MILD THUNDER

iTrader: (3)

Anyone running these heavier oils in their drives? I know that Ford, and some other manufacturers, have specified 75w140 when towing heavy, in the rear diffs. I would think, that your typical sterndrive that is pushed pretty hard, whether it be due to HP, boat weight, prop style, etc, is a pretty severe load. I know the bravo drives that dont hold alot of fluid, can get pretty friggin hot. People think 75w90 is some super duper thick fluid, but when its at 200+ degrees its pretty watery thin.

I've been running your typical 80w90 in my SSM IV drives for the past few years since I've owned them. One drive was getting a little fuzz on the magnet at oil change. Thinking about going to the thicker oil. I can care less if it costs me a speed loss, IF it protects the gears from the severe loading/unloading (throttling) in a heavy boat with 800HP per side.

BUP

iTrader: (9)

I use to run Synergyn 80w-140 Syngear II back early 2000's. Things I notice about using was - of course harder to pump in the outdrive and took a long time to drain when changes. Next the outdrive was quieter under load compared to Merc Hi perf gear oil. It also came out very clean and no material on the magnets.

A friend of mine who does oil analysis use to do all my oil analysis and the reports came out very well. I never had gear oil tested in anything over 575 hp. I will say this Mercruiser Gear oil High perf new and used samples were not impressive according to my friend. The first question he asked was, how much is the cost of their gear oil. After I gave him my cost (dealer) he laughed and said for the money they charge, you could do a lot better. I have not kept up with oil analysis service in years.

pqjack

I run 75w110 Amsoil

MILD THUNDER

iTrader: (3)

I see the newer Ford trucks call for 75w140 in their diffs. My 2008 Grand Cherokee, calls for 75w140. My 1997 Chevy dually calls for 75w140. My Lincoln Town Car calls for 80w90, BUT, if it were a limo, with the same diff, they call for 75w140.

I cannot see any of those gears, being under as much stress as my boat drives, being held at full throttle for long periods with 800HP per side, in rough water.

thirdchildhood

iTrader: (6)

You might be on to something. My '08 F150 calls for 75w140 synthetic gear lube in the rear axle. Do different oils affect operation of the cone clutch in the drive? Could there be any other drawback? (besides a little speed loss)

MILD THUNDER

iTrader: (3)

I don't have any clutches in my drives, but that seems like a good question.

I was shocked to see 75w140 specd on my jeep cherokee. Esp with how hard the car manufactures try to meet mpg concerns.

I know people hear "90" or "140" and they think it's sludge. But a 90 weight gear oil, isn't like a 90 weight engine oil. I'd think if my Jeeps diffs been working just fine with 75w140, in the extremely cold winters we get around here, for the past 150k miles , it should be ok in my drives that never see operation in subzero temps. ? Just thinking out loud here

MILD THUNDER

iTrader: (3)

With the bravo drives obvious heat problem (low fluid capacity, white chalky buildup, need for drive showers), is the 75w90 getting too thin at high temps?

We often debate the brand of oil used to our ears bleed. But nobody ever discusses the weight of the oil?

buck35

Great post mt
this could use some testing, do you gain heat with a thicker oil or after warm does it all even out plus the added protection

ICDEDPPL

iTrader: (1)

'YOUR OIL IS FLOWING TOO FAST!!!'

Good idea on slowing it down with thicker oil ..... = more cooling

MILD THUNDER

iTrader: (3)

Heres a good read on gear oils. Looks like out of the group of gear oils, Amsoil Severe Gear took first place.

http://www.lastgreatroadtrip.com/wp-...comparison.pdf