Just got through cleaning the Wagon rear differential and housing, going back together with new axle seals and bearings. Thinking this might be time to take advantage in technology advancements and pick up an extra freebie in the mileage dept. I'm just a little leery that I may create a pinion seal leak. Is there enough gains from the synthetic to warrant the extra expense? I will be towing the Fly and our vintage travel trailer. It's a 10 bolt Chevy rear end, non posi .
Ive run synthetic fluids ina all my vehicles,my OT ford SD has had it since new in both diffs with 190k on it now,has never leaked a drop. The storys about synthetic leaking more than dino are IMO a load of crap. On the other hand, the only good reason to run it in a diff or trans is if you are towing and heat buildup is an issue. Synthetics hold up far better than dino in high heat/load conditions.
Twenty years ago changing to a synthetic oil was a problem with seal leaks. Today synthetics can be mixed or changed to without harm to gaskets or components. The big worry is with anti wear additives or the lack there of due to the reduction of these additives to protect the precious metals use in catalytic converters.
I run synthetic in all my cars, however they all leak. Coincidence ? Maybe, all my cars have 135k and up...... All the seals are new except the pinion seal and it shows no signs of leakage.
Synthetic won't cause a leak, but if you have a small leak, synthetic will usually find it. I run synthetic in all my stuff, except the rear in my 40; it has an Auburn posi and they say not to.
if synth find a leak the seal needed to be replaced anyways is how I look at it . it runs cooler and lasts longer . but smells the same ... and I have changed mineral oil gear oil out on 25 year old /500-750K mile semi trucks that was mineral based to synthetics and never had a leak issue , and that a heavy load and high temp use .
I'm replacing ALL THE SEALS and GASKETS with ALL NEW BEARINGS so I'm leaning towards the synthetic too. But the old mineral based 90w lasted over 100,000 with no issues!
i put it in the rear end (CHEVY) in my 38 leaked some thing awful . took it out put the regular stuff in no leaks. so it is not bs .
I just got a new 9" chunk from quick performance in Iowa with a Trutrac posi. They specifically stated No Synthetic lube. I'm wondering if it has something to do with the gear set initial break in.
I just changed gear oil in my F100. Almost all the oil they had was syn. They had a couple of off brand qts of dino but I needed 3. They said they would probably phase it out because most people want syn.
since there is no real bearings inside the unit , I would say its more of a clinging /cushioning effect the mineral oil has vs the synthetic . synthetics drain off quickly .
So mineral based is better in your opinion for the differential? I'm trying to figure out the best lube myself the more you read the more you wonder?
Hey Hey Roothawg, I don't think that you'll ever work that rear hard enough to justify the extra cost of synthetic gear lube. The wider viscosity synthetics were developed for the almighty MPG numbers for the manufacturers. And to squeak out a little extra fuel mileage for the long haul guys. And remember they can call it a semi synthetic and its still 99.5 % conventional. And it will be quieter with plane old 80/90 in her. Good luck !!!
if you seen how that difs ( tru track) made , you see why , as for a hypoid its sliding faces you want to lube and synthetic will not break down as fast as the molecule chain will not get torn apart and not sticking to the surface will allow a better cooling of the part . and also will lower windage loss he has a point , only reason why OEms use it is for the CAFE STANDARDS , as thye have to sell the vehicle in the form it was tested in , and they look over the average of the total MY sold , not just one . on the semis , we do see the improvements as we check our MPG down to the very minimum ammounts considering the milage we drive a year is 100-150K , and I can say the rear end temps do drop 10-15* but you do not pull a 45K load .
SORRY! Didn't want to hijack your thread Roothawg but I am very curious myself I'm just going to go back with mineral based 90w hey it lasted over 100,000 miles so it should last till I'm gone! HA HA