Hi,
I have a 1998 toyota tacoma 4x4. I was wanting to change the rear diff oil. I have been reading other posts on what weight of oil to use and there are a few different answers. I was wanting to use Mobil 1 syn. and was curious what is the correct weight to use in the rear diff.

Thanks,
Craig

 

75-90

 

SYNTHETIC !!

Imo is the best in everything

 

75-90 syn. Amsoil Severe Gear. We run it it our race cars with no rearend failures since using it.

 

Any comments on how the Amsoil products compare to Redline?

I've had good luck with Redline MT90 in my manual tranny, and 75-90 gear oil in the diffs.

 

Try this its the gear lube test they did on all the gear lubes:
https://www.amsoil.com/lit/g2457.pdf

 

A close friend of mine who works at the dealership says he pulls out all synthetic gear oil from diffs and replaces with dyno. Apparently there have been a huge increase of blown diffs, he feels its the synthetic, but, ti could be other things.

 

We run it (Amsoil) in all our late model dirt cars and we have not had a failure or a oil related failure since using it. Over 5 years not a month or two.

 

Yeah, he says he gets about 3-5 cars a week with broken ring and pinions. Ever since the factory started using synthetic gear oil. He was saying that it doesn't hold up as well under high pressure. He's been a gear head for 45 years, so he's sort of old school... Thing is that he knows (close to) everything about anything about cars... Just throwing that out there. Just an experience of mine, it may not have any relevance.

He made a good point though... Which is that we've used dyno oil for close to 100 years, and as long as you keep up with the maintenance, everything will work fine. Plus, it costs less. Dirty oil is dirty oil, no matter what, you need to change it.

 

where's mkgarrison to push his views on the 140? i'm sure he'll chime in soon for ya on that subject

 

And how does synthetic oil exactly break them?

 

3-5 cars a week? Something funny there$$$. Im sure our race cars put a hell of alot more abuse and shearing forces on the (gear lube)than passenger cars and trucks. Bouncing a truck off road, Spinning,bouncing up and landing down again breaks ringears and drivetrain parts usually a u joint.Alot of people are buying 4x4 trucks without a clue and think they can take anything they throw at them. We have been making cars for 100 years also, you wouldnt drive a modelT everyay as your DD if there was something better.

 

The molecular bond not being as strong (and preventing correct lubrication) under high pressurization/heat.

I'm NOT advocating this. I am just offering another side.

 

I've been biased towards Dyno after my bad experiences from Amsoil as well. I've never had problems with dyno oil ever. The first year with Amsoil, and 3 oil changes was the first time I've ever had problems in my life.

For instance, this was with amsoil in the diff: (Probably had nothing to do with it though...)



And after an Amsoil engine flush, and switched to synthetic, all my engine seals weakened and started leaking.

My next new car I will use synthetic though from the get-go. I don't think it is wise to switch to synthetic after using dyno in a vehicle due to its lack of lubrication. Dyno is much thicker and higher quality imo.

 

How many miles did your engine have on it?
Did you have any or previous UOAs done on it?
How much crud did the flush flushout? Evedentlty it did its job
Have you read the waranty. If it was Amsoil related they wil pay for it. You said proly not and i doubt it also so why bash it.
What were you doing when it broke?
Amsoil doesnt cause leaks, prolly enough sludge and gunk from oils you used in the past got cleaned out. If seals started leaking it was a underlying problem anyway.
Personally I have never had a leak start from using Amsoil, or customer wise that i change the oil in
Is it true that installing AMSOIL or other synthetic oils will cause my engine to leak oil?
Answer: In modern vehicles, there is no risk of AMSOIL motor oil leaking. In fact, AMSOIL motor oil is fully compatible with modern seal materials. It is properly formulated to condition seals, keeping them pliable to prevent leakage.

 

Thats very abstract. So what potentially can happen with synthetic? Will the teeth sheer off? Will something overhear and melt? Like in real terms, not theory on the molecular level.

I'm not advocating either dino or synthetic, both will work just as well as the other, and most toyotas would be heaps of rust before the effects of "inferior" choice of lubrication in the diffs will show up. Everyone stresses so much about lubrication when realistically all they'll be doing is replacing electronic sensors and normal wear & tear items parts during the life of their yota

 

i use amsoil severe gear mix of 75/90 and 75/140 (50/50) with no issues and smooth... the newer 75/90's are thinner than previous blends (this goes for most synthetic gear lubes) look it up. its on the thinner side of the weight.. amsoil came out with 75/110 which is the old 75/90 weight..... if any of you dont believe me please look it up and research before you talk trash... go to amsoil and find out yourself

 

I gots amsoil 75w110 in my front and rear.

I tow a lot.

 

OP: Use 75-90

Myself, i use Royal Purple synthetic in my Figure 8 race cars in the transaxle. No problems yet, and this car gets ABUSED!

 

he doesnt have to use 75/90.. he could use 75/140 if he wants with no harm... if its just an everyday driver then 75/90 is fine for fuel mileage. BUT if he tows, offroads and etc a heavier weight would be ideal.