Matching front and rear diffs. (shift on the fly front)

[afree4all]

So I have gone back to the 4.2 exhaust and remounted the drivers side diff. hanger.  I remember bloing up a transfer case but not sure If it was before or after I swapped the fronts diff to a shift on the fly version.
I figure I didn't pay attention to the ratios and the transfer case was the weakest link. and boom goes the dynamite!!!
So before I install the front driveshaft I need to be sure they match.
So unsure of open or LSD. I jacked up front wheels and pass. side turns and the driver twitched in the same dirrection, but seemed to jamb.  (I tried to turn the driver by hand and it does have a tight spot, Looks like the half shaft is to blame) 
If they both turn same way is this a LSD or locked diff.  Is this how a shift on fly diff should be?
I turned the the pass side with the driver on ground.  I watched the input shaft turn twice and wheel about 1.75 times.  I came up with this.
1/1.75= 0.5714  x 4= 2.2856.     
2.2856  is very close to 2.35 so I assume they are 2.35,  correct?
I will do same on rear, but the concern now is the other day I tried to move it in 2wd. it was frozen in LOL.  only the pass rear spun so that would indicate it was a open diff, No?   
Can I run open rear,  and a lsd or locked front?  If that is what I have...
I almost bet my rear ratio is same,    I am going out to check now.

[afree4all]

Why would the front wheels turn in same direstion if it was a "open" diff?
I checked the rear and with trans in neutral & both wheels in air it acted as expected.   turn drivers side forward and the pass rolls backwards.   
as for the ratio I am little confused to what the rear is.  i get about 1 5/8 (or 1.625)tire rotation to the 2 turns of driveshaft.
so 1/1.625 = 0.6153  x4=  2.4614
2.46?      Was there a 2.5x gear ratio available?

I had tried the 1 turn of the wheel thing before. but never got the same results twice.  was told that the number doing it that way should be (x2).  on a open diff.
Is that 1/8 of a turn less on rear going to blow up this transfer case again?  Could the fact the drive shaft isn't installed in the front, allowed it to spin just that much more than the rear?
Can a bad half shaft cause transfer case problems?  Not to mention I drove it without the support hanger on the driver side.  So probaly was shifting abit.

[mudkicker715]

I would never trus the method of axle ratio check you did. just pop the cover and physically count and do the math

[afree4all]

car is for sale didn't want to do this much already.  not willing to pull covers on front, or sink another dime into fluids. LOL
Only thing I ACTUALLY need to make sure is that both turn the same amount.  Right?  don't matter if I turn 1 or 50 times as long as I do the same to front and rear.  and get the same results?   I peronally don't care what ratio is in there as long as I can put front shaft in safely.
Hard to trust that math.  But consider that if we know they make a 2.35 ratio.  Using my method 1 divide by 1.700=0.5882    muliply by 4= 2.3528.
I figured mine at 1.725 and came up with 2.2856.  You are right .025 is very easy to miss if doing this way but its so close I Belive the front estimate. 
The only for sure way is to count teeth But someone else can do that, later.

[txjeeptx]

You ruin an Eagle's transfer case by driving it with the front driveshaft removed - it toasts the viscous coupler. Never never never drive an Eagle without both driveshafts in place.

[afree4all]

I never put in 4wd without the shafts installed.   Was told by 2 shops that it is fine to do so In 2WD. the front shaft will just go along for the ride anyway. Connected or not?
Didn't get many miles on it that way anyway.  But thinking of fixing the exhaust up proper and finessing it around the driveshaft again. 
Just want it gone, Don't want to work on it anymore or I will never let it go!!!

[BenM]

There should be a metal tag on the front axle, probably hiding behind the cross member and some grease. There is a stamp on the machined part of the housing where the cover fits on the passenger side. One or two letters.

Depending on wear, it's entirely possible for the differential to spin both front wheels instead of the pinion. I've seen it.

Eagles came with 2.35 and 2.72 axles, what year is yours? Certain combinations were only available some years and that may help us.

Never factory limited slip, although the front is a long-pinion Dana 30 and the back a common AMC 15, both of which have lockers available. All that said, the rear axle was available in some years in other cars with a 2.53 axle...

The 2.35 front will say "20-47" on the tag, the 2.72 will say "18-49".
The 2.35 rear will have an "L" stamped on the axle, the 2.53 will be "K", and the 2.73 "H" or "J".

Yes the front is 18:49 or 2.72 and the rear is 15:41 2.73, or 0.41% different.
Similarly, the front 2.35 axle is 20:47 and the rear is 17:40, or 0.12% different.

I have it all in a spreadsheet.

[afree4all]

Thanks Ben.  I didn't really want to know that the rear may be able to have a 2.53.  LOL  But the original rear end is a 84 DL limited wagon 4.2L  With air and allmost all acc.  The front axel is from a 86' I think.  It has no shift motor (for shift on fly)
I know there is no marking on that axle.  It went in spotless and of course no tags on either.  Only a casting number on the bottom. LOL I tried to run VIN to see what was in original and no dice.
I thought I remember a guy telling me that the fulltime front axle (shift on fly) will act like a locked diff?  Both wheels turning same direction.?   If you apply vaccum to a shift motor on early models will both wheels turn same way?
I will have to install the front shaft and recheck my rotations front and rear I guess.

Like I said it almost seems that the rear wheel is "lazy" by a 1/8 of a rotation compared to the front.  (with 2 turns of driveshaft.)   It doesn't seem like much. since as you guys say, a front can be a tooth or so out. 

[mudkicker715]

Never any sort of posi came original

[carnuck]

I have 3.08s from an '80 for mine (actually the front is non-vacuum 3.08 I'm putting in my '81 and the rear will be Chrysler 8.25 from an XJ)

[carnuck]

I would do an AX-15 before I'd do a T5. Much stronger. I saw a couple last year at the Puyallup swapmeet for like $75 each (T5s) I'll check the front diff ratio from the '80 wagon I parted (dug it out last night) I'm pretty sure it's not the original because I put the matching rear in my Spirit and when my speedo read 80, people were passing me like I was still standing still.