Does anyone know if there are any physical differences (other than the obviously slanted pan) between a Slanted Pan Hydro and a Flat Pan Hydro? Does the bell housing mounting position or angle change? Is the total length to the tail shaft different. Have a project with a small block Chevy, that had a frame set up else where using a slant pan, and the end product will be taking a flat pan, which is however out being rebuilt and the builder is in the great black out hole of California right now so I can't obtain any dimensions. Anyone here have a flat pan and mind taking some measurements? Any help is greatly appreciated. Block mounting surface to center of the bell housing mount hole. (which is hopefully roughly at a 45 degree angle) Block mounting to tail shaft/housing.
I have a B&M slant pan in the shop. I can get measurements tomorrow morning if you need them. r Sent from my iPhone using H.A.M.B.
Block mounting surface? Front of the transmission case where it bolts to the bellhousing? The overall length of the transmission case on both my flat pan Hydros is 13 7/8"... from the bellhousing mounting surface to the tailshaft housing mount surface. Don't quite understand what the other dimension you're looking for means; sorry.
B & M also made bellhousing/adapters to use flat pans and slant pans with engines that did't come with them, in order to have the trans mount the way it was "intended". The slant pans were only used in 54-56 Olds and 55-56 Ponts, and only the front band could be adjusted externally; the rear band had to be adjust internally; other Hydros were all flat pans, and could adjust both bands externally. The slant pan/flat pan are basically the same transmission, with the slant pan mounting off center, so-to-speak. These are the single and dual range, single coupling Hydra-Matics the B & M Hydro-Sticks were the basis of, and other race trans builders such as C & O Hydro, Vitar, and others of the day. By using the B & M bellhousing adapter, you could also use the easier to find manual trans/cast iron Powerglide trans starter motor, and they bolted up "normally", with the solenoid on top, and not hanging down underneath like it did in V-8 Chevrolet pickups and bigger trucks; there was a recess machined into the aftermarket bellhousing to accomplish this. A slant pan Hydro will bolt up to a stock Chevrolet V-8 hydro bellhousing, but pan will be at angle; I had one like this, and as long as the pickup remains submerged in trans fluid, they'll work fine. Slant pans were made so the trans hump/floorboards could be flatter in the 54-56 Olds and 55-56 Ponts. There were a few different output shaft/extension housing lengths, such as Cadillac