[Road Ripper]

I installed the 3rd gen axle so I could put 4th gen hubs, backing plates, Calipers, and rotors on the van. I removed the weight sensitive proportioning valve and installed an adjustable Wilwood proportioning valve.

Yes, but it shouldn't have fit! The 3rd gen axle is over an inch wider at the leaf spring mounts. You should have had to move the leaf springs outward with the forward mounts and the rear shackles somehow.

 

[donchicago48]

I did move the springs about 1/4" outboard at the front Spring brackets. The multi-leaf springs mounted on the axle ok using the rubber isolators and longer bolts. I had a friend's body shop check the wheelbase on both sides and front/rear wheel alignment. They said no adjustments were necessary.

 

[Road Ripper]

Cool! I wasn't trying to be snobby; just curious what was needed to make it work. You deserve extra credit for doing the one-off stuff like that.

 

[donchicago48]

Cool! I wasn't trying to be snobby; just curious what was needed to make it work. You deserve extra credit for doing the one-off stuff like that.

I had to find an axle that had the same hub bolt pattern as the 2007 donor vehicle. The key parts were the rear brake backing plates that supported the 2007 era caliper mounting. I also took the old 2007 calipers from the donor vehicle as cores for rebuilt calipers. I bought new rear hubs, rotors, pads, and parking brake hardware. I studied the Dorman catalog to find the correct length parking brake cables that could fit my setup. It was completely different from the 1991 design. I bought stainless brake hoses that would fit the brackets on the axle and the 1991 body. I replaced all the rusty steel brake lines with copper/nickel lines.
I also fabricated upper rear Sway Bar brackets from angle iron and used stock Chrysler rear Sway Bar links from a 2007 era Chrysler van. The brackets fit 4 existing threaded holes on each side of the 1991 frame elements. I bought an aftermarket rear sway bar and attached it to the brackets on the 1999 rear axle with stock rubber bushings and brackets. I will snap some photos of the rear axle when the weather warms up.

 

[donchicago48]

The '98-'00 183 head (Left) was replaced by the '01-'07 688 head (Right). The 688 head has a larger Intake Valve and a smaller Exhaust Valve in its revised Combustion Chambers. I don't know the Combustion Chamber Volume yet so cannot calculate Compression Ratio. The 688 heads also have larger Intake Ports and flattened Exhaust Ports that require later Intake and Exhaust Manifolds. Valve stems are smaller diameter and ports are designed for greater flow.
I am evaluating use of the 688 heads on my build. They are used on the later, more powerful 3.3/3.8L engines. I have the matching Camshaft for the 688 heads, so it would make sense to use the later heads, Intake, and Exhaust Manifolds. I would have to find a suitable Throttle Body compatible with my non-electronic throttle setup. It appears that Chrysler used non-electronic Throttle Bodies at least through 2007 models.

 

[donchicago48]

I picked up the engine block, crankshaft, rod/piston assemblies, and backcut intake valves from Lee Auto Parts machine shop in Waukegan, Illinois recently. They have been a joy to work with. They provided a lot of good advice along with expert machine work. I am now almost ready to assemble the engine.

 

[Mr. Minivan]

I installed the 3rd gen axle so I could put 4th gen hubs, backing plates, Calipers, and rotors on the van. I removed the weight sensitive proportioning valve and installed an adjustable Wilwood proportioning valve.

Do I understand correctly, you fitted a 3rd Gen rear Axle onto your 1991 Minivan? No customisation needed? Stuff just bolts together? Distance of the Leaf Springs in the same?
You mention the weight sensing valve, so you don't have ABS? This could be an issue with ABS equipped vehicles regarding number of teeth, sensor mounting and sensor situation overall.
Could you provide some pictures?

 

[donchicago48]

I had to move front spring Hangers about 1/2" farther apart. I used the rubber isolators and clamps from 1999 DGC. I had to use longer bolts to clamp the 1991 multi-leaf springs. The rear track is a bit wider than the 1991 rear track. I used wheels from a 2002 Acura TLS. The 17" Acura wheels have more negative offset than the 15" Dodge wheels had. I used a router and aluminum-cutting bits to open up the center bore of Acura wheels from 64 mm to 72 mm. I used a wheel spacer/

adapter as a template. I had to fabricate custom brake lines and order custom stainĺess brake hoses. I have now completely replaced all the steel brake lines with copper-nickel lines and have a new Wilwood brake proportioning valve. The rear calipers and backing plates are from 2007 era Town & Country van. I used 2007 rear hubs too.

 

[donchicago48]

I had to move front spring Hangers about 1/2" farther apart. I used the rubber isolators and clamps from 1999 DGC. I had to use longer bolts to clamp the 1991 multi-leaf springs. The rear track is a bit wider than the 1991 rear track. I used wheels from a 2002 Acura TLS. The 17" Acura wheels have more negative offset than the 15" Dodge wheels had. I used a router and aluminum-cutting bits to open up the center bore of Acura wheels from 64 mm to 72 mm. I used a wheel spacer/ View attachment 70099
View attachment 70098
adapter as a template. I had to fabricate custom brake lines and order custom stainĺess brske hoses. I have now completely replaced all the steel brake lines with copper-nickel lines and have a new Wilwood brake proportioning valve. The rear calipers and backing plates are from 2007 era Town & Country van. I used 2007 rear hubs too.

 

[donchicago48]

Here is the block after boring, honing, and decking.

 

[donchicago48]

Do I understand correctly, you fitted a 3rd Gen rear Axle onto your 1991 Minivan? No customisation needed? Stuff just bolts together? Distance of the Leaf Springs in the same?
You mention the weight sensing valve, so you don't have ABS? This could be an issue with ABS equipped vehicles regarding number of teeth, sensor mounting and sensor situation overall.
Could you provide some pictures?

I do not have ABS.

I just snapped a photo of the rear axle area from behind the van. Not everything is visible, but you can see the left backing plate and part of the right rear caliper.