b7800 locker problems

[captin_insano]

Anyone else have troubles with their diff lock? I bought my b7800 in aug of 07 after doing my research on here to help determine if it was a decent machine. I believe kubota makes a fine product, my dad bought a new b21 around 1992-93 that has never had an issue. Based on my experience with his kubota (approx 1000+ hours of seat time) and help from the online reviews of the 7800 I walked into pristows of johnstown pa on aug 22 2007 and handed them a check for $15,794. Jan of 09 with about 130 hours on the machine and in the worst snow of the year the rear locker quit working. I was without the machine while it was repaired which sucked but I was glad it was repaired without incident. Even though the case was full of metal shavings when they split it I was ok with just the locker repair. Now one year later and with over 30" of snow on the ground and a long drifted driveway I have a B7800 with around 220 hours on it that I cant use because the diff lock has failed again. Last time the case was full of metal shavings so I cant run the thing. This time now I'm having troubles with the warranty. I'm frustrated, I'll detail the warranty issues after the problem is solved. I'm current on my service and dont abuse the machine. I feel I have a lemon and this isnt a common problem but was wanting to hear from everyone if I'm in fact this unlucky? Thanks for listening.

 

[MikeInEburg]

I haven't heard of anyone having this issue on B7800 (or any other Kubota for that matter). I wonder if the mechanism isn't releasing (or engaging) all of the way, leaving it partially engaged when it is not intended. For a second round of nearly identical circumstances, I'd look for a root cause.
Mike

 

[captin_insano]

I hope to get a root cause but unfortunatly after today I get the feeling kubota just wants to say I'm the problem. I know better, I know how the machine was used and am no stranger to equipment so I have found this quite frustrating. I need to vent a little bit of it. The tractor has had a few little issues that I didnt worry about, like a broken hydro line shortly after purchase. I replaced it on my dime and did the 50 hour maintnence. No biggie, I expect that kind of stuff to happen. It began having starting issues too. I had the dealer look at it and they said they adjusted the hydrostat pedal. It worked for maybe a dozen starts, no biggie, when it quit again I simply bypassed the hydrostat safety switch so that I didnt have to deal with it anymore. Then the locker went the first time which bummed me out but was fixed...I guess. Now the locker again and the realization has set in pretty deep that I made a poor purchase with this machine. I do think kubota has quality equipment and suspect this is a rare bad one but so far kubota has really left me less than impressed with their customer service. At first I assumed my tractor was out of warranty since the basic had expired. The warranty rep confirmed to my dealer that the machine was out of warranty, it wouldnt be covered and in fact they would likely not cover it under warranty anyway as they rarely cover locker failures. They "couldnt believe it was covered the first time". I had to call california and the dealer several times and actually read their powertrain warranty to them as written. "36 months" and I read the powertrain definitions as written. So its under warranty but now the best they can do is tear it down and "email pictures" to kubota who will determine if it is a reimbursed claim. Now I'm no metalurgist but I was a machinist prior to my current profession and I dont know how you, for example do a rockwell hardness test on a picture. I feel like I'm being treated like an idiot. I wasnt given any clear answer by kubota customer service as to how it will be determined if the product was defective other than by pictures. I want these answers because I'm not going to accept anything less than a repair paid in full and I refuse to be stuck with a defective tractor and a repair bill. The dealer replied by stating the worst case scenario if warranty was refused and I didnt want to pay for the repair was I'd have to pay the tear down labor and diagnostic time but then I'd have to buy the parts and put it back together. I could be ok with that "risk" but I was just told they cant believe it was covered last time. Theres more yet but I chewed your ears enough for a night. Thanks for letting me vent.

 

[MikeInEburg]

I'm thinking that, short of you driving around with your heel on the pedal, or using at very inappropriate times (use during a turn when on hard surface) you'd have a difficult time causing this issue.
Mike

 

[bstrom]

What are they saying is causing the problem with the diff lock?

 

[captin_insano]

What are they saying is causing the problem with the diff lock

They havent said. last time though the tech working on it showed me the metal shavings in the case and part of the locker and said the new part was "different and probably better". I trust the tech at pristows, he seems to know how to turn a wrench and I didnt even ask what all was replaced.

I think I'd have a difficult time causing it too Mike. Especially since I have 17-18 years on b series kubotas. Over half of my life and by now I should know the machines. I understand very well the bind when turning too, (look at my tinkering post in the build forum). I'm very knowlegable in axles and lockers. As soon as I can get my trailer out of the driveway (enough snow already) its going in for the tear down. I'll personally inspect all the parts and their workings this time and give my opinion. I still think kubota can be a class act, that this is a rare problem and I'll get taken care of. We'll see.

