AMC Eagle Den Forum
The Shop => 4X4 and Driveline => Topic started by: IowaEagle on June 11, 2004, 12:46:01 PM
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Thanks to Jim Bolton who did the research and originally posted the info on the web in 1999.
AMC used three different transfer cases; The Eagles all used the 23 spline transfer cases, regardless of the transmission they were used behind. This is different from Jeeps, which also used a 21 spline case, typically found behind 4 or 5 speed standard transmissions.
The cases used were:
NP 119 - '80 thru early '81 -- Full Time 4 Wheel Drive; Viscous Coupling
NP 128 - 1986 only; Open Differntial
NP 129 - mid '81 thru '88 -- Select Drive Models; Viscous Coupling
These cases were manufactured by New Process and were designated models 119, 129 and 128. The 119 was 4 wheel drive all the time, whereas the 128 and 129 were switchable to 2 wheel drive. The 119 and 129 used a viscous coupling differential unit in the case, which allows some slippage between the front and rear output shafts and allows use of 4 wheel drive in any road conditions. The 128 case used an open differential to allow slippage. The differences in these methods of differentiation can be likened to the differences between a limited slip rear-end and an open rear-end. A worn out viscous coupling will behave much like an open differential.
This information was obtained at http://www.n0kfb.org/homepage/amc/tech/transfer_case/swap/index.htm and they also provide swap info for members who want to install a hi-lo transfer case.
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So how do I tell the difference between transfer cases?
I have about 4 of them laying around and I would like to install the one that appears to be rebuilt. It has also been sand blasted and painted! Woot... but I want to make sure that I it as "on the fly 4x4". The 80 model is obviously all-time... my 82 has a switch but I never paid attention to it because the vacum lines were never hooked up and the only one I ever owned and drove with the switch was my 81... and I had to stop to switch it to 4x4 and back.
Well, when I got my 85.... Brandon was telling me how cool it was that mine was "on the fly". Upon further inspection... he was right! That's just the coolest! So... how do I make sure that I am able to retain this feature when swapping transfer cases? I believe the pretty one is from an 83.
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There should be a red aluminum tag screwed to the case. All 129 and 128 cases are switch on the fly capable. It was the axle disconnect that made them stop and shift.
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I would love to have a 128 open Differential. I could lock the diff and be less likely to get stuck. I like the idea of both drive shafts spinning the same .( Never had may eagle stuck anyway)
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Thanks for the info IE... I'll make sure I install one or the other. So as long as I use the original axles from the 85, then I'll be good? Sounds easy enough.
I have never noticed a red aluminum tag though. Probably because most of them have been black from old grease... the rebuilt one has been painted, but I'll find it. Thanks again!
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Yeah, the '85 is a shift on the fly version.
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Sweet! That's good to know! Thaknks!
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I Just bought an '86 Eagle wagon and after reading this, I'm starting to think maybe the 128 transfer case is less desirable than the 129 in my '84 parts car. Would there be any advantage to switching to the 129? I'd definitely like the '86 to be as capable off-road as the '84 I used to drive was. I'm also curious about the locking front axle. I've read that the shift-on-the-fly Eagles don't have this, and would like to know how this affects the 4-wheel drive. It would be a big help if anyone knows a bit more about this than I do...
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The 129 will swap right in and provide you with the safety and security Roy Lunn designed into the Eagle. The non locking axle is felt by many to be a good thing as that means there is one less thing to go wrong when you need 4WD.
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so if the front end in my 84 has the axle disconnect in it but i permantly locked the hubs together does this mean that i can "shift on the fly"?
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Yes.
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sweeeet!
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To answer Mav's question about ID of cases without the build tags(a 2" round tag with a screw in the middle of it and lettering stamped in it) -
The 119 case will have no linkage attachment where the shift fork comes out of the front half of the case, it will only have a locking nut to hold the non-moveable shift fork in place, or it is a bolt plug, if there is no shift fork(haven't had a 119 apart, haven't looked at an exploded diagram to see if theres a shift fork er not).
