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Power-Lok limited slip in Dana 25
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smfulle View Drop Down
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Points: 6140 		Post Options Post Options   Thanks (1) Thanks(1)   Quote smfulle Quote  Post ReplyReply Direct Link To This Post Posted: 06 July 2022 at 2:36pm
This thread had evolved some from how do I install my Power Lock to opinions on Power Locks. So here's mine. It's the same as I have stated in other threads.
I have never run a power lok so my opinion is from observation only.
From what I have seen, they lock when you don't want them to (steering), and don't lock when you want them to (climbing stuff).
Some responses ive gotten to this opinion are "I've never broken an axle with a PL". My response is, did you get up the obstacle? Another response is "they work great if you set them up right." Ok fair enough, how often do they need attention to be set up right? Every time you go out? Once a year? 
For me, the upside is not good enough for the downside.
Again, my experience is limited and as always, your milage may vary.
Stan
48 CJ2A (Grampa's Jeep)
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oldtime View Drop Down
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Whenever a “pinion” is turning that force is next transmitted to the “ring gear”. The ring gear slows rotational speed and thereby amplifies torque.
The ring gear being attached direct to a “differential case” allows the differential case to have this same available torque.
As the differential unit spins foreward within the “carrier” (aka pumpkin), the “pinion mate cross shafts” and the “pinion mate gears” (spider gears) spin likewise.
The pinion mate gears are engaged at a right angle to the “side gears”. And the side gears are splined direct to the “axle shaft” which must thereby rotate. One or both axle shafts will rotate.
All Jeep differentials basically function in that manor.

The Powr Lok functions exactly same as an open differential when it is not under any stress.
Stress occurs whenever one axle begins slipping or spinning faster than the other. 
Only then will the Powr Lok engage. 
The engagement occurs when the stress forces the cross shaft up into its ramp.
This puts pressure into the clutch pack and this engagement is fully automatic.

If the clutch pack is assembled as “standard” for the axle then it slips very much like an open differential and this seldom if ever increases any steering effort.

Upon engagement the Powr Lok can only provide to the wheels the torque rating that is built into the clutch pack.
After the wheel with greatest traction reaches that amount of torque; the Powr Lok again slips. 
So in effect your have limited traction or limited grip.

If the clutch pack were to be built overly tight then it can essentially become a Lincoln Locker and will not slip. Building a tight clutch pack with increased torque capacity will certainly increase the steering effort. 

With an auto locker you have the same scenario excepting that they do engage sooner and do so much more harshly. After they engage they have no torque limit. The amount of transmitted torque is unlimited until you break an axle shaft.
Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963)
Zero aftermarket parts

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smfulle View Drop Down
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Points: 6140 		Post Options Post Options   Thanks (0) Thanks(0)   Quote smfulle Quote  Post ReplyReply Direct Link To This Post Posted: 06 July 2022 at 7:12pm
Originally posted by oldtime oldtime wrote:



With an auto locker you have the same scenario excepting that they do engage sooner and do so much more harshly. After they engage they have no torque limit. The amount of transmitted torque is unlimited until you break an axle shaft.

OR you make it up the obstacle.
Stan
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Steelyard Blues View Drop Down
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Interesting information. 

How would you tell is the clutch packs were correctly set up for a torque rating that would work on a stock 2A?

Besides Herm, does anyone else sell the conversion kits?

Micah

Oh, and no, I am not attempting to follow Stan. I think I have seen a couple of his videos where the wheels are pointing up Cool


Edited by Steelyard Blues - 06 July 2022 at 7:40pm
1947 CJ2A 106327, Engine J109205, Tub 97077. Luzon Red

https://www.thecj2apage.com/forums/steelyard-blues_topic41024_post397981.html?KW=micah+movie#397981

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Stan, Ha Ha Ha, you win ! Your killin me.
I shouldda knowed better than to get into a knock down drag out crawl with a man who is always locked and loaded! 
Remember wheels down, roll cage up. 

Yeah Micah you just need reference to show you how plates are set up for the D27 differential.
All Dana axle models use different disk configurations.



Edited by oldtime - 06 July 2022 at 9:04pm
Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963)
Zero aftermarket parts

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flatfender47 View Drop Down
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Originally posted by smfulle smfulle wrote:

Originally posted by oldtime oldtime wrote:



With an auto locker you have the same scenario excepting that they do engage sooner and do so much more harshly. After they engage they have no torque limit. The amount of transmitted torque is unlimited until you break an axle shaft.

OR you make it up the obstacle.

..or not...
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Since my wingman jumped in, I’ll dip a toe. Need campfire topics anyway. Stan and I have had this discussion before.

