3720 MFWD issues

   / 3720 MFWD issues #1  


Veteran Member
Feb 21, 2005
Central WI
Today my 3720 started making clunking noises when changing directions. It only does it in 4wd and only seems to do it when the initial load is applied. The front wheels do appear to drive. I looked at the front driveshaft (unimpressive to say the least) but couldn't see any glaring issues. The dry splines and floating/roll pinned collars on the shaft have me scratching my head.

At any rate has anybody had any diff/driveshaft issues?

I should add that the sound seems to border on a clunk and a pop and seems to change where it is coming from. Some times it seems to be up under the front diff and other times it sounds like it's midship.
   / 3720 MFWD issues
  • Thread Starter
Well I think it's the driveshaft splines. I did not get a chance to study thoroughly, but it's not very impressive. There are at least 2 short splined couplings. The rearward one is pinned with a roll pin. The front one slides free or at least mine does. All I did was slide it around a bunch trying to see what movement was allowed. These splines really should be lubed in my opinion.

Anyhow, I went to do a different task and tried it and it worked fine.

I have to say, the front PTO shaft setup on my 455 is more robust that this spindly little thing...
   / 3720 MFWD issues
  • Thread Starter
What I have learned so far is that both of these splined couplers are supposed to be pinned. My forward one is not. probably won't get to lok at this for a week or so, but I have a coupler and pins coming. from what I see i would highly recommend disassembly and greasing on these with a super good moly grease like Cenpeco Mega Moly.
   / 3720 MFWD issues #5  
For what it's worth - the front driveline on my 110TLB is pretty "spindly", too! And the front collar joint is pinned with a roll-pin as well.

Have never heard of anyone twisting or breaking the collared joints, though.

Since the shaft does not slide back and forth with any up and down motion - the front axle and transmission are solidly fixed - and the distance does not change; grease would only help to deter corrosion.

I would be more concerned with possible damage to the front axle hub.

   / 3720 MFWD issues #6  
did you try checking your front axel thrust bolt, my tractor did that and once i retorqued it and it stoped specs are in owners manual , might help
   / 3720 MFWD issues
  • Thread Starter
OK I had to take it apart as it started jumping splines again. The frontmost coupling splines are severely worn as are the pinion splines as well. The others are just fine. For the moment I flipped the coupling iuntil I can get a new one. The roll pin is just in the coupling and used to limit floating.

My advice to all is to pull this shaft down and grease the splines before it makes a mess.

Pop the roll pin out of the rear coupler and slide it rearward. then slide the front coupler all the way forward and the shaft will fall on your head. Thankfully it's light and my head/ear are tough...
   / 3720 MFWD issues #8  
I'm having the same issues right now. I'm hoping it isn't the cable that controls the movement of the shaft with the lever.

I can put the shaft into 4WD mode by hand, but it won't stay in 4wd mode. The shaft jostles free after using it for a few seconds.

I am really puzzled, because it looks like the roll pins are in place on both couplers.

Any ideas?

It doesn't look like my splines are worn too badly.
   / 3720 MFWD issues #9  
I would send it to dealer, but I'm afraid once it is there, It will snow, and I'll have nothing to use.
   / 3720 MFWD issues #10  
I dont remeber the torque spec but it is in the manual. These bolts seem to be very loose on all machines from the factory. Check it out.