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JD420 drive shaft u joint replacement

2654 Views 12 Replies 7 Participants Last post by  HappyValleyJD, 
HappyValleyJD
Since the weather in central Pennsylvania has finally warmed up a bit, I decided to take the sheet metal off my new-to-me 420. As this is my first Deere, I figured it will pay to have a look on the insides.

After I replaced the engine and tranny fluids, I fired it up. Yeah to me, it started and didn't blow up.:tango_face_grin: Unfortunately, I noticed that the rear end of the engine-to-tranny drive shaft has a horrible wobble, with lots of play in the universal joints, and a little at the rear splines. The front end is tight.

I would really, really, really like to avoid disrupting the engine mounting in order to replace the cross and bearing assemblies. Has anyone every tried to replace them in situ? Is it even physically possible? I have exactly zero experience with these, but I'm very willing to get greasy and work.

I suppose that if I must slide the motor forward, I will, but at first blush, that seems like a lot more work. Heck, I don't even know if there is a shaft at the back of the motor, or if the flange simply bolts on. That would certainly make it easier.

This has a relatively new Honda GXV 670 in it, if it matters.

Thanks for any thoughts. Free beer to anyone near State College.
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No Quarter
The drive shaft bolts to the flywheel and yes the motor will need to be unbolted and moved forward.
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oaks1450
I didn’t need to move the motor to take out the drive shaft. It’s a pain and I think I un hooked a couple hydraulic lines to help with the removal. Getting to the three bolts towards the motor was tuff! I recommend jacking the tractor up and I think took the side cover off the pedestal. Hope this helps.
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RussKish
A 420 with a P220G has 4 bolts from driveshaft to flywheel, IIRC the B48G has the same number of bolts to be removed. Search the various forums, there are threads on finding replacements (ebay, craigslists, auctions), to building complete new ones. I'm not sure on a Honda replacement engine, so it must have an adapter if the old drive shaft with 4 bolts to an engine with three bolts on the flywheel. Remove adapter an it might give you more room to play with.
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inspectorudy
I had a 400 with that Honda in it and the drive shaft could be removed with the engine in place by removing the four bolts on the engine end and then after removing the rear fender and disconnecting two hydraulic lines the whole shaft can be removed. I believe the 400 and the 420 are very similar. You need to remove the rear fender anyway if you just bought it to see what is in there. If you have a pressure washer that would be a good time to blast the years of crud off of the frame and the other parts. There was a spot on the rotation of the engine at the top that each bolt could be removed as the engine was turned 90 degrees for each bolt.
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HappyValleyJD
Thanks for all the notes so far. The front end of the shaft has holes for four bolts, but only two are in place. I don't yet know if the Honda has holes for the missing bolts or not. I'll put in all that it will hold by the time that I'm done.

I really wish I could post a video to show the amount of play in the back end. It's amazing it has not come apart on its own.

I won't be able to get back to the tractor until the end of the coming week. I'll drop the front end to see if that allows enough room to get the shaft out. Without a shaft coming from the engine side, I don't see why there wouldn't be enough wiggle room to get the thing out. I'll let ever one know what I find out, with some photos, of course.
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RussKish
As you work on it, keep in mind that the straighter and more true you keep the shaft from engine to the shaft on the hydro-static pump/transmission, the longer the u-joints will last. It will also make for the most efficient transfer of power.
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inspectorudy
Be careful if you are driving it now. Remember what is sitting right above the drive shaft "U" joint! Also, there are four spacers that go on the bolts for the engine adapter. On my 400 the guy who put the Honda in it used galvanized pipe nipples that worked great and were the exact length.
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HappyValleyJD
inspectorudy said:
Be careful if you are driving it now. Remember what is sitting right above the drive shaft "U" joint! Also, there are four spacers that go on the bolts for the engine adapter. On my 400 the guy who put the Honda in it used galvanized pipe nipples that worked great and were the exact length.
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InspectorRudy,

Oh so true. I don't want to break the nuts near the shaft before I get the u joints fixed. It's been parked and on jack stands since I found the problem.

I'm now back with the tractor, and have the parts that I needed. I was happy to read that the flywheel end just bolts on.

I initially tried to unbolt that end, only (not surprisingly) to find that the shaft and motor turned over as well. I thought I was being clever to get a pipe wrench on the shaft, until I realized it would hit the hydraulic valve. A small scrap of wood fixed that, and the bolts came right out.

Now the problem is that the flange seems to have welded itself to the aluminum spacer on the back of the Honda motor. It was too late and dark last night to work well. I'll give it a love tap to see if it's just bimetallic corrosion or something.

From what I have seen on replacing the cross and bearings, that doesn't look too hard.

More to follow.

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HappyValleyJD
Well, the job is done.

In the end the wobble was coming from the drive shaft rear yoke, not the universal joints. The female splines were shot and worn badly. Fortunately, the transmission shaft was unharmed.

I put some photos of the back of the engine and other pieces here:
https://www.wfmachines.com/forums/showthread.php/127260-Request-for-photo-of-420-drive-shaft

Without much in the way of a shop yet, replacing the cross bearings turned into a circus. I now have a nice big vise to work with.

Because I needed a new female yoke anyway, I just bought a used complete drive shaft that had a clamp-on rear yoke. It went in easily and runs much straighter than the original.

Now I'm off to building a wiring harness for the rear PTO and trying to see if I need a non-3 point rock shaft before I add the tilt dump MCS.

Thanks for the help on this great forum.
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mrbeef
Sounds like a good resolution to the problem. Also glad the input shaft wasn't worn. That would really be a pain.
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R
Happy, It's little late now, but I'll mention this anyhow.

You mentioned, "Now the problem is that the flange seems to have welded itself to the aluminum spacer on the back of the Honda motor." When two metals come in contact with each other, they can...but not always, depends on what the metals are... produce a small electric charge and actually weld the two pieces together. It's actually a common occurrence! Coating the contacting surfaces with an anti-seize product will prevent this. I'm unsure if all anti-seize products will do this, so read the label. You're looking for it to read: "Prevents Galvanic Corrosion." I use it like Frank's Red Hot, "I use that **** on everything!" Bob
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HappyValleyJD
Unfortunately, right now the tractor and I are over three hours apart... and there's little to no online access there.

Here is a picture of the worn input shaft, and hopefully a short video of the original wobble. I'm shaking the thing by hand.

I don't know how I didn't take a photo of the finished product. I'll grab that the next time.

Thank you to all for the help and direction. This has been a steep, but pleasant, learning curve for the past few months.

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