Case 970 tach

[Dairy Farmer]

well i got the new cable for the tach but now the tach needle seems to jump around a lot when the engine is running steady and it says full throttle is 2500 RPMs. Is my tach going bad too? or is there a problem with the sending unit. the needle don't move an amazing amount but just a little the the left and righ.
thanks
DF in WI

 

[IHr190]

DF, Its probably then the tach drive gear.This runs off of the cam, and it is what the cable connects to going into the block. It is still available, and costs around $100. I had the exact same problem with my 770. New cable, and tach, still the needle only jumps. You also need a special puller to remove tach drive. It is a pressed fit into the block. My dealer will rent it to me for $15. I hope this helps.

 

[Anonymous-0]

The tach drive puller is easy to make and most likely it is the tach drive. They have a resin gear that wears and causes all sorts of problems.

 

[INCase]

could be what the others have mentioned. but could be in the tack too. The mechnanical tachs and speedo"s drive a small drum that has a friction couple to the needle. A clock spring takes the needle back to 0. as the speed increases the friction grabs the needle drum more and resists the clock spring thus moving the needle. If the friction drive is too dirty or gummy from age the needle could bounce around as it grabs and lets go. I can"t say what you"re supposed to use to fix or lubricate (if any) these things. You could try a speedo repair place. gaugeguys.com??? I"d say a sparse amount of graphite for the hour meter gears as they can get gummy too and resist the drive cable too much. Is it an open cab? Those gages tend to lead a tougher life too. Good luck.

 

[Dairy Farmer]

no it has a cab. it worked fine before the old cable went caput. now it bounces around
thanks

 

[4435]

Not to be a smartass or such but it might be that simple. Tom

 

[Dairy Farmer]

oops fergot to do that. how do you lube it. with what? sorry never had to put one in until now.