Jump to content

Unofficial Home of Old Simplicity & Allis-Chalmers Garden Tractors

Sign in to follow this  
mbsengineer

Rear diff locked, how to unlock?

Recommended Posts

mbsengineer
On my 7119 the rear diff is locked currently, and I don't know how to unlock it. I looked through the parts and operators manuals, and can't find any reference to it. I also looked over the axle to see if there is a lock, but again, I can't find anything. I hopeful it can be manually unlocked. As always, thanks for any help!

Share this post


Link to post
Share on other sites
osenga
If I recall inside the diff I think to lock it you have to flip every other gear inside diff so they match up. So you might have to tear into it and flip them back maybe. Just a idea hope that helps out some

Share this post


Link to post
Share on other sites
HubbardRA
I had one that was locked when I traded for it. I got hold of the manual and it was set up as the manual said. I removed two of the three washers that were on the left side of the left axle gear and put them on the right side of the gear and the diff was unlocked. If that gear is able to move too far to the right, it will engage both sets of spider gears and lock the axle. The axle gear is made with the teeth positioned to one side of the gear. The teeth need to be to the left side of the tractor (inward). If someone has flipped this gear over, that will make the teeth engage both sets of spider gears and lock the diff too. Two ways it can be locked without being broken. 1.) washers on wrong side of axle gear. 2.) gear flipped over backward. This can be checked and fixed without removing the differential. You just have to remove the right side hub to get to these parts. Download the manual and look at the parts assembly diagram. You should be able to see what I am talking about.

Share this post


Link to post
Share on other sites
CarlH
I also acquired a 7100 with the differential locked. In my case the PO had replaced the axle tube and reassembled the differential with the gear in backwards.

Share this post


Link to post
Share on other sites
HubbardRA
As Ray asked, if it just started happening, there is one item that can cause a lockup without parts breakage. When you push side to side on the tractor does the axle move back and forth within the transaxle? If the collar on the left side behind the wheel that holds the axle in place comes loose or moves at all, that can let the whole axle move to the right. This will cause the diff to lock up, but maybe not all the time. It would be primarily in a right turn when the axle would be pushed to the right. It may release in a left turn or going straight. Of course, it may also be locked all the time, depending where the gears would sit with normal loading. If this is the case, then just jack the tractor up with both rear wheels off the ground, loosen the set screws on the collar on the left side, push the entire axle assembly as far to the left as it will go, then push the collar to the right, and re-tighten the set screws. The axle shaft should sit tightly within the transaxle, with no significant left-right motion within the unit. And to answer your very first question, these later differentials are internally spring-loaded to control the traction and are not adjustable. I came up with a way many years ago to increase the friction by shimming the springs, but that is not a factory adjustment. Also, flipping the gear over on the later axles, or putting the spacer washers behind the gear on an older axle are techniques used primarily by tractor pullers to lock the axles and increase straight line traction. Flipping the gear or moving the washers is not a factory adjustment. None of these things are mentioned in the manuals.

Share this post


Link to post
Share on other sites
mbsengineer
This is a recent purchase, and has been locked since purchased. I know it will NOT disengage on a left turn, so it's probably not the axle/transaxle issue you mentioned, but I'll check that, along with the gears and washers, when I can. Thanks for the info!

Share this post


Link to post
Share on other sites
MikeES
Any single spider gear in the wrong position will lock the diff. As a tractor puller I have had these diffs apart many times, and I have reassembled one wrong even with all that experience. You really have to be careful and review and double check the assembly before putting it back in the tractor.

Share this post


Link to post
Share on other sites
mbsengineer
quote:
Originally posted by MikeES
Any single spider gear in the wrong position will lock the diff. As a tractor puller I have had these diffs apart many times, and I have reassembled one wrong even with all that experience. You really have to be careful and review and double check the assembly before putting it back in the tractor.
What do you mean by "having a spider gear in the wrong position?" Do you mean backwards, or otherwise? How do you know which way they are supposed to go ... I was just looking over the parts manual, and it doesn't seem like those gears have an orientation. Honestly, from what I just saw inside that "thing" (with all those gears around in a circle) this diagram doesn't begin to do it justice to attempt to get it put together correctly. At least I get to take it apart first, instead of work from scratch, but I don't know if it's currently assembled correctly. Thanks!

Share this post


Link to post
Share on other sites
HubbardRA
The spider gears alternate on the bolts. One left, then one right, one left, one right, and so forth. If you have two on the same side, then it is locked. The teeth of a left gear will mesh with the teeth of a right gear. The other end of the left gear meshes with the gear on the axle and the other end of the right gear meshes with the gear on the right hub. It is the mesh up and relative rotations of the gears that gives the equalization in a turn. If you have two gears that are both on the same side and meshed, then they have to rotate in opposite directions, but if they are on the same side the both mesh with the same axle or hub gear. This will keep all of the gears from rotating, thus the diff is locked.

Share this post


Link to post
Share on other sites
MikeES
Good explanation Rod. The bolts that the spider or pinion gear fit on are not evenly spaced but spaced in pairs, and the pairs have to be set up as Rod described.

