Hi. I'm new to the forum and new to ATVs. I've been a 2-wheeler my whole life. I recently found this Terrapro, YFP350U, on CL. It has a PTO and Bush Hog but is only 2wd. It is in great shape.

However, When I go it home I noticed that the differential will not lock - so I am currently 1WD. I adjusted the lock cable as far as I could but it wouldn't lock.

I'm not afraid to get in there and check things out, but wanted to know if there are any simple ways to narrow done the problem before I start opening things up.

When I jack it up and spin the tires, there is no noise or grinding. The bike runs fine otherwise. I just cant lock the rear end.

I'm glad I found this site. It looks very helpful. Thanks.
Phil

 

I know this is old but when I was looking for this answer I could not find it so I am posting it later rather than never.

I had the same thing and had to open up the differential in order to fix it. There is a spring that pulls the diff. lever to lock the diff. on the outside of the axle. If you have the wheels elevated and rotate by hand you should be able to move the lever by hand (after removing the springs), engage and disengage the differential. If you can't get the diff to disengage you will have to split the differential and fix the problem. My guess is that the "lever" was pulled out of the axle and then pushed back in. this process allows an internal spring to get in the way which will not allow the lever to be pushed into the correct spot. The only way to fix this is to split the diff. and access the inner lever area to move the spring. It was a time consuming job for me but I am glad I did it so that I understand my machine better. I was thrilled to see how clean the inside of the diff looked. The manuals did not to do the work except show an explode view. It is pretty obvious once you get it open what to do.

 

I am glad you posted the reply. I have a terrapro I recently got and it has the same issue. The Diff won't lock. I tried a number of things and tracked the cable to the spring you mentioned. the lever is hard to get at in front of the axle on the right side. My plan was to see if I can move the lever by hand and make it engage but likely will also have to split the case. Already did a carb rebuild and repaired a chunk or harness that mice ate and am currently rebuilding the brush hog it came with. then on to the diff.

After dragging the hog in unlocked mode I see why the need for the locker mode. It likes to spin with only 1 wheel pulling.

If I discover anything new I'll update the info and would appreciate it if you wee the new post if you share anything else you learned about the Terrapro.

 

My terrapro hade the same problem the lever behind the rightrear tire was rusted oil and move it back and forth and now it works like a dream

 

I have just purchased my second Terrapro because my first has been so good to me as I mow trails through the woods. I enjoy learning how to work on these machines.

Testing your diff. switch.
Raise your machine from the center of the the rear swing arm so that both tires are off the ground. Locate the differential lever on the front side of the swing arm on the differential side. There should be some springs connected to it. Be careful not to pull the switch out of the swing arm. You should be able to manually turn it, and you must be able to turn it in order to engage and disengage the differential. In neutral you should easily rotate the tires and turn the lever until the diff. engages or disengages.

If the differential will not disengage it is probably because the switch was pulled out and then put back in. You can't put it back in the right place unless you take the diff out. But you don't have to open the diff. like I have done in the past.
Here is my easy fix. You may want to drain the diff first. Remove rear tire, diff. side. Disconnect the brake lines diff side, and the two breather tubes. You can change your brake fluid when you are done (as a bonus). Separate the diff. from the swing arm by removing a total of ten bolts/nuts. Remove the shield with 2 bolts. There are 8 left, 4-17mm and 4-14mm. When you remove these 8 you can pull the diff out and get at the part you want. You can now play with the switch and see how it works. You need to pull the diff lock clutch out of the swing arm and push the diff lock switch in until you feel it click. I take the time to clean it and lube it well. Once in, put in the diff lock clutch piece and turn the lever to make sure it moves the clutch piece in and out. Now put the spring on and reassemble in the reverse order. After assembled bleed the brakes from the left side. I like to replace brake fluid because most people don't and it is cheap to do. I use a piece of aquarium tube connected to the bleeder and put the other end into a jar or can, open the bleeder and pump out the old while I pour new fluid in. Fill or top off the gear lube 80 W, I use 80-90.

I hope this helps.

 

I have posted a better fix to the differential lock out problem.

 

thanks for the details. I was pretty sure I'd have to pull the diff. The manual said might need to do the shock and a few other things as well so if I can do it easier, that's great. I am not sure if Switch and lever are used interchangeably in your message but seems like it is. the diff lock clutch I assume is inside the diff and what the lever attaches to? thanks again

 

by posting a better fix, do you mean the one you posted above?

 

I should have looked at the manual before I started typing, switch and lever meant the same thing. The manual calls it the Differential lock lever assembly which is pushed into the swing arm on the front side near the diff. itself. It is a funny lever which I wished they would show a diagram of how it works. It is obvious once you take it apart. The part of the lever which sticks into the swing arm has a cam on it and it pushes the diff lock clutch in-towards the diff which locks the axles (no differential use) when turned the other way a small spring pushes the diff lock clutch away from the diff and you now have the use of the diff. It works great and you can mow your lawn without tearing it up. The machine also steers better with the diff engaged. I was using the rough-cut mower in the woods and one tire was spinning and I was getting stuck, so I knew I had to fix the problem . It was not too hard to do if you have the tools and a jack. It would not hurt to drain and refill all the fluids as you work on it.

 

Well I pulled the wheel this morning and it only took me an hour... for 4 nuts...
One of them rounded so nothing to grab at all so I had to cut it off with dremel tool and chisel! Pulled both springs off the lever and I see the issue. Mine has popped part of the way out of the housing. The rubber o ring is not inside the tube as it should be so I think the cam on the back side of the lever is not engaging as it should. Can't seem to put it in without taking the diff apart, so I'm going to do that after getting lugnuts. Will try to shoot some pictures and post for fellow Terrapro nuts as I do the job tomorrow.