8 Pinion Limited Slip test with Spring results

[pfrederi 17,128]

A couple months ago my C-141 8speed locked up.  Swapped it out and put the bad one on the shelf.  With all this talk about making 8 pinions Ltd Slip I decided we needed a little more action so I opened her up fix it and run a test.  8 teeth had broken off 3 gears.  Found all the teeth and lucked out to find replacement gears in my tranny spare parts.   Put one of Lowell's springs in the 8 pinion and put her back together. I did notice it was a lot easier to get his spring in the 8 pinion than when I put springs in 10 pinion units.  Hooked up my tranny tester and filmed the results. 

[stevasaurus 22,229]

I could not get the sound to work Paul.  It looks like it wants to work on one side.  Is that what you see?? 

[AMC RULES 36,941]

Momentarily works, until the differential action kicks in causing the opposing hub to turn in the opposite direction. 

Paul ended by saying...this doesn't work. 

[pfrederi 17,128]

It was in second gear.  Both turned ahead as expected until i held one hub.  When I stopped one hub it the other kept spinning.  You could feel a jerking in the hub I was holding.

 

With out the motor running and in neutral the hubs would turn in the same direction but then they would start going opposite again with a jerking sensation

 

 

Bottom line it doesn't work!!!!

 

 

Edit:  Tried some more things turns out in neutral motor off if you turn one hub slowly the other goes the same way ...but if you try to turn the hub faster it starts the jerking and the other hub goes the opposite direction.

Edited December 30, 2018 by pfrederi

[953 nut 51,511]

The spring you were using was a new spring from Lowell, right? Correct me if I am wrong, but aren't the axle gears in the four pinion, eight pinion and ten pinion units all the same outside diameter?  Kind of odd that it wouldn't go in the eight pinion as tightly as the ten.

[pfrederi 17,128]

Yes it was a brand new spring.  The extra pinions on a 10 make for a tighter circle for the spring to fit into.

[stevasaurus 22,229]

I think the outside of the axle gears in the 8 and 10 are the same...not sure about the 4 pinion axle gear.  They have different part numbers, but then they would.  the 4 pinions are 1" axles. 

[pfrederi 17,128]

The axle gears for 10 pinions are different than the 8 speed.  The have a different gear tooth design and are slightly small outside diameter (front gear in Picture is 10 pinion)

 

Also I tried putting a used 10 pinion spring in an 8 pinion it went in easily just like Lowell's.  i also tried one of Shawn's and it went in easily as well.  As I said getting the spring in a 10 pinion is much harder.,

 

 

[stevasaurus 22,229]

You know Paul, it looks like if you put both of those axle gears on the end of one axle, they would fit the axle and the difference would be the length of the teeth.  The bottom of the teeth in both gears might line up.    I think the jerking that you were getting is that part of the spring that is open hitting one of the pinions.  It might be catching a little as it goes by. 

[pfrederi 17,128]

The 8 speed is bigger.

 

10 pinion OD 2.156   Valley to valley 1.864

 

8 Speed OD  2.248     Valley to valley  1.890

 

 

Looking at my [picture above I think the jerkiness may be a result of the sort of flattened ends of the spring.  Leaves a big space away from the pinion teeth as it passes..not snagging slipping....

Edited December 30, 2018 by pfrederi

[stevasaurus 22,229]

Thanks Paul for doing this...I could not sleep either. 

[Cetan08 311]

So we have concluded that you cannot make an LS out of an 8 pinion with the spring from a 10 pinion if I am reading this correctly.

It is my idea then to redesign the spring so that we can achieve our goal of making the 8 pinion an LS.

I agree with the gap in the spring causing the jerking and the ease of installation indicating the need for a larger and stronger spring for the 8.

[pfrederi 17,128]

10 minutes ago, Cetan08 said:

So we have concluded that you cannot make an LS out of an 8 pinion with the spring from a 10 pinion if I am reading this correctly.

It is my idea then to redesign the spring so that we can achieve our goal of making the 8 pinion an LS.

I agree with the gap in the spring causing the jerking and the ease of installation indicating the need for a larger and stronger spring for the 8.

 

That is what I believe now.  

Wish you good luck with the fabricating a new spring.

 

I will stick with the 10 pinions...they work for me. Haven't broken any and now with replacement springs available they will probably outlast me.

Edited December 31, 2018 by pfrederi

[wallfish 15,907]

1 hour ago, pfrederi said:

That is what I believe now.  

Wish you good luck with the fabricating a new spring.

After your hands on testing and actually working with those parts, do you believe a properly sized spring with more tension applied to the pinions could possibly work?

 

 

Like most other members I have no need (at the moment) for a limited slip differential and my horses work perfectly fine the way they are now. My interest is more for the challenge of finding a simple way to make it work, if possible. That being said, hope people don't mind just throwing $&!# against the wall to see what sticks.

 

Like using thin thrust washers on the shoulders of the pinions? or in conjunction with a spring?

Recently had to work on a clutch slip system in the gearbox of a concrete core drill. The clutch action is accomplished by a thrust washer pinched between 2 gears. The clutched gear just spins on the shaft and only turns the other gears through the tension created by the pinched thrust washer. Once it reaches the friction limit, the gears slip. Tension and friction between those 2 gears can be adjusted by turning the nut that holds them together. Could this same principle be used on the shoulder edges of the pinions?  Certainly some trial and error involved to find the "sweet spot" like thickness of washers,1 washer each pinion, 2 per pinion, only on 1/2 the pinions, tightening of the nuts, ect. ect. ect.

 

 

[Cetan08 311]

I can see where wheelhorse would not develop an LS 8 pinion. First it would take away from the specialty of the 10 pinion LS. Secondly it would require time and costs in development along with working against the one thing they worked hard to achieve, standardization.

It would be nice for us to come up with something simply because so many would like to have it along with the fact that there are limited numbers of 10 pinion LS's available.

Clearly the open diff. works as proven by history but it sure is sweet having that little extra when its needed.

[953 nut 51,511]

            I think the primary factor may have been the change of ownership of the company. In 1974 the Ponds sold  to AMC and that may have been the turning point.

[stevasaurus 22,229]

@Cetan08  I suggest you give it a go when you get the new spring also.  A 2nd opinion never hurts and it just might give you some ideas if you are still going to try to tackle this. 

[Cetan08 311]

Definitely going to look into it. I love a challenge like this. I have the time and the determination.

[R. L. Addison 299]

The gap in the spring is a disaster in its self. That will wipe out pinions & sun gears (on ends of axles).

[Cetan08 311]

13 hours ago, R. L. Addison said:

The gap in the spring is a disaster in its self. That will wipe out pinions & sun gears (on ends of axles).

I agree. That gap may be close on the 10 pinion but any gap is prone to catching on teeth and chipping. I will try one without a gap and a different shape.

[Skipper 1,788]

The spring is Originally bend a bit inwards in the gap, so it is supposed not to catch. Just info

 

And you will want a small gap to allow the spring to flex a little bit, but clearly as little as possible.

 

I may be getting a rear end with a 10 pinion soon. If so, I will take it apart and start experimenting on adapting to 8 pinion too

Edited January 2, 2019 by Skipper

[R. L. Addison 299]

It will need to be longer, & chamfering corners would help I think. 

[ebinmaine 62,959]

Following along in the interest of cool science...

 

Thank you to those who are taking the time to do these tests and Also the ones putting the thought processes through.

 

It's fascinating to see and we really could put an LS diff to work here on a regular basis. 

I only have one 10 pinion transmission but several 8s and 4s so a positive final result would be a huge help to us.