As I am always curious about the type and critical oil levels of my vehicles I decided to check the fluids on my differentials and my transmission ('93 Mitsubushi). Differentials were both at acceptable levels and had the usual smell and weight of an 75-85W gear oil.
BUT the transmission was not the same story! Oil level was fine but the sample I pulled was a very thin, fast pouring transmission oil. Almost seemed like a 40w-50w, light amber almost clear in color.
My question is could this be a more modern synthetic transmission oil? I certainly question the popular opinion on this forum that a 75-85W range is acceptable for both diffs and transmission after finding this strange oil filling my tranny.
I have had great luck with Mobil synthetics for both tranny and differential and even the Redline synthetics for older trannys that require a GL-2, 3 or 4 oil.
Any of you guys have any ideas on this mystery oil?
I have english owners manual for this truck. In trans. it calls for 0.73 qts. of 75w-85 0r 90w depends on temp. Differential-front 0.83qts. 80w-90
rear 1.34qts. 90w. I hope this helps.
My Japanese Mitsu owner's manual calls out "SAE 75W/85W (GL-4)" for both the transmission and transfer case. For the differential, SAE 90 above 10 degrees C, SAE 80W below 10 degrees C. When I had checked my tranny level, seemed like normal gear oil...not sure I can answer your question about that.
I ended up using Mobil synthetic transmission oil as I had some on hand and it has worked great in the farm truck (a '95 Isuzu diesel NPR). It has the same consistency of the oil I drained from the tranny when I checked it. I don't have to worry about changing it for a long time now as the synthetics can go so long and are much more stable over that extended service life.
Caution with synthetic's... it will break down seals that have "real rubber" content.
The only seals syn. oils will affect is the old style hemp seals used back in the 1940's and earlier. Syn. oil in older engines may clean out solid deposit matter in seals and make the engine use a liittle oil. But if you install a syn. oil in a trouble free, low mileage engine test have shown nothing but positive effects. Increase h.p., lower running temp.,better mpg. I do not own nor have any relation with amsoil other than being a customer of them. I highly recommend amsoil. The best oil on the market hands down. We have beem running amsoil in formula one road racing
engines since 1978. We have proven that amsoil is the best oil we could find on the market.I also run amsoil in everything i own--chain saws,4 wheeler, tractor,chevy truck, bmw 330i, welding machine, bass boat, jet boat with a 455ci olds rated @420hp., I install amsoil in all the mini trucks I service for retail sale( low mileage trucks), and I run the amsoil gear lube in all the trans. reguardless of miles, I my experience, installed in good running equipment syn. oils are the best and amsoil is the best of best in syn. oils.
I echo the above...except I am a Mobil 1 and Mobil Delvac 1 fan and also use their synthetic transmission and differential fluids. Never a problem. I also like the Mobil 1 High Mileage oil for use in engines with some miles. It has seal enhancement additives that actually help keep seals pliable! Can't beat that!
To get the most out of your oil get it sampled. Otherwise you are shooting in the dark. We sample everything on the farm. Tractors are 150% normal interval, cars up to 200% and well engines at 400-500 hours on 5.9 cummins power units. The math....500 hours at 75 mph is 37500mi. Forget to tighten an air cleaner once and the next sample will be high in silicon (dirt).
I personally think that if it reads seal enhansments it should say solvents. They cause seals to swell and temporarly stop leaking.
Use caution on gear lube in transmissions. For example Ford changed from a GL5 gear lube requirement to Type F, similar to ATF, in the late 80's. Had a hired man change an 89 ford to 85/90 from type F. Ran for a few months. Tranny failed from too thick of fluid. Transfer case lasted a bit longer. As for damaging seals, not by synthetics. In a conventional oil the molecules are different sized and larger. A synthetic oil has uniform molecules and are smaller. Smaller oil molecules will excape where the large conventional oil molecules won't. That is where the leak comes from. A full synthetic oil will also allow a smaller micron filter to be used. Do not use synthetic filter with conventional or synthetic blends. Too fine of filter media.
Goretex will allow air molecules through better than larger water molecules and you feet stay drier.
so what should i run in transmition/transfer case on my 98 suz carry?
i put 140 in my rear diff cuz the fluid in there looked pretty bad and all i had on hand was 140. should i change it to 90?
I sure would...unless you live in the desert where it never gets below 60 F.
Multi-weight synthetic or if you like the traditional oils, a 75-80W gear oil.
and the tranny requires the same?
Hyploid multi-weight oils are acceptable for both tranny and F/R differentials. More modern synthetics break this rule as the tranny oils are typically like a 40-50W oil while the differential oil is a bit heavier. The synthetics are noted for their ability to run longer thus reducing having to change them as frequently.
just changed all my drive line oils over to castrol full styntec 75w-85, and driving on the weekend it seemed to roll better and shift smoother and the 4 wheel drive locks up even faster, working good for me.
if i use 75W85 for both front and rear differential for my 1990 sambar, would that be affect anything?
the trans and the transfer case are one part using the same oil on my mitsu and everything works great. the pore rate of 50w motor oil at room temp seems the same as full syntic 75w85, so you should not have any trouble with your blocking rings when it gets cold.