Is this transmission fluid a good full synthetic transmission fluid to use even though it says Dexon VI - Mercon LV? for a rebuilt TH400? On the back it does say that this is compatible with all GM Hydra-Matic trannys and I know the TH400's use Dexron VI. Ive done some googling and see that the Mercon LV fluid is NOT the same as Dexron VI. it seems like a lot of fluid I've looked at have been the Dexon VI - Mercon LV.

1. Am I able to use this fluid without any issues? or should I be looking for exclusively Dexron VI?

 

When I search Summit for Mercon LV, it appears just about every offering combines it with Dexron VI. Given that I'd say it's fine. Or, if you have a ticking eyelid over it, go with Delco Dexron VI - that's what my rebuilt TH400 has in it.

 

Dexron 3, non-synthetic
https://www.napaonline.com/en/p/NOL75200

 

LV is Light Viscosity , I would use Dex/Merc for the slightly thicker fluid on 3 and 4 speed GM automatic transmissions but LV will work

 

A lot depends on the clutches used during rebuild. Good 'ole Type F works great and helps firm shifts. Years ago, Dexron was considered a "high lubricity" fluid to shift smoother and Type F was considered a "High Impact" fluid. Most shift kits tell you to move to Type F. Newer fluids are geared toward fuel mileage and tighter tolerances.

Race folks will often use Hy-Gard fluid from John Deere to work even better in T-400's, PG's etc.

JIM