Category: Car repair

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Dana 30 gears

Dana 30 gears

I finally completed the regear of Jennifer’s XJ the weekend. This has been a much longer project than I first expected.

She has had a gear set on her shelf for a few months now waiting for me to install it. However, we had to collect all the various parts needed. The first being a matching set for the rear. Once the rear gears were in, I finally proceeded to work on the front.

I began by stripping down the old gears. This swap involved going from the stock 3.55 gears to 4.10 ratios. There is a different carrier required for the 4.10 gears due to the thickness of the ring gear.

The first step was to move the spider gears from the old carrier to the new one. The ring gear had to be removed to provide clearance for the cross pin to be removed. The cross shaft is held in place by a roll pin that has to be driven out with a punch. My proper sized punch seems to be missing, so I used an old drill bit instead.

With the spider gears transferred, I then mounted the new ring gear on the carrier. I removed the bearings from the old carrier to retrieve the shims being careful to keep them on the correct sides. I took a set of slightly worn bearings and reamed out the inner race with my die grinder until they slipped on easily. I used these for the trial fits before installing the new bearings.

I pressed off the old pinion bearing to retrieve the slinger under it. I then heated the new bearing and slipped it onto the new pinion with the slinger under it. I noticed after it cooled that I could rotate the slinger slightly so I tapped it down tighter with a punch and hammer.

I used a punch to drive out the races from the housing. There is an oil baffle under the inner pinion bearing that will be destroyed in the removal process. We had some trouble locating a new baffle. Although they cost less than two dollars, no one in town had one in stock. Most 4×4 places wanted $8 to $16 to ship one. We finally found a place with reasonable shipping and bought two just in case.

One of my XJlist members gave me the tip to measure the oil baffle and replace it with a shim during the set up process. This keeps you from destroying more of these baffles while performing the set up tests. My baffle measured exactly 0.020 inches so I used a 20 thousandths shim in place of it during set up.

The pinion depth on the Dana 30 adjusts by shims under the bearing race in the housing. This means driving the race in and out until you get the shims right. I took and old outer pinion bearing and reamed it out so it would easily slip on an off during set up. I assembled the pinion with bearings and slingers but no preload shims. I snugged up the yoke nut to take out all end play.

I then set the carrier in place. I used a soft hammer to drive it into the housing rather than using a case spreader. I set the caps in place and tightened them down. I then coated some of the teeth with the yellow marking compound that came in the overhaul kit. I then rotated the assembly around to get a pinion depth pattern.

I had used the chart in the Jeep FSM to select the pinion shims. Basically each pinion gear is marked with its variance from zero depth. In this case the old gear was marked 2 and the new gear was marked 6. This meant I needed to remove 4 thousandths of shim from the shim pack under the bearing race. I measured the shims that came out and removed a 10 and added a 5 to make up close to 4 difference. I then added a 20 to substitute for the baffle.

I almost cheered when this shim pack gave a beautiful wipe pattern showing the contact patch right in the middle of the gear. I also found that the yellow gear marking compound which is actually made by GM makes a much better mark that the Prussian Blue I have used in the past.

I set up my dial indicator and verified the back lash. It was a bit hard to read the indicator but it was well within the .006 to .009 spec in the manual. That meant the same shims from under the old bearings would work.

I almost wished I had put the baffle in. I carefully drove out the race and replaced the shim with the baffle and reinstalled it.

I prepared to set the pinion preload with the new bearings. That is when I noticed that the rebuild kit contained the wrong outer pinion bearing. It was one for a low pinion Dana 30 rather than the XJ style high pinion. This difference has plagued this install from the beginning. (See the earlier posts.) I obtained a replacement from Advance Auto but not without some difficulty getting the right part even with the old bearing in hand.

I prepared a set of shims based on what had come off the old pinion. These proved to be way too tight. I then built a thicker stack of shims. These were too loose. The pinion preload is supposed to be between 20 and 40 inch pounds when installing new bearings. The preload is adjusted with shims on the XJ contrary to what the FSM says. Some Dana 30s use a crush sleeve like the Dana 35 but not this axle.

I then made up a shim pack that measured 55 thousandths. This was too tight, so I made one that measured 60 thousandths. This was just a bit too loose. Luckily, I do have an inch pound torque wrench so I could make accurate measurements. I would have been very frustrated if I were trying to use weights and a string as some forums recommend.

I came down to where 55 was too tight and 59 was too loose. I was not able to build a pack in between with the shims I had. I finally gave up a made it just a bit loose. I hammered in a new seal and made the final install of the yoke. I had upgraded her to the U bolt style yoke from the strap style while we were in there.

I then replaced the set up bearings on the carrier with new ones from the rebuild kit. I once again used my soft hammer to tap the carrier into the housing and torqued the cap bolts to spec. I rechecked the backlash and pinion wipe pattern with the new bearings. Nothing changed.

With everything in place, I left her put the new gasket on the newly pink diff cover. She bolted it up and filled the housing with oil. She then put up her drive shaft and skid plate.

A test drive indicated that the new gears ran nice and quiet. We then took it for a quick run in the woods and enjoyed the new crawl ratio.

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Jeep Speedometer Calibration

Jeep speedometer Calibration

When changing gears or even tire sizes, the speedometer calibration will change. Jeep Cherokees have a gear driven speedometer sensor even after the speedometer head was changed to electric. A gear dives a pulser unit that sends a signal to the dash.