Share this post


Link to post
Share on other sites
mbsengineer
Thanks for the follow-up comments. I'm still not 100% on what you're saying, but I'll probably get a better idea when I start to take it apart. I'll post my progress when I have time. =)

Share this post


Link to post
Share on other sites
MysTiK
I'm thinking if you can possibly contact the PO, that perhaps he can shed some light on the situation - i.e. did he change it, or work on it, or deliberately lock it. ???? or was it used as a pulling tractor? Also, I saved this info below, a while back - might be related. Here is the thread - on some other forum. It mentions shimming the diff to enhance the ATC Automatic Traction Control, or limited slip. Seems like going too far to improve things, or refresh performance, can also cause (positraction) lock. Maybe helpful. http://www.mytractorforum.com/showthread.php?t=196968

Share this post


Link to post
Share on other sites
MikeES
BTW...As a tractor puller, I don't know why anyone would lock the differential for pulling. I have seen the results of people who have done this...the first time you get uneven traction the tractor takes a hard turn right out of bounds and nothing you can do about it. I took the springs out of our pulling tractors differentials and put the spacers in (older style diff.) because I broke a couple of diffs when the springs compressed and the pinion gears did not fully mesh. We have never had a one wheel wonder with the springs out. Our tactors go straight down the track better than any Cub Cadet.

Share this post


Link to post
Share on other sites
MysTiK
I must confess, I actually know very little about this - I just keep reading stuff, and save stuff for future reference - hoping my understanding will evolve in the process. I am pretty hesitant to take on rear diff - but this shimming idea is attractive. When pulling a heavy aerator, etc. across an uphill/sidehill combo, I often develop one-wheel-spinning - I lean over to shift my weight to help the spinning wheel, and that gets me going. But the idea of improving this is attractive. I have the impression this is accessible from the right side, and does not require major surgery - so it's tempting for me to just tweak it a little bit. Anyway, this seems like one of several possible solutions to the problem - maybe. But me taking on the disassembly of the entire rear end would make a very funny movie. sm01 Like with several things on my tractor, I bail out under the "if it works, don't fix it" clause. sm01 Perhaps the scariest part is that a lot of this stuff seems to be making more sense - I guess that's evolution through osmosis or something. sm01 Thanks to all here for what seems like my personal growth happening all by itself. Still got a ways to go. sm01

Share this post


Link to post
Share on other sites
MikeES
Graham, the differential comes off easy especially if the last person that had it apart installed the diff with the nuts facing in on the hub. Then you can remove the diff without the pinion gears all falling out of place. Just remove the right wheel, remove the right hub, unbolt the diff and lay it on the bench. If you add washers to increase spring tension you will need a way to compress the two half of the diff housing against the added tension of the springs. Then reassemble. Other than dealing with the grease all over and clean up (if you want to put in new grease) a 15-20 min job.

Share this post


Link to post
Share on other sites
MysTiK
Haha, you make it sound easy. 15-20 min for me has a way of becoming 15-20 days. I get the idea (kinda), and I will save this info for future ref. (it's what I do), and then I'll read more "diff threads". The info overlaps eventually, and the picture becomes more clear. For now, I'm watching. The scary part is I read threads where people have problems working on one side, and the solution is to work from the other side and I just read this and think OMG. OO A lot of my fear stems from the very early early days when I bought my tractor w a busted deck. Soon I was way over my head in spindle parts and dirt and grease everywhere, not to mention parts I ruined during disassembly. Only good that came out of that was the challenge to master "decks"; so today I can be pretty helpful in deck threads. And one of these days, I will open the box of deck parts and restore the original "fail". :D (I have the entire deck as a spare 48). A friend recently helped me resto my bgb - good thing I had help there, cos this bgb was in very serious condition - and he had expertise and spare parts lying around to add "what else" was needed to do it right. But it seems that seeing it done is the best education. And that can be with or without help. Thanks for the info. Much appreciated, even tho it only makes partial sense at this moment. This entire thread is a learning experience. Thanks to others here - esp. Rod. dOd But I hope mbsengineer gets through this problem - since it is his thread, and his main concern.!

Share this post


Link to post
Share on other sites
CarlH
Another thing to do when assembling/disassembling a differential is to replace every other bolt that holds it together with longer bolts. Then everything doesn't come apart in a surprising way.

