Best Break-In Oil for Rebuilt Tranny?

I have an '89 Toyota Pickup w/ 22RE engine and W56 5-speed manual
transmission. I am replacing the tranny with a rebuilt unit from Marlin
Crawler. I'd like to run Red Line MT-90 transmission oil in it, but feel I
should use a cheaper oil for an initial break-in period. I realize that
rebuilt transmissions don't require extensive break-in because the gears
have already been broken in, but the synchros and bearings are new, plus it
will allow me to flush out any dirt or grit that got into the tranny during
the rebuild.

Here's the problem, most of the auto shops seem to only carry 75W-90 GL-5
gear oil with EP additives for use in hypoid differentials, as if that's a
one-size-fits-all lubricant. I've read that oil with hypoid EP additives can
make shifting hard (and accelerate wear) because it's too slippery for the
synchros to effectively mesh.

Any recommendations on a brand/grade oil to use and how long I should keep
it in before switching to the Red Line oil?

Thanks,
Michael

DeepDiver wrote:[color=blue]
> I have an '89 Toyota Pickup w/ 22RE engine and W56 5-speed manual
> transmission. I am replacing the tranny with a rebuilt unit from Marlin
> Crawler. I'd like to run Red Line MT-90 transmission oil in it, but feel I
> should use a cheaper oil for an initial break-in period. I realize that
> rebuilt transmissions don't require extensive break-in because the gears
> have already been broken in, but the synchros and bearings are new, plus it
> will allow me to flush out any dirt or grit that got into the tranny during
> the rebuild.
>
> Here's the problem, most of the auto shops seem to only carry 75W-90 GL-5
> gear oil with EP additives for use in hypoid differentials, as if that's a
> one-size-fits-all lubricant. I've read that oil with hypoid EP additives can
> make shifting hard (and accelerate wear) because it's too slippery for the
> synchros to effectively mesh.
>
> Any recommendations on a brand/grade oil to use and how long I should keep
> it in before switching to the Red Line oil?
>
> Thanks,
> Michael
>
>[/color]
The problem with some GL-5 differential gear oils in a synchromesh
transmission is that sulfur-based extreme pressure agents cause
damage to yellow metals, bronze, brass, in the transmission. Some
newer formulations of GL-5 gear oils are dual-rated for GL-4 and do
not damage yellow metals.

Or, find your own GL-4 gear oil at an auto parts store and fill with
that.

Specialty Formulations is a new boutique blender of lubes that is
equal to Red Line and has some products that work in situations
where Red Line isn't the best. You might take a look at their products.
[url]http://www.specialtyformulations.com/index_files/Page457.htm[/url]


Ken

"Ken Shelton" <shelton@cablespeed.com> wrote in message
news:xeqdnZDxbYzEV_7fRVn-iQ@cablespeedwa.com...[color=blue]
>
> Or, find your own GL-4 gear oil at an auto parts store and fill with that.[/color]

That's the problem, it seems that auto parts stores no longer carry GL4 gear
oil. In fact, they carry very few choices (as if no one ever changes their
gear oil -- which may be close to the truth). It seems that in order to save
shelf space, all the gear oils they carry are dual rated GL4/GL5 EP oils.