The Ford Barn

nosoup4u · 07-20-2021, 09:41 AM

Just an update. You may remember my previous post on a model A differential on a speedster with differential problems. Disconnected everything at the rear axle and the coupler at the front of the drive shaft. As I pulled it back the driveshaft came out the end of the torque tube. Yeah, that wasn't supposed to happen. Since I'm a bit of a simpleton I am presently looking for a model A mechanic in my area to properly put things back together again.
Question though, if the only thing that happened is that the pinion gear came off, should the differential still be working in that if you turn one wheel with both off the ground, the other should turn the opposite direction?

nkaminar · 07-20-2021, 09:56 AM

Where are you located?

To have the wheels move the opposite directions you must have the ring gear kept from turning. Usually that is accomplished by putting the car in gear. However if the pinion gear is not connected to the drive shaft then the ring gear could move and you may not get the wheels turning the opposite directions.

Bob Bidonde · 07-20-2021, 10:26 AM

Assuming that the rear axle assembly is from a Model "A":
The drive shaft is secured to the pinion gear with a castle nut & cotter pin. A shear key between the driveshaft & pinion prevents the pinion from spinning on the shaft.

There is no way the driveshaft should come out of the torque tube unless the cotter, nut & key are taken off first!

nosoup4u · 07-20-2021, 10:29 AM

They were off. Nothing but threads on the end of the shaft.

Jim Brierley · 07-20-2021, 10:33 AM

Slip an axle into the pinion gear, with a key, then you can see if the pinion is rotating. What happened to you is most unusual, I would take the diff totally apart to see if there is any collateral damage. You'll probably have to take it apart anyway to retrieve the nut that came off the drive shaft. These rear ends are not rocket science, you can probably do it yourself with guidance from Tom Endy. Tom has videos posted on many operations, do a search.

katy · 07-20-2021, 10:49 AM

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Be careful w/that rear spring.

Tom Endy · 07-20-2021, 10:55 AM

I have seen this several times. What probably occurred is that the last person that had the differential apart failed to install a cotter pin in the end of the drive shaft or did not torque the nut to 100 ft. lbs. The nut came loose and backed off until it hit the rotating carrier. The carrier began grinding the nut down. Depending on how long this went on determines how thin the nut became.
If you are lucky the nut remained jammed between the end of the drive shaft and the carrier until you pulled the drive shaft out, then it dropped into the banjo. The only damage then is a lot of metal in the oil and damaged bearings. If unlucky the nut became thin enough to drop into the banjo during operation and do a number on the ring & pinion. You will need a pinion gear assembly puller that mounts behind the first large pinion nut in order to get it apart.

Tom Endy

rotorwrench · 07-20-2021, 11:13 AM

The drive shaft being disconnected might simplify the pinion and bearing removal for inspection. Certainly check out Tom's tech articles on the Santa Anita A's web site.

If it has an underdrive unit on there then hopefully the drive shaft is still usable.

07-20-2021, 09:41 AM	#1
nosoup4u Senior Member Join Date: Dec 2010 Posts: 111	Differential part 2 Just an update. You may remember my previous post on a model A differential on a speedster with differential problems. Disconnected everything at the rear axle and the coupler at the front of the drive shaft. As I pulled it back the driveshaft came out the end of the torque tube. Yeah, that wasn't supposed to happen. Since I'm a bit of a simpleton I am presently looking for a model A mechanic in my area to properly put things back together again. Question though, if the only thing that happened is that the pinion gear came off, should the differential still be working in that if you turn one wheel with both off the ground, the other should turn the opposite direction?

07-20-2021, 09:56 AM	#2
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,897	Re: Differential part 2 Where are you located? To have the wheels move the opposite directions you must have the ring gear kept from turning. Usually that is accomplished by putting the car in gear. However if the pinion gear is not connected to the drive shaft then the ring gear could move and you may not get the wheels turning the opposite directions. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

07-20-2021, 10:26 AM	#3
Bob Bidonde Senior Member Join Date: May 2010 Location: Long Island, NY Posts: 3,463	Re: Differential part 2 Assuming that the rear axle assembly is from a Model "A": The drive shaft is secured to the pinion gear with a castle nut & cotter pin. A shear key between the driveshaft & pinion prevents the pinion from spinning on the shaft. There is no way the driveshaft should come out of the torque tube unless the cotter, nut & key are taken off first! __________________ Bob Bidonde

07-20-2021, 10:29 AM	#4
nosoup4u Senior Member Join Date: Dec 2010 Posts: 111	Re: Differential part 2 They were off. Nothing but threads on the end of the shaft.

07-20-2021, 10:33 AM	#5
Jim Brierley Senior Member Join Date: Jun 2010 Location: Temecula, CA Posts: 4,084	Re: Differential part 2 Slip an axle into the pinion gear, with a key, then you can see if the pinion is rotating. What happened to you is most unusual, I would take the diff totally apart to see if there is any collateral damage. You'll probably have to take it apart anyway to retrieve the nut that came off the drive shaft. These rear ends are not rocket science, you can probably do it yourself with guidance from Tom Endy. Tom has videos posted on many operations, do a search.

07-20-2021, 10:49 AM	#6
katy Senior Member Join Date: Jun 2015 Location: Red Deer, Alberta Posts: 5,042	Re: Differential part 2 Sponsored Links (Register now to hide all advertisements) Be careful w/that rear spring. __________________ If you don't hear a rumor by 10 AM, start one!. Got my education out behind the barn!

07-20-2021, 10:55 AM	#7
Tom Endy Senior Member Join Date: May 2010 Location: Southern California Posts: 3,130	Re: Differential part 2 I have seen this several times. What probably occurred is that the last person that had the differential apart failed to install a cotter pin in the end of the drive shaft or did not torque the nut to 100 ft. lbs. The nut came loose and backed off until it hit the rotating carrier. The carrier began grinding the nut down. Depending on how long this went on determines how thin the nut became. If you are lucky the nut remained jammed between the end of the drive shaft and the carrier until you pulled the drive shaft out, then it dropped into the banjo. The only damage then is a lot of metal in the oil and damaged bearings. If unlucky the nut became thin enough to drop into the banjo during operation and do a number on the ring & pinion. You will need a pinion gear assembly puller that mounts behind the first large pinion nut in order to get it apart. Tom Endy

07-20-2021, 11:13 AM	#8
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,420	Re: Differential part 2 The drive shaft being disconnected might simplify the pinion and bearing removal for inspection. Certainly check out Tom's tech articles on the Santa Anita A's web site. If it has an underdrive unit on there then hopefully the drive shaft is still usable.

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