Some Questions About Rear Axle (Dana 80) - Dodge Cummins Diesel Forum
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post #1 of 7 (permalink) Old 04-14-2019, 02:56 PM Thread Starter
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Some Questions About Rear Axle (Dana 80)

Fine folks, I've done lots and lots of searching to answer as many of my own questions as possible but I still have a few things to ask to clarify some confusion I have and also ask about sources for some parts.

1. What is the correct technical name for the "limited slip differential" in my Dana 80? I've heard it referred to as Power-Lok and also as Trak-Lok.

2. I've noticed that the "limited slip differential" function on my axle works pretty well in mud and most dirt/gravel/rocks/sand but not well at all in icy or snowy situations; it seems that where there would be a better mix of some grip and some slip it works but on the super slippery stuff the left rear wheel will free spin and the right rear wheel will stay still. If I "feather" in the brakes a bit I can get the right rear wheel to spin some but it is a difficult trick to do with the 5 speed and still effectively shift gears. Does this indicate that the clutches are crapping out on the diff? If not is it normal operation?

3. I've had to replace the rear axle seal specifically on the left side three times in less than two thousand miles. At first I thought it was a bad batch of seals but now I'm wondering whether there is a slight impression in the axle shaft right where the seal touches. I bought the better OEM seals for the next time I replace the rear seals ( I originally bought non OEM seals ) but as I'm replacing the rear seals if I notice that the axle is somewhat scored in the area the seal touches, what is the best place to purchase new axle shafts? I'm assuming everyone around here recommends replacing only with OEM Spicer Axle Shafts?

4. Since my rear brake shoes are soaked with gear oil, what are some recommendations for replacement brake shoes? Also what would be the best source for those shoes?

5. Lastly, if I decided to replace the rear brake cylinders with the GM units, what is the best source for some of those? Is there anything else to replace at the same time just to get some better braking out of the rear axle assembly?

Thanks as always.

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post #2 of 7 (permalink) Old 04-15-2019, 11:17 AM
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The seal does not run on the axle it runs on the axle housing. you can put a speedy sleeve on it. also have you cleaned the vent? it must be clean to relieve pressure.

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post #3 of 7 (permalink) Old 04-15-2019, 01:15 PM
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Originally Posted by turbocruiser View Post
Fine folks, I've done lots and lots of searching to answer as many of my own questions as possible but I still have a few things to ask to clarify some confusion I have and also ask about sources for some parts.

1. What is the correct technical name for the "limited slip differential" in my Dana 80? I've heard it referred to as Power-Lok and also as Trak-Lok.

2. I've noticed that the "limited slip differential" function on my axle works pretty well in mud and most dirt/gravel/rocks/sand but not well at all in icy or snowy situations; it seems that where there would be a better mix of some grip and some slip it works but on the super slippery stuff the left rear wheel will free spin and the right rear wheel will stay still. If I "feather" in the brakes a bit I can get the right rear wheel to spin some but it is a difficult trick to do with the 5 speed and still effectively shift gears. Does this indicate that the clutches are crapping out on the diff? If not is it normal operation?

3. I've had to replace the rear axle seal specifically on the left side three times in less than two thousand miles. At first I thought it was a bad batch of seals but now I'm wondering whether there is a slight impression in the axle shaft right where the seal touches. I bought the better OEM seals for the next time I replace the rear seals ( I originally bought non OEM seals ) but as I'm replacing the rear seals if I notice that the axle is somewhat scored in the area the seal touches, what is the best place to purchase new axle shafts? I'm assuming everyone around here recommends replacing only with OEM Spicer Axle Shafts?

4. Since my rear brake shoes are soaked with gear oil, what are some recommendations for replacement brake shoes? Also what would be the best source for those shoes?

5. Lastly, if I decided to replace the rear brake cylinders with the GM units, what is the best source for some of those? Is there anything else to replace at the same time just to get some better braking out of the rear axle assembly?

Thanks as always.
1) Trac-lok. This link may help answer some questions. http://dodgeram.org/tech/specs/axle/286RBI_specs.html

2) LS carriers work by torque applied and the amount of traction on both tires. Thats why dragging the brake helps force both tires to spin more equally. LS carriers can be very effective but OEM units are usually set with a low static pressure to offer the best on road characteristics. Also, if someone has added too much friction modifier then the clutches will be too slippery to work properly.

3) As mentioned by 1070, Speedi Sleeve might be what you need.

4) Any OEM replacement brake shoes will be fine and trying to clean the oil soaked ones wont work. Also...its important to know that the shoes must be match fit to the interior diameter of the drum. You do this by running them along the interior surface and then sanding the shoe until the entire surface area of the shoe is touching the drum. Otherwise you'll get spongy brake feel and poor braking performance out of the rear drums.

5) You can replace the cylinders with GM 1 ton cylinders but the lines arent a "perfect" match and will require some bending to get the fitment correct. As for what to do for better braking? Make sure the star adjuster is working correctly and the shoes are adjusted correctly and remain adjusted correctly. You do this by assuring the adjuster is installed correctly and works and then applying the brakes or e-brake while the truck is moving backwards. Then make sure the hydroboost system is working good and has quality clean PS fluid in it. Then making sure the front brakes are in good working order as well. Corrosion is a brake system destroyer as it can cause the caliper pistons to stick in both directions. And abusing your brakes will degrade their performance as it changes the metallurgy of the discs/drums and compromises the organic material of the pads/shoes.

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post #4 of 7 (permalink) Old 04-15-2019, 02:21 PM
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The wheel cylinder were a direct fit on my D70. They show in the interchange as being used on all sorts of OEM D70 and D80 applications.

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post #5 of 7 (permalink) Old 04-15-2019, 10:09 PM Thread Starter
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Thank you all for all your advice! I'm going to do a little learning on the speedi sleeve tonight. I'm just running Royal Purple 75w140 without any additional modifier; I don't know if that is a good fluid choice for this axle/differential? As far as the "limitations" of limited slip diffs, when we converted the truck to a Dynatrac Free Spin setup up front we also added a Detroit True Trac. Would that be better than the stock LSD in the rear? Thanks Again.
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post #6 of 7 (permalink) Old 04-15-2019, 10:21 PM
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Youll want the chevy dually wheel cylinders and they are a direct replacment, Ive installed several sets and never had to modify lines. I get them for a 1995 chevy dually, not single wheel.

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post #7 of 7 (permalink) Old 04-17-2019, 08:05 AM
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https://downtofab.com/products/10006...=1608599666713

Try one of these. It's the same seal that dana 70 uses. I am running them in my dana 80 and they are awesome. The skf part number is 28759. Skf calls it a scotseal. I originally used 2 skf seals amd one of them installed hard and started leaking so I replaced it with either a spicer or maybe national equivalent, I dont remember but I liked the second one I used better.

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