Jump to content

AMC Eagle Differential Help


Recommended Posts

I have purchased an 1983 AMC EAgle SX4 with 2.38 gearing and Select drive.  I would like to switch to sonme 1980 axles with 3.07 gearing.  But that was a full time 4wd model.  I think the rear will directly swap.  but what about the front?  Isn't there a vacuum actualtor on that axle?  If so can I just switch the internal? Carrier?  Posted here because the Eagle is closely related to the Xj.  Any help appreciated.

Link to comment
Share on other sites

  • Administrators

Yes, Safariwagon, 1980 is full-time 4x4 while 1981 Eagles were available with either part-time or full-time 4x4.  The full-time unit for 1980-82 is a New Process 119 single speed transfer case.  (1982 full-time 4x4 with the 119 transfer case is very rare.) 

The part-time 1981-85 units are an NP129 design.  For lower gearing (numerically higher), a 3.08 and even a 3.31 axle ratio was available in 1980.   For 1982-84 four-cylinder Eagle 4x4s, a 3.54 ratio was available.  Through 1985, the part-time model 129 single speed transfer case was available.

1981-84 part-time front axles have similar axle shafts.  1980-82 full time 4x4s share the same axle shafts—so there is a difference between these full-time and part-time front axles and their axle shafts.  For your 1983 model, I would look for 1982-84 Eagle front and rear axles from a part-time 4x4 Eagle with the NP129 transfer case.  You can get either 3.07 (front and rear) or 3.54 (front and rear) ratios.  (Ratios must match front to rear.)  The 3.54 axles would be from a 4-cylinder model.  These 1982-84 models, like your 1983, should be part-time 4x4 with the exception of the rare 1982 full-time 4x4 model.

On your 1983 model, an axle shaft disconnect mechanism should be outboard of the differential and carrier on the right side axle housing tube.  Do you currently have a vacuum shift mechanism on your 1983 AMC Eagle front axle's right/passenger side axle tube?  Post some photos of your front axle and the disconnect plus the transfer case I.D. tag.  We can identify what you have on the car. 

Moses

Link to comment
Share on other sites

Thanks for all the information Moses.  I was unsure on the years.  My 1983 does have the disconnect mechanism you talk about on it.  Can you take the carrier and gear set out of a full-time 4wd model from 1980-82 and install it in my 1983 axle?  It seems to me once you get to 1983 everthing has 2.38 gear just about. Maybe 2.72 on occasion. so finding a suitable 1983 axle or axles (i know they have to match) will be very difficult.

Link to comment
Share on other sites

  • Administrators

Safariwagon...You're looking for the 4-cylinder applications, and they're probably rarer.  Since you simply want a gearing change, consider new ring-and-pinion gearsets that would fit your existing axle housings and mount to the OEM carriers.  Try some of the gear specialty sources like Randy's, Yukon or Revolution gear.  Typically for Dana 30 axles, there's a differential carrier change at a given ratio (like 3.73-up).  If you have a typical Dana 30 front axle and common AMC rear axle, sticking with gearing to 3.54/3.55 ratio or so, there might be a ready parts source.

If these gear sources draw a blank, research Dana/Spicer OEM replacement parts.  Dana offers ring-and-pinion replacement kits complete with bearings, gears, shims and other parts involved with a ring-and-pinion gear set changeout.  Dana catalogs may offer more insight into what will fit your existing axle housings and work with the OEM carriers.  This might be cost effective in the long run with the assurance that you have new gears and bearings.  You will need to set up the axles properly.  I cover Dana 30 and AMC 20 axle builds in my Jeep CJ Rebuilder's Manual (1972-86) or you can find model specific information in a used factory workshop manual for your Eagle.  For a Dana 30 high pinion axle build, see my article at the magazine:  Dana 30 high pinion axle build.  This would be XJ Cherokee or YJ Wrangler.

Let us know how this works out.  Others will find the information useful.  If you do the gear change, you'll need to change the TC speedometer driven gear to compensate.

Moses 

Link to comment
Share on other sites

Well I did pick up the 3.54 axles, but they are early 1981 and the full-time version.  Got me thinking about swapping to a Jeep AW4 tranny and a dana 300 transfer case with a flip kit.  would tha tbe possible?  Would it give me manual operation of the 2wd to 4wd mode and have overdrive to help with the gearing.  I know it is a electronically controlled transmission, but I believe I have found others that have made it work properly.  One thing I am wondering about though is the 1980-86 Cj had lock out hubs i believe.  My eagle does not.  Is that a problem?

Link to comment
Share on other sites

  • Administrators

Safariwagon...The Dana 300 would need to be clocked for the AW4, splines need to match, too.  This is done but would involve Advance Adapters pieces to complete the changeover.  Then there would be the driveline lengths, mounts/crossmember for the Dana 300 TC, etc.  This would provide the overdrive and manual shifting of the 2WD to 4WD.  

Have you compared the 3.54 gear set parts to your current part-time type axle pieces?  Is everything the same within the center sections of these axles:  carrier, ring and pinion, differential side gear splines of the 3.54 gears versus your current gears, and so forth?   If the 3.54 ring-and-pinions can be installed in your existing axle housings, that would be much easier than the conversion to an AW4 with a Dana 300 transfer case.  You may have other motives for using the AW4, perhaps the overdrive justifies the swap?  The 3.54 gears would work with the AW4 overdrive, the current 2.38s would be too tall.

The difference with the 1981 full-time 4x4 front axle is that your 1983 part-time right side axle tube has the disconnect mechanism, which means you have a two-piece axle shaft at the right side as well.  You should be re-using those front axle disconnect parts with the 3.54 ring-and-pinion gear change.  Your only concern is whether the ring-and-pinion and differential pieces are the same between a part-time and full-time axle.  Compare these parts.

Regarding lock-out hubs, you could run a Dana 300 in 2WD mode without the need for lock-out front hubs.  You'd have the normal wear-and-tear of your Eagle's half-shafts and CV joints.  The transfer case would be unaffected. 

Moses

Link to comment
Share on other sites

  • 1 month later...

So I am swapping in a NP219 out of a 1980 Wagoneer.   Seemed to be a good fit since my axles don't have the vacuum locking mechanism.  This transfer case does not use vacuum either.  4Hi, 4lock, Neutral and 4low.  Does anybody know what order these gears are in and which gear I should be using on pavement?  Feel stupid for asking but that's better than ruining stuff.

Link to comment
Share on other sites

  • Administrators

Safariwagon...This should be the pattern for your NP219:  4L-N-4H-LOCK

It should be easy to determine which direction the shifter moves for these positions.  4L is obviously reduction gearing followed by Neutral in the TC.  4H should be full-time 4x4, the NP219 uses a viscous coupler for the full-time 4x4 mode.  "LOCK" should be full-on locked front to rear drive, which would likely cause a steering input reaction on hard, dry pavement or cement if the LOCK mode were engaged during a tight turn.

Let us know that this is correct...

Moses

 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...