Differential Man Products

   Back in early 80's, I owned and operated Gear Train Enterprises. I was at the front counter and behind me was my display of Gears, Axles and Carriers. A Man walked in and asked if we did such and such work. As we were talking, he pointed at the carrier in the center. He asked me, do you know how that works? I said yes and started explaining it to him. He said kind of loud, No, that's not how I designed that. I hesitated and said, what do you mean designed. He said, me and my team designed that carrier for GM. He said, pick that up and bring it here. I set it on the bench. He said, you see these, don't call them internal gears. There wedges, not gears. When ever you apply torque to the differential, the wedges (Spiders and Side Gears ) push away from each other and push against the clutches. I jumped in and said, I thought the springs put pressure on the clutches. He said NO! you don't even need the springs. We put them in there just to snug everything up. Then the bigger gears don't have to travel so far under torque. 

   Then he proceeded to tell me the correct way to lock up the posi. He said the worst thing you can do is to slowly give it the gas when stuck. One tire starts turning and you burn up the clutches. What you need to do is put your foot on the brake. Give it the gas, lock it up for a second and release the brake. Now the clutches are locked up and both wheels will have traction. 

   I had another posi there with bigger thick springs. I asked  him why are the springs so skinny and not big like the other posi. He explained that having pressure on the clutches all the time would wear them out prematurely. Every time you turn a corner, your wearing them. Finally when the clutches get to thin, the wedges or gears, ( He laughed ) move anyway, they start hitting on the edges. that's what breaks them or wears them out. 

   For the past 5 years when I rebuilt various posi carriers, I would decrease the pressure on the clutch pack. You could turn corners without hearing that noise. Also, both tires would lay down rubber equally. The clutches and the internals would wear a lot longer. 

   Then a few years ago, I had a dodge truck on the lift. I spun the wheel and the other wheel rotated the other direction. I thought, that's weird, why is there an open carrier in a 4X4. When I took the cover off, I was surprised and saw a posi with no springs, no concaved washer and no pressure on the clutch discs. 

What ZF did was they set the internals at zero clearance, yet rotated smoothly. Then when torque was applied, the Spiders and side gear push away from each other, and it locked up.

 

   I started laughing and thought, WOW, it took all these years to find out they were right in the 50's.

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