3.9 L Mirada CMX

BudW

Moderator
Staff member
Joined
Mar 4, 2012
Messages
4,640
Reaction score
1,295
Location
Oklahoma City
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
 

Joe12459

Well-Known Member
Joined
Sep 21, 2012
Messages
935
Reaction score
159
Location
Catskill Mountains, NY
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
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.
 

BudW

Moderator
Staff member
Joined
Mar 4, 2012
Messages
4,640
Reaction score
1,295
Location
Oklahoma City
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
 

Joe12459

Well-Known Member
Joined
Sep 21, 2012
Messages
935
Reaction score
159
Location
Catskill Mountains, NY
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
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.
 

BudW

Moderator
Staff member
Joined
Mar 4, 2012
Messages
4,640
Reaction score
1,295
Location
Oklahoma City
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
 

Joe12459

Well-Known Member
Joined
Sep 21, 2012
Messages
935
Reaction score
159
Location
Catskill Mountains, NY
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
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.
 

BudW

Moderator
Staff member
Joined
Mar 4, 2012
Messages
4,640
Reaction score
1,295
Location
Oklahoma City
The 6 on 4.5" bilt pattern is shared with the Jeep Honcho, and Dodge Viper.
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
 

Joe12459

Well-Known Member
Joined
Sep 21, 2012
Messages
935
Reaction score
159
Location
Catskill Mountains, NY
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.
 

Joe12459

Well-Known Member
Joined
Sep 21, 2012
Messages
935
Reaction score
159
Location
Catskill Mountains, NY
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.
 

Duke5A

Well-Known Member
Joined
Apr 6, 2018
Messages
1,037
Reaction score
455
Location
Michigan
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.

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.

 

Joe12459

Well-Known Member
Joined
Sep 21, 2012
Messages
935
Reaction score
159
Location
Catskill Mountains, NY
3.9Mirada.jpg

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.

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.
 

Duke5A

Well-Known Member
Joined
Apr 6, 2018
Messages
1,037
Reaction score
455
Location
Michigan
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.
 

Joe12459

Well-Known Member
Joined
Sep 21, 2012
Messages
935
Reaction score
159
Location
Catskill Mountains, NY
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.
Hmm, I never thought of that. After he drives it a while, that might be the direction we go in. Thanks for the info!
 

Joe12459

Well-Known Member
Joined
Sep 21, 2012
Messages
935
Reaction score
159
Location
Catskill Mountains, NY
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.
 

Joe12459

Well-Known Member
Joined
Sep 21, 2012
Messages
935
Reaction score
159
Location
Catskill Mountains, NY
Just got back from a 50-ish mile shakedown run. Everything seemed to run really well, no issues. Joe Jr. didn't have enough, though. He's out in it right now, putting it through its paces.
 

slant6billy

Well-Known Member
Joined
Dec 21, 2011
Messages
2,939
Reaction score
629
Just got back from a 50-ish mile shakedown run. Everything seemed to run really well, no issues. Joe Jr. didn't have enough, though. He's out in it right now, putting it through its paces.
What is the RPM and powerband like? Cruising RPM @50 mph?
 

Joe12459

Well-Known Member
Joined
Sep 21, 2012
Messages
935
Reaction score
159
Location
Catskill Mountains, NY
You had to ask me that! I didn't really take note of the cruising RPM, as I was mostly on rural roads, and the electronic speedo doesn't like the signal from the trans sensor, but it seems very comparable to any newer car. It was around 2500 RPM at what I would estimate to be 75MPH. I used a 3.55 rear, which is the same ratio as the donor truck, so it should be pretty similar to the Dakota. It has plenty of low end power to break the one wheel free, and climbs the hills here with no problem. I ordered a GPS speed sender, so I'll let you know exact rpm/speed when I get that set up.
 

slant6billy

Well-Known Member
Joined
Dec 21, 2011
Messages
2,939
Reaction score
629
You had to ask me that! I didn't really take note of the cruising RPM, as I was mostly on rural roads, and the electronic speedo doesn't like the signal from the trans sensor, but it seems very comparable to any newer car. It was around 2500 RPM at what I would estimate to be 75MPH. I used a 3.55 rear, which is the same ratio as the donor truck, so it should be pretty similar to the Dakota. It has plenty of low end power to break the one wheel free, and climbs the hills here with no problem. I ordered a GPS speed sender, so I'll let you know exact rpm/speed when I get that set up.
I had a thought. Could you use the piggy back mechanical cable for cruise control and allow the electronic speed sensor an alternate spot. Last time in the junk yard I saw a cruise control unit and it looked like it could be the piece to give both a mechanical and electrical point of connection. I'm not 100% certain, but it crossed my mind.
 

Joe12459

Well-Known Member
Joined
Sep 21, 2012
Messages
935
Reaction score
159
Location
Catskill Mountains, NY
I had a thought. Could you use the piggy back mechanical cable for cruise control and allow the electronic speed sensor an alternate spot. Last time in the junk yard I saw a cruise control unit and it looked like it could be the piece to give both a mechanical and electrical point of connection. I'm not 100% certain, but it crossed my mind.
What would I connect the cable to? The 42RE has only the electronic sensor, which it needs for the computer control. The problem is that the pulse from that signal is switched on the ground side, but my electronic speedo wants a positive pulse. The GPS sender I ordered provides a 16000 PPM positive signal, so it be a really easy solution.
 
Top