I understand how the lock right works and I understand how the Powerlock works, but I have never used either. I have observed them all in action. My focus is on making the obstacle, … period. Hope I don’t break anything but if it happens, it happens. Not necessarily the best strategy but I want you to understand my perspective. I have read many comments on this forum and other about how good powerlocks are if they are “set up right”. The thing is, it seems like every single time we go out to wheel with these guys, the powerlock fails. By fail, I mean acts like an open differential when you need a locker. By fail, I mean, everyone with lockers makes it but the powerlock does not because only one wheel is spinning. I hope you believe me when I tell you I’m not just embellishing here. I have lots of video evidence that I choose not to post because some of it is of mutual friends from this and other forums. I want to be respectful and I want to learn so in the spirit of respect, is there any PL users here who feel that there diffs are setup properly and would be willing to publicly demonstrate their effectiveness on real obstacles? Maybe we can meet up in Utah or Colorado? I’d like to be open minded about this but I’ve just seen too many failures.

If the objective is to not break as many axles at the expense of failing on the obstacle then I’m on the wrong page, I fully understand , and I withdraw the question.

Thanks and I appreciate the forthcoming constructive feedback.

Edited by jpet - 06 July 2022 at 9:31pm
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One thing I have seen on the trail with the Powr Lok is you can modulate or load up the clutch discs with a little use of the brakes. Also with both axles locked all of the torque can be in one axle shaft and that kind of puts you out of the stock axle strength.
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Under that brake tapping scenario; what ones doing is inducing stress into the Powr Lok diff. 
Specifically the differential continues to spin forward but the axle shafts have stopped and so that causes the pinion mate shafts to “ramp up”.
It is this ramp up of the pinion mate shafts that puts pressure into the clutch pack and thereby forces all tires to grip.
And so the tires continue to grip until they reach the max capacity of the clutch pack. 
A loose or worn out Powr Lok clutch pack is exactly the same as an open differential in its function.

The Powr Lok itself is extremely well built differential and will withstand lots of abuse. It is much stronger than an open differential. When the Powr Lok was developed, Spicer simultaneously upgraded from 10 spline milled axle shafts to the 19 involute splines. The extra axle shaft strength was required and so 19 involute became the new axle shaft standard in late 1956.
A standard set up Powr Lok will never outperform any sort of locker concerning available traction. It will however outperform most units concerning ease of operation, road manners and durability. I do not recommend them for dedicated rock crawlers.
I recommend them for anyone who needs a highly versatile and durable jeep.
A Jeep that sees lots of on road use.
The only other traction device that truly works well on road is a selectable locker.


Edited by oldtime - 06 July 2022 at 10:56pm
Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963)
Zero aftermarket parts

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ClapClap
Well said Ken.
Thank you.
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I can agree with that
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I'll jump in as someone who installed a Power-Lok in their Dana 25. It was the most disappointing modification I made to my axle. As others have mentioned, it never seemed to work when I needed it. 

After playing in the mud and water a few dozen times which destroyed the axle bearings, I couldn't even give the axle away. Just tossed it in the scrap bin (housing wasn't the greatest anyways).
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How old is that picture?

Is it too late to pull out the special spacer so I can use it to install mine?
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What a shame and waste.
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Well, I think I'm going to give it a shot. I'm going to get the parts while I still can and put them up in the attic until I decide to do a full tear down. If something comes up before I install it that changes my mind, I can always sell it. If I later on don't like it, I can go back to stock. I like the idea of having something that can pull me out of a spot. I'm not looking to doing any crawling. I hope that it does not have any effect with normal 2wd steering.

Does anyone besides Herm sell the conversion kits?

Thanks for all the information.

Micah
1947 CJ2A 106327, Engine J109205, Tub 97077. Luzon Red

https://www.thecj2apage.com/forums/steelyard-blues_topic41024_post397981.html?KW=micah+movie#397981

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Points: 630 		Post Options Post Options   Thanks (0) Thanks(0)   Quote BD1 Quote  Post ReplyReply Direct Link To This Post Posted: 08 July 2022 at 8:22am
Oldtime, could you post a list of the correct Power-Lok numbers and ring gear bolt counts for the Dana 25, 27, 30 and 44 axles?  Looking at what is offered on eBay I see various numbers listed as being for the Dana 27, with the majority being number 22480. Searching on this site I've found the Dana 27 Power-Lok being #22477.  You seen to have the most experience with these, so I'd be more confident in your info than some seller on eBay.
BD
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BD,
The ones you are seeing on eBay are from the previous owner of QTM. Not all of the stock was sold with the business and he appears to be selling the remainder off on eBay.

I called QTM. They had one left on the shelf. Really nice condition. I grabbed it. 



I previously overlooked the post by Steve in April 2019. The note regarding the plate order for the installation of the Power-Lock in the front is interesting. Maybe it is the key to eliminating any steering issue. 

Micah
1947 CJ2A 106327, Engine J109205, Tub 97077. Luzon Red

https://www.thecj2apage.com/forums/steelyard-blues_topic41024_post397981.html?KW=micah+movie#397981

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Originally posted by flatfender47 flatfender47 wrote:

What a shame and waste.

Not really. The mud/water destroyed the unit. Other parts in the bin were custom from my M151 conversion that I reverted back to an original L134.

Originally posted by Joe Friday Joe Friday wrote:

How old is that picture?

Is it too late to pull out the special spacer so I can use it to install mine?

Yeah, June 2021. QTM had so many of them they were practically giving them away.
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