John Deere 4600 MFWD will not engage

[pctwst]

Hope you enjoy taking things apart to find out what is wrong. No fun if pinched for time, tho.

Lol thanks. I do enjoy it but finding time is the key.

 

[tjandrews]

So I did some further checking today. I was wrong on my original thought that the linkage at the rear of the tractor was the problem. It works. I slid the front driveshaft cover back on both sides to expose the front drive shaft. With the mfwd hanlde up (engaged) the shaft does not spin. Down it does. So the issue appears to be in the front differential and not the trans where I originally thought. So no I need to figure out what the problem is in the front differential/axel. The front wheels spin freely with mfwd engaged or disengaged. It makes no difference. they do not spin the shaft and if the shaft is not spinning (Handle up) the wheels spin freely.
So, is it the pinion gear, ring gear or could it be something else and what is the best way to determine the cause of failure. Do I have to drop the front end out and take it apart? Or is there a better way to check?

Ours did that, too. We bought it used, and it is our first and only 4WD tractor. We did not check the front axle fluid as we should, and it was low. Could have been low when we got it. Anyway, the front differential and several bearings and associated parts were bad, according to the JD dealer. They fixed it, didn't really take long, but with many parts it was $$$$.
Cheapest way out, though. Our skills and tool inventory would not have been up to the task.

 

[pmsmechanic]

With the MFWD disengaged and with one front wheel on the ground and the other in the air, the front drive shaft should rotate when you turn one of the front wheels. If it doesn't and your drive shaft and couplers are good then the issue is in the front axle.

 

[Hoss710]

I could be wrong. but I thought there may have been a shear pin going from the drive shaft to the differential ??

 

[5030]

All I know is Kubota uses a non hardened sliding collar secured with 2 roll pins to connect the output shaft to the front axle pinion shaft (both harden and tempered) and it wears out before anything else and is acessable from under the tractor by removing 3 screw and sliding the transmission to front axle cover off. It costs 50 bucks and is a dealer item. I've replaced a couple on my Kubota M series over the years, it's a 1 hour job with simple hand tools.

 

[pctwst]

Ours did that, too. We bought it used, and it is our first and only 4WD tractor. We did not check the front axle fluid as we should, and it was low. Could have been low when we got it. Anyway, the front differential and several bearings and associated parts were bad, according to the JD dealer. They fixed it, didn't really take long, but with many parts it was $$$$.
Cheapest way out, though. Our skills and tool inventory would not have been up to the task.

Thanks. I haven't had the chance to drop the axel or work on it. It is getting picked up tomorrow.

 

[pctwst]

With the MFWD disengaged and with one front wheel on the ground and the other in the air, the front drive shaft should rotate when you turn one of the front wheels. If it doesn't and your drive shaft and couplers are good then the issue is in the front axle.

Thanks. The problem is definitely in the front axel.

 

[pctwst]

I could be wrong. but I thought there may have been a shear pin going from the drive shaft to the differential ??

Thanks. There are roll pins on either side of the shaft in the couplers. I haven't seen any other pins.

 

[pctwst]

All I know is Kubota uses a non hardened sliding collar secured with 2 roll pins to connect the output shaft to the front axle pinion shaft (both harden and tempered) and it wears out before anything else and is acessable from under the tractor by removing 3 screw and sliding the transmission to front axle cover off. It costs 50 bucks and is a dealer item. I've replaced a couple on my Kubota M series over the years, it's a 1 hour job with simple hand tools.

Thanks. The shaft has a coupler on both sides of the drive shaft with a roll pin in each one. Sadly, they are still connected, lol

 

[beenthere]

Post some photos of what you are seeing. May get some helpful suggestions.