Hello, I just had my TH400 transmission rebuilt. I was told to go with fully synthetic fluid. Redline, Royal Purple and a few others were mentioned. I’m just curious what people are using. Please let me know. Thanks.
I’ve had good luck with Type F-supposedly it has more frictiony stuff in it than Dexron II or its modern successors. Patrick
I use Valvoline Max Life fluid in both my cars. It is full synthetic and Dexron 6. https://www.amazon.com/Valvoline-Multi-Vehicle-Synthetic-Automatic-Transmission/dp/B008QDV2JG
A buddy of mine has been doing transmissions for over forty years. For my prostreet with a TH400, he told me to use Dexron III/Mercon because synthetic is too slippery. When I bought my Gear Vendors overdrive, it said you could use any type of trans fluid even a combination of standard and synthetic but they recommended non synthetic for racing because it's too slippery. The only benefit that I see of synthetic fluid is that it can withstand more heat before breaking down. I run Dexron with a trans cooler.
Yes, Gear Vendors currently recommends Dexron 3. When I first got my GV, they recommended a synthetic GM manual transmission fluid which was very expensive and harder to get.
I swapped to Tractor Hydraulic fluid a couple years ago. Shifts are nice and firm. It works great. I would not hesitate to use it in any TH400/TH350/TH200-4R whatever. My transmission has never shifted better. I personally used Shell Spirax https://www.lecinfo.com/products/shell-spirax-hydraulic-oil but there are many others. This is not regular hydraulic fluid. It has to be for tractor transmissions and hydraulic systems. I did quite a bit of research and many performance transmission shops recommend it and even rebrand it to sell as their performance transmission oil. I would consider it to be similar to using Type F or B&M Trickshift. Greg
Question for all, is changing over from Dexron to tractor fluid doable, or is there a cross-contamination concern? Devon
I intermixed. I still had fluid in my convertor. Much of the info I had read about tractor hydraulic fluid recommended adding a little Type F or Dextron II with it for some colour as it is clear and can be hard to read on the dipstick. My old TH400 has a B&M stage II shift kit. It has always had a good 1-2 shift. The 2-3 was always a little mushy. The Tractor Hydrualic Fluid firmed it right up. If you want to find some good info on oils, check out https://bobistheoilguy.com/forums/ . There are some posts about using Tractor Hydraulic fluid in place of ATF there. The Turbo Buick forums have some info as well. Quite a number of Grand national guys using Tractor Hydraulic fluid in there TH200-4Rs for racing and that was recommended to them. Greg
Nah it mixes fine,..I would run it for a few cycles then flush and refill to get the most benefit,...it will tighten the converter just a touch
I was just trying to figure out if I could use Dexron III in my 1974 Cub Cadet's hydrostatic unit because the Hy-Trans fluid was so expensive. I'm replacing the axle seals and I was concerned that changing fluid type would cause other issues with the unit. I drained out over two gallons and have not jacked the front up to drain the rest or changed the filter. It's $30-40 a gallon!