 

[bstrom]

I step on the diff lock after letting off on the HST pedal somewhat and one rear wheel is spinning slowly then it seems to lock in. Sometimes I step on it before I think the wheels might spin without much HST pedal then it goes all the way down just as they spin. Does that sound like correct ways of doing it? Sometimes I feel like I am doing it wrong but I don't know. It sure seems like you would really have to abuse it to grind metal.

 

[manganos]

When I use diff lock I make sure I'm stopped first ....

 

[captin_insano]

The dealer says you need to be stoped but you can find conflicting info on this. Mine hardly ever locks at a stop, like yours I usually have to move/spin a little before it goes in. Good rule of thumb for any locker is never jam it in while one tire is spinning. Although a slow spin (slow being the key) like you do shouldnt hurt a quality component, it makes perfect sense the parts need to move in order to line up and engage. My dads always seemed to go right in, mine on the other hand has never worked like his. Mine you have to put alot of weight on it or it will make like a "skip" and kick out. The more torque to the locker the more it seems to want to kick out. I actually thought about putting an electric actuator on it because you have to push it so hard and mine is mostly used while pushing snow in straight lines. I assumed (or tried to convince myself) it was the way the 7800 was, especially after they fixed it the first time and it functioned the same way.

I've come to 2 conclusions and I'm convinced one of them is correct. Either its a weak inferior locker and I just use mine enough to have the problems (its used alot to push snow). Or conclusion 2, there is some reason its not engaging properly. Once its torn down I'm asking to have the old parts to inspect myself. I'm going to get a rockwell hardness at least just so I know if it's a qulity component from a metallugical standpoint. I may even try to calculate actual torque the locker sees at its wear/stress points when in use and determine based on the strength of the steel just how well they are built.

 

[captin_insano]

My dads kubota is a 92 b2150. Anyone know if these lockers are the same as mine or if they interchange? The rears look real similar, his just works much better. If I have to pay to fix mine I'm going to try to do it once and do it right.

 

[Verticaltrx]

I haven't looked at the diff lock on my B3200 closely to see what/if there is any linkage, but that is the first place I would look. There were a couple of linkages on my tractor that were not set up properly when I got it (the 4wd was almost impossible to engage/disengage), but once adjusted they are all working good. The diff lock pedal may not be fully engaging the locker which of course would shear off the mechanism under a heavy load. I only have 120hrs on mine, but I use it for a lot of heavy work including a lot of excavating and dirt work with the loader and pushing out brush, so far no trouble.

 

[bstrom]

I actually don't use the the darn thing much anymore because the front wheel assist is so effective. I was coming uphill out of the woods in fairly deep snow in 2 -wheel drive and started slipping even with chains. I stepped on the diff lock - a little better but not great. Shift into front wheel assist and without the diff lock it takes right off through the snow.

It seems to be more effective in reverse for me, if I am stuck backing up a hill or through snow, it seems to really pull me out if I step on that thing. Maybe I don't know what I'm doing or maybe -just maybe - mine is busted too! Now I'm worried - I'd better check it tomorrow.

 

[Verticaltrx]

I looked at my shop manual last night and there really aren't any adjustments on how the locker engages. The only thing that could affect its engagement would be a bent foot pedal or engagement fork.

The way it work is there is circular plate on the carrier that is pretty thick with a big notch (about 3/8 of the circle.) On the right hand axle shaft there is another plate with the matching tooth that locks into the cut out when slid into place by the engagement fork. When they lock together it locks the right hand axle shaft to the carrier, which therefore locks the right hand side gear and spider gears which makes the other side turn. Its nothing like any of the automotive based lockers I've seen before, but it does look pretty stout, especially since its upstream of the final gear reduction. If you don't mind post up some pics of the failed parts when you get them, I would be interested to see exactly how they failed.

 

[captin_insano]

Thanks for the input. I looked at the linkage and had seen there was no adjustment. Its kind of a poor design IMO and I can see from looking at it that the linkage is at least part of the reason its hard to press compared to the older b2150. Once its fixed and the warranty is out I'll definatly upgrade the linkage to at least have some sort of bushings where it piviots. I'll put a little leverage on it too to make it easier to operate.

