Technical Question Shortening drive shaft

I recently had my drive shaft from a 46 ford closed rear shortened for my AV8 Build. They went the route of cutting and machining down the adaptor/coupler and interference fit pressing on the adapter. The guys at the shop cut the wrong end of the drive shaft off. I have taken the shaft home and test fit the length and fits perfectly. My question is more about the small divet or ring that is in the end of the drive shaft that connects to the trans yoke that was cut. They offered to put this back in the shaft for me, however I wanted to make sure the fit and purpose of this ring. I thought it was a holding spot for maybe a retaining clip, but after assembling the shaft and torque tube I am not sure anymore. Thought some of you with lots more experience would have an idea here. photo below is the section that was cut off.

 

The grove is for a retaining clip that holds the speedometer drive gear and roller bearing in place.


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You said the coupler was installed with an interference fit. They welded it too, right?

 

for sure, welded in place. So i will need them to create that spot for the retaining clip to make sure the speedo gear will stay in place. Thank you folks.

 

I just did this, make sure you pre-assemble it and mark the spot for the groove, if it’s too far back from the front you won’t be able to get the C clip in. And if it’s too far forward your speedo gear will float. And don’t forget to install the thrust washer before the speedo gear.
Also did you come up with some kind of seal to keep the oil from the rear diff from coming forward?
I tried the baffle from VernTardel but it still allowed oil to seep by. I ended up installing one of the seal kits that Bruces Rod Shop custom makes.


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I always thought that seal behind the speedo gear , on the front end of the drive shaft torque tube was there to keep the trans gear lube from filling up the rear axle with trans lube. The 30s-40s Ford transmissions do not have a seal on the back side of them for the purpose of allowing some gear lube to get past to lube the "U" joint and speedometer gear. That grease fitting on the clam shell drive shaft/trans coupler is there to lube the clam shell bell on the front of the driveshaft torque tube. There is no way you could pump enough grease through it get to the "U" joint !
Any rear axle gear lube that might work it's way uphill to near the speedo gear would surely drain back downhill once the car was parked. Without that seal behind the speedometer gear all the trans lube would eventually end up in the banjo housing.

 

The problem of rear end lube working its way into the transmission happens when we lower our cars a lot. The engine is in the front, the low end, and taller tires are on the rear, the even higher end. Now the torquetube points downward and the lube goes forward.

 

^^^^ This. In spades... More than a few customers came in with this problem...disbelievers, one and all.
My job: to make them believers. I did, eventually. But neophytes with mysterious old Fords are hard to convince.

 

I measured a lot of rear ends to try to determine the clearace between the snap ring and the speedo gear. The consensus was .100
I cut some input ends off some 35-6 shafts. I may still have one if you want one.

 

You had trouble convincing them that oil runs down hill? Wow....lol








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