I switched to MT90 in my J-type two years ago and the OD works fine 
without any problems what so ever.  In my case it's normal street 
driving so Bob's comments may apply to a racing scenario.
Gary
Digest
www.tracltd.org
> Date: Thu, 5 Jan 2006 11:37:16 -0500 (EST)
> From: "Robert M. Lang" <lang@isis.mit.edu>
> Subject: Re: Red Line Gear Oil?
>
> On Thu, 5 Jan 2006 Pimento73@aol.com wrote:
>> which RedLine gear oil would you use in a J-overdrive gearbox? and  why?
>>  
>> MTL  (70W80 GL 4)
>>  
>> or 
>>  
>> MT 90 (75W90 GL4)
>  
>
> Use the MT 90. I understand that the MTL has friction modifiers that work
> great for synchros, but are too slippery for the O/D clutches.
>
> BTW, I believe that Quantum Mechanics suggests that you use a
> non-detergent motor oil like 40 or 50 weight. Check his web site:
> quantumechanics.com  - he has tech tips there.
>  
>> Thanks
>> Jack Mc
>  
>
>
> regards,
>rml
> - 
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