You wouldnt have an exploded view of the locker by chance would you? If not, no biggie dont go out of your way because I'll just pester my dealer to get me one. Where is there a gear reduction past it, if there is a gear reduction after the locker it should in theory be pretty strong under torque. I think the L series looks like it has the reduction after the locker but looking at mine together I cant see any obvious place where there would be one.

My pedal isnt bent, it has plenty of room to travel but the fork I cant comment on yet. Again, thanks.

 

[herringchoker]

1. You wouldnt have an exploded view of the locker by chance would you?
2. Where is there a gear reduction past it, if there is a gear reduction after the locker it should in theory be pretty strong under torque.

1.You can get a pdf parts manual for your tractor at :

TractorSmart.com is your online source for Kubota online parts.

I have one for the B7800, but being a computer dummy, I can't figure how to pull out specific pages for you. If you get a pdf file, the exploded view of the locker is in the REAR DIFFERENTIAL and DIFFERENTIAL LOCK PEDAL sections. It's pretty much as Verticaltrx describes.

2. The REAR AXLE section shows the gear reduction outboard of the differential case.

Hope this helps.

 

[captin_insano]

I looked at the other B tractors on the lot at the dealer when I droped mine off today. They had b3030's, 3200's, 29xx, 7510, etc. All the tractors there had a very different linkage and a MUCH better feel to the locker. I'll get some pictures of my linkage, its a pretty crappy set up compared to the others I looked at. I would assume this is a b7800 thing or is it possibly a model year difference? If I would of actually seen this (its hidden pretty good) before I bought I would of went with a different tractor. Its like something you would expect on a lawn tractor from the walmart. I hope theres an upgrade by now. There was a 7510 there sitting outside with the rear torn apart. The diff was covered with plastic and I assume it to have been a customers so I didnt mess with it but I really wanted to get a look at its guts.

 

[crbr]

I looked at the other B tractors on the lot at the dealer when I droped mine off today. They had b3030's, 3200's, 29xx, 7510, etc. All the tractors there had a very different linkage and a MUCH better feel to the locker. I'll get some pictures of my linkage, its a pretty crappy set up compared to the others I looked at. I would assume this is a b7800 thing or is it possibly a model year difference? If I would of actually seen this (its hidden pretty good) before I bought I would of went with a different tractor. Its like something you would expect on a lawn tractor from the walmart. I hope theres an upgrade by now. There was a 7510 there sitting outside with the rear torn apart. The diff was covered with plastic and I assume it to have been a customers so I didnt mess with it but I really wanted to get a look at its guts.

PM sent to you. I can send you a parts manual in PDF or click here (below on the thumbnail picture).

.

 

[captin_insano]

Thanks crbr. I'll save you the time on the manual, the pic you posted gives me a good idea what I need to look at. I do appreciate the offer though, I just hate to take up anyones extra time on this. I Imagine it would take a little effort for you to attach and send it and the pic gives me a good idea of what I'm looking at. The locker itself should be self explanatory when I see it. Again thanks for the offer, mighty fine of ya.

 

[whistlepig]

My B7800 has over 400 hours on it. I rarely used the differential lock until this past week. Over 40 hours of moving snow with the loader and used the differential lock countless times with no problems. I do know that the differential lock can't be engaged with the rear tires spinning. That's a guaranteed way to destroy it. Doesn't necessarily make the B7800 a bad tractor. I owned a 1964 MF135 (which was a tank) and it was the same way. The owners manual said not to engage the differential lock while the tires were spinning or it would shear the differential locking pin. It may only take once.

 

[captin_insano]

I'm not saying the 7800 is a bad tractor. Mine obviously has some issues I need to figure out though and based on my experience with it and now comparing it with others I wouldnt make it my first choice again. I'm not happy to say that but it is what it is. So far just looking at it I can see the linkage is not on par with the other b series I've put my eyeballs on. I WILL upgrade this linkage once the warranty is out. The problem i see with it is for starters where the linkage goes through the figure c420 in the picture. if you look under the seat you'll see this is just a notch in the metal with a bent chunk of metal "pinching" the linkage in there. It looks like it will pinch in tighter the harder you have to push it. The foot lever section is long with no real gussets or mounts to support it before that pinched spot. The final lever near number 110 is short and offers little leverage. I think I can improve on this linkage set up for starters. My locker has never worked or felt like the aforementioned b2150, nor does it feel like any of the other b tractors I checked out today and I think this linkage is at least part of the problem. I think theres more to it but i really do think this can be improved for starters.