Got a question about a strong thud noise coming from my transmission. Being the first Land Cruiser I've ever owned, I'm not too familiar with the internals of the Toyota 4 speed yet. My Land Cruiser is a 78 FJ40 with the stock 4 speed with a chevy 350 for power. When I let out the clutch and press the gas with the transmission in gear there is thud that is definitely coming from withing the trans. You can feel it in the stick. The more gas you give it and the faster you let the clutch out the louder it is. However is does get quieter as you work up from 1st to 4th. You can also hear it if you simply let off the gas to coast and then accelerate. Other than this noise the transmission seems to be in perfect condition. No vibrations or other noises, no leaks, shifts easy. Could this be a shifter fork or something moving around? When I bought the FJ in October the transmission had been recently rebuilt. Also what grease would anyone recommend for the trans and T-Case. I've recently drained them both and replaced with good Valvoline gear lube. But I was thinking about switching that out to synthetic.