For no other reason than to put a check mark next to a question on a list of things I'd just like to know, why did bell housings go from unattached on manual transmissions to integral on automatic transmissions? I'm thinking the automatic transmissions could have been manufactured to use the bell housings already readily available. Larry
I've learned some things. First, there are manual transmissions with integral bell housings. Second, there are automatic transmissions without integral bell housings. I've also learned that there are people who, rather than broaden the base of knowledge, would rather.. Nevermind. I've broadened my knowledge. Thank you, I appreciate it. Now to reword my question so hopefully I can seriously learn more, is there a reason why some, most, a few, many, automatic transmission manufacturers went with the integral bell housing? Larry
I'd chalk it up to wanting to have as few castings as possible. One casting for an auto trans means less machine work and the bell is specific to the new wizbang converter/slushbox combo that comes out of detroit. But a standard bell for manuals means whatever gearbox you purchase from Saginaw, BW, NP etc. will bolt on. That's my theory based on the fact that bean counters look at everything. -rick
The original automatic transmission (G.M. Hydramatic} had a separate bell housing. Later G.M. automatics didn't, but starting in 1964, there was the Chevrolet pattern and the "B.O.P." pattern, which Cadillac eventually adopted as well, so two patterns covered almost every application. Ford had several different block patterns, so a separate bell housing made sense.
Bell housings for stick need to have a way to operate the clutch. Automatics need to fit the torque converter and sized to a hydraulic pump. While maybe one could be designed to do both, back in the old days the transmissions were designed by different people. GM had a Hydro-matic division Manuals were made by another for example. They did not share information. Job security.
Separate bellhousings mean the transmission can be used on numerous different engines. Single castings are cheaper to make. It's a trade-off. I can assure you, from direct experience, the choice for either is strictly a financial one.
Probably due to early auto companies having every marque building their own engine designs. One tranny for Chevy, Caddy, Buick, Olds, & Pontiac totally different engines. Even the ubiquitous Hydramatic auto trannys used adaptors since they went onto all the different GM engines, Lincolns, Willys, Hudsons, Nashs, Kaisers, Rolls Royces, Bentleys, Ramblers, and Austins. As the auto trannys were refined, companies started standardizing engine designs which makes sense.
Generally it gets down to production costs. Easier to make one piece and not have to machine more surfaces to get two pieces to fit together properly. Also, some manufacturers used the same transmission on multiple brands within their corporation. In those cases, a two piece transmission/housing allowed them to build the same trans and use it in different vehicles. Today, who knows why they do it. Some of the transmissions made today were made as one piece units and then later they switched to 2 piece units but still use them on the same engine series. I'm guessing that the reason is that they wanted to use the same basic trans and use the 2 pc set up so they again could use the trans behind multiple engine types.......but I don't know enough about later transmissions to say thats a fact. At one time, GM made automatic transmissions with more than one bolt pattern.
I'd like to know why they went away from using round SAE standard sizes. That way any make trans can fit on any make clutch housing. Trucks have always been this way, and in the early days many of the auto makers did it too.
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