rwd to 4wd

[WeezyBlue]

New member here. I'm new to the Comanche world also, but I'm not a stranger to Jeeps or the 4x4 hobby by any means.

 

I just picked up a 1987 2wd 2.5 ax5 short bed. My plan was to just daily drive it into the ground, but it turns out it's really pretty solid, save for the driver's floor.

 

Now I'm considering swapping it to 4x4. I want to keep the 2.5 for simplicity, and I already have a boosted 4.0 in my TJ so I'm just looking for something a bit different.

 

I found a listing for a mostly stripped down 1986 Comanche parting out a couple hours from here. It was a 2.5, but the motor is gone. What's left is the 5 speed and tcase, and both axles.

 

So a couple questions I have, or rather things I just want to verify with common consensus:

The transmission in that truck would be an AX15? I know they're very similar. Can that bolt on without having to mess with my AX5's clutch, slave, etc?

I believe both trucks should have 4.10 gears? I also believe the rear axles would both be d35s, so I'd just be taking the d30.

Do I need a different trans crossmember and/or mount?

 

Seems like it would all be mostly plug and play, just need driveshafts.

 

TLDR:

Can I easily swap my 87 2.5 2wd AX5 to 4x4 with parts off a 86 2.5 4wd?

[89 MJ]

The trans is NOT an AX15. The AX15 came behind 4.0s in the later half of 89. I’m not sure about the crossmember, but I doubt you’ll need a new one if you will go with another AX5. You will need the driveshafts too. 

 

You could probably do this , but easy is a relative term. If you have a lot of experience (it sounds like you do), then yes, it would be easy. 

[Jeep Driver]

The '86 trans will be a AX5.

The '86 does have an external slave but is unique to the '86, passenger side slave. 

 

Yes, the truck will have 4.10s but the front axle will be CAD, I would not have one but...........if you get it cheap it will get you to 4X and you can swap later. 

 

Ideally you'd want to find a 94 XJ for the swap, better bell, no CAD.

 

Drive shafts? Just have new ones made. 

Your existing Xmember will work. 

And of course the TC. 

 

Your existing bell will attach to the 4X AX5 if you want to maintain your existing internal slave. 

[WeezyBlue]

1 hour ago, 89 MJ said:

The trans is NOT an AX15. The AX15 came behind 4.0s in the later half of 89. I’m not sure about the crossmember, but I doubt you’ll need a new one if you will go with another AX5. You will need the driveshafts too. 

 

You could probably do this , but easy is a relative term. If you have a lot of experience (it sounds like you do), then yes, it would be easy. 

 

Ah ok I knew the ax15s came behind the 4.0s but I just kind of assumed it was the same with the 2.5 and 4x4 to handle the different torque forces that come from the gearing reduction behind it. Thanks, good info.

 

1 hour ago, Jeep Driver said:

The '86 trans will be a AX5.

The '86 does have an external slave but is unique to the '86, passenger side slave. 

 

Yes, the truck will have 4.10s but the front axle will be CAD, I would not have one but...........if you get it cheap it will get you to 4X and you can swap later. 

 

Ideally you'd want to find a 94 XJ for the swap, better bell, no CAD.

 

Drive shafts? Just have new ones made. 

Your existing Xmember will work. 

And of course the TC. 

 

Your existing bell will attach to the 4X AX5 if you want to maintain your existing internal slave. 

 

Ok so that's some good and some bad. Just to summarize, I pick up this transmission and tcase, swap the bellhousing between the two, and everything should bolt up in place, no rerouting the slave. Same clutch/flywheel (which are new)

 

The CAD axles on these Jeeps I believe have the disconnect on the passenger side shaft? Been a long time since I've looked at one. Can you just replace that axle shaft with a one piece, worst case? Either way it sounds like I want to pick up the trans and tcase at a minimum.

 

I've been toying with the idea of swapping the 5.13 D44s from my TJ into the manche and getting some Dynatracs or something for it, but that's a bit more than I want to invest right now

[Pete M]

you can easily lock the CAD for free using one of a variety of methods.  should be a couple of 'em in the link in my sig.   

[WeezyBlue]

Looks like I'll be picking up the whole truck for $150 tomorrow, so can't beat that. Thanks for the info, guys

[Eagle]

1 hour ago, Jeep Driver said:

Yes, the truck will have 4.10s but the front axle will be CAD, I would not have one but...........if you get it cheap it will get you to 4X and you can swap later. 

