Weekend Freedom Machines banner

400 rear pto, upgraded to take 2000rpm equip.

3825 Views 15 Replies 8 Participants Last post by  nc400
HI BLACKSHEEP, Here is how I modified my 840rpm rear pto to 1754rpm. this mod will allow you to use the 2000rpm equipment like the 318/420 etc. no longer will you be confined to ''400 specific'' implements that use the original 840rpm pto.
before we get started here, let me say this, you DONT have to do everything I did to my unit. basicly, all you have to do is replace the top sprocket. I just saw ways to improve on the original design and built to my own taste and for my own needs.
I used sprocket dia., not tooth count to figure the gear ratio.
bottom sprocket from jd is 12T or 2.71'' dia. we will stay with a 12T here.
top sprocket from jd is 30T. we will replace that with a 14T. that measures 3.11''.
3.11 divided by 2.71 = a ratio of 1.14 to 1.
so with a 2000 rpm input speed, you will net 1754rpm out-put speed.
at this point you are asking why did I not use a 12T on top and get the full 2000rpm, the 1 to 1 ratio? here is where you run into problems that involve MORE time, money, machine work, parts availability, fitment, etc. this will be shown later. It CAN be done however. but the 14T upper sprocket avoids a lot of problems. and with only a 12.5% drop in performance at WOT I believe us 400 owners can live with that. Keep it simple!
all work was performed with basic tools, a welder and 5 1/2'' hand grinder, and small phneumatic die grinder. the exception being to key ways were cut at machine shop. the key ways only apply if you go to the extent that I did.
So lets get started.

on the left are the original sprockets and shafts. NOTICE; that they are welded to the shaft on one side only. the weld is lathe turned also. the sprockets are oriented like they go. why they weld is on the back side of top sprocket, I don't know. at this point, if you replace the top sprocket your done. on the right is the new set-up. NOTICE; the spacers on top of each sprocket, installed. there are corresponding spacers on the underside also. each shaft pair is identical except there is a relief cut to clear the weld on the one that fits on that welded side. NOTICE; the upper shaft. you see how close the chain comes near the spacers outer shoulder? this is where you run into problems if you go with a smaller sprocket. CONTACT. 13T. same results, CONTACT. Turn them down in a lathe? these things are as hard as automotive lifters. make your own? yes, if you want to. Get a set like on the bottom shaft from JD, which are a smaller outer dia.? your stumped again; one side is n/a.
so go with a 14 on top and be happy!
new 1'' shafts are made from cold drawn shafting rod obtained from Mcmaster Carr.
NOTICE; the amount of free play in shortened chain. this chain is used. but good as new. I could not find a reason to replace it. I used a half link to obtain this amount. you can see it located in the lower rt. corner. a master link in place of a half link will yield slightly more play. you will have to find your on SWEET SPOT in your unit as chain condition warrants. the original jd chain has no master or half link. so get you one of each to ease the build. this is 50 PITCH standard duty.

here is an upper and lower spacer. sorry I have no photo showing the inside where the relief area is to clear the weld. all 4 spacers are the same thickness. where the spacer meets the weld is a non contact surface between the weld and spacer. if you don't have a lathe like me also, just grind down your weld at a 45 degree till spacer sits flat on sprocket. that's all there is to that.

here is a new sprocket. these are the keyed, collar mount type. I cut the collar off and ground flush. they are from SUPPLY CENTER. 6 OR 7 bucks each. they will still press on good on to a new shaft and self a line for a square fit. if you can find some from a different supplier without the collar, you can save yourself some extra work. I didn't bother, unfortunately.

view of original lower shaft assy. minus spacers. this shows outer cap needle bearing, sprocket, front caged needle bearing, jd seal, woodruth key. NOTICE the factory weld I spoke of. this shaft has wear at the bearing surface and seal contact area. this is where weeds, etc., get twisted up on the drive shaft input connection and destroy the seal resulting in 90w fluid loss. then excessive wear. unit holds only a few ounces, 6 or so. it aint much. I will build an entire new assy. NOTE, that is a new $11 JD seal in the photo. I will use a better seal here shown later. I will replace old key style with plain key stock. that will allow me 1/4'' longer contact area with the yoke. yoke has the space available.

here is a view of the old top showing the outer cap bearing, and weld surface. if you need a new 15 spline shaft, SC has 2 versions I believe that could be made to fit, for $22 or so. check with them. I will build a new shaft with a standard 6 spline 1 3/8'' dia. for my preference. NOTE, if you get all new bearings for your unit, pay attention to the one at the 15 spline output. it contains a small seal that faces to the outside. don't confuse it with lower shaft input bearing. the upper and lower cap bearings are the same.

this shows that bearing, near spline end.

this is the new lower shaft and seal.my seal selection protrudes un like the jd seal. but it has no clearance issues.