The gear is mounted in the transfer case on the 4wd models. There are two different gears used. There is a short shaft gear used in the 1993 and later Cherokees and a longer shaft use dint he earlier versions. The long shaft version is the same gear used to drive the cable speedometers used since the 1970’s.

The gears have different tooth counts to provide different ratios to calibrate the speedometer. They are also color coded.

To determine the gear you need you can reference a chart of tire size and gear ratios like the one on Marcus Ohms site. You can also calculate the one you need if you have an accurate speed reference like a GPS or a measured mile.

To select the proper gear for Jennifer’s Jeep, I used a GPS to get a speed reference. I drove at several steady speeds and recorded the indicated speed on the speedometer and the actual speed given by the GPS. Note that most GPS units only update the speed every three seconds, so you have to maintain a steady speed to get an accurate reading.

In this case I found that the speedometer showed 70 when the GPS showed 57 MPH. 55 MPH on the speedometer showed about 45 on the GPS. This gave me a ratio of about 1.2 to 1.

Next I pulled out her drive gear to see what tooth count it was. The gear is held in place by a clamp and a single bolt. There are four different ways to turn the housing so pay attention to which slot is toward the bolt when removing the housing. You can count the teeth but the number is stamped o the gear as well. In her case is as 29.

29 times 1.2 gave 34.8 or rounded up to 35. This matched the chart on Marcus’s site so we set about finding a 35 tooth gear.

Prices vary widely for these gears. My supplier only stocked the short shaft so we had to look elsewhere. Surprisingly the cost from the Jeep dealer was very reasonable and about half the cost of many aftermarket venders. Jennifer was able to source a used on from Ebay for half that however.

Hers came from an AMC Javelin demonstrating the wide variety of cars and trucks that use these same gears. The 35 took gear is coded orange.

To install the new gear, I had to rate the housing to a different position. The gear tooth range for each position is clearly marked o the housing so it is just a mater of making sure it is aligned with the right slot.

Now she has an accurate speedometer reading for her 33” tiers and 4.10 gears.

[phpbay]jeep speedometer gear, 10[/phpbay]

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Where was your car built?

Where was your car built?

I remember one day overhearing some one bashing another guy over him not buying an American car. He was complaining that the fellow with the Nissan that he was taking jobs away from American workers. The argument ended when I pointed out that the Nissan was built right here in Tennessee and the fellow doing the complaining drove a Chevy built in Mexico.

These days it can be confusing as to what constitutes an American car. I know for sure my Jeep was built in the USA. The 1 in the fist digit of the VIN number confirms it as well as the door tag that says “Made in the USA.” Surprisingly, my Eagle Talon that is really a Mitsubishi is also “Made in the USA.”

If your VIN starts with a 1, 4 or 5 then your car was built in he USA. If it starts with a 2, then in Canada. A 3 means Mexico. A 6 would mean Australia. J is for Japan and K for Korea. Wikipedia has more details.

Here is an interesting video that points out the seeming contradictions about what we consider an American car and what we consider a foreign made car.

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Replacing the electric fan on a Jeep Cherokee

Replacing the electric fan on a Jeep Cherokee

It is funny what wears out after 340,000 miles. The electric fan on my XJ has been making a noise all summer. I can always tell when the AC compressor kicks in because the fan is so noisy.

When the Freon got low and I needed to top it up, I really did not want to listen to the noisy fan while I waited for the can to empty. So I looked around at the parts Jeeps and found one with a good fan.

All I had to do to remove it was remove the two 8mm headed bolts at the top, disconnect the wire and lift it off the locating tabs. To reinstall it in my Jeep, I first disconnected the radiator overflow hose to make it easier to slip into place. One side of the fan is wider than the other and you have to warp it just a bit to get it to slip in and lock the tabs at the bottom. After a couple of tries, I got it to slip into place properly.

I tightened up the bolts, put the hose back on and connected the wire. When I turned on the AC again, it was much quieter.

If you are buying a new fan to replace yours, look into the later model fan with the curved blades. These drop right in place in your older Jeep. They are supposed to flow more air and run quieter.

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Summer Safety Slogan

Summer Safety Slogan

This summer I have had more than my fair share of injuries in the shop. It may be the heat. It may be the humidity. Louise Hay suggests that accidents and injuries are responses to anger and heat can trigger the emotion of anger.

So far this summer, I have burned my ankle with hot metal and injured my shoulder when a heavy drive shaft fell on it. In the first case, I was not wearing the proper protective equipment. In the second case I was simply not taking proper precautions.

I have read psychological reports that suggest that the summer heat has an effect on mood. In some cases the heat can cause depression. In other cases it has been links with an excessive feeling of mental fatigue. We have all observed that tempers flare more as the temperature rises.

I am sure dehydration plays a role in increasing accidents as well. I can see my own mental function start to fade and my muscle coordination also diminishes when I am dehydrated. These factors could easily contribute to accidents and injuries.

So in the summer heat my advice is to slow down, take more breaks and drink plenty of fluids. Take an extra amount of time to visualize the job process including things that could go wrong and take measures to prevent their occurrence. Wear the proper protective clothing even if it is hot.

If you fail to take proper precautions to deal with the added stress of summer heat you will then need to head my favorite safety slogan: “If you are gonna be dumb, you gotta be tough!” Have a safe summer.