 

 

The CAD front axle won't be an issue behind a 2.5L. My '88 XJ and '88 MJ (both with the original CAD front axles) have both been wheeled at Paragon, and the XJ has seen other trails around New England as well as fire roads and Forest Service trails in New Mexico. Just shift the CAD into the engaged position and lock it there.

[Jeep Driver]

27 minutes ago, Eagle said:

 

The CAD front axle won't be an issue behind a 2.5L. My '88 XJ and '88 MJ (both with the original CAD front axles) have both been wheeled at Paragon, and the XJ has seen other trails around New England as well as fire roads and Forest Service trails in New Mexico. Just shift the CAD into the engaged position and lock it there.

Several years ago I lost a Ujoint cap on the passenger side, I was in the middle of BFE. Shaft ends were damaged. 

Fortunately someone let me use their shop and tools to remove the damaged shaft. 

I went to the PnP and got a pair of CV shafts....this is when I made the change.....

I was able to slide the new shaft in and be back on the road in a few hours. 

 

Had I had the CAD..........I'd be SOL. 

 

That aside, CAD is a POS, I don't like anything that is a POS, I will avoid PsOS at all costs. 

 

I like all things that are straight forward, I like all things to be straight forward. 

 

I don't have one, I'll not have one. 

 

[DirtyComanche]

Easy to just drop a regular shaft in a CAD axle.

[Eagle]

3 hours ago, DirtyComanche said:

Easy to just drop a regular shaft in a CAD axle.

 

Not necessarily. Some of the diff housings on the CAD axles aren't machined to accept a seal on the right hand side of the housing.

[gogmorgo]

If it's a just-need-to-get-it-home situation, if you can't find an alternative you can still slide a one-piece shaft into the CAD housing without messing with seals. You'll just end up covering the inside of your wheelwell with gear oil until the level drops in the diff, and the diff won't lose enough oil to be a serious concern, so long as you take care of the seal situation as soon as possible once you do get it home. 

[WeezyBlue]

Got the donor home. Looks like everything I need is here. Bonus for the three spoke steering wheel and power steering box.

[dasbulliwagen]

I used an 86 donor for all the swap stuff in my 87 2.5. Including the external slave bellhousing. The actual bellhousings for internal and external are the same, theyre just set up differently. I did have an issue with the clutch master, as I think the bolt pattern is different between 86 and 87. You won't have an issue with the CAD, especially with the 2.5. Just make it work properly or lock it over permanant, or buy a cable lockout to connect or disconnect at will. If your truck is a shortbed, youll need to have a rear driveshaft made or get the 86 one cut down. The 86 donor truck will also have the NP207 transfer case, which is weaker than the 231, but its a 4 cyl, and you don't expect to heavilly modify it, so again, you shouldnt have any issues. This is also a good time for some front end upgrades, like WJ control arms, ZJ V8 tie rod, bigger sway bar from ZJ or XJ, Dual Diaphragm. 

[WeezyBlue]

5 hours ago, dasbulliwagen said:

I used an 86 donor for all the swap stuff in my 87 2.5. Including the external slave bellhousing. The actual bellhousings for internal and external are the same, theyre just set up differently. I did have an issue with the clutch master, as I think the bolt pattern is different between 86 and 87. You won't have an issue with the CAD, especially with the 2.5. Just make it work properly or lock it over permanant, or buy a cable lockout to connect or disconnect at will. If your truck is a shortbed, youll need to have a rear driveshaft made or get the 86 one cut down. The 86 donor truck will also have the NP207 transfer case, which is weaker than the 231, but its a 4 cyl, and you don't expect to heavilly modify it, so again, you shouldnt have any issues. This is also a good time for some front end upgrades, like WJ control arms, ZJ V8 tie rod, bigger sway bar from ZJ or XJ, Dual Diaphragm. 

What'd you do for the speedometer? I'm halfway through the swap and the cables connect differently. It's a shame cause I just bought a new full featured cluster with the newer style cable

[dasbulliwagen]

Actually, I have yet to hook the speedo back up..... Its been several years now. I couldnt use the original cable due to length issues, but I bought a new one for the application, and it is sitting in a box behind my seat! I still have the original dummy light cluster. This question may be worth starting a new topic for.

[schardein]

For my future 4wd conversion, I scored a front axle out of a 1986 XJ.  Factory 3.73 gears, and it's a non-cad axle.  Came with the 242 transfer case, or whatever was equivalent that year.  Got a set of axleshafts from a 96 XJ with the bigger u-joints that will go in it.