The 128 and 129 will look the same from the outside. Both will have a shift-able linkage attachment. On the 128, you will be able to relatively easily turn the front and rear outputs against each other(turn each the opposite direction of the other) when it is in 4wd mode, since it has an open differential. I'm not sure if its a lock-able differential like the NP 242, where the differential is locked when the case is in 4wd Low mode. Its probably not lockable. Anyway, the 129 has the viscous coupler, and it should take some considerable effort or even a wrench to turn the front and rear outputs against each other when the transfer case is in 4wd mode.
So - 119, no shifter linkage attachment
- 128, has shifter linkage attachment, open diff, can turn outputs against each other in 4wd
- 129, has shifter linkage attachment, viscous coupler, difficult to turn outputs against each other in 4wd
Even a worn out viscous coupler will have much more resistance than the open diff.
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I have an 88 wagon with 85,000 miles, i thought low mileage would be a good thing but bad things can happen when they sit for long periods of time. but im hoping the year/type transfer case thats in mine will still get me through snow, mud, and occasionally a mild jeep trail.
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You have the NP 129 in your '88. It is a good transfer case and can be driven on any type of road surface. The NP 128, found only in 1986 models, is the one that has some minor issues but it is pretty bullet proof.
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Just a bit off topic here, but also remember, the 119 uses 10W30 instead of ATF.
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My newest Eagle is an '86, so it should have the NP 128 Case. Now if I took a NP129 case, and bolted it to my '86, could I still shift on the fly?
would there be a NP129 case on my '84 that would do? Could I just swap them over?
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whuntmore: you can shift (your TRANSFER CASE) on the fly as long as your front axle is engaged, either permanently or with the disconnect axle already connected (this must be done at a stop, or at least with the wheels locked, lol)....
anyway, the axle is not supposed to shift on the fly while it is turning, the shift fork is tiny and there no synchronizing from what I understand...what you get your car to do wheeling in the desert is between you and the coyotes
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Both the 129 and 128 cases can be shift on the fly. It was the axle disconnect that created the stop and shift version. You either need a non-disconnect front axle; or lock the disconnect axle into the "connect" mode to have shift on the fly.
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Ok, but since my 86 eagle is already shift on the fly, and the front end is already set up for this, and I'm not changing the front diff, then the front end shouldn't be a consideration here. Is this just you guys thinking that my Car isn't already shift on the fly?
I mean maybe there's something I'm missing here, but it seems to me if my car is already 'shift on the fly' and the transfer case I want to change to is also 'shift on the fly' and all I'm doing is changing the case, it should work.
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I believe that the 80 & 81 and 86 and later all had the locked front axles. It was from 82 to 85 (?) that had the select-trac that you had to stop the car and shift. So, if you have a set up that is already a shift on the fly, changing out the transfer case with either the 128 or 129 will not affect that. I pulled my 129 out of my 84 wagon, then locked the front axle and installed a 119. I like the idea of full time AWD. the difference in MPG is negligible and I don't have to worry about shifting the T-case whenever the road conditions change. There is another 81 wagon at a local wrecker with a 119 in it. They want $100 for it, and I am considering getting it to have a spare.
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Ok, but since my 86 eagle is already shift on the fly, and the front end is already set up for this, and I'm not changing the front diff, then the front end shouldn't be a consideration here. Is this just you guys thinking that my Car isn't already shift on the fly?
I mean maybe there's something I'm missing here, but it seems to me if my car is already 'shift on the fly' and the transfer case I want to change to is also 'shift on the fly' and all I'm doing is changing the case, it should work.
Yes, all you are doing is changing transfer cases. You will retain your shift on the fly capability.
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A 229 T-case can be installed in place of the 129 or 128, this way you still have the viscous coupler and you have low range. You would have to install a shifter to shift from low range to high range. Other than the shifter it's identical to a 129. These can be found on the AMC Grand Wagoneers behind V-8's, but the bolt pattern are the same as a 129 or 128.
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Just a bit off topic here, but also remember, the 119 uses 10W30 instead of ATF.
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How much damage can you do by using ATF instead of 10W-30? I just changed mine back to 10W-30 after reading it in the manual. I was under the impression that they all used ATF, in fact that's what was in it when I bought it. Guess that's where all of my winning is coming from, sounds like it's going to explode any day now.
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You never mentioned what year or what. Case.
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I believe it was mentioned somewhere that the factory later recommended ATF over 10w30.
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To my understanding if you swap for a 229 you need to do something different with the speedometer cable. A 90degree adapter I think.
