to the tranny that transmits sound. that would make sense. particulary since it takes some effort to shift it. my wife drove today over a high pass in the rockies and she had a hard time shifting it. i dont have any trouble.

i am just suprised it is as loud as it is.

thanks

tom

fulltiming · 06-19-2007, 06:20 AM

Shouldn't be hard to shift and shouldn't make that vibrating sound.

encantotom · 06-19-2007, 06:26 AM

then another thing to put on my find out how to fix list. if anyone has any suggestions, then let me know.

thanks

tom

encantotom · 07-01-2007, 01:09 AM

ends up i have one of the few transmissions that has a shift level and a cable that runs clear back to the transmission. they said to follow it to the top of the back of the transmission and look for an L bracket that has the cable go through it. there is a grommet that goes in the bracket around the shift cable that wears out. just replace the grommet and the noise should decrease. i will let you guys know if it works.

tom