Need an IH 766 drivetrain expert!

I'm thinking about purchasing an IH 766 diesel project tractor. The engine starts up great and purrs like a kitten, and the tractor is in overall good shape. Also, I already know that the T/A will need replaced, as the seller says it worked only on the direct drive side and not the torque side.

But, here's where I need the expert. Something is wrong in the drivetrain somewhere, and I don't really know what the issue might be. The seller says that he was using it in the field, he turned around at the end of the row, and after he started back in the other direction it just "stopped moving forward" according to him. I asked him to clarify, and he said that the tractor didn't die, the motor was just spinning and the tractor wasn't moving. After I started her up when I looked at her, I tried putting her in all the forward gears. With the T/A on the direct drive side, it would act like it wanted to move the tractor for a split second, but then would make a "popping" noise from the rear end (I think) and just free spin after that.

Does anyone have any idea what could be wrong in the drivetrain to cause these symptoms? I assume it is not something as simple as a bad clutch, but I'm unsure. Also, could it be that the T/A did finally totally shoot craps on the direct drive side as well, and it just seems like the noise is coming from farther back in the tractor?

Any help would be greatly appreciated. I think I can pick up the tractor for about $1750, but I don't want to get myself into a project where I'd be dumping a lot of money into it after I purchased it.

I can't think that anything in the transmission or rear end would just stop. I would think it's the T/A or the master clutch.

Is there any leakage from an axle? A failed inner axle bearing may allow the bull gear and bull pinion gear to slip under load. If that is the problem you should also see the wheel shake as the gears jump teeth. Teeth broken off the ring gear could also cause those symptoms you describe.

With the TA ahead and the transmissions in forth and high range you have eliminated all the transmission gears. The power flow is straight from the clutch disk through the TA high side clutch. Forth gear is coupled to the output quill of the high side clutch and high range has the range transmission main shaft directly coupled to the speed transmission output shaft. Providing you have hydraulics for the brakes that should eliminate the transmissions as the problem.

If you remove the bracket where the upper arm of the three point hitch attaches to the rear frame, you can see the ring gear and the inner axle bearings.

The TA on a 766 is completely different from a mechanical TA like on a 400.

Once a hydraulic TA goes out on one side, the other side is not far behind.

With the old mechanical TAs, the low side would fail, but you could run indefinitely on the high side. That's not the case on this 766.

Replacing the TA should fix the problem.

Before you take anything a part check the wheel bolts where the hub is clamped on the axel . I've saw more than one tractor hauled in thinking something was out in the rearend . All it took was new bolts .

Anyone else have any ideas, or does everyone pretty much agree with what has been posted?

(quoted from post at 11:36:20 04/30/10) Before you take anything a part check the wheel bolts where the hub is clamped on the axel . I've saw more than one tractor hauled in thinking something was out in the rearend . All it took was new bolts .

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Maybe on an M or a 560, but not on a 766. With the old clamp wheels, the bolts could come loose, the keys could fall out, and the round axles could spin in the wheel centers.

The axle on a 766 has a HUGE keyway that's part of the axle. It can't fall out, and for it to spin freely in the hub, a HUGE chunk o' hub would have to have broken out. The tractor would make an awful grinding noise but the noise would obviously be coming from the OUTSIDE. The tractor would also be going up and down about 2" on one side. Very noticeable.

Odds are that the TA is the main problem with this tractor.

I have seen those wheels where they lost enough material so that the axle spun inside the wheel. It is easy to see if this is the problem.

On that style axle the wheel must contact the flats on the axle and not the rounded part. If the flats are not carrying the load the wheel will move on the axle until it chews away enough material for it to slip.