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February 2005 4x4 Tech Questions - Tech Line

Posted in How To: Tech Qa on February 1, 2005
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Question: I have a '79 Ford reverse-cut Dana 60 that I purchased out of a junkyard. The shafts were centered in the axlehousing tubes with the stock open differential. I installed a spool (it was being installed with hydraulic steering to compensate for the understeer problems) and slid the shafts in to find that they would go all the way in but both sides barely touch the inside front of the axletube.

Finding this unacceptable, I sold the spool and went with a Detroit Locker. When the shafts were slid in, the problem was reduced and the shafts could be pulled back to center due to the slop of the dog clutches in the locker; as the spool had no moving parts this was not possible when using that.

I reinstalled the open carrier and, due to slop in the spider and side gears, the shafts would not move anywhere within the tubes. I tried checking for bent tubes but they appear to be straight. It also puzzles me how both tubes would be bent similar distances backwards even though the lengths are different. If a collision with a ledge or curb caused this I would expect the longer tube to have been bent more due to the additional leverage working against the long tube. I would also have expected damage elsewhere in the axle, namely a broken knuckle. These tubes are 1/2-inch thick, as you may know.

I never noticed this type of problem with my D44 but was curious about your thoughts about it. Also, my fear is that even though everything went together (hubs, lockouts and so on) the dog clutches inside the locker may not be meshing as they should, due to having to pull the shafts backwards to line up the hubs and lockouts. The shafts were replaced with new shafts due to pitting on the seal surfaces so I'm sure they're not bent.
Chris Harrington
Ashland, Kentucky

Answer: Wow, that's an interesting problem, and one that puzzles me. The tubes have to be bent-that's the only thing that I can think of. OK, maybe there's one more thing. The area where the differential rests maybe was not machined properly so that the differential does not sit in deep enough, but then I would think that the pinion gear would not mesh properly with the ring gear.

I guess my question to you is, just how did you check out the tubes for being straight? The only real way that I can think of is to machine bushings to go into the outer ends of the tube, then use an alignment bar with the proper size bushings in place of the differential bearings. When you put the bar in from one side to the other and if the bar doesn't line up, the housing is bent.

Yes these axletubes can be bent and broken. I built a rearend from one that had been crashed so hard that it actually broke the tube on one side and bent the other as well as egg-shaping the area where the tube pressed into the housing. I ended up cutting out the tubes, machining a special tube insert for the housing and installing new tubes. (I should never have used it; it was free, but way too much work.)

Here is a little trick if you're working on a semi-floating rearend some time and want to check it for straightness. On each end of the housing flanges bolt on a straight piece of, say 2 x 2 x 1/4-inch angle, about 4-feet long or longer. Mount these so that they are parallel to each other. Then measure from one to the other at each end and compare the measurements. If they are different, the housing is bent.

Question: I have a '74 Chevy 4x4 which I thought was a 1-ton, but upon inspection I see that on the front differential it says 44-50. I am at a loss as to what that is. I can find a Dana 44 and a Dana 50. I have been told that there is a regular 44 and a heavy-duty 44. Is the only difference the hubs, or is there more to it?
Dave Ferguson

Answer: A quick way to tell if your front end is a 44 or a 60 is to look at the bolts that hold the front cover on. If the bolt head takes a 1/2-inch socket, it's a 44, while if it requires a 9/16-inch socket, it's a Dana 60. Chevy 1-tons always used Dana 60 front axles. The 3/4-ton K20 models used a Dana 44 with larger axletubes and larger steering knuckles that accepted a bigger hub and spindle assembly with the eight-bolt pattern. (You Ford and IH owners don't have to write to correct me, as I know there were some Dana 60s used with 5-on-5.5 bolt patterns for the heavy-duty 1/2-tons.) There are a lot of differences between the various Dana 44s. Some have larger-diameter axletubes than others, while some have thicker tubing. Those used on 3/4-ton trucks have larger and heavier knuckles, hubs and spindles. Some have a bit more material around the housing. Naturally, there are different axle lengths. Scouts, for instance, have heavier-wall tubing than Jeeps and have longer arms on the steering knuckles as well as eight bolts, instead of six, for the spindle. Some 44s used smaller axle U-joints then others. There were closed-knuckle designs where the axle U-joint was in a sealed housing and lubricated with gear lube. There are 44s that have a reverse-cut gear with the pinion at the high side of the housing versus mounted lower. Generally speaking, ring gears are interchangeable, except for the high-pinion/low-pinion designs, but not always. There are some strange aluminum-housing 44s such as used in Jeep Grand Cherokees and other vehicles that are a bit different and take a different gearset and differential setup. And then there are some even more strange combinations, such as the Ford-used Dana 50 that has Dana 60 outer components and a special ring gear that is the same diameter as a 44.

Question: I had a 4-inch lift put on my '98 Wrangler and was wondering if the upper suspension arms should be left stock, or if I should take them off. Can you please comment?
Jody Allen

Answer: What I hope you mean is, should you replace them with heavier units, not remove them entirely. I think that the answer to that question depends upon how hard you use your Jeep. Generally speaking, the stock upper arms will hold up just fine. If you plan to seriously abuse your Jeep, then go with some aftermarket arms.

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