[qb] Just an update, i have been having an email chat with the guys at Redline Oil in the USA since we started discussing the oil in this thread as i wanted to get the info from the horses mouth rather than use sales brochure type info. It's been worthwhile i think.

I sent them a link to this thread a few days ago, this is how the conversation went.

Pats quote: "The Heavyweight Shockproof is very viscous. If it weren't then it wouldn't be necessary to heat up the bottles prior to pouring, unless you have a burning desire to read the entire text of "War and Peace" while you're waiting for the first bottle empty Even when hot, it is considerably more viscous than a "normal" 75W90 gear oil."


Redline's comment: "At operating temperature the ShockProof Heavy would have the fluid viscosity/drag of a 75W90."


Pats Quote: "Did you know that some gearset manufacturers will void the warranty on their gearkits if this oil is used? It's too viscous to flow up the centre oil channel and effectively lubricate the inner races nearer the front of the shaft!"


Redline's comment: "I am not aware of that, so can't comment specifically. In a synchro application the ShockProof can be too slippery for the synchros, also in a drilled main shaft the moly can centrifuge out of suspension so wouldn't be recommended. The ShockProof gear lubes are very unique and perform well in a number of very specialized applications though aren't necessarily ideal for all."


JohnF question to Redline: "Can you just confirm what you mean by "also in a drilled main shaft the moly can centrifuge out of suspension so wouldn't be recommended"

Does that mean redline shouldn¹t be used in that application or is moly referring to other conventional oils?

Also, could you comment on the statement made in that thread that redline HSP loses you noticeable acceleration/power? It¹s not something I have ever noticed.


Redline's comment: "That was referring to the moly in the ShockProof and the possibility of centrifuging it out of suspension in a drilled main shaft. The ShockProof wouldn't be recommended in a synchro application or one with a drilled main shaft.

I wouldn't expect that the ShockProof Heavy would have any more drag at operating temperature than a 75W90 viscosity gear oil."

Johnf question to Redline: "Thats interesting, I have run that oil in my impreza STi5 with standard syncros for a couple of years with no problems. I found no issues at all with syncro action on this box.

As I understand it the syncros in the Impreza boxes are designed to use thicker oils due to the front diff being in the gearbox. Do you still suggest you don’t use HSP knowing this? And if so what oil should we be using? I found a big improvement in gear selection on track using HSP with the Impreza, conventional oils generated a lot of heat which caused the syncros to get tight and baulk."

Redline's comment: "Based on the fluid called for by Subaru in their transaxle we would recommend the 75W90NS, suitable for the synchros and the differential. The ShockProof is a very unique product and performs extremely well in numerous applications, but we don't recommend it in street vehicle synchro applications."

JohnF question to Redline: "This gearbox has a plated centre and front LSD, is the oil you just suggested suitable?"

Redline's comment: "I am unfamiliar with a plated center differential.
The 75W90NS would be suitable for the transaxle and limited slip differential. What type limited slip is fitted?"

JohnF to Redline: "The front LSD is a conventional plate and ramp type LSD.

The centre diff is known as DCCD (driver controlled centre differential), it is an electrically controlled variable lock/torque split centre diff assembly that uses an electromagnet controlled clutch pack to vary the lock ratio between a fully open state (works as a normal open diff) and fully locked (works as a locked diff). In its in-between states it uses a ramp and plate arrangement to apply the % LSD effect you require.

I have attached some cut out diagrams of the unit so you can see how it is constructed."

Redline's comment: "Thanks for the info, that is quite an impressive unit. The 75W90NS would be suitable for the transaxle, in the unlikely event that you experienced chatter from the clutch type front limited slip when making a slow/tight turn then I would add a slight amount of friction modifier. You don't want the fluid to become too slippery for the synchros, I wouldn't want to add much more than 1%.


Back to me So it looks like HSP will not lose any power when up to operating temperature and in fact it has a lower coeficient of friction compared to conventional oils causing issue with syncro's. Based on this i must be a driving god as i never had problems matching my gear speeds. LOL

So it looks like HSP is a great choice for dog boxes without a drilled centre shaft, but it isnt a good option for a road syncro based box, which is what Bob was saying he found on scoobynet recently. [/qb]