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]

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]

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]

https://cimg8.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/220x400-1/80-amsoil10w_40oil_zps1b85b817_1__41d3919364091164299 d0398c88b0200970babe8.jpghttps://cimg3.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/220x400-1/80-twscastrol_1_1__c1196a14dcbe3d2d9a30ba7bb55af67e39 289f75.jpghttps://cimg4.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/220x400-1/80-d3ded310_224a_4048_a7ae_97472f98f64e_1__661c7e57ee 53c43aad9a807cd44d0fe6438cbb72.jpg
https://cimg7.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/800x600-1/80-353a8770_2463_4a3d_bd53_860920b2b618_1__215baaf45f a8310b57b69078bd80040f5003d62d.jpg

[XfireZ51]

So now I am wondering, is the Amsoil 5W-30 too light for a black tag when using a Fidanza? Would that promote the kind of noise that generates false knock?

[Great White]

My car has a fidanza lightweight flywheel and the accompanying gear rattle. When I first purchased the car, I was in dire need of anything to replace the old oil in the trans. I used the new Synthetic Lucas Oil Stabilizer for several months before finally putting in Amsoil 80w90 Manual Transmission gear oil. It is quieter and shifts are smooth, but I've had to just accept that this transmission won't ever be silent. (I'm used to it now and it doesn't bother me anymore.)

[richarde]

Talking about quieting the ZF gearbox whilst on idle with an aluminum flywheel fitted, has anyone tried the Carolina Clutch C4 Shim Kit, sold for this purpose? It includes a countershaft shim that is just over 0.005" thicker than stock, reducing the 'gear rollover noise' when not under load. The gearbox needs to be out of the car to fit, although actual fitment does not take long.