bobschultz wrote:
Fom what Ive been told Allison Trans Co. approved Dextron III for many years before the introduction of Transyd. Dont know of any documented failures of the transmissions due to fluid type. I know that lack of normal maint and overloading the trans. has caused more problems than anything else. Correct me if Im wrong. Bob S.
Bob,
Allison did approve DEXRON-III ATF for many years until I saw a need to change that. The problem was always viscosity loss in DEXRON type fluids. They were good fluids from every other aspect but they tended to lose viscosity (some could lose as much as 50-60%). So the problem we had was keeping the drain intervals low enough to avoid significant viscosity loss that could affect transmission durability. If you use a TES-389 fluid (DEXRON-IIIH) you need to drain it per recommendations. These fluids lose viscosity and could result in wear if you run them too long. Also, cooling efficiency drops due to reduced flow in the cooling circuit because the fluid is thinner. So, as long as you're following recommended TES-389 drain intervals, you'll be OK. However, unless you're changing it yourself, the labor to change fluid will eventually be more than the TranSynd since you can run it 150,000 miles in the 1000/2000 Series and 300,000 miles in the 3000/4000 Series.
PS: That's why I'm on this forum. I'm here to settle all the arguments concerning Allison fluid recommendations and specs since I'm the guy that wrote all of them.
PSS: TES-389 fluids are all DEXRON-IIIH fluids. That's why the drain intervals are so short compared to TranSynd and TES-295 fluids. We launched the TES-389 specification because some folks just could not bring themselves to spend the extra money for TranSynd or another TES-295 fluid. But, it's false economy .... TranSYnd and the other TES-295 fluids are worth it (by a large margin).
Hope this addresses all of your concerns !!
