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Swapping Dana 44s and a Dana 300 into a YJ

Side view of Jeep

by Lars

Scout Swap

Main
Rear Dana 44
Front Dana 44
Final Notes

One major concern with the Scout II axle swap is the transfer case. The Scout II uses a passenger drop transfer case, so the front differential is on the passenger side. All the Wranglers use a drivers drop transfer case, so the solution is to use a Dana 300 from a 80s CJ. This also means that the exhaust needs to be rerouted around to the other side. There are also other details to the swap, some of the details are related to doing a spring over axle conversion.

Transfer Case

After removing the crossmember/skidplate and NP231 transfer case, I temporarily bolted the D300 to the automatic tranny. It fit perfectly although the front output end of the case hung down quite a bit. Not much I could do there. Re-indexing the way the case mounted to the tranny was not an option.

My skid plate With the case in place, I was able to take measurements which I needed to fabricate a new crossmember/skidplate out of square tubing. In retrospect, I think it would be easier and save space if I just hacked up a stock crossmember/skidplate. I'll probably do that later this year.

I also marked out which part of the floor pan needed to be pounded out in order to make room for the transfer case shifter. An easy way to do this (thanks to Wil for this tip) was to jack up the entire vehicle and then lower it onto a tall jackstand which will then push against the part of the floor which needs to be pounded up.

While I had the skidplate removed, I cut off the exhaust hanger hoop which is mounted on the passenger's side of the transmission mount. I then welded it onto the driver's side of the mount so it could be re-used when the exhaust gets re-routed.

I used a torch to put the necessary bends in the shifter so that it crossed over the transmission and came up in the same place that the factory shifter did. An alternative method I've heard of is to simply turn the transmission tunnel cover around so that the shifter plate/boot is on the passenger-side.

The speedometer cable and breather tube hooked up to the Dana 300 without problems. Well, that's not quite accurate. I did manage to break the nut which holds the speedo gear assembly in the transfer case. It's a cheap, cast metal part so be very careful when tightening it. Fortunately, I was able to obtain a replacement the very next day from Gary's Autowrecking.

I was planning on using a CV driveshaft with 1310 u-joints, so I installed a yoke on the rear for this drive shaft. I also changed a couple of seals.

Drive Shafts

I was hoping to use a front CV shaft but there wasn't enough room for the CV. It would have hit the auto tranny's pan under easy axle movement. I had to use a regular two-u-joint driveshaft in the front.

The rear axle installed even more easily than the front. I used an early Ford Bronco front CV shaft for the rear. It was short by 1 or 2 inches but would suffice for temporary street use.

At the driveshaft shop they lengthened, re-furbished & balanced the Bronco CV shaft I had in the back and re-tubed a skinny '88 YJ front shaft. Because of its small diameter (but 1/8" wall) and low mass, I didn't have it balanced and even so, there is absolutely no vibration when I drive with the hubs locked in.

Springs

With both the front and rear axles, I used a "fresh" set of used YJ springs. To these spring packs I added a main leaf (with the eyes cut off) from my old packs. The extra leaf should help reduce spring wrap with the spring over axle conversion.

Wheels

By the way, if you haven't already guessed, the Scout axles use the 5 on 5.5" bolt pattern. This meant that I had to buy a new set of wheels and swap my tires onto them while I had the Jeep supported on its frame.

Exhaust

Rear under carriage view I cut my original exhuast off from the header back because it needed to be rerouted straight down the driver side. I took the back roads to get to the local muffler shop where they re-routed the exhaust so that it stayed on the driver's side until it got close to the gas tank where it then bent up and over the driveshaft and exited in the standard location.

Brakes

I was planning on using a CJ master cylinder which I heard works well with this swap but it wouldn't bolt up to my YJ booster. I decided to fore go this modification and keep my stock master cylinder and booster. The result was the same old soft pedal but much better braking performance. Rob Bryce gave me a list of vehicle brake specs and the late CJ mcs seem to have the same mc piston size as the YJ mcs. I think the reason the CJ stuff might have worked better is because it's possible to adjust the pedal/push rod leverage. I might try that on my YJ by buying one of those adjustable rods.

