Quote:
Originally Posted by Bigdav160
Off the top of my head, Up through '84 the input shaft was the same size as the 200-4R. The biggest improvement in the early models was a simplified forward sprag and improvements to the pump to make it more reliable.
1986 the low roller was strengthened from the previous TH350 piece it was using.
1987 Hydramatic redesigned the case to accept a forward accumulator system to cushion shock going into drive. Some one-piece seals replaced scarf cut seal previously used and the pump vane count was increased again.
There were other minor changes made through the years. Many of the changes retrofit to earlier models. Some items, do not retrofit backwards but I don't see them as a big deal.
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They used a 27 spline input shaft until 1986, after that was a 30 spline input shaft. Every thing you mentioned makes the 1987-up models that much better because every one of those increased the performance of the transmission. There is no reason to use a 81-86 trans for any kind of a performance build unless thats what you have and you do the upgrades. My stock 305 killed a stock 1985 700R4 so I would think a performance application would have a much shorter life. Mine was rebuilt with 87-up internals. Not only are they stronger but a lot of the rebuild parts arent available for the early transmissions. The way I see it is if they arent a "big difference" to the performance of the transmission GM would never have changed it.