Dana 27 posi upgrade ring gear fit?

Hello guys,
I'm pretty new to opening up my axles, and I need some help.
I tried searching forums but came up empty.(my error?)
I have a Dana 27a front axle with an open diff, and I would like to swap in what I believe is a Power-Lock diff. I have both carriers removed, and they look to have the same dimensions except the offset of the ring gear mounting surface. Will this diff work? Do I need a different ring/pinion? a thinner ring gear or smaller pinion? I have 3.73 gears(41-11). It's almost a quarter inch difference.

Here is a picture to help with what I'm asking about.
https://www.dropbox.com/s/sazes38sb5lay8h/image.jpeg?dl=0

Any help would be greatly appreciated. I look forward to learning from you guys!

 

The Powerlok pictured is for use with 4.27, 4.88, 5.38 ratios.
Hence the diffferent offset of the cases.

 

Oh! That makes sense. Smaller pinion on the 4.27 would need the ring closer to center.
My mistake, I thought the diff split meant they had two different ring gear bolt hole diameters, but it is actually for the two different ring gear mounting surface offsets.

So to use that posi I need 4.27 gears, then I'd have to change rear gears to match, meaning I'll need a new rear carrier also. Not as easy as I thought, but I feel a lot smarter now.

In 3rd high I'm at 3500rpm going 80mph, 1st high is a big jump from rest. Low gears are great offroad.
I'm curious how much 4.27 gears would effect my top speed on the highway, I have to cruise the highway to get to the trails, and I don't want to be screaming to keep up with traffic.

Thanks jpflat2a !

 

It would be nice to know what year model and drive train your working on.................If you have a Dana 18 Transfer case behind the D-27 front axle.........a Warn Overdrive would be the logical solution to use the 4.27's or Lower gear ratio's..........4.88's w/ the Warn OD would just about get you back to where you are now for final drive ratio. Of course tire size is important as will as the engine that's driving all of this..........the nice part of the low gears is of course off road.

 

80mph in a jeep? If I were selling insurance, I wouldn't let you in the door. As a race promoter, I'd be buying you drinks (after the race)...

Put in the 4.27s, it'll keep you under 70

 

Nah, that's right about where mine runs at too. 3.73's, running 265/75R16's, which I think is *roughly* a 32" tall tire

 

3234 RPM at 80 mph with 3.73's & 31" tires.

 

I'd be interested in buying it if you decide to get something else.

 

You could always find someone that is into Studebakers and see if they have a limited slip for a model 27 Dana. Pretty common in their 6 cylinder rigs.

 

I have a 27a in the front and a 44 in the rear(2-piece axles). I only have 30" tires on it right now, and doubt I will go anything bigger than 31 or 32 in the future. T90 and Dana 18 drivetrain.

 

Highway speeds go up to 80mph in the straights, and I like to keep speed with the rest of traffic when I'm heading out to the trails. The jeep has plenty of power and handles great. No speed wobbles, and 9-leaf suspension front and rear.
My father raced jeeps when I was a little guy and I've always been more interested in sliding sideways than crawling over rocks. Unfortunately due to circumstances I was never able to get into offroad racing when I was younger, I only got to race my dads jeep a handful of times.
I love fixing/building/fabricating things, and I'd love to race offroad. I have to finish my Mechanical Engineering Degree before I start having disposable income to spend on real upgrades.
This jeep I've had to build back up from parts, and any mods I have done have been ones of necessity and safety, and I use the offroad racing rule book of our most local racing organization as a guide for any mods I make.
Racing around where I live isn't big like it used to be when I was a kid. You have to go down over the border to Oregon or Washington for the PNW4WDA races to see anything like the large events I got to see when I was kid.
Offroad my low gears are sufficient, just High gear 1 on the road is a bit of a jump from being stopped.

 

I was thinking of getting Aussie lockers (PowerTrax Lock-Right) for front and rear, but realize that even with 30" tires that might be a recipe for disaster. I also noticed a previous owner welded the spider gear pin into the case, so I'd need to buy a new case to use a lunchbox locker.
I need to decide if I can throw in some lockers into these diffs, or if I'm wasting my money and should just upgrade to a new front and rear axle assembly. I could use a few inches of added stance width front and rear, and front disks would be nice. Maybe a 30 in the front and a 44 with one-piece axles in the rear? On a student budget price rules all...