14 Automatic Sunstrand hydro differential gear noise

[Short Circuit 27]

Hello WH enthusiasts,

I recently purchased a 1973 14 Automatic that was a "no issues" tractor. After getting it home, I noticed the left rear axle hub was loose. I started to check it out and found after jacking up the whole rear end, and rotating the left wheel, I could feel the differential gears meshing with each other as if they were lacking any gear clearance. It was also rather hard to turn. There is plenty of oil in the transmission case, and the tractor operated forward and back as designed. Do I have to take this apart and check it out, or does anybody have any ideas?

[TT-(Moderator) 1,145]

:WRS:

Was the drive belt disengagement/parking brake lever pulled up when you were rotating the tire?

[Short Circuit 27]

Either position of the brake has the same results. Both wheels are removed and the transmission is on jack stands. I turn one wheel hub and the other hub turns in the opposite direction as expected because of the differential gear action. The gears are just tight and you can feel each gear tooth as it meshes with the mating gear tooth in the differential, as if the have no gear clearance. Could the differential assembly bolts be loose?

[TT-(Moderator) 1,145]

Did you open the bypass (tow) valve?

[squonk 41,346]

Did you open the bypass (tow) valve?

I was thinking the same thing.

[Short Circuit 27]

It makes no difference whether the tow valve is open or closed. I'm not testing the whole transmission gearing, just the differential assembly. I'm going to drain the oil out and take it apart to check it.

[TT-(Moderator) 1,145]

I'm sure you are aware, but there's nothing but a couple reduction gear shafts and the differential inside the transaxle housing. When you rotate the differential assembly, you are rotating everything inside the cases - and the hydro motor.

If your 14 Auto has the 10 pinion "limited slip" differential, which it very well could, there is a possibility you will feel each tooth of every rotating pinion as it passes over the spring ring.

It's entirely up to you, but I wouldn't tear it apart - especially if it's working correctly.

[Short Circuit 27]

Thanks for the information TT.

The model of my Sunstrand unit is 90-1136, serial no. is 03-NA 19366.

The tractor model is 10435 8, and serial is 936585.

Is there any way to identify if my trans is actually a limited slip unit from these numbers?

[TT-(Moderator) 1,145]

From the book.........

1-0435 has the #5089 Uni-Drive (the complete hydro / transaxle assembly) with the 10 pinion limited-slip differential and piston-to-piston hydro unit. (if original)

[sorekiwi 761]

My 14 Auto had the 10 pinion diff (and still does). It feels like crap when you turn the wheels with the tractor up in the air. I had mine apart (for a different reason) and all the gears looked great.

I've pretty much decided that anything with a limited slip diff (cars included) will feel that way.

[Short Circuit 27]

Thanks Terry,

I just looked at a downloaded copy of the 1973 14 Automatic WH tractor manual. On page 6 of the specifications, it states that the 12 and 14 HP models are equipped with the limited slip transmission. The 10 HP model has a 4 pinion differential and the 16 HP model has an 8 pinion differential. I'm pretty sure that the transaxle is original. Seems I may not have a problem after all.

Now all I have to do is find a replacement wheel hub as the left side one is really chewed up at the woodruff key area.

[Short Circuit 27]

_{Thanks mike,}

_{I was typing while you were sending.}

[Callen 64]

I have never had one of these apart. Can someone tell me what keeps these from just rolling around the axle gears?

Chester

[TT-(Moderator) 1,145]

I'm not exactly sure what you're asking, but see if you get an answer from all of this.

The 10 pinion / limited slip Transpower differential was built with good intentions, but it's definitely not the best design.

The spring ring forces the pinion gears against the carrier halves and the friction is supposed to "lock" the differential until rotational force overcomes the holding power of the spring. Unfortunately, the tension of the spring ring decreases over time and the pinions & carrier bores wear with use. Forty-some odd years later, many of these are so weak that they perform more like an "open" differential.

If you're trying to figure out what keeps the axle gears from catching the spring ring and rotating it within the pinion gears, it's the axle design. The ends of the axles will butt against each other long before the spring ring gets pinched. Because the axle gears float on the splines (and everything is coated with oil) there isn't enough pressure to rotate the spring ring.

[Callen 64]

Terry, Thanks. In the open difs, what holds the pinions still so it turns the axles when the carrier turns?

[TT-(Moderator) 1,145]

Nothing has to hold them. The entire differential assembly rotates together unless one tire loses traction or when turning sharp enough to require the outside wheel to speed up and/or the inside wheel to slow down.

Because the opposing pairs (one left hand and one right hand - meshed with each other) of pinions are are inserted into the differential end caps and directly mesh with the axle gears, they drive the axle when the end cap turns. If the axle has to slow down or stop, the pinions begin turning in the end caps.

Beyond that, I'm not sure how to explain it.

Some people believe that the design of a differential came from aliens..... I would probably agree with that idea. :handgestures-thumbup:

[Callen 64]

Thanks,Terry, That pics is worth a million words. I've never seen a pic of it assembled like that. Now it makes since. Thanks again.

[kpinnc 12,535]

I turn one wheel hub and the other hub turns in the opposite direction as expected because of the differential gear action.

If this is correct, you don't have a 10-pinion differential. The opposite hub/ wheel should turn in the SAME direction with a 10-pinion.

The 4-pinion or 8-pinion differential would produce the opposite hub turning the opposite direction.

[TT-(Moderator) 1,145]

The opposite hub/ wheel should turn in the SAME direction with a 10-pinion.

That only holds true when the ring gear can turn freely.

If the ring gear can't rotate, the pinion gears will make it act like an open differential ~ but the axle(s) should be harder to turn.

[kpinnc 12,535]

That only holds true when the ring gear can turn freely.

If the ring gear can't rotate, the pinion gears will make it act like an open differential ~ but the axle(s) should be harder to turn.

Good to know. I have a Sundstrand hydrogear that is a little harder to turn (hubs only, no wheels mounted), and I thought something might be wrong with it.

Thanks TT!