left my seal, right jd seal. both are double lipped with a spring. NOTICE, the larger contact area of the one on left. the one on left is for the axle of a troy-bilt horse tiller, if your interested. cost about half.

another view

here is a mod I came up with. I cut a slot in each case half on top, at upper output shaft to help with bearing lubrication. a feeder channel of sorts. cant hurt.

here is new 6 spline shaft from SC, FOR $30. It comes with 2'' long inside hole. I cut it down to 1 1/4'' long inside. relocated set screw. also installed a second set screw 180 degree opposite. the reason I cut this is so equipments drive shaft does not get to short, causing yoke bindage in raised position. every little bit helps. so modify this now.

here is the tensioner installed. a new jd is $14 or so. mine had some wear. not real bad. I filled it with JB weld after routhing the surface. use original formula, not the KWIK SET, original is more than twice the tensile strength.

here is unit installed. NOTICE, I cut a second grove of notches for lock pin, they are 3/4'' inbound from original. again, better safe than sorry. keeps the drive shaft longer, and gives full contact to the yoke. I used a air grinder with double helix carbide bit, 3/8'' to do this. mark a straight line with tape around the shaft on both sides of cut. no lathe, no problem. just test fit each slot with your yoke.

another view


another view, NOTICE, full yoke.

NOTE; I used all new bearings from JD, lube added, job COMPLETE. Only thing left is to go and kick some earth worm ass!!!
in closing, I would like to say this. I don't want to hear any whining or BLEATING about the 400s rear pto limitations. if I can up-grade mine, anyone can if they so choose. it was more aggravating doing this post than the rebuild and conversion!!! I have done so many modifications and up-grades to this 400, I call it PROJECT-X. Like the yellow 57 chevy Popular Hotrodding was always testing out equip. on back in the 70s. later, J.Z.M.
See less See more
1 - 8 of 16 Posts
Thanks David, SC list it as ''splined pto adapter''. it is made by G&G mfg.co. of Nebraska. it comes in 1'',1 1/4'',1 1/2'' bore dia. I suspect it is made for hyd. motors or pumps??
no I haven't done the foot control, YET. I have been looking at all the versions I can find. fellow member Jay Erickson has in my opinion the best design I have seen. his is a simple, clean, well thought out design. I had been holding off on selecting one to attempt because of the rt. foot ergonomics involved. then along came Jay, and he NAILED IT. later, J.Z.M.
Thanks Ron, just now got finished getting some ''WORM TIME''. Soil finally dried out enough for a shake down run. ran her at 4'' deep, engine rpm 2600-2800rpm on the tach. everything went flawlessly. tilled about 5000 sq.ft. don't want to push it to hard yet, still breaking in that new k582. my next goal is to replace that disconnect at the mid pto with a pinch type clamping yoke. I can see and feel some play there. I will gladly sacrifice convinence for smoothness and durability. the shaft is fine, its that weak little quick disconnect.
those 26x12x12 rear deestones I bought here while back that turned out to be a true 10 1/2'' wide paid off in the end. the tiller did not need to be off-set. a true 12'' wide tire?? maybe not. I am a little happier with them now. made up for the disappointment I had when they were mounted. so all in all, in the end everything worked out for the best. I can stop my own BLEATING now. ha. later, J.Z.M.
HI Everyone, Just wanted to do a quick up-date on this mod. After about 10 hrs of use I have developed a slight leak at the out-put shaft. I refer you to photo #10 showing the small feeder channel I cut.
I don't know if this is the culprit or if all of these units share this problem.
I do know this is a new JD bearing with the built in seal and its installed correctly, and the shaft is new and built from quality, tight tolerance material. {$12 a ft.}
Correct amount of 90w gear oil also.
This winter I will go back into it. If seal and shaft look good, I will fill the channel on this case half.
I have been studying the idea of running it packed in grease by 50% volume instead of the few ounces of gear oil. Like some of the tiller chain drives.
How ever keeping the upper shaft bearings lubed sufficiently in this manner gives me pause.
Other than this issue everything continues to work great. Just wanted to give a heads up to anyone contemplating this mod. later, JZM.

PS. 400 project Xs foot/hand control still going strong. Gotta find the time to post it. Started on my FEL build 4 weeks ago. No store bought plans here. 90% brain cavity/10% chicken scratches on paper...lots of body scratches too! ha. later, JZM.
See less See more
UPDATE, I tore the unit down and found what was causing the leak issue on the top out-put shaft.
I also discovered some other issues which I shall discuss here, and the steps I took to correct them.
I also took the unit to a true 2000rpm version.

Here is what I found.

This is the top out-put shaft I made with the 14t sprocket. NOTICE the wear at the bearing contact area just above the sprocket.
It measures .006 under. The steel used was low carbon 1018 in its ''normal state'' with a Rockwell hardness of B70; which obviously is to soft.