[WeezyBlue]

On 7/23/2019 at 8:28 AM, Jeep Driver said:

The '86 trans will be a AX5.

The '86 does have an external slave but is unique to the '86, passenger side slave. 

 

Yes, the truck will have 4.10s but the front axle will be CAD, I would not have one but...........if you get it cheap it will get you to 4X and you can swap later. 

 

Ideally you'd want to find a 94 XJ for the swap, better bell, no CAD.

 

Drive shafts? Just have new ones made. 

Your existing Xmember will work. 

And of course the TC. 

 

Your existing bell will attach to the 4X AX5 if you want to maintain your existing internal slave. 

 

Just an update and a heads up to anybody that might find this thread with the search function, NO, the 86 MJ with 2.5 does not necessarily have 4.10 gears. The donor I picked up is geared 3.54. It's a factory X with 2.5 and ax5

[Minuit]

1 hour ago, WeezyBlue said:

 

Just an update and a heads up to anybody that might find this thread with the search function, NO, the 86 MJ with 2.5 does not necessarily have 4.10 gears. The donor I picked up is geared 3.54. It's a factory XLS with 2.5 and ax5

Typically, that gear ratio was used with a 2.5L with 4-speed transmission. The truck being 33 years old now, it's entirely possible that either the transmission or axle(s) have been swapped out. Swapping to an AX5 from an AX4 is a fairly popular and easy swap. Or AMC just had 3.55 geared axles sitting on the shelf that day and decided "screw it, they won't notice"

That's why it's good practice to check the axles themselves, either by reading an axle tag, counting the teeth on the ring and pinion, or by spinning the wheels and counting driveshaft revolutions.

[WeezyBlue]

I would have checked if it was a more important build. This is a fun side rig project. For $150 for the donor Jeep I didn't really care what it had. Just sharing info

[WeezyBlue]

Also I'm not sure how swapping an ax4 to ax5 would change the gear ratios

 

[DirtyComanche]

15 minutes ago, WeezyBlue said:

Also I'm not sure how swapping an ax4 to ax5 would change the gear ratios

 

 

It won't.  The AX-4 trucks came with 3.54s typically as they didn't have OD.  Put an AX-5 in place of the AX-4 and you now have an AX-5 truck with 3.54s.

 

But gear ratios are all Schrodinger until the cover is off.

[Jeep Driver]

2 hours ago, WeezyBlue said:

Also I'm not sure how swapping an ax4 to ax5 would change the gear ratios

 

 

 

I cannot count the number of members here who has complained about having to downshift to 4th as you approach any kind of incline at highway speeds. 

Any gear taller than 4.10s will render OD/5th useless. 

2.5/AX5 with 4.10s is a 99% rule of thumb. 

 

What went on with your donor? Who knows, as stated, after 33 years, anything. And there was a time when trucks could be ordered....again......who knows? 

 

No one here gave you bad advice. 

 

 

[Eagle]

7 hours ago, WeezyBlue said:

 

Just an update and a heads up to anybody that might find this thread with the search function, NO, the 86 MJ with 2.5 does not necessarily have 4.10 gears. The donor I picked up is geared 3.54. It's a factory XLS with 2.5 and ax5

 

Are you certain it's an AX-5, not an AX-4? Virtually all 2.5L XJs and MJs with the AX-4 (4-speed transmission, no overdrive) had 3.54 gearing. The AX-5 has an overdrive 5th gear -- it's the trucks with the AX-5 that had the 4.10 gearing.

[Pete M]

has the donor truck been added to the VIN registry yet? 

[WeezyBlue]

It shifts into what would be a fifth gear sitting on the floor... How do you identify it by the case? Stamping somewhere? 

I haven't even seen the vin registry, I'll have to check.

 

What makes the most sense is that the transmission was swapped at some point then. I have pulled the covers, they're indeed 3.54.

 

I found this info on another forum, supposedly out of an AMC service manual. 8th digit in vin

7=x model 3.31 or 3.54
8=xl model 3.31 or 3.54
9=xls model 3.31 or 3.54
F=Custom(metric Ton-pkge) 4.11
G=x (metric Ton-pkge) 4.11
H=XL (metric Ton-pkge) 4.11
J= XLS (metric Ton-pkge0 4.11

 

Obviously doesn't mention transmission option