urS4 trans additive?

[Chris Thorp]

On Oct 18, 2006, at 4:14 PM, John Cody Forbes wrote:

> Brett Dikeman wrote:
>> Almost....any GL4 compatible synthetic gear oil.  Some GL5 gear oils
>> had an additive that was not compatible with brass syncros and they
>> would be destroyed in short order.  I think most manufacturers have
>> stopped using said additive, but I don't know for sure, and god knows
>> what's sitting on the shelf at Shady Supply.
>
> I was going to use GL5 compatible Mobil 1 75w90, any input there?  
> Thats also
> what I put in the rear diff since we didn't have an straight 90  
> weight.
The problem with using synchro-safe GL5 in a trans, at least what I  
gather, is that the hypoid differential friction reducers do such a  
good job that the synchros, whose job is to have friction, don't work  
as well and shifts will be slower as a result.

-Chris