Share this post


Link to post
Share on other sites
HubbardRA
If the diff is assembled with the bolts through the axle flange and the nuts on the outside of the diff, I get a complete new set of bolts. I then remove the nuts from the outside of the diff, and I slowly pry the diff off the axle flange and at the same time I feed the new bolts through the diff. This way, when the diff is removed from the flange it is still intact with all the parts in the same places with the threaded ends of the bolts pointing toward the axle flange. If someone just pulls the diff off the bolts, like I did the very first time I worked on one, he will have a diff in his hand with the inside full of gears, spacers, and springs just laying in a big pile. That requires you to really know how a diff works to get the diff reassembled with all the parts in their proper places. Not an easy task for the first time you have worked on one. From my experience it seems the factory assembled these diffs with the nuts on the outside in all cases. I have found that the entire task of working on a diff is much easier with the bolts reversed and the threaded ends thru the axle flange with the nuts on the back side of the flange. This makes the assembled diff easy to install on the tube and also gives you a way of removing the entire diff as a unit if you need to inspect or do some work on the axle, inner gear, or keyways. I turn the bolts around in all of mine. I have run the axles both locked and unlocked in tractor pulls. I prefer the factory setup with additional shimming to tighten the diff. Most of our stock tractor pulling was in a class with 10.5 rear tires and this setup worked well with them. Be aware that if the diff is locked, the only way to actually steer the tractor is through the movement of the driver's weight. He can put more weight on one wheel or the other sliding or leaning to one side which will shift weight from one tire to the other and change the traction that the tire has. This does not work well on these tractors because of the way the driver sits on these tractors. He is very much confined to one place. I did run a locked diff (straight axle) on a homemade tractor that I ran in the modified classes. This tractor was setup differently to make it much easier for the driver to do the body weight steering. It always ran straight because I had to be concerned with and doing body steering right from the time I released the clutch. If would not go straight on its own, I had to drive it straight on every run. Because of that, I was the only person ever able to drive this tractor and do any good in a pull. Most other people just ran out of bounds as soon as one wheel caught a little more traction than the other.

Share this post


Link to post
Share on other sites
MikeES
Rod, even with an unlocked diff, I've had to the mamba butt dance to keep the tractor straight. Like I said earlier we never had a situation of a "one wheel wonder" with these tractors. Even at the end of the pull with the front wheels off the ground and both back tires spinning. I have seen many cubs doing the "one wheel spin".

Share this post


Link to post
Share on other sites
Brettw
I had the opportunity to pull the diff from a spare rear end I have. I figured I would clean it up and have a spare. When I opened it there were numerous broken springs. I suspect from fatigue over the years. Fortunately, all the gears were in fine shape. Springs were still available at the dealer, they were reasonable, and I replaced them all and rebuilt the diff. I think there are two thought processes going on here. Pulling, and general working use. A locked differential while trying to yard work is a WAY different issue than trying to run a straight line, pulling. When I had the Sunstar, and you put the diff lock lever down, you couldn't turn the tractor on dry pavement. Likely one of the reasons why front tires seem to me to be heavily worn on Sunstars I have seen/ had. With a locked differential, all the "mamba butt" in the world isn't going to help you cut around the that tree or do a 180 to make the return pass cutting the lawn. }:)

Share this post


Link to post
Share on other sites
mbsengineer
quote:
Originally posted by HubbardRA
I had one that was locked when I traded for it. I got hold of the manual and it was set up as the manual said. I removed two of the three washers that were on the left side of the left axle gear and put them on the right side of the gear and the diff was unlocked. If that gear is able to move too far to the right, it will engage both sets of spider gears and lock the axle. The axle gear is made with the teeth positioned to one side of the gear. The teeth need to be to the left side of the tractor (inward). If someone has flipped this gear over, that will make the teeth engage both sets of spider gears and lock the diff too. Two ways it can be locked without being broken. 1.) washers on wrong side of axle gear. 2.) gear flipped over backward. This can be checked and fixed without removing the differential. You just have to remove the right side hub to get to these parts. Download the manual and look at the parts assembly diagram. You should be able to see what I am talking about.
Okay, so I found one problem (as one you pointed out) ... the gear is backward with the teath facing out. I don't know how many spacers are in the inside (left side) of the gear ... I find that out once I pull the gear to reverse it ... but I don't see any on the outside. I'll double-check it when I get in front of it later today ... or perhaps one is stuck to the inside of the hub assembly and I didn't notice it. Just to verify, it looks like the retaining ring is the only thing holding that gear in place, correct? I assume once I get that off, I can slide the gear off the axle?

Share this post


Link to post
Share on other sites
RayS
Have you looked at the link below in Tech tips forum? It is a step by step post from the repair manual. http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=117669

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Who's Online (See full list)

    • Ronald Hribar
  • Today's Birthdays

    1. B-16_IC
      B-16_IC
      (46 years old)
    2. Flannelman
      Flannelman
    3. Glen112
      Glen112
      (71 years old)
  • Recent Status Updates

    • Bubba1997

      Bubba1997

      Searching for a Sleeve hitch and breaking plow and other equipment if price is right and also a deck for a B1 thank you 
      · 3 replies
    • Dean McFadden

      Dean McFadden

      Good morning peeps! I’m always searching for helpful information with my AC collection. Hope to find out new information and pass on my own experience in restoration. Here are some pics of my babies. I’m still looking for front rims for the 410 so yesterday I put the 310 wheels on took it for a drive. Working pretty good but still needs some carb work. Gotta get the 310 running next. Have a great day!😁
       

      · 1 reply
  • Adverts

×