7045 Diff Lock Not Releasing

Never heard of that problem before. A service manual would show how it works inside the tractor. Thats the only advice i can give you

Thanks. I pulled up the service manual. Nothing revelational. From what I can tell, pressurized oil gets directed to piston(s) which engage a lock bar in the spiders. But as far as I can tell from the hydraulic schematic and cross-section view of the mechanism, if the pedal is up and spool is retracted fully (which mine is), it should release. Looks like maybe spring release of the piston? But the manual doesn't say explicitly.

Had a few more minutes this afternoon, so I jacked up the right rear and tried rocking it back and forth with engine off, trans in neutral (both levers - PD trans). Still locked solidly even with engine off and no hydraulic pressure. Rather worried it may be a more major rear-end issue.

Is there an easy(ish) way to look in the rear end to inspect the diff? I'd like to at least try going down the hydraulic fill cap with my inspection camera, but I can't find my camera for the life of me.

Thanks Doc - I had responded before I saw your last reply. I was a little worried it might be something like that. I assume it's a pretty major rear end overhaul to fix. Anything I should/could do to inspect and verify before tearing into?

Thanks. I had the filter housing off once already while I had it drained to do the hydraulic pump. Thought it worthwhile to pull it and clean out any sludge from the bottom of the rear-end sump (surpsigingly clean). Wish I'd taken a better look while I was in there.

Sounds like as big a job as I worried it might be. Blast. Not sure I'll want to bother. As I say, I don't really need this tractor and got it for scrap price. But it would sure be handy for some things. And it sure does run well.

If the pinions are welded to their shafts, I assume that means replacing them and their shafts (at the least)? Wonder how much those parts will be, if they're even still available... I'm not really too eager to pour much more money into it at present.

Edited by DanielW - 18 Jul 2026 at 8:08pm

Im sure somebody has had that kind of problem but i believe its very rare. Ive ran 7and 8000 series since the 7040s came out and ive never seen the inside of the rear end of one. Ive never saw one apart at the dealer either. The ones we have had got worked not abused but worked. Did have to build the transmission in the 7040 at about 7000 hours but no rear end trouble

Thanks again all. One last question for the Doc if I may: Thinking about it overnight, I think I will pull it in the other shed and work on it some time in the fall when things are less busy. Wondering about getting a new set of pinions & shafts if I see some come available, knowing they're probably NLA from Agco.

The design with a long shaft and two short shafts became effective (approx) with the black chassis series. It cost less $$$$$ to build. The gears might be the same p/n's but the shafts do not interchange between the old housing and the newer housing. There shouldn't be a problem finding used in a salvage yard, as very low oil levels are the cause of failure.

I don't care about metalurgy. When they get operated 10 gallons low on oil, it isn't the metalurgy's problem. And I have seen them that low on oil many times. The rear end holds 17.  So, with 7 gal still in there the power steering and hydraulics still work. And quit driving it around !!!  You may not have damaged the ring and pinion, but if you keep driving it you may.

Edited by DrAllis - 21 Jul 2026 at 11:59am

SteveM C/IL wrote: Yeah,tempting fate with the "brake stomp while driving " deal.

True, you're not wrong. If it was a tractor I cared more about I maybe wouldn't have done so. But in my defence, it wasn't like I was 'stomping' on the brakes to bring it to a stand still or anything - just fluctuation back and forth to give a little resistance variation as I was driving the 200 yards to the barn. Engine barely even bogged down as I was doing so - I just wanted a little back and forth feathering. And if I was in first low I could more understand breaking something. But I was plugging away in 4th. In a taller gear like that at a lower RPM I would have expected it to stall first - even if the teeth were worn from previous neglect.

But oh well. Don't think I damaged anything that wasn't already. In the barn now and a new set of spiders and pinions is en-route. Don't have the shafts, but if needed I can make those at work pretty easily out of 4140 and send them off for nitriding with one of our batches. Worst thing I can foresee at this point is if the axle splines are stripped. But if so I'll bush either the axle or the pinion and double/triple key it to take the place of the splines. And if something else is awry, I'll just park it as a stationary power unit for the Sawmill. Still don't have much more than scrap price invested at this point, so I'm not overly fussed how it all turns out.

