Thread: LT95 oil

Originally Posted by Red90

I agree ZDDP is a bad thing. You want higher friction, not lower. That is the selling point of MTFs. They include additive to increase friction.

That said, in my testing back to back between engine oil and MTFs with various gearboxes has not shown any difference in synchro feel. Viscosity seems the biggest factor. The thicker it is the longer it takes for the synchro to do its job.

Engine oil tends to shear a lot faster in use, too, compared to a dedicated MTF.

Boxes like the R380 can be idiosyncratic, the sweetest shifting fluid I used (except at below 0° start temps) was Motul Gear 300 (75w-90) but some seem to shift better with an ATF.
A good syn ATF was hands down the best at a low ambient but as soon as the 'box started to warm up shift quality went away quickly, becoming baulky on the up change.

Forgot to mention that the 'normal' sulphur/phos EP additives used at GL5 diff oil levels tend to interfere with synchro performance too, so I'd guess ZDDP would act in a similar manner.
That GL5 transaxle/manual trans fluids work as well as they do is pretty impressive.

I want to rant but it's not worth it.

Luddites cannot be convinced that modern fluids are inherently better, longer lasting and better performing over a wider range of operational parameters than something defined in a 1958 landfover service manual.

Oil threads should be banned from fora.

I need an aspirin to ward off the evil spirits.

BTW do not use straight 90 in the LT95.
Particularly if the temps go below 0C in winter.
My LT95 in Saudi also had a broken oil pump shaft.

Regards PhilipA

I've put in some 15w-40 synthetic. Done about 20kms and shift does seem better. Also discussed fluids (not oils) with Castrol Tech department. Their feedback was:
15w-40 in good oil is ok
They do not recommend 75-90 Syntrax MTF as its a GL5 rating and not as well suited to bronze etc as GL4.
They were on the fence re Syntrans 75-85 as the viscosity was closest to 30w engine oil.
The oil they thought was most suited IF using a MTF was Syntrans 75-90 Heavy Duty which is only available in 20ltr drums. This is used in truck manual gearboxes. Suggestion was that if going this route go to a truck workshop and buy some oil from them rather than buying a 20ltr drum.
So - will leave 15w-40 in and see how it goes for time being. Thanks all!

Nulon G70 gearbox treatment works miracle in cold and noisy gearboxes ....

Smooth Shift Manual Gearbox and Diff Treatment (G70) - Nulon Products Australia


I've used it for years in my old cars. Particularly the ones with tired 2nd gear synchros.... it quietens them right down too.

Originally Posted by Meccles

I've put in some 15w-40 synthetic. Done about 20kms and shift does seem better. Also discussed fluids (not oils) with Castrol Tech department. Their feedback was:
15w-40 in good oil is ok
They do not recommend 75-90 Syntrax MTF as its a GL5 rating and not as well suited to bronze etc as GL4.
They were on the fence re Syntrans 75-85 as the viscosity was closest to 30w engine oil.
The oil they thought was most suited IF using a MTF was Syntrans 75-90 Heavy Duty which is only available in 20ltr drums. This is used in truck manual gearboxes. Suggestion was that if going this route go to a truck workshop and buy some oil from them rather than buying a 20ltr drum.
So - will leave 15w-40 in and see how it goes for time being. Thanks all!

They should know better about their own products, the sulphur/phosphorous additive pack is buffered in Syntrax 75W-90 so it isn't reactive to bronze.
The vehicles its designed for (cars with transaxles, e.g. Pirsche 944, Alfetta's, Subaru, etc) use bronze synchros

Originally Posted by DoubleChevron

Nulon G70 gearbox treatment works miracle in cold and noisy gearboxes ....

Smooth Shift Manual Gearbox and Diff Treatment (G70) - Nulon Products Australia


I've used it for years in my old cars. Particularly the ones with tired 2nd gear synchros.... it quietens them right down too.

We have used it in whining diffs as well,seems to sort them out.

Originally Posted by rick130

They should know better about their own products, the sulphur/phosphorous additive pack is buffered in Syntrax 75W-90 so it isn't reactive to bronze.
The vehicles its designed for (cars with transaxles, e.g. Pirsche 944, Alfetta's, Subaru, etc) use bronze synchros

The problem with modern gear oils is not copper corrosion. The problem is the EP additives stick to the white metal on the synchros and then pulls the white metal off when sheared. It is a well known issue and the reason why you can't use gear oils that contain EP additives in a synchronized gearbox.