In the case of aftermarket gears I'd disregard what the vehicle owner's manual says.
Metal bits found in rear diff
- Thread starter kcjaz
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I’m running synthetic. No idea about the diff temp… I should probably snag an IR gun…
First, I'd want to know how they determined your gears were OK. Did they take photos? If so, I'd want to see them. Any surface degradation on bevel gears will make them noisy.
Second, synthetic gear oil is gear oil. Unless it's olive oil, it's OK to use. The second number (140 in your case) is the viscosity at operating temperature. You should see a temperature rise comparing 90 weight and 140 weight oil, but that's not the whole story. Although thicker oil runs hotter due to increased friction, it also insulates metal better than thinner oil. The difference in operation depends on external cooling capacity and oil volume. This is hard to assess in the case of an axle, unless you've got experience with the specific design.
FWIW, when I built 4WD axles for industrial/farm use, the specification was for either 90 or 140 weight. The difference came down to ambient temperature more than anything else. Corn field tractors run hotter than rice paddy tractors. Same axles.
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- #44
Thanks. I don’t think they did much in the way of gear condition or gear setup evaluation. I think it’s more like they didn’t notice anything obviously bad. I think they had a customer saying I think its a bad bearing and that is what they found and all they did was replace both pinion bearings.
I called West Coast Differentials and ECGS. WCD said when they had a service shop, they used 75w-90 in everything (not sure they guy I talked too really knew a lot about oil). ECGS said if they were to build (or rebuild) my diffs with 4.88’s they would use recommend 85w-140. The guy said that is pretty much what they exclusively use unless the client is in a cold (as in below zero) type of climate. This tracks somewhat with your field/rice paddy comment.
Here is a write up on gear oil from ECGS:
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I'm sure your choice of oil will be fine, whatever you choose. As to the condition of your gears, they will work, even with scars on the teeth. They just won't work quietly.
A whine upon deceleration is what my failing 8.2" developed prior to me sending it back to ECGS. First it was the metal bits, then the light whine on acceleration, then it progressed to a light whine under part throttle prior to me sending it back. All of that metal going through your diff likely caused some additional wear. I would expect that it will get worse with time, it's just hard to say if that timeframe is in the thousands, tens of thousands, or hundreds of thousands of miles. Personally the noise drove me crazy, and I was happy to get it fixed.
Regarding the temps, my much smaller 8.2 when towing usually runs around 160F-190F, with ECGS-recommended 85W140. I never really check it when not towing, so I'm not sure what an unloaded temp should be. I would personally not be concerned with a diff temp int he 170s.
Regarding the temps, my much smaller 8.2 when towing usually runs around 160F-190F, with ECGS-recommended 85W140. I never really check it when not towing, so I'm not sure what an unloaded temp should be. I would personally not be concerned with a diff temp int he 170s.
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- #47
Well, I decided to give the 85W-140 a try and switched the front t it. The thicker oil seems to run slightly hotter compared to the 75W-90 as I said above but it’s only 20-30F with no towing highway miles on a cool day. When I got home from the lake (140 miles of 80 mph) the rear differential was 135F at the bearing. The noise is better. Sometimes I think I hear it but then I’m not sure. I’m a bit paranoid now so I think I hear gear noises in every vehicle I ride in now.
Unfortunately, I discovered that my rear locker isn’t working. I checked the air supply and it’s all good to the diff housing. I think they crimped the copper line inside the 3rd that goes to the actual locker when they reinstalled the 3rd. #%$!, back to the shop hopefully tomorrow but for sure Tuesday. Luckily I have a buddy that has a locker on his shelf and he’s letting me have the tube off it so I don’t have to wait for the shop to order it. Wednesday, I head out to Moab, rear locker or not.
Unfortunately, I discovered that my rear locker isn’t working. I checked the air supply and it’s all good to the diff housing. I think they crimped the copper line inside the 3rd that goes to the actual locker when they reinstalled the 3rd. #%$!, back to the shop hopefully tomorrow but for sure Tuesday. Luckily I have a buddy that has a locker on his shelf and he’s letting me have the tube off it so I don’t have to wait for the shop to order it. Wednesday, I head out to Moab, rear locker or not.