3.9 L Mirada CMX

J Body General Discussion

  1. BudW

    BudW Moderator Staff Member

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    Joe,
    There is a write-up about adding the Rear Wheel ABS a few years back, in Mopar Action. For a car you plan on driving often – I recommend installing it (which I plan on doing). If car is only going to be driven every so often – then I don’t see the need. I plan on driving my cars every day, in snow, ice, tornado’s etc. – so it makes sense to install it.

    I need to find that article again, for my own needs.

    Going by memory, you need a '90's Pickup, B-van or Dakota (or some Jeeps) that has Rear Wheel ABS. You need the grab the Master cylinder with the solenoid block (you don’t need the master cylinder, per se – just less work when taking parts off of the vehicle), the computer (under dash) and pigtails for both – as well as pigtail for differential.

    Two holes will need to be drilled into the differential case. One is the hole for the speed sensor and the other is the hole for the hold-down bolt. Take some measurements from a differential – might be helpful.

    The ABS ring presses right on/off onto any 8¼” (as well as any 8¾”) carrier.

    Chrysler 8¼” differentials use the same internals from ’73(?) To present. The 8¼” first came out in ’69 B–bodies, but on the top of my head is telling me not all parts for those first few years interchange with the ‘73(?) and up versions.

    An important note: the axle splines changed in ’96 or 97 (not sure of the changeover year). Non limited slip carriers will interchange – IF you chang the spider gears (that contact the axle C-clip). Limited slip differentials are a bit harder to interchange – because that spider gear is not always interchangeable. The rest of the newer differential parts are the same.
    Some of the newer 8¼” use compressed air activated as well as electrical activated limited slip – but I don’t recommend changing one over to either design.


    I like the idea on moving the engine forward some. That might allow the A500 (or A518) to use the same transmission mount location, possibly.
    It might also allow usage of a truck oil pan – possibly.
    BudW
     
  2. Joe12459

    Joe12459 Well-Known Member

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    Thanks for all of the info. My son drives the car every day, so the ABS install makes sense. I have the whole 98 Dakota, so that's exactly what I plan on doing. Thanks for pointing out the difference in splines. I don't think the v6 Dakota has SureGrip, so it shouldn't be an issue changing the spider gears. I've had luck before, playing with the motor mount location, so I'm hoping to get the 42RE in there without a lot of tunnel modification. If it ends up close to the stock trans mount, that would be a nice bonus.
     
  3. BudW

    BudW Moderator Staff Member

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    The ’98 would have the different splines (as well as 6-lug wheels). The spline count will be 29, for ’97 and newer.
    27 splines for ’96 and older.

    I just measured a differential out of a ’98 Dakota 2*4 and updated my differential file accordingly, on Friday. Also I just tried to access that file just now and file is now corrupt (head bang onto desk . . .)

    If yours is a 2*4 then (going by memory) the Dakota differential is close but wider than original, it might fit with few differences – but the 6-lug axles might be a killer part.

    I need to ask why Dodge went with 6-lug wheels on Dakotas – for they are the only thing they put them on, that I’m aware of.

    If you decide to drill your existing differential for ABS speed sensor – take lots of pictures, please.


    The 42RE (A500) will need to use the engine computer or some kind of work around for transmission to work correctly.
    BudW
     
  4. Joe12459

    Joe12459 Well-Known Member

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    Yup, my goal is to use the carrier and gears from the Dakota in my Mirada housing, which I will drill for the sensor. I now know I will have to use the Mirada spider gears, too.
    I plan on using the engine and trans with entire harness and all of the electronics from the Dakota, so trans control is not an issue.
    I'll definitely post lots of pics.
     
  5. BudW

    BudW Moderator Staff Member

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    Do you have a spare K-frame?
    If so, you might want to make a jig like I’m planning on making – for this project.

    I have plans on installing a pair of big blocks into my cars. I’m also getting rid of the rubber K-frame biscuits, and several other changes at same time.

    With car on level ground, I took measurements from ground to K-frame in front of front biscuit) and rear K-frame (rear of rear biscuit) as well as ground to transmission at transmission mount.
    Also measured from rear of K-frame to transmission crossmember – so I could get that square on my jig.

    With my spare K-frame, I can get K-frame into same measurements and drop my 318/999 police engine back (using new mounts) onto it to get an accurate crankshaft center line. In your case, this might be helpful to know where front of harmonic balancer is to front of K-frame.

    This might be handy for you to get engine mounts in correctly, to test your oil pan creation and to check on transmission crossmember for fitment – maybe.

    What are you going to do about speedometer operation?
    BudW
     
  6. Joe12459

    Joe12459 Well-Known Member

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    Hmm, that's a good idea. I do have a spare k frame, from a v8 car. That would probably make the mockup a lot easier.
    I plan on installing Speedhut gauges in the factory Mirada instrument panel/bezel, so I'll use a GPS speedo for ease of installation. I thought of modifying the dash and using the Dakota cluster, but my son likes the stock Mirada look, and I tend to agree with him.
     
  7. 80mirada

    80mirada Well-Known Member

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    The 6 on 4.5" bilt pattern is shared with the Jeep Honcho, and Dodge Viper.
     
  8. BudW

    BudW Moderator Staff Member

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    I’ve not looked that close to a viper yet – other than what I can look at via a car show – so really don’t know much about them.
    BudW
     
  9. Joe12459

    Joe12459 Well-Known Member

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    Well, today I finally had a chance to make some progress. I now know the drivetrain fits in the stock /6 k frame with the truck pan, mounted forward of the stock position, with no trans tunnel mods. I haven't finished fabricating the motor mounts yet, but the engine and trans are in the car, in position. The tail of the trans falls approximately 1 inch short of where the stock 904 ended, so I will likely get away with the same driveshaft, and just a longed yoke. Pics to follow.
     
  10. Joe12459

    Joe12459 Well-Known Member

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    I'm thinking the biggest challenge is going to be closing the hood. The truck efi intake is a little high. I'll probably have to build a shorter air box, but otherwise it should be ok.
     
  11. Duke5A

    Duke5A Active Member

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    This guy did the 5.2L swap into a Fifth Avenue and kept the beer barrel intake. I don't think the intake on a 3.9L is any taller.

     
  12. Joe12459

    Joe12459 Well-Known Member

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    3.9Mirada.jpg
    Yup, that looks very similar to my setup. My engine is a few inches further forward, but the height is the same. If I use low profile air cleaner like he did, it will clear without an issue. I have to stop calling it mine, though. This one is actually my son's.
     
  13. Duke5A

    Duke5A Active Member

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    Looks good! I just went back and read the rest of the thread. I looked into cheap boost for another project a while back and did some reading on Eaton M90 superchargers. You can get them for under $200 on eBay all day long. Originally came equipped on GM 3.8 V6 engines. I've seen some remote mount setups people have fabricated with these and M112 units. Would be dirt cheap, but would also be a ton of fabrication. Or you could mill the stock intake down and fabricate mounts to bolt it on top.

    Also, I think V8 throttle body will interchange with the one on the 3.9L too.
     
  14. Joe12459

    Joe12459 Well-Known Member

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    Hmm, I never thought of that. After he drives it a while, that might be the direction we go in. Thanks for the info!
     
  15. Joe12459

    Joe12459 Well-Known Member

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    Got the motor mounts done yesterday, and a good start on trans mount. So far everything looks good. Trans angle/driveshaft angle looks like it will be good without tunnel mods. Of course, I have other plans today, so no work will get done.