I will be making a trip this weekend and while I am there I am planning on changing my differential fluid. I have a 1996 Chevy Blazer without a G80. My manual calls for 80W-90. I have found locally 75W-90 in Royal Purple and Mobil 1. Can I go to the 75W-90 and not harm anything or should I stay with a 80W-90??
Question on which gear oil??
- Thread starter DoubleDee
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75w90 synthetic is a great replacement for 80w90. I have 75w90 amsoil or mobil 1 in both my vehicles.
I'd go with a synthetic GL-5 75W-90.
75w90 will be perfect for your blazer.
Just make sure you clean out the old stuff really well and on the rear diff spray it out good with brake cleaner and allow it to evaporate out. This is if you are removing the back plate off of it.
I have a 98 chevy truck with the same rear diff as yours and have run Mobil 1 75W-90 fluid in both front and rear for years. Of course I can't tell you if it helps because I just had to have the pinion bearings replaced in the rearend with only 77,000 miles on the truck. This is on a vehicle that has seen very minimal hauling and towing and has had the rear end fluid changed regularly.
I might have just gotten a bad rearend but I doubt I use Mobil 1 again. I think I might just stick to a dino oil and change it more often.
Wayne
I might have just gotten a bad rearend but I doubt I use Mobil 1 again. I think I might just stick to a dino oil and change it more often.
Wayne
Although I am now a firm believer in synthetic fluids, including diff gear oil, FWIW, a local diff/transmission shop here has said they do not recommend synthetic gear oil for the diff's.
The claim they made was that they see a lot more bearing trouble with synthetic gear oil, as opposed to the 80w-90 dino. So, even though GM calls for 75w-90 synthetic fluid for my G80 diff, they wanted to put the 80w-90 dino stuff in. I politely said "no, thank you".
I don't know what factors exactly to look for in a diff lube, but the specs posted for Mobil 75w-90, don't seem that great: 100 degree C vis of 15.2, and flash point of 347 dgerees F.
Bob W.
The shop that repaired the rear diff on my truck recommends synthetic so I don't know who is right. They told me they see alot of pre 1999 10 bolt chevy rearends with bearing problems because supposedly the pinion bearings in these diffs are too small. They said they don't see the problems in the new body style chevys because they use a bigger pinion bearing.
I used to be a big synthetic fan, especially Mobil 1, but after not getting very good oil analysis results on the engine oil and now this problem with the rear end, I think I will just stick with conventional lubes. I don't think my luck will get any worse.
Wayne
I used to be a big synthetic fan, especially Mobil 1, but after not getting very good oil analysis results on the engine oil and now this problem with the rear end, I think I will just stick with conventional lubes. I don't think my luck will get any worse.
Wayne
I was set on using the Mobil 1 since it is easy tp get. I am a little concerned about the wear that has happened with other diff's. What about the Valvoline blend??
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