Mid-Illini Jeepers

I put the above oil in my new tranny. Was told it was a bad idea as it wasn't "Yellow Metal Safe". I have brass synchronizes. Valvoline's site was of no help, but finally found some independent testing lab results that closes the issue. Oils are rated 1a through 4c with 1a and 1b consider safe.

Here's the others tested.


SAFE GL-5 Oils
Amsoil M/T Fluid MTF..5W-30.............. 1A Light Orange
Red Line MT-90.......75W-90 GL4......... 1A Light Orange
Amsoil Long Life FGR 75W-90 GL5......... 1B Dark Orange
Amsoil Severe Gr SVG 75W-90 GL5....... 1B Dark Orange
Amsoil MT & Gear MTG 75W-90 GL4...... 1B Dark Orange
Mobil 1 Synthetic....75W-90 GL5......... 1B Dark Orange
Castrol Hypoy C......80W-90 GL5......... 1B Dark Orange
Castrol SYNTEC.......75W-90 GL5........ 1B Dark Orange
Citgo Citgear Std XD 75W-90 GL4........ 1B Dark Orange
GM Synthetic Axle....75W-90 GL5........ 1B Dark Orange
Pennzoil Gearplus....80W-90 GL5.......... 1B Dark Orange
Pennzoil Synthetic...75W-90 GL5......... 1B Dark Orange
Red Line NS Gear Oil 75W-90 GL5......... 1B Dark Orange
Red Line 75W90 GL-5..75W-90 GL5....... 1B Dark Orange
Torco SGO Syn G LS....75W-90 GL5...... 1B Dark Orange
Valvoline High Perf..80W-90 GL5........... 1B Dark Orange
Valvoline SynPower...75W-90 GL5......... 1B Dark Orange

MARGINAL GL-5 Oils
Delo Gear Lubric ESI 80W-90 GL5.......... 2A Claret Red
Delo Trans Fluid ESI 50W..................... 2A Claret Red

UNSAFE GL-5 Oils
Royal Purple MaxGear 75W-90 GL5......... 4A Trans Black
Mopar Syn LS additive..75W-90 GL5....... 4A Trans Black
Lucas 75/90 Synthetic75W-90 GL5......... 4B Graphite Blk

Intereting. In my NP435 (M37) and NP420 (my brothers M37) I run the Lucas Synthetic 50 wt. Trans Lubricant (http://lucasoil.com/products/transmissi ... -trans-oil) which is suposed to be "yellow metal" safe as well. I will admit I do more damage to the trans than I think any of the oils will do based on how I use the truck.

I started out with 85-90 gerar oil, but they call for 50wt, and it sure shifts easer when cold with the 50wt.

I've stuck with Mopar trans lube with partial Lucas oil stabilizer all these years. Had no trans failure to this date.