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782D Driveshaft Upgrade

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mgonitzke

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Matt Gonitzke
I've been wanting to do this mod to my 782D for awhile. My Dad was using it to bag grass this spring, and a stick or something went through the hydro fan and took out all of the blades. This tractor had the disconnect clutch option, which uses a different fan, and the fan was nearly $100 from most sources I was able to find. The OEM driveshaft components don't last particularly long in the diesel models, and I've already been into this a couple times on this tractor in ~60 hours. Driveshaft servicing is not easy or fun, either. Tractor has to be taken really far apart, or leave it together with patience and busted knuckles.
IMG_20191224_152601.jpg

Solution:

Shortened 2000/3000 series driveshaft, pictured below in its original form.


This same driveshaft, presumably in a variety of lengths, was used in all 2000 and 3000 series tractors. To my knowledge, all of them are long enough to be shortened and used in any older machine with about any engine, including a super garden tractor with a V-twin transplant, which requires a fairly long driveshaft. It is a fairly simple design. The driveshaft itself is a heavy-wall tube with a fitting pressed over and welded to either end, and a ring on both ends. Eight polymer barrels connect the ring to the shaft and allow for some misalignment. The replacement barrel kits are fairly inexpensive (~$18 per kit, two required) and are the only wear parts, within reason. The bolt circle on the rings is the same as the existing Kohler flywheel end driveshaft couplers used on Cub Cadet garden tractors, and also the same as the CV joint driveshaft used in the "cyclops" models.
IMG_2586.JPG

This guy makes engine and transmission couplers for a variety of Cub Cadet models that make this a nearly drop-in modification. I bought the Kubota engine coupler and "plain" hydro input shaft coupler from him.

IMG_20191209_144933.jpg


All that's required to shorten the driveshaft is to cut off the welded-on end piece through the original weld on one end, grind off the weld on the end piece, punch out the short piece of driveshaft tube, shorten the driveshaft to the required length (I cut mine such that the assembled driveshaft was between 1/32" and 1/16" short to allow for thermal expansion of the engine and transmission), and then re-weld the end piece. I'm not sure it was necessary, but I made sure that the drive barrels were clocked the same on both ends when I welded the end back onto the shaft. Installation is much easier than the original shaft.

IMG_20191224_152614.jpg


IMG_20191224_152633.jpg


Time will tell how long it lasts. I have the same driveshaft in my 1872 with Kohler Command V-twin, and have about 40 hours on that so far. The donor tractor for that one had over 700 hours and had very little wear on any of the parts, except the drive barrels. In my opinion, this is a better design than the CV joint driveshaft I have seen a lot of people use. The CV joint driveshaft is overly complex for what it does, must be re-greased periodically, and all of the individual parts are expensive. Shortening or lengthening the CV joint driveshafts is also not easy to do well.
 

Oak

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I'm curious too Matt. I think someone did one over on OCC and it came apart. They were thinking that the barrels came out of place from the engine not being a ridged mount. I have not seen any issues with ones in the air cooled machines yet and I have twisted all my 3k machines pretty good and never had an issue. Do you think that the misalignment of the engine and rear input shaft will be an issue?
I pull all my disconnect clutches off and toss them in a box, they are not needed in my area and I'm thinking I don't need any unbalanced extra weight spinning on the drive line.

+1 on Jeff, he does awesome work. I have purchased several parts from him over the years.
 

mgonitzke

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I am pretty skeptical of the claim that the rubber mounted engine is a problem. It would require an insane amount of deflection to change the center-to-center distance between the engine and transmission enough to have it spit the barrels out. For example, the driveshaft in the 782D is about 15" long. For the center-to-center distance from the two couplers to increase by 1/8", a lateral deflection of nearly 2" of the engine relative to the transmission would be required. Short of the engine mounts being completely destroyed, there is NO WAY that amount of deflection can occur. I'd have to wonder if they didn't replace the drive barrels or something. When those are new, everything is a pretty tight fit, and you have to pound the coupler rings onto the driveshaft to fully seat them.

The 2k and 3k tractor frames aren't overly stiff. I suspect they twist enough to cause some misalignment in normal operation, as well.

I think the misalignment will wear the drive barrels faster (as it does the ball bushings in the original driveshaft) but they will be easy to replace in comparison, so I'm not too worried about it.
 

jknight

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joe knight
The cv joints with the blue plastic balls will not hold up to the torque on a Diesel. That should give you some idea of what to look for. Use the CV Joints that are steel. My 782D is on three years now. The only weak link in this is the spiral pin in the rear adapter to the trans. The original donor shaft was cut and spliced together with a press fit sleeve over both pieces then removed from the lathe and welded.
 

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mgonitzke

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The cv joints with the blue plastic balls will not hold up to the torque on a Diesel.
So what was the failure mode? What happened? Did you install new drive barrels or re-use old ones? The D600B is not a particularly powerful engine. I can't find it, but at one time I had a torque curve for it. I would not be surprised if modern 23 and 25 hp V-twins have more torque.

I am not interested in the CV joint driveshaft for the reasons stated above.
 

jknight

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I was looking at using the newer plastic blue balls. When someone had that shaft and cv joint set up in their CC it failed. Never questioned why; I just looked for what works in Automobiles. Steel.
 

mgonitzke

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I think I found the thread on OCC. Two failures, both operator/installation error in my opinion. One guy caught the edge of a concrete slab with his loader and likely twisted the hell out of the frame, the other was doing heavy ground engaging work and popped out the barrels, but he admitted had worn parts. Should not be an issue with new drive barrels.
 

jknight

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Fourth year now with the steel CV joints. Plowing snow, pulling cut down trees, plowing and rototilling the garden, cutting grass and picking up leaves.
 

akiszka

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Anthony Kiszka
I have struggled with drive shafts in my 1512 for years. I use my tractor like a tractor, plowing snow, grading driveway, pulling loads of wood in my utility trailer. I have turf tires with chains. This late winter / early spring I found that I had a broken front axle bolt on the left side. I nursed it through the rest of plow season. I decided to pull the axle, trans, and pump all together. I had a 1872 complete assembly so I decided to swap them. During disassembly I found both front trans to frame bracket bolts missing on the trans side. SO the steel brackets were keeping the assemble centered, but allowing it rotate around the axle axis. I decided to add the axle support brackets available online. This triangulated the axle and the front pump input shaft is as rigid as anything. I had to use the splined rubber doughnut adapter on the supers pump input. This made installing the driveshaft a lot harder. I had to unbolt the ISO mounts allowing engine to slide forward, this gave me enough room to install the 1512 drive shaft. So far so good, been roto-tilling weekly. Took some time to get the hydro linkage all readjusted but its fine now. Currently working on putting the fine splined axle shafts from the 1512 into cast iron housing from a 1450. Going to machine the 1450 housing to accept the dipstick tube.
96104521_3729187293819620_6404358513979555840_o.jpg
 

mgonitzke

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Hi Matt,

So how is your plastic barrel couplers holding up in your 782D cub?

Thank you for putting the driveline upgrade idea in my head.

My 782 #1 Cub currently working install power steering and need some more room....

https://www.onlycubcadets.net/forum/showthread.php?p=498963

using the later style driveline.


Bob G.

So far so good on that one...my Dad uses it a few hours a year, so it is going to take some time to accumulate a lot of hours on it.

I have put the same driveshaft in my 1872 and 682 loader tractor. No issues thus far, and I don't anticipate having any. Those 2000/3000 series driveshafts work very well in their original application.
 

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