Synthetic oils OTHER than engine oil

[79300sdtd]

I am having my tranny rebuilt and i was wondering if i should replace all the oils with synthetics. I plan on Mobile 1 ATF for the tranny. I have also read on here that this is good for the Power Steering too. is that correct?

Also should i get 75W90 Synthetic Gear Oil or 75W140? I think in my other cars i ahve gone the 75W140 route. which is the better choice?

[justinperkins]

I just had my tranny rebuilt and wanted my indy who did the job to put Mobil 1 synthetic in, but he was pretty adamant about the fact that "these transmissions are not designed to use synthetic". I didn't really believe him, but didn't feel like pressing the issue.

I'm interested to hear what people have to say about your question.

[79300sdtd]

Here are the different Synth Gear Oil Specs per the Mobil 1 Site. 75W90 first then 75W140.

75W-90
API Gl-5/MT-1 X

Typical Properties

Mobil 1 Synthetic Gear Lubricant LS
SAE Grade 75W-90
Viscosity, ASTM D 445
cSt @ 40ºC 106
cst @ 100ºC 15.2
Viscosity Index, ASTM D 2270 150
Pour Point, ºC, ASTM D 97 -46
Flash Point, ºC, ASTM D 92 175
Density@15C kg/l, ASTM D 4052 0.859


75W-140
API GL-5 X

Typical Properties

Mobil 1 Synthetic Gear Lubricant LS
SAE Grade 75W-140
Viscosity, ASTM D 445
cSt @ 40ºC 179
cst @ 100ºC 25.3
Viscosity Index, ASTM D 2270 175
Pour Point, ºC, ASTM D 97 -51
Flash Point, ºC, ASTM D 92 221
Density @ 15ºC kg/l, ASTM D 4052 0.863

[Gurkha]

If you don't plan to do lots of wading in the water or face a prolonged heavy monsoon, synthetic oil makes sense with their extra level of protection and high shear strenght leading to extended component life, apart from Mobil-I, people seem to ignore the excellent Boron based Chevron Delo tranny oils, they contain no EP additives and instead rely on boron to form the sacrificial layer, they work out excellent with trannies using brass or other soft metal components.

[Hatterasguy]

My entire driveline is Mobil 1 and has been for years. The only downside of synthetic is the cost.

[aersloat]

Mobil 1 ATF works very well in both the transmission and for the power steering pump. I just drained my differential and used Amsoil 75W-90. The transmission really seems to like the mobile 1 ATF. I drained it just about a year ago.

[bgkast]

What about for those of us with manual transmissions?

[H-townbenzoboy]

Mobil 1 ATF can be put into manual transmissions without problems.

[dannym]

Originally Posted by 79300sdtd

Here are the different Synth Gear Oil Specs per the Mobil 1 Site. 75W90 first then 75W140.

75W-90
API Gl-5/MT-1 X

Typical Properties

Mobil 1 Synthetic Gear Lubricant LS
SAE Grade 75W-90
Viscosity, ASTM D 445
cSt @ 40ºC 106
cst @ 100ºC 15.2
Viscosity Index, ASTM D 2270 150
Pour Point, ºC, ASTM D 97 -46
Flash Point, ºC, ASTM D 92 175
Density@15C kg/l, ASTM D 4052 0.859


75W-140
API GL-5 X

Typical Properties

Mobil 1 Synthetic Gear Lubricant LS
SAE Grade 75W-140
Viscosity, ASTM D 445
cSt @ 40ºC 179
cst @ 100ºC 25.3
Viscosity Index, ASTM D 2270 175
Pour Point, ºC, ASTM D 97 -51
Flash Point, ºC, ASTM D 92 221
Density @ 15ºC kg/l, ASTM D 4052 0.863

This is all well and fine but it's meaningless unless you can compare them to dino oils.
I've been running Mobile 1 in my tranny for almost 2 years now with no problems.

danny

[WD8CDH]

Best synthetic for a manual tranny would be Redline MTL or MT90. They are GL-4 oils rather than GL-5 oils so the syncros work better.

For the diff, if the manual says 80 weight, 90 weight or 80W-90, then use 75W-90 to replace it.

If the manual calls for 80W-140 or 85W-140 then use 75W-140 as a replacement.

GL-5 is best in the diffs.

[rwthomas1]

Originally Posted by Hatterasguy

My entire driveline is Mobil 1 and has been for years. The only downside of synthetic is the cost.

What he said! RT

[rwthomas1]

Originally Posted by WD8CDH

Best synthetic for a manual tranny would be Redline MTL or MT90. They are GL-4 oils rather than GL-5 oils so the syncros work better.

For the diff, if the manual says 80 weight, 90 weight or 80W-90, then use 75W-90 to replace it.

If the manual calls for 80W-140 or 85W-140 then use 75W-140 as a replacement.

GL-5 is best in the diffs.

I agree. Synchronizers are often attacked by the high-pressure additives in GL-5 oil. The GL-4 oil is a better choice. I have Redline MTL and MT90 in my truck 5speed and it shifts "like butter" which is saying a lot if you have ANY familiarity with the NV4500 truck transmission.....

RT

[79300sdtd]

Originally Posted by dannym

This is all well and fine but it's meaningless unless you can compare them to dino oils.
danny

i was not trying to compare them to dino, i was trying to compare them to eachother to determine which one to use in the diff.

[WD8CDH]

Originally Posted by rwthomas1

I agree. Synchronizers are often attacked by the high-pressure additives in GL-5 oil. The GL-4 oil is a better choice. I have Redline MTL and MT90 in my truck 5speed and it shifts "like butter" which is saying a lot if you have ANY familiarity with the NV4500 truck transmission.....

RT

It's not just attacking the syncros by the EP additives in GL-5 oil, it's primarily that GL-5 oils are too slippery for the syncros.

Most modern GL-5 EP additives don't attack brass now.

[Ken300D]

I can strongly recommend Mobile 1 ATF for the automatic transmissions. It cleans and protects components very well. It also has excellent cold-weather characteristics. I also used Mobile 1 ATF in my 240D manual transmission with excellent results.

I can also strongly recommend Mobile 1 synthetic gear oil for the differential. 75W90 is what I recommend, and I use it in everything. This oil also cleans and protects components well.

Just an opinion.

Ken300D

Carfax vs. Autocheck - Who do you prefer?

Have a nice day.