Differential issue, any ideas?

[Mike Lebsack-Iowa]

I was driving my 1915 yesterday. All going very well until I lost power to the rear wheels. Car basically free wheeled with no resistance. I brought it to a stop with auxiliary brakes, no problem. Pulled to my shop. Jacked up rear axle so both wheels off the ground assuming I may have sheared an axle key. Both wheels free wheel, by this I mean that when I turn one wheel, the other would typically turn in the opposite direction, right? This is not the case, either wheel can be turned forward or back without affecting the opposite wheel. This is a Ruckstell axle. The shift lock is fully engaging in high and low with a solid locking sound. Right now I am thinking the key at the pinion gear may have sheared? Could it be one of the keys on either of the axle gears? Any ideas out there?

[farmboy]

Spider or axle gear issue

[Wayne Sheldon]

Could be almost anything from the rear hubs (hubcaps and wheels rotate together?), all the way to the U-joint, and even beyond into the output driving plate inside the transmission!
Pushing, pulling the rear wheels in and out while jacked off the ground might give a clue to narrow down the possibilities. However, it is almost a certainty that you will have to take the rear end apart in order to fix it. So may as well jack the thing up, SECURELY block the frame just a couple inches higher than its normal height, then drop the rear end out and get to it.
I would recommend that you check/test the output end of the transmission to make certain the problem isn't in the transmission itself. I have known a couple people that sheared the rivets in the transmission output driving plate. One person I heard from had gone completely through the rear end, finding nothing wrong, before he discovered he had to pull the engine the replace the driving plate. Driving plate failures are rare. But with the rear end out of the way, it only takes about a minute to check it.

Good luck! And be careful.

[Scott_Conger]

Mike

I believe you think right.

[JTT3]

Mike, Just some thoughts, some questions are already answered, you need another person to help but if you put the T in low, power off & hand crank does the car move forward? With the rear lifted and repeating the previous do the rear wheels turn? Transmission inspection plate off, hand cranked over does the drive plate shaft move with rotation, you can also challenge this using the rear wheels by turning them and seeing if the transmission is turning. May help you isolate the issue. Last thought and hopefully not and issue, rear of car lifted, pull out on the wheels, if you end up with a wheel and part of an axle in your lap… well not good. A mentor of mine was frugal in his efforts. He would remove the grease cups on the drive shaft & bell, then stick a brass rod in the holes to feel the universal and or the drive shaft rotating while help would turn the engine over

[Norman Kling]

I agree with most of the above suggestions. You will not know for sure what the problem is until you take things apart.
I will share an experience I had with my first T. On the first tour before I even had a trailer, I drove all the way to the start of the tour which was about 50 miles from here and then went on the tour. On the way home, I was wondering whether I would need to turn on the lights for the last few miles. I started out from a signal and there was a big bang and I was in free wheeling! Fortunately I t was a 26 with the large drums and I had also installed auxiliary brakes. I was able to push the car into a parking lot and called home and my son came down and took us home. Didn't need the lights! Next day borrowed a trailer and took the car home.
This is what I found! Someone had welded the front part of one driveshaft to the rear part of another shaft. They had only welded it around the edges, not all the way to the center. The weld had broken.
So you see the cause cannot really be found until you take it down and look inside.
Norm

[Ken Lefeber]

Mike,
The same thing happened to me 3 weeks ago.
This is what happened to mine.
Hope yours is just a pinion key.

[RajoRacer]

Ken - was that a Ford script pinion ?

[Ken Lefeber]

No.
Bought new and installed about 2 years and 2200 miles ago.

[RajoRacer]

Reason I inquired was that some pinions were made a while back with the keyway in the incorrect position - can't recall which way it was but I have enough Ford pinions to check against yours.

[TRDxB2]

In looking at the diagram just referencing the one as an example
If one wheel spins freely on the axle (not affecting the other side) and the axle doesn't move then... sheared hub key?
If one wheel spins freely on the axle (not affecting the other side) and the axle moves with it .... sheared Differential gear key (Axle gear key)?
If something was damaged in the spider or on the way to the u-joint ... wouldn't that make some noise and/or make one side harder to move than the other? The spider is where one wheel cause the other to rotate is it not.

[BHarper]

Hi Mike,
Does your car have safety hubs?
If so, you may have a broken axle or, a sheared axle key.
Good luck with your project. Bill.

[KBurket]

Example of keyway in wrong position. Corner of key way should be centered under gear teeth.
Left gear wrong, right gear correct.

Old post with discussion. http://www.mtfca.com/discus/messages/70 ... 1496334174
Another post, which I can’t find now, concluded there were some repro gears that were of incorrect hardness.

[RajoRacer]

Thanks for posting that photo !