Have you tried lucas oil stabilizer? It's a bit stickier, and helps the syncros grab without wearing out so much
I don't think the oil being thicker has anything to do with syncro function. Redline MT90 is a synthetic GL4 rated 90wt oil that works great in the Toyota transmission compared to a synthetic 75w-90 gear oil that is GL-4/GL-5. Something in the additives for the GL-5 changes the "slipperiness" and has a negative impact on the syncro function, but they are the same 90wt viscosity.
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1989 4Runner: Dual Ultimate (Inchworm front & Marlin 4.70 rear), Marlin Twin Stick, 1200-lb clutch, 4.88 R&P, Aussie Front, Detroit rear, 30-spline Longs, Long hub gears, ARP hub and knuckle studs & 35x12.50 Cooper STT PRO tires. Marlin rear bumper & sliders. FROR front bumper. SAS with Alcan springs & Rancho 9000XL shocks. Budbuilt Bolt-on traction bar. Custom Interior Cage by Those Guys Rod and Customs.
Moab Tested & Rubicon Approved
