Castrol Transmax Z

[Oxman]

We have a customer (Bell/John Deere) who insist on using Castrol Transmax Z in their transfer case. They claim that using any other fluid invalidates their warranty and charge an absolute fortune for the stuff ($20.00 per litre).
Is there any magic in this product? From what I can deduce from reading the data sheet, it's a full synthetic ATF but not much else.
This product is quite scarce here, but there are other sources for a synthetic ATF but do not carry a ZF approval.
Having read a forum related to ATF, several people claim that the only performance advantage of synthetic ATF's over dino is longevity of the oil. There are obviously other advantages otherwise manufacturers wouldn't produce it, but as a rule of thumb is this true?

 

[Gary Allan]

The basic advantage to synthetic fluid is longevity. Fluid tends to decay on a Time Weighted Average with how much heat it sees. Synthetics would tend to last longer/oxidize less.

Now if you take something like Dex VI, I don't think you can manage a fluid like that without it being a synthetic.

You can probably manage a conventional ZF fluid in that application, but it would be wise to analyze the fluid at the price break even point.

Without knowing the transfer case's internals, it's hard to say why they require the ZF spec in a synthetic. Many fluids can be used and only have to match performance spec's to be suitable for use in multiple applications. They just can't meet the material spec's for the approval/certification. There are exceptions. That is, just because a given trans used Dex III as a fluid ..and Dex VI is suitable for Dex III applications (supersedes it) ..doesn't necessarily mean that Dex VI is suitable for use in THAT trans.


For example the Jeep Chrokee (also Toyota) AW4 (Aisin Warner 4 speed auto) spec's Dex IIe or Dex III. Amsoil recommends both of their products that are suitable for Dex III applications. They don't recommend their ATL which is a Dex VI alternative. So, in this case Dex VI is not a suitable replacement for Dex III

 

[badtlc]

Fluid temperature can also be a possibility. I don't know why but I do know synthetic fluids can stay cooler than conventional. The only reason I know/think this is due to the father's GMC Jimmy. When using conventional fluid, it would get too hot and the ATF would boil/over flow. Switching to synthetic completely alleviated the overflow problem.

 

[Gary Allan]

I've never seen fluid boil over except in something like a mud bogging application. Too much raw hp applied in too short a time span that you can't adequately cool it.

I'm sure it can happen, but you're into an out of control/runaway situation for it to occur.

 

[roadrunner1]

we had the very same issue; a zf gear gehind a deere we kept having issues with, after the 2nd new gear and 1 rebuild zf said to only use castrol.
had something to do with clutch material compatitbility, although the clutches were not what we were having trouble with, it was a ring gear issue, but irregardless we are using the castrol 40wt.hypuron, as per zf directive