Awd18... Can You Build A Bias Powerlock?

Don't worry about the application... but can you build a powerlock to lock-up quicker on one side than the other with the shim cone stacks?

Let's say it's plowing a field with duals on just one side. I want the sidecwith duals having more bite than the single rear wheel...
In reality I don't have a plow, duals, powerlock or a running jeep so this is all conceptual.

 

2nd question... what are the dimensions for a powerlock carrier without the ring gear flange?
Diameter, thickness between halves at the center and a general thickness where the halves bolt together?

 

It doesn't seem like it. If you bind up one axle to the carrier through the clutches, you're also binding up the other one through the spider gears.

 

my thought is to manipulate the spring rates so the spiders favor traction on the dual wheel side. So when the single side has more traction than the duals it is in more of a neutral position, the clutch packs would be soft and or it hits a pressure limit.
Inversely when the dual wheel side has traction the springs ramps and all make everything bind up faster.





Now... put this in an AWD dana 18.
The "dual wheel" side is the rear output and the "single wheel" side is the weaker 3/4" front shaft.
The bolts that split the powerlock case are the fasteners holding it to the D18 output shaft so that spherical inner surface is not needed inside the D18 output shaft for the spiders, it would be a simple flange and bolts.

 

Fire up the lathe and mill.

Fireball's dad made an AWD Dana 18 in 1975. It's just 5 machined parts and a d25 spider gear kit. One shaft is just a bit too much work so I was exploring alternatives. The powerlock looks promising as a center differential.

http://www.earlycj5.com/xf_cj5/index.php?threads/140436/

 

This is the problem part...

 

But the shafts are not independent. They are geared together and attached to the case via the cross-pin. The average speed of the shafts MUST match the speed of the differential case. If one slows down, the other has to speed up. If one gets clutched to the case, the other is also effectively clutched to the case through the spider gears.

The ramps get actuated by the torque being applied to the axle shafts from the case. If one axle goes to zero traction and can't hold any torque, you will slide down the ramps and be left with whatever preload (static break away torque) is on the clutches. It doesn't matter which axle it is.

Are you trying to make a full time D18 like my dad did back in the 70s? A lockable Torsen setup would be the ideal thing and is what Subarus, Toyota, Porsche, ...etc. use in their full time transfercases. It's easier to gear in static torque split between the front and rear, and it also has the built in bias that allows the traction side to have more toque than the low traction side.

I've often thought the easy way to have full-time in a old Jeep is to use a Land Rover LT230 transfercase. It's got fulltime (but with no limited slip), up to a 3.2 low range, an assortment of high range gear sets available (they typically are not 1:1 in high range), and it has both front/rear passenger side outputs. The difficulty is adapting it to your transmission of choice. It looks like there used to be T18 kits back in the day but the seem to be NLA now. It's also got tapered rollers throughout and even has a PTO output on the back like a D18. It basically is an updated D18 with fulltime 4wd.

Here's a great article about the LT230: https://www.autoexpress.co.uk/land-rover/range-rover/100624/lt230-the-best-ever-transfer-box

 

For those who are interested and haven't seen it before, here's what my dad built while taking machine shop classes in community college back in the 70's. It uses D25 spiders in the differential:


It's been on the Jeep and working for around 48 years now:


He loves the concept of full-time 4wd and decided to make his own. He's a much smarter man than I.

 

Got it! Fill the ramps on the rear side of the case with weld so it is effectively an open diff (or very little travel) when torque on the front shaft is greater than the rear...effectively an open differential and the ramps/clutch pack on the front will still engage.

Done AWD rally or drag jeep that can lift a wheel or two.

 

If you look at the drawing, the old front axle engage/disengage lever now locks/ulocks the center diff. Of course, that won't work if you break that long 3/4" front output shaft between the spider gear and shift collar, but will work for driveshaft issues.

 

Yes the weak link is the base of splines at the 3/4" shaft. The 4wd collar allows power to go to the front if the internals or rear shaft fail. If the front shaft or universals fail (i'ld go v6 u-joint to hopefully save the 3/4" internal shaft) you can lock the 4wd and run on the rear. But wheel lift would be a problem if your rig is not short n flexy.

I'm taking measurements off the drawing and known part dimensions. This will be a long project but I figure I will eventually 3d print everything then when the kids are older I can fire up the lathe. It's also gonna have a 2 speed pto for a powered trailer. Possibly a doubler.

 

I think your question regarding if the PowrLok can be biased has been answered. It still drives through spider gears, so the power will be distributed to either side, not one or the other. If your trying to do this “limited slip” transfer case as an exercise to see if it can be done, have at it.
From a practical standpoint, Fireball’s suggestion regarding the Land Rover (post #8) transfer case would be a good place to start. The Rovers AWD transfer case works very well, and there are several automatic and manual transmissions that mate to it. Rover does things differently by almost exclusively using a 3.54 axle ratio, and varying the effective ratio with different gearsets in the transfer case. I have a Rover LT95 heavy duty 4 speed with one of these transfer cases on the back.
Also look closely at Jeeps own version with the Borg Warner 1339 (original) QuadraTrac. The 1339 was used in the early/mid ‘70s in the CJ7, Wagoneer, and trucks. This also has a limited slip diff inside the transfer case between the front and rear driveshaft outputs, and can be manually locked solid via a shift lever. The 1339 has a low range planetary with a very useful 2.57 ratio.
It sounds like you are trying to re-invent the wheel when there are similar systems already out there.
Both the Rover and 1339 have output shafts offset to the right, about the same distance as the D18.
-Donny

 

This is a D18 project, because I already started the cad work years ago on the gears.

Yes The powerlock question is answered. It will only have ramps on one half of the case. No ramp = no pressure on the opposite clutch pack aside from preload.

The 6x6 D18/20 is from another historic jeep.

I'll figure them out like jigsaw puzzles and I want to 3d print em. Eventually I'll try to build it but not in the next few years.

 

If you ever make some print outs of the CAD drawings, send some my way. My dad would get a kick out of his stuff being computer drawn up.

 

Nope...

What I do need are some rough sketches of the housings, the front output and rear output. Scanned gaskets for hole patterns etc.