* Original Transmission: What transmission did your 1984 Silverado come with originally? This is crucial. If it originally had a TH350 or TH400, swapping in a TH400 is likely relatively straightforward, though it might require some adapter plates or modifications depending on the specific engine and year. If it had a different transmission (like a 700R4 overdrive automatic), it becomes significantly more complex.
* Engine: The engine's power output will influence the suitability of the TH400. A high-power engine might overwhelm a stock TH400, requiring upgrades.
* Driveshaft: The driveshaft length might need to be adjusted or replaced to accommodate the TH400's different output shaft length.
* Crossmember: The transmission crossmember will likely need to be modified or replaced to properly support the TH400.
* Wiring and Controls: While the basic linkage might be adaptable, electrical connections for things like the transmission's neutral safety switch may need attention. This is particularly true if the original transmission was electronically controlled.
In short, while *possible*, swapping a TH400 into a 1984 Silverado isn't a simple bolt-on affair. It's a significant mechanical project requiring expertise and potentially custom fabrication. You'll need to research the specifics of your truck's original setup and consult with a transmission specialist to determine feasibility and the necessary modifications.
