12:05 Garage- ’70 Duster build

[bjkadron]

Learned something new over the weekend. I always thought my sure grip was the cone style so I never bothered taking the diff apart to inspect. I don't even know why I thought it was the cone type. I've had it forever! Well after trying out a new street recently opened near the house with a 1 mile straight, I'm happy to say the road is smooth, even at high speed. I give the road work guys and A+, hahaha. After 3 rips I noticed an odd sound coming from the rear end. Considering I was planning on autocross on Sunday, I figured it would be a good idea to inspect further. Well, it turns out it is a clutch type diff, and they are slap worn out. I'm assuming the spider gears didn't care for the additional clearance so they self destructed. Honestly, the diff is literally the only component on the car I've never inspected or rebuilt. I can't complain, it's my own ignorance/neglect. Also got lucky catching it before debris destroyed the ring and pinion. Tough year breaking stuff. First the lifter in the small block and now this. Let's hope that's it for a while.

Just curious, if you didn't know you had the clutches, were you running a friction modifier in the oil? If not that may have hastened it's demise. Also are you upgrading it or just replacing with stock clutch style?

 

[racerjoe]

Just curious, if you didn't know you had the clutches, were you running a friction modifier in the oil? If not that may have hastened it's demise. Also are you upgrading it or just replacing with stock clutch style?

I've always run oil with friction modifier. I'll just rebuild this one. Looks like Dr. Diff has the parts.

Does anyone know if the clutches actually have some type of organic clutch material on them? The ones that came out are all steel with no remnants of clutch material.

 

[bjkadron]

I've always run oil with friction modifier. I'll just rebuild this one. Looks like Dr. Diff has the parts.

Does anyone know if the clutches actually have some type of organic clutch material on them? The ones that came out are all steel with no remnants of clutch material.

So weirdly enough the pictures I'm seeing online don't look like there is any friction material. Does it just use the metal plates? Strange but technically possible. Not sure what that means for your root cause analysis. I'd maybe call Cass and ask. I've never had one of these apart.

 

[racerjoe]

So weirdly enough the pictures I'm seeing online don't look like there is any friction material. Does it just use the metal plates? Strange but technically possible. Not sure what that means for your root cause analysis. I'd maybe call Cass and ask. I've never had one of these apart.

I sent him an email. He says they are steel without any type of organic clutch material and should be generously coated with straight friction modifier during assembly. Mine do look pretty beat up. I ordered all the new parts from him today. As far as the failure analysis, maybe it's just 50 year old junk deciding to give up on life. His website says something about his parts being "heavy duty". Perhaps the original style had a weak point.

 

[bjkadron]

I sent him an email. He says they are steel without any type of organic clutch material and should be generously coated with straight friction modifier during assembly. Mine do look pretty beat up. I ordered all the new parts from him today. As far as the failure analysis, maybe it's just 50 year old junk deciding to give up on life. His website says something about his parts being "heavy duty". Perhaps the original style had a weak point.

That's really interesting that it is all metal as the friction material. I guess that is why it lasted as long as it did.

And also, if I'd been beaten on for 50 years I'd probably get a little tired too. Especially if this is the same rear you used for drag racing... that is quite a few shock loads.

 

[racerjoe]

That's really interesting that it is all metal as the friction material. I guess that is why it lasted as long as it did.

And also, if I'd been beaten on for 50 years I'd probably get a little tired too. Especially if this is the same rear you used for drag racing... that is quite a few shock loads.

This one had a fair amount of drag passes on it until I started making enough power that it would make the car drift left on the launch. I built another rear with a spool after that. Lets not forget the 150+ autocross runs in the last few years also.