Notice all the wear is on one side. This I deduct is from natural torque loading when a load is applied.
I ruled out the other possible causes such as bearing alignment, trueness of outer shaft diameter, shaft warpage from manf., or distortion from welding the sprocket to the shaft which is on the under side of the sprocket.
There are two solutions to this shaft wear problem. If you use 1018 steel you can ''surface'' harden it up to a Rockwell hardness of C60.
Or you can build the shaft out of 4130 alloy which has a ''normal'' hardness of R-C20. It also has good weld ability. It can be hardened ''throughout'' to R-C54.
I suspect 4130 or something close to it is what JD used because upon cutting a factory shaft into, I noticed its hardness is consistent across the full cut.
Weld sprocket to shaft before hardening. If using 1018 heat to a medium orange color and quench in water.
If using 4130 it may be good to go in its natural state. ''I haven't tried it yet'' But if you do decide to harden it further, remember it is an alloy steel and it needs to be quenched in OIL not water. Water will cool it to fast and turn it brittle.
If you use 4130 and have oil hardened it and you experience shaft breakage later in use; then the next new 4130 shaft will have to be ''tempered'' after it is hardened.

OK, on my lower 1018 shaft that I originally built there was only slightly wear discoloration visible. It mikes .001 wear. I surfaced hardened it and reused.
If and when I ever need to replace a shaft assy; I intend to try 4130 in its natural state, and see what happens.
For my current needs of a replacement top shaft I decided to use my old original JD lower shaft with a 12t count.
Resulting in a 1to1 drive ratio, 2000rpm.
All I had to do was fit the long end to my 6 spline pto. stub. This entailed shortening the long end of the shaft 1/4'' and using the factory woodruth key instead of 1/4'' key stock.
For my two smaller diameter spacers that go on each side of the sprocket I made some out of ''shaft collars''.
Here is a photo of another ''NO,NO'' or ''DONT DO'' I tried.

The JB weld I used to fill in the wear on the old tensioner block will not hold up. Spend the $12 and get a new one from JD!
Also in this photo is one of the small spacers you need to run the 12t sprocket. This one is the one that is beveled out to clear the weld, where the sprocket is welded to the shaft. It is no longer available from JD.
The spacer for the other side of the sprocket is flat on both sides. It is available from JD for $30.
SOLUTION; by two, cut one down.
Or when you cut the shoulder off of your new sprocket leave the thickness of one spacer on that side. Then buy one and cut down. These spacers are hard so if you don't have a lathe you can use a die grinder with a double helix carbide bur. You only need to clear the weld. Be sure and leave the flat surface at the edge as shown in photo. This must mate true to the sprockets side surface.

Here is the new set up.

Chain was shortened as needed, a master link was required instead of the earlier half link.
The sprocket on the right is the top out-put shaft. Notice, there is some wear on the sprocket teeth. When it goes, I will weld on a new sprocket or build new out of 4130 as stated earlier.
I also replaced the bearing that was involved at the wear area because it contains a seal.

Now for a new modification. I have decided to run grease in the chain case instead of those few ounces of oil.
Three, 1 lb cans will give you about 50% volume. I decided to do this because those few ounces of 90w oil could quickly disappear if some thing such as a vine or other trash gets wrapped around the lower shaft at the seal area, destroying the seal, and if you are tilling the evidence is immediately tilled into the soil and the operator is ignorant to the fact he is operating with a dry case.
At the front lower pto shaft; on the rear section of the shaft is the same type of cage bearing. It is greased upon installation, then its on its on. It is subjected to 2000rpm at WOT.
So there is no reason the four bearings in the pto case should not hold up. They were packed on installation also and they are exposed to being replenished; unlike the bearing at the mid pto out-put.
Another benefit is my pto is much quieter now, and seems to run smoother.
The only thing I can see right now that might come back to bite me in the ass is the spacers made from shaft collars. They may not be hard enough. I will give the unit 10-15 hrs. use when conditions permit and do another inspection.
later, JZM
See less See more
Here is some photos of the Bush Hog made for CC, 442 tiller since I painted it last spring to the JD colors.

Left door chain off for now. I hate to scratch up the new paint. Haven't needed it so far anyway.

I have the wheels in the wide stance here. I have yet to off-set the tiller in these photos. It has a max of 4'' adjustment left or right, capability. Needs about 3'' for wide stance.
Narrow stance, centered is fine.

Here is a photo of the drive shaft coupling I am running in place of the quick disconnect style. It gives a much better fit.
No, the quickie is not for sale. Saving it for my old age. I will prefer IT, then.

A tease photo of my new, lever/ foot control design I intend to post when time warrants.
Maybe the next polar vortex. ha. later, JZM
See less See more
This photo failed to load.

Terry to the rescue?
See less See more
Travis, That poker is currently in the fire. Along side a FEL build and bottom plow build.
Time & Money...Time & Money. You know the tune. later, JZM
1 - 8 of 16 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.