JD 620 Tach drive

RMOMN · Mar 3, 2013

What does it take to replace the drive gear for the tach cable

gtx1967jewison · Mar 3, 2013

Cable is driven by the governor shaft. Not a gear

TIMAR · Mar 3, 2013

I have a correct rebuilt original tach if you are interested

RMOMN · Mar 3, 2013

My understanding is that there's 2 plastic gears on the shaft that drive the cable?

Bob Harvey · Mar 3, 2013

INSIDE the tach. HTH

RMOMN · Mar 3, 2013

What is happening is if I drive the tach cable with a drill the tach is working. Then I reattach the cable and start the tractor the tach needle is jumping all over

Scott 730 · Mar 3, 2013

620 and 630 tractor speed hour meter drive gear set AF 2709 R subs to

F 2547 R $22.06

F 2548 R $15.02

RMOMN · Mar 3, 2013

Scott have you done this repair I'm wondering what it takes to replace the gears? Is the repair straight forward to do?

Canadian Ken · Mar 3, 2013

I replaced the gear on my 720 gas

-remove the cap from the distributor
-drill a small 1/8 hole in the 2 or 2-1/4 inch welsh plug
-screw a metal screw in hole and pry out welsh plug with j bar
-remove cover from left side of governor housing
-pull governor drive gear to the left
-remove old plastic tach drive gear
-grease shaft of gear assembly and install new gear
-push governor shaft in slowly to mesh plastic driven gear with teeth on governor shaft
-make sure gasket on governor is still good -or -replace with same thickness gasket/shim
-reinstall cover
-braze hole shut that was drilled in welsh plug if it is re-usable -hammer center of plug out into a concave shape
-re-install welsh plug and tighten with hammer striking center of plug
-install tach cable
-replace distributor cap

Ken

Scott 730 · Mar 3, 2013

(quoted from post at 20:28:12 03/03/13) Scott have you done this repair I'm wondering what it takes to replace the gears? Is the repair straight forward to do?

Replaced gears in my 730 diesel. I would guess the gassers would be a similar job. I had to pull the governor shaft out of the housing to replace the drive gear on the shaft. It would be wise to replace both gears. Not a good idea to mesh 1 new gear with 1 old one.

RMOMN · Mar 3, 2013

Thanks Ken and Scott that is exactly what I was looking for. Sounds like a pretty straight forward job.
Bob

Anonymous-0 · Mar 3, 2013

Does anyone know where you can buy the plastic worm gears in the hour meter of the 620/630 and for a new generation 3020?

Tyler-MO · Mar 4, 2013

It sounds like your little nylon tach drive gears are just about stripped off. I believe it's possible to do the job just by removing the welsh plug on the governor housing and the tach drive assembly that the cable attaches to. It will be tight, but I think you might be able to remove the snap ring and spring on the end of the governor shaft and ultimately remove the old drive gear and install the new one without removing the governor shaft...although you're going to run the risk of dropping small parts into the crankcase.

Tyler in IL

JD 620 Tach drive

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