Edited by DanielW - 21 Jul 2026 at 3:55pm

I think Lynn had a picture of carrier with pinion cut about an inch downstream...

Thanks kindly for th info. Found one of Lynn's old posts with those photos (link to thread below). Quite the damage.

Dr Allis, sounds kind of like our 7060 when the diff turned into a solid locker......I wonder if he will find evidence of bad/poor heat treating.

Would the 7045 of had the newer design as well?

DrAllis wrote: The 7060 was a black chassis and had the newer designed differential with the 8 inch long 3/8" bolt holding in the two stub shafts. When that bolt breaks you get to buy a ring and pinion too.

With the 7045's all being black chassis, I know I have that three-piece shaft. As soon as I saw what it looked like in the parts book I disliked it. I'd much rather have the nested shafts and the two-piece carrier that the maroon-bellies had.

When that bolt breaks, what specifically causes the ring and pinion to fail? Jamming up somehow and shearing? Or crapulence getting caught in the teeth?

It'll be interesting to see what I find. I bought a set of pinions and spiders because I was able to get a good deal on an online set. There are only two ag wrecking yards within several hours of me that have any old Allis's. The nearest one only has one 7000 series - a 7030. Which will have the two-pinion rear end, and which they say has been sitting in their yard with the lift cover off for years, so who knows what that means. The next nearest yard (3 hours away) has a 7060, but they don't allow you to pull your own parts, and say for the cost to have them pull the diff it would be the same price to buy the whole rear end, at $3000. Which I think is rather high for a rear end of unknown condition (tires not included), and it'd be more than I paid for the tractor. So when I saw a set of pinions and spiders for a couple hundred bucks online I thought I'd grab them before they're gone. They were of the earlier style with the nested shafts, but according to the parts books the gears are the same. I'll likely have to make my own shafts (assuming nothing else is wrecked - which is a pretty big assumption). But we have some pretty good CNC tooling and lots of alloys to work with at work, and we send stuff for various heat treating processes all the time. If I can, I'll send an old shaft and gear to them because they do hardening analysis for us (we can do simple hardness testing at work, but the place we send parts for hardening does much fancier analysis). The old chap who runs the place is great to talk to, and often does analysis for us free as we're a common customer.

What I wonder about (and half suspect) is if Allis had similar hardness pinions and shafts. Which was a common mistake in the 60's and 70's - certainly not limited to Allis. When dealing with hardened metals (especially higher carbon alloys) it's important to have metals that are in dynamic contact with each other to be of dissimilar hardness. I always said at least 5 points on the Rockwell C scale different, but the Googles is telling me 10. Whatever the minimum difference is, it's for this reason: If you have metals of dissimilar hardness rubbing together, if they're lacking lubrication (if, for instance, someone ran the rear end 10 gallons low on oil), at least with dissimilar hardnesses one is just going to wear out and they'll just wear and get sloppy. But if they' re similar in alloy & hardness, instead of wearing out they'll gall/weld themselves together. Which sounds like what happened with the spiders on their shafts.

It's something we've ran into at work frequently, and was a notable problem in the 70's when plasma nitriding became uber-popular. Suddenly it was easy to send everything for superb hardening, with a method that maintained original geometry and eliminated the need for post-hardening machining operations. Nitriding was cheap, easy, and left the mechanical properties intact (it didn't embrittle the parts, like other hardening processes did). And it was easy to achieve 60+ HRC with no distortion, and everyone assumed that was more than sufficient regardless of what it was in contact with. So everything just got sent for nitriding and it all came back around 60 HRC. And galling became a major problem.

I know some Cases were well known for having galling issues, but can't remember the series or parts off the top of my head.

Edited by DanielW - 23 Jul 2026 at 7:16pm

No such thing as Rockwell C on nitrided parts. Nitriding is superficial hardening, like.01 to .02 thick. A true HRc test would blow through that like it wasn’t even there. You would use a 15N or 30N Rockwell test and scale which uses much lower penetrating loads. Then, yes, you can cross reference for a C scale equivalent.