ZF Gearbox Oil spec

[richarde]

I have a 1990 ZR-1 with an Aluminum flywheel. I purchased this in Jan 2019. Currently the engine and gearbox are out of the car, the car not having been run since 2012. My question relates to the best oil to use in the gearbox to reduce the transmission noise associated with an ali flywheel. On Marc's website, he advises Red Line Shockproof Heavy oil. The FSM specifies a viscosity of 5W-30 Manual Transmission Fluid. In the UK, the only Red Line Shockproof Heavy oil that I can find is rated as 75W-140. Is this the oil to buy as there seems a big difference between 5W-30 and 75W-140!!
Thanks

[Paul Workman]

Originally Posted by richarde

I have a 1990 ZR-1 with an Aluminum flywheel. I purchased this in Jan 2019. Currently the engine and gearbox are out of the car, the car not having been run since 2012. My question relates to the best oil to use in the gearbox to reduce the transmission noise associated with an ali flywheel. On Marc's website, he advises Red Line Shockproof Heavy oil. The FSM specifies a viscosity of 5W-30 Manual Transmission Fluid. In the UK, the only Red Line Shockproof Heavy oil that I can find is rated as 75W-140. Is this the oil to buy as there seems a big difference between 5W-30 and 75W-140!!
Thanks

I'm using the Redline Heavy Shockproof that Marc recommends. Castrol Syncromesh synthetic also has favorable reports.

Bill Boudreau (ZFdoc) told me after I experienced a failed ZF in my (base) 95 to use a synthetic transmission oil: Castrol TWS 10-40. (Since then Castrol changed the formula for the TWS, hence the Redline recommendation.)

[richarde]

Thanks Paul - Is the Red Line Shockproof Heavy you are using a 75W-140 viscosity or is there a range of different viscosities available with this product? Here in the UK, the only RL Shockproof Heavy oil that is available is the 75W-140.

[XfireZ51]

I switched from the BMW Castrol oil when BMW dropped Castrol in favor of their own. So I switched to the Amsoil Manual SynchroMesh, which IIRC Marc had been recommending.

[-=Jeff=-]

Amsoil Oil User here.. Specifically:

Manual Synchromesh Transmission Fluid 5W-30

[We Gone]

I would think 75W-140 is to heavy, just changed mine went with GM Manual Synchromesh Transmission Fluid.

[Karl]

Amsoil in the zf-6 and Royal purple in the Dana 44 with the 4.09 gears.

[Paul Workman]

Originally Posted by richarde

Thanks Paul - Is the Red Line Shockproof Heavy you are using a 75W-140 viscosity or is there a range of different viscosities available with this product? Here in the UK, the only RL Shockproof Heavy oil that is available is the 75W-140.

The 75-140 is what I have in mine. The viscosity rating for gear oil is different from motor oil - I don't know where the RL would be placed.

Amsoil Synchromesh too gets good reviews by some users here. But, the RL seems to make my gear box happy. AND, I also use the same oil in the Dana 44. I did add the friction modifier to it, but since I've read where it may not be necessary. (I'll have to do a burnout and let you know if the limited slip is working.)

[richarde]

Thanks for all the input. I have decided to go for the Red Line Shockproof Heavy oil - 75W-140. Paul's comment that the viscosities for engine oil are quoted differently to gear oil rang a bell with me. I assume (a dangerous thing, I know!) that the GM Manual Transmission Fluid GM 1052931 is quoted as a 5W-30 oil based on the standard SAE ratings, whereas the Red Line Shockproof Heavy oil quoted as 75W-140 is based on the SAE Gear Oil rating. An article was written in a UK Motor Industry Magazine some years back, where it includes a comparison chart between ISO, SAE Engine Oil and SAE Gear Oil. In it, it indicates that an SAE Gear oil rating of 75W has a similar viscosity to that of SAE 15W or 20 grade engine oil. So the approximate viscosity of the Red Line Shockproof Heavy 75W-140 relates to 15W-70 engine oil!

[Dynomite]