M923A2 Tach Issue

[brock]

Hello All!

I just concluded my first trip to Glamis Sand Dunes in my 923A2.

Let me first say it was overwhelmingly successful. This truck went everywhere and had no issues. Its slow going but is just remarkable how well these things do when pushed. Also, I averaged 10 mpg on my trip up and back totaling 400 miles.

On my way home I noticed the tach hovering around 1500 rpm when cruising. I stopped at a gas station and verified that it wouldn't indicate above 1500 rpm. I know the motor is revving higher cause I can comfortable cruise at 55-60mph.

Any ideas as to what to look at next? I verified the cable isn't broken and the cable is firmly attached to the back of the tach.

Truck has 3300 miles showing on the ODO with a little less than 100 hours on the clock.

Thank you!

Heres a couple pics of our time out!

 

[fuzzytoaster]

Check if the tach cable is properly seated and tightened on both ends. While you are there spray some lubricant (I use graphite) inside the cable sleeve to help it. I've had 3 frozen cables in the past 5 m939 trucks (tach and speedo), typical issue for a truck that sits a while.

 

[brock]

Okay, great. Thanks.

 

[MtnSnow]

Also make sure you don't have any sharp bends in the cable/housing

 

[M35A2-AZ]

I had a truck that the tech would work fine till you got to 1500-1600rpm then it would jump up to 23-2400rpm.
It was the tech.