I found this to be a handy chart.
(http://i687.photobucket.com/albums/vv240/dodecafarm/t-case.jpg)
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Just reclock it.
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While I was at the Calgary PnP helping El Matador strip an eagle there, a guy who used to be a (long standing) member with our AMC chapter came up and started chatting. he still owns a few AMC cars.
I told him I had a 129 case I was gonna swap out (get rid of my 128 case) and he suggested that I go with a 208 case from one of the full sized wagons (wagoneer... whatever)
Now, is there such a case as a 208? Or did he have his numbers wrong, and he really meant a 207 TC? I've never heard of a 208 case.
If there is such a beast, would this be a good upgrade?
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Just reclock it.
I have heard this will cause leak issues?
Hear is a link to a page on common t cases it has info on the np 208 mentioned above.
http://www.off-roadweb.com/tech/1005or_common_transfer_cases_guide_high_low_ranges/new_process_gear.html
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will a 231 or a 242 bolt up to my tranny? i have an 85 and i think the tranny is an 727 or a 904?
and also whats the spline count on my 129?
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Lif auto than most likely a998. Will bolt up, but driveshaft mods come in. You can use the eagle intermediate housing to save some so you do not have to mod the front driveshaft. However the rear slips into a 242. And than needs ca. 10 inches added to it.
I run a 242
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However the rear slips into a 242. And than needs ca. 10 inches added to it.
i dont know what your trying to say right there ^ but i would like to run a 242 or 231 i know i may need to modify the driveshafts but will they mate to my transmission?
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The rear output of the 242 has the shaft slip into it instead of bolting on.
Yes it will bolt up
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The eagle has a fixed rear yoke. The drive shaft bolts up to the transfer case. On the 242 the rear shaft slips into the transfer case.
Fixed
(http://www.4wd.com/aux_incl/images.ashx?i=TRAN_150.jpg)
Slip
(http://t2.gstatic.com/images?q=tbn:ANd9GcT_ipCxkYr49AkMmlU9AGQwNcjkKvh-lAtiGMkdQcz7wO0KaJG6Uw)
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Ok so a 242 will work and a 231? I have an s10 with a 231c in it, I guess the 231 c means Chevrolet? Any chance of that working? Also what's the spline count on that 242? Y'all are helping me a ton!
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28
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S10 case won't work. But would be good for someone who wanted to adapt a GM 700r transmission to their AMC engine and not want to spend the extra money adapting the Eagle or a Jeep transfer case since the S10 TC is driver's drop.
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i didnt think the s10s would but i got a 231j installed last night, now i need driveshafts and my eagle is done! :)
BTW i have a 129 for sale if anybodys interested..........
its disasembled but all the pieces are there it just needs a bearing, it still works fine but the bearings are about to go
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My Chilton's says that the 80-81 model transfer case uses 1030 motor oil. I'm thinking that is just for the 119 t-case, and not for the NP129 that I have in my 81. It says to use Dexton II in 1982 and later, which I also assume are all outfitted with NP129s like mine. Make sense?
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AMC later recommended to use Dexron in all the Eagle transfer cases.
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"all" as in every year, every model? Just want to be sure since i'm in the process of doing a clutch and changing all fluids.
Don't mean to change subjects but is Dextron suitable for the t4 as well? I read conflicting info. Some say 90w and some say Dextron.
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The Eagles all used the 23 spline transfer cases, regardless of the transmission they were used behind.
Can't say for certain, but here's the source:http://www.n0kfb.org/homepage/amc/tech/transfer_case/swap/index.htm (http://www.n0kfb.org/homepage/amc/tech/transfer_case/swap/index.htm)
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Good to know. Thanks.
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There's a pretty neat chart on that page, which lists the features and characteristics of the New Process transfer cases...
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The Eagles all used the 23 spline transfer cases, regardless of the transmission they were used behind.
Can't say for certain, but here's the source:http://www.n0kfb.org/homepage/amc/tech/transfer_case/swap/index.htm (http://www.n0kfb.org/homepage/amc/tech/transfer_case/swap/index.htm)
Some of the 4 cyl Eagles came with AX-4 or AX-5 trans which was 21 spline
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I figured that sounded a little too.. conclusive to be certain.