DEX/MERC automatic transmission fluid meeting GM Dexron III and Ford Mercon specs for older GM and Ford automatics like the 700R4, 4L60E and AOD.
Servicing a 700R4 in a classic C10, a TH350 or TH400 swap, a 1990s 4L60E Silverado, or a Ford AOD or C6 that was built for DEXRON III or MERCON? Castrol Transmax DEX/MERC is a dual-spec ATF that meets GM DEXRON-III and Ford MERCON performance requirements, sold here as a single one-gallon jug of 128 ounces. It suits owners who want to service an older unit with the fluid type it was designed around.
In a 700R4 or early 4L60E the fluid is pumped into line pressure that applies the clutches and the 2-4 band, it drives the torque converter, and it carries heat to the radiator cooler. Its friction modifiers set how smoothly the clutches engage. That is why Ford created MERCON in 1987: GEARS Magazine notes the spec was released to stop converter clutch shudder that the DEXRON fluids of that time did not prevent. A DEX/MERC fluid is blended to satisfy both sets of tests.
Read the dipstick hot, with the engine running and the selector cycled. Fluid that is burnt with clutch material on the stick means fresh fluid will not save the unit, and it is time to price a rebuild instead. Our 700R4 fluid type and capacity guide and 4L60E fluid type and capacity guide cover the level check and how much each unit takes.
Use it where the factory spec is DEXRON III or MERCON. On the GM side that means the TH350, TH400, 700R4, 4L60 and 4L60E, 4L80E and 4T60E built before GM switched to DEXRON VI. GM's 2005 bulletin set that switch at 2006 production and states that 2006 and later models are to be serviced with DEXRON VI only, so a 2006-2013 4L60E should get DEXRON VI, not this. On the Ford side it fits the C4, C6, AOD, E4OD and 4R100 that called for MERCON. Some 4R70W units call for MERCON V, so read the stamp on the dipstick handle and buy MERCON V if that is what it says.
Be aware of the direction of compatibility. Ford revised MERCON V to be backward compatible with MERCON before 2007, and GM approved DEXRON VI for 2005 and earlier DEXRON III units, so the newer fluids can go into older units. The reverse is not true. If you would rather fill a late GM unit with the current spec, our ACDelco DEXRON VI three-gallon case covers it. Parts for these units are on the 700R4, 4L60E and AOD collection pages.
| Meets | GM DEXRON-III, Ford MERCON |
| Typical applications | Older GM (TH350, TH400, 700R4, early 4L60E, 4L80E) and Ford (C4, C6, AOD, 4R70W, E4OD, 4R100) automatics |
| Also usable as | DEXRON III power steering / hydraulic fluid where specified |
| Volume | 1 gallon (128 fluid ounces) |
| Additive package | Calcium sulfonate and molybdenum disulfide |
| Ships from | USA |
No. GM's DEXRON VI bulletin states that 2006 and later models are to be serviced with DEXRON VI only. Use DEX/MERC in units built for DEXRON III, such as a 1993-2005 4L60E or a 700R4.
Only if the dipstick or owner guide calls for MERCON. Many 4R70W units specify MERCON V, and MERCON and MERCON V should not be swapped in that direction. Check the stamp on the dipstick handle.
Yes. GM approved DEXRON VI as a replacement in 2005 and older DEXRON III models. DEX/MERC is the option for owners who want to stay with the original fluid type.
Plan on two gallons. A pan drop takes about five quarts per GM owner manuals, and you will want extra to set the level hot. A dry rebuild takes roughly 9 to 11 quarts.
Yes, where a power steering or hydraulic system specifies DEXRON III fluid. Check the reservoir cap or owner manual first, since many later systems use a dedicated power steering fluid.
