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Sales / Scratch & Dent
Manual Transmission Fluid
&
Gear Oil
GL-4 or GL-5? It matters. GL-5 gear oil carries a heavier dose of extreme-pressure additive than GL-4. That suits a gear-drive transfer case, but in older manual transmissions those additives can attack the brass ("yellow metal") synchronizer rings and bushings.
- AX15: Synchromesh
- T18, T19, SM420, SM465, NP435, T14, T15, T90, T98, T150, T176: 85W-90 GL-4
- Dana 18, 20 and 300 transfer cases: 80W-90 GL-5
New Process chain-drive transfer cases (NP231, NP242 and others) take ATF, not gear oil.
Synchromesh Manual Transmission Fluid
The fluid we recommend for the AX15, whether it's one of our new-production TurnKey units, a rebuild, or a master rebuild kit going into your own. Synchromesh is a lighter manual transmission fluid that suits the AX15's synchros, so shifts stay smooth even when the gearbox is cold. Plan on 4 quarts for a full fill.
SAE 85W-90 GL-4 Gear Oil
Heavyweight GL-4 gear oil for the classic gearboxes: Borg-Warner T18 and T19, GM SM420 and SM465, New Process NP435, and the Warner and Tremec Jeep transmissions (T14, T15, T90, T98, T150, T176). It's the right weight for these older designs and is safe on their yellow-metal parts. Most of them take about 4 quarts. We sell it by the quart (Liqui Moly) and by the gallon (CRC Sta-Lube).
SAE 80W-90 GL-5 Gear Oil
For the gear-drive Dana transfer cases: about 2 quarts for a Dana 18 or Dana 20, and 3 for a Dana 300. Fill to the bottom of the fill-plug hole. If you've added a deep billet bottom cover, it holds more, so keep filling until the level reaches the plug.
What Takes Gear Oil
| Application | Fluid | Amount | Order |
|---|---|---|---|
| Manual Transmissions | |||
| Aisin AX15 | Synchromesh MTF | 4 qt | |
| Borg-Warner T18 (Ford & Jeep) | 85W-90 GL-4 Gear Oil | 4 qt | |
| Borg-Warner T19 | 85W-90 GL-4 Gear Oil | 4 qt | |
| GM SM420 | 85W-90 GL-4 Gear Oil | 4 qt | |
| GM SM465 | 85W-90 GL-4 Gear Oil | 4 qt | |
| New Process NP435 | 85W-90 GL-4 Gear Oil | 4 qt | |
| Warner T14 | 85W-90 GL-4 Gear Oil | 4 qt | |
| Warner T15 | 85W-90 GL-4 Gear Oil | 4 qt | |
| Warner T90 | 85W-90 GL-4 Gear Oil | 4 qt | |
| Warner T98 | 85W-90 GL-4 Gear Oil | 4 qt | |
| Tremec T150 | 85W-90 GL-4 Gear Oil | 4 qt | |
| Tremec T176 / T177 / T178 | 85W-90 GL-4 Gear Oil | 4 qt | |
| Transfer Cases | |||
| Dana 18 | 80W-90 GL-5 Gear Oil | 2 qt | |
| Dana 20 | 80W-90 GL-5 Gear Oil | 2 qt | |
| Dana 300 | 80W-90 GL-5 Gear Oil | 3 qt | |