Shocks

The long DoetschTech shocks which came with my RE SOA kit were too long for my new axles which utilized the higher axle-side shock mounts. I ended up with 3" available compression in the front and 2" in the back. I was actually bottoming out my shocks on mild street bumps. I solved this problem by moving the rear DoetschTechs to the front and putting a pair of cheap ($20 each) Canadian Tire MotoMaster shocks in the rear. These cheap shocks were discards from my friend's FJ45 Land Cruiser which he had just converted to SOA. I was able to move the rear shocks to the front because my Rubicon Express spring over conversion kit changed the front shocks to eyes on top and bottom.

Conclusion

It sure is nice to have free-wheeling hubs again. I can finally run 33" tires and lockers without worrying about snapping axle shafts. This project was a lot more work than I anticipated and this short write-up doesn't do justice to the long hours involved. On the other hand, a more organized person could do this faster and better than I did.

I would strongly recommend having a schedule and setting intermittent goals to keep the project moving along without getting yourself stressed out. I could have saved money by thinking long-term and determining all the pieces I would need. The sooner you know this, the more opportunity you have to find these parts in salvage yards or through private sales.

I expected the short shocks to lower my articulation but when I ramped it 5 days later, it scored a 1052 RTI. Not bad at all! This was the first time I had ever ramped my Jeep so I can't compare it to my older SOA performance. But that's not the point. The point is that even with these shorter shocks, I still have a very respectable amount of suspension travel.

The ride with the extra full-length leaves was a bit firmer than the older springs but much more stable. It handled highway bumps better without ruining the comfortable ride. It also allowed me to travel much faster offroad, absorbing large bumps easily.

Moving the lower shock mounts higher made a HUGE difference offroad. I took my Jeep out for three days of offroading once I got it back on the road and I only hit my diffs once. If you do an SOA conversion without moving the shock mounts, you're missing out on a major advantage of the SOA.

Even though I had setup the front pinion angle for a CV shaft and the non-CV shaft I ended up using was not balanced, I've detected no vibration even at speeds up to 100 km/h. I think a lot of that might have to do with the fact that the front shaft is one of the skinny ones used in pre-1990 YJs.

The bigger brakes on the Scout axles are great. While my brake pedal still feels too soft for my liking, the brakes grab much better and can lock up my wheels without too much effort. Since my Jeep is my daily commuter vehicle, it's no wonder that I appreciate the bigger brakes more than any of the other advantages gained with the axle swap.

The 3.55 gears which these axles came with were an improvement over the 3.07 ratio in my D30/D35 axles. However, it's not a huge improvement. I'd still like to have 4.11 gears with my 33" tires.

Still To Do

I still have to re-route the vent lines to the axle breather tubes. I found an NPT fitting that I could screw into the front D44 but the rear had a very coarse thread. I may have to drill a new hole back there and thread it to NPT specs.

To prevent the dreaded axle-wrap problem, I have to build some kind of anti-wrap bar. I'll probably make one which mounts firmly to the axle housing and is shackled to the xfer case crossmember.

Bronco or Scout II?

After seeing Chris Waterman's Early Ford Bronco axle swap, I think that would be the route I'd strongly consider it for future YJ axle upgrades. It requires less work and is much less intimidating than the Scout axle swap. However, I can take solace in the following benefits over the EB axle swap:

  • Scout front D44s come with disc brakes and large u-joints.
  • The Scout front D44 allows a slightly sharper turning radius.
  • Rear D44 uses 30-spline axle shafts vs. the Bronco's 28-spline units.
  • Rear D44 has a higher pinion, requiring a less severe driveshaft angle.

I'd be hard pressed to say which swap has the overall performance advantage. The point to keep in mind, though, is that there are at least two relatively easy and affordable ways to turn a Jeep YJ into a extremely reliable offroad machine, able to compete head-to-head with the best.

Thanks

I wouldn't have been able to do this swap without help from a lot of people. In particular, I'd like to thank:

John Barron
Louie Belt
Rick Boiros
Rob Bryce
John Edgar
Wayne Foster
Wil Girindra
Ron Gooch
Phil Gough
Herbert Leung
Grant Klavatalks
Ed Mah
John Nutter
Vern O'Connor
Brad Peden
Steve Prinz
Richard Reimer
Chris Waterman
Jim Weed
Paul Weitlauf
Alan Wicker
Jonathan Yim
Jonathan paints the axle housing
Jonathan

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Last modified Wednesday, 01-Dec-2010 09:24:00 MST


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