Regearing to 4.88.. what oil do you guys use?

[Paulocon]

Hello i just regeared to 4.88 and they used synthetic oil.. I’m wondering after the 500 mile break in period which oil you guys are using? I’m getting mixed answers.

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[BDinTX]

Take a look here:
https://www.jlwranglerforums.com/forum/threads/differential-oil.28127/

edit: you’ll continue to get mixed answers

I picked up this:
https://www.amazon.com/gp/aw/d/B000BRCT38?psc=1&ref=ppx_pop_mob_b_asin_title

 

[word302]

Amsoil severe gear.

 

[Jeep’n Jay]

Valvoline synthetic. 75w140 in the rear, 75w90 in the front. Ran it in my last 3 Jeeps, never an issue, only thing I have ever used.

 

[Qjoh5510]

I only use Dino oil in my diffs. Some companies out there state to only use regular oil with their gears. I believe Currie had a huge deal with their axles whining and having failures due to synthetic oil. They said the synthetic oil doesn’t transfer heat as well and caused lack of lubrication. 80-90 in the front and 85-140 in the rear.

 

[CarbonSteel]

50 people respond with 50 different answers.

I recently re-geared to 4.88 and here is what I am doing (yes, I know it is overkill):

-- First 500 miles used the oil the shop installed (Valvoline 80W-90). I gave them Shell Spirax 85W-140, but they hosed up and used the 80W-90.

-- Next 500 miles used Shell Spirax 85W-140

-- Next 1000 miles using Valvoline HPO 85W-140

-- Next 1000 miles using Shell Spirax 85W-140

-- Next 1000 miles using Valvoline HPO 85W-140

-- Next 1000 miles using Valvoline HPO 85W-140

-- Next 1000 miles using Valvoline HPO 85W-140

After the OC at 6,000 miles, I will be switching to Amsoil Severe Gear 75W-110 in the front and 75W-140 in the rear. I seriously considered Valvoline 75W-140 in both but already had a stash of Amsoil.

I had the Shell and Valvoline laying around and based upon the metal these axles generate, I want to thoroughly flush out both axles before switching to synthetic.

I am running UOAs each time just to see how the axle is breaking in.

 

[CarbonSteel]

I only use Dino oil in my diffs. Some companies out there state to only use regular oil with their gears. I believe Currie had a huge deal with their axles whining and having failures due to synthetic oil. They said the synthetic oil doesn’t transfer heat as well and caused lack of lubrication. 80-90 in the front and 85-140 in the rear.

They need to back away from the crack pipe...

 

[DanW]

I only use Dino oil in my diffs. Some companies out there state to only use regular oil with their gears. I believe Currie had a huge deal with their axles whining and having failures due to synthetic oil. They said the synthetic oil doesn’t transfer heat as well and caused lack of lubrication. 80-90 in the front and 85-140 in the rear.

If they blamed synthetic gear lube they are full of BS. That makes no sense at all. There may be a use for dino for initial break-in, but generally, the synthetic would be superior in just about every way.

 

[Qjoh5510]

If they blamed synthetic gear lube they are full of BS. That makes no sense at all. There may be a use for dino for initial break-in, but generally, the synthetic would be superior in just about every way.

I’m no scientist and was full on synthetic for diffs too until I read that. Not sure how they came up with that conclusion but I don’t see a company like Currie just saying that for no reason. They did warranty all cases and took care of their customers when it happened though.

 

[Qjoh5510]

If they blamed synthetic gear lube they are full of BS. That makes no sense at all. There may be a use for dino for initial break-in, but generally, the synthetic would be superior in just about every way.

Okay I did a little digging. After the failures Currie built a special housing so they could measure the gear temp separately from the gear oil during operation. They found that when running synthetic oils the oil itself was cooler but the gears were running much hotter due to the synthetic oils lesser ability, compared to conventional, to extract the heat out of the ring and pinion. So while the synthetic oil itself was able to stay cool and most likely last longer, it did not have the ability to pull the heat out of the gears and bearings like conventional did. Like I said I’m no scientist, but this is a widely known thing that happened. Currie investigated it and found the issue. Dynatrac also recommends conventional gear oil as well.

 

[DadJokes]

Okay I did a little digging. After the failures Currie built a special housing so they could measure the gear temp separately from the gear oil during operation. They found that when running synthetic oils the oil itself was cooler but the gears were running much hotter due to the synthetic oils lesser ability, compared to conventional, to extract the heat out of the ring and pinion. So while the synthetic oil itself was able to stay cool and most likely last longer, it did not have the ability to pull the heat out of the gears and bearings like conventional did. Like I said I’m no scientist, but this is a widely known thing that happened. Currie investigated it and found the issue. Dynatrac also recommends conventional gear oil as well.

Heavier oil at operating temps (centistokes) transfers less heat. This is a known for high end engine builders as well. I suspect this is what was observed.

 

[oceanblue2019]

Heavier oil at operating temps (centistokes) transfers less heat. This is a known for high end engine builders as well. I suspect this is what was observed.

Are you suggesting the synthetic held the design viscosity which resulted in lower heat transfer than Dino oil which would have had a lot more viscosity change (thinner) due to operating temps?

 

[DadJokes]

Are you suggesting the synthetic held the design viscosity which resulted in lower heat transfer than Dino oil which would have had a lot more viscosity change (thinner) due to operating temps?

I only suspect that viscosity “may” have been a factor based on experience. I didn’t conduct the testing so there’s no way to know the competency of the test procedures, equipment, and other variables. Perhaps it did hold viscosity better thus transferring less heat away from the parts and dispersing it. That’s where we would do a tear down, inspect, and repeat with a thinner oil. As long as protection is maintained for the conditions and the time the engine would experience those conditions, we went thinner and thinner sometimes resembling something near the viscosity of water cold out of the jug.

 

[WilhelmSR]

Take a look here:
https://www.jlwranglerforums.com/forum/threads/differential-oil.28127/

edit: you’ll continue to get mixed answers

 

[CarbonSteel]

Okay I did a little digging. After the failures Currie built a special housing so they could measure the gear temp separately from the gear oil during operation. They found that when running synthetic oils the oil itself was cooler but the gears were running much hotter due to the synthetic oils lesser ability, compared to conventional, to extract the heat out of the ring and pinion. So while the synthetic oil itself was able to stay cool and most likely last longer, it did not have the ability to pull the heat out of the gears and bearings like conventional did. Like I said I’m no scientist, but this is a widely known thing that happened. Currie investigated it and found the issue. Dynatrac also recommends conventional gear oil as well.

Without knowing the two temperatures (oil and gear set), it is not possible to glean much from their statements. In the end, synthetic oils handle heat and cold much better than conventionals and the oil in the housing is typically 10°-20°F cooler than the contact points of the gears.

With that said, they would seriously need to pony up some data that quantifies any of their statements related to synthetic oils causing failures and synthetics not handling heat transfer as well as conventionals (thereby suggesting or stating that synthetics do not protect as well as conventional oils).

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