I just installed a set of 3.55's and have some interesting insights on a possible design issue with the differential housing. Here are the details:
1. The bolts that hold the diff cover to the diff housing are M10 X 1.5. They are approx one inch long, but, do not have threads at the beginning. That area is tapered and lacks threads. The bolt also has a captive washer that is approx 1/8" thickness.
2. The cover thickness is approx 1/2". What I am leading up to is that the bolt does not thread into the housing much more then 3/8". That usually will be enough if everything is perfect. The recommended torque is 35 ft-lbs.
3. I think Dodge used a standard bolt that almost fit and did not bother to get a custom length bolt that would thread into the housing further. As stated this will probably work most of the time.
4. Here is the possible problem - the diff housing and cover are machined surfaces. There is no gasket, however, the recommendation is to use silicone on the mating surfaces. Gear oil is the worst fluid to make leak proof, it attacks everything. Permatex makes a silicone specifically for gear oil. The recommendation is to put a 1/8" bead near the outside of the machine surfaces and to put a circle of silicone around the bolt holes. I think there are 9 bolts.
5. I applied the silicone and set an electronic torque wrench to 35 ft-lbs and proceeded. A couple of bolts felt funny as though i reached their elastic limits. I check the torque wrench and it was set at 35. I continued and stripped a thread in the housing.
6. I pulled the bolt and that thread hole had silicone inside. The silicone acted as a thread lubricant ( which is bad) and the result was the stripped hole. When using a lubricant on a bolt, the torque should always be reduced. That is why you see so many stripped spark plugs holes in aluminum heads when anti-seize is used.
7. Obviously if the silicone did not creep into the hole there would be no problem, but, if you cut back on the amount, you may then have a leak. In addition, there was not an over abundance of silicone used. The problem I have is the fact if the bolt was longer and threaded further into the hole, probably it would not have stripped. Again, they probably used an off the shelf bolt and didn't bother to purchase a bolt that was longer had more contact with the threads in the hole. As stated previously, the bolt only threads in about 3/8".
8, The fix was pretty easy, the hole is threaded at least 3/8" deeper than the bottom of the factory bolt when it is fully seated. I merely used a thread chaser (not a tap) to clean out the threads and bought a bolt that was 1/4" longer and it holds the 35 ft-lbs. I also made sure the silicone was cleaned out of the hole.
In summary, the diff cover bolts are too short for the recommended torque. They may work most of the time, but, if the silicone or any lubricant gets into the hole you could strip the threads in the hole. I may replace all the bolts with a product that has a longer threaded area.. I will also make sure that I remove any silicone before I torque the bolts.
1. The bolts that hold the diff cover to the diff housing are M10 X 1.5. They are approx one inch long, but, do not have threads at the beginning. That area is tapered and lacks threads. The bolt also has a captive washer that is approx 1/8" thickness.
2. The cover thickness is approx 1/2". What I am leading up to is that the bolt does not thread into the housing much more then 3/8". That usually will be enough if everything is perfect. The recommended torque is 35 ft-lbs.
3. I think Dodge used a standard bolt that almost fit and did not bother to get a custom length bolt that would thread into the housing further. As stated this will probably work most of the time.
4. Here is the possible problem - the diff housing and cover are machined surfaces. There is no gasket, however, the recommendation is to use silicone on the mating surfaces. Gear oil is the worst fluid to make leak proof, it attacks everything. Permatex makes a silicone specifically for gear oil. The recommendation is to put a 1/8" bead near the outside of the machine surfaces and to put a circle of silicone around the bolt holes. I think there are 9 bolts.
5. I applied the silicone and set an electronic torque wrench to 35 ft-lbs and proceeded. A couple of bolts felt funny as though i reached their elastic limits. I check the torque wrench and it was set at 35. I continued and stripped a thread in the housing.
6. I pulled the bolt and that thread hole had silicone inside. The silicone acted as a thread lubricant ( which is bad) and the result was the stripped hole. When using a lubricant on a bolt, the torque should always be reduced. That is why you see so many stripped spark plugs holes in aluminum heads when anti-seize is used.
7. Obviously if the silicone did not creep into the hole there would be no problem, but, if you cut back on the amount, you may then have a leak. In addition, there was not an over abundance of silicone used. The problem I have is the fact if the bolt was longer and threaded further into the hole, probably it would not have stripped. Again, they probably used an off the shelf bolt and didn't bother to purchase a bolt that was longer had more contact with the threads in the hole. As stated previously, the bolt only threads in about 3/8".
8, The fix was pretty easy, the hole is threaded at least 3/8" deeper than the bottom of the factory bolt when it is fully seated. I merely used a thread chaser (not a tap) to clean out the threads and bought a bolt that was 1/4" longer and it holds the 35 ft-lbs. I also made sure the silicone was cleaned out of the hole.
In summary, the diff cover bolts are too short for the recommended torque. They may work most of the time, but, if the silicone or any lubricant gets into the hole you could strip the threads in the hole. I may replace all the bolts with a product that has a longer threaded area.. I will also make sure that I remove any silicone before I torque the bolts.
Last edited:
