Build Thread Wooly's 78 CJ7

[Hedgehog]

When figuring RPM or other things, make sure to actually measure your tire from the center to the ground = x radius, diameter = 2x. There can, actually will be a surprising difference between advertised and actual tire diameter. I have cooper 31's, but they measure 28" and change.

 

[Posi]

Giving your driving habits, and options offered I would suggest option 2, "if" the used axle set is in good shape and ready to run, $AMC 150 is a decent price. Any parts you will need including rear locker can be paid for on the sale of the 20 shafts and locker. Additionally you will improve your gearing from 3.54 to 3.73
I have your current crawl ratio at 45.1 adding the 3.73 it would bump up to 48.1.

If there is an issue with the used axles then I would suggest option 1 and do the work yourself. I would do just the bearings and locker and wait until a set of wagon/Cherokee 44s fall into your lap.

Personally I wouldn't invest my time or money into a rear 20 unless I was doing a stock restoration with no upgrades.

 

[Woolyworm]

Thanks guys. Time to let the soup simmer.....hmmm. Option 3, new bearings for the 20, throw in the locker and call it good.


Wooly

 

[caveman]

Another option just to mess with your mind. I have a stack of AMC 20s out back and you can have one if you want it. Just measure your wms to make sure we've got a match.

 

[Petescj]

Thanks guys. Time to let the soup simmer.....hmmm. Option 3, new bearings for the 20, throw in the locker and call it good.


Wooly

How about doing this and buying the 30 and 44 for $AMC 150 . Then build them as time and money allow? If you change your mind or life interrupts you can more than double your money putting them on Craigslist.

 

[Woolyworm]

That's an idea. There is also an 89 wagoneer on craigslist here in Maine for $600 with a working 360 and front and rear 44's


Wooly

 

[Woolyworm]

I think for now I'm just going to add shims to both sides to tighten it up and run it. Thanks for all the help everyone. I might take you up on one of those housings Caveman!


Wooly

 

[Petescj]

That's an idea. There is also an 89 wagoneer on craigslist here in Maine for $600 with a working 360 and front and rear 44's


Wooly

You talked me into it. I'll take the 360. All this talk about 360s is making me wish I wouldn't have grabbed another AMC 258 i6 / 4.2l .

 

[Woolyworm]

Easy there! I didn't say I wasn't going to buy that as well! LOL


Wooly

 

[Posi]

I think for now I'm just going to add shims to both sides to tighten it up and run it. Thanks for all the help everyone. I might take you up on one of those housings Caveman!


Wooly

You mean remove shims from one side and add shims to the other.

The 89 wagon front 44 won't work it's a driver side drop.

 

[Woolyworm]

My plan is to add the same number and thickness of shims to both sides to increase preload.

I plan on flipping the jeep to make the axles work


Wooly

 

[Petescj]

Just trying to help you move this along. Seriously though I saw a pic where you were entertaining the idea of 35s. If you think there's a chance you'll go up from 33s the 4.10s are a no brainier.

 

[Woolyworm]

Thanks Pete. I will probably go down to 4.10s at some point but with my new rank and skid and the locker my checkbook is sweating already so maybe next winters project


Wooly

 

[Woolyworm]

Okay, so after all the discussion and help - thanks everyone - I decided to put the locker in and button everything back up. I will be purchasing a master rebuild kit and 4.10s for the 30 and 20 over the summer and having a local mechanic install them. I just couldn't see friggin around with shims and backlash and all that without changing out those gears and bearings.

The locker install went very well, it's a powertrax no slip. I put a new spring kit in it and performed all the checks - everything went well. I also prepped to install the tank and skid tomorrow hopefully.

Cheers


Wooly

 

[Hedgehog]

A locker will add a huge amount of extra stress to an already compromised system .....

 

[Woolyworm]

That all depends on how you drive it. If Im going over stuff that is beyond what I should be without the locker and working the heck out of everything to do it - having the locker to allow me to fitness it will be easier on everything. Again - I needed to put it all back together to get it to the shop anyway.

I'd also argue that the R&P always gets to see 50-100% of the engine power. What gets stressed more it the carrier and the axle shaft since the locker allows 100% to one axle is some instances.


Wooly

 

[Hedgehog]

I'm no longer trying to convince you to do this one way or the other. However this opens up an interesting line of thought. I wonder, we see the stress on our equipment while 4 wheeling, but I wonder about everyday street use. A hard unyielding surface at speed, turning, slipping on sand bumping over pot holes and speed bumps, two axles constantly looking for 100% traction. When 4 wheeling the rear end is dealing with soft yielding surfaces with tires slipping and moving over uneven ground. If it were possible I would be interested in knowing which surface brings more stress to a differential.

 

[Kane]

Hedgehog consider this. The compound low gearing multiplies torque so much higher that the rear and front differential will see much higher twisting force and especially shock load if you drive a stick when hitting bumps and ruts.

 

[Woolyworm]

Agreed. My thinking is this;

2 wheel drive - the R&P gets the burden of all power to the DS at all times. That power is transferred then to the spider gears via the pinion shaft in the carrier. Assuming traction at the tires is equal, the power is split 50/50 from the spider gears out to the tires. When one tire looses traction, the spiders let that tire get all of the power and since it's got no traction, there is little if any torque put on anything.

When you install a spool or a lock right type locker, the same remains true except for the fact that you take all the power from the pinion shaft and transmit it to one tire therefore everything from the pinion shaft out to the tire can now receive 100% of that torque and it that tire happens to be getting good traction you are putting in essence up to 2 x the stress it would normally see - on road or off.

I don't think a locker puts much if any additional stress on the R&P.

I would also argue that the front or rear diff on the opposite end of the side loosing traction will appreciate the help since the same holds true when you start looking at it as the Transfer Case being the splitting point of the power from engine to tire.

My 2c for what it's worth.

I did just get the tank up. Went pretty well. I had to drill new holes for the front since it didn't quite line up with the existing CRISS member holes. I also had to grind out a bit of the rear crossmember to allow the tank strap to fit. And yes, you can jack the vehicle up with that skid plate.

Wooly

 

[Lumpy Grits]

IMO-A true 'locker' evens out the driveline R&P load torque and reduces shock loading to very little. An LSD does about the same to a lesser degree. The 'open' type diff beats a drive line to death when off-road.
Remember-The the lower the R&P ratio(4:10 and 'deeper')takes ALLOT of torque load off the tranny and t'case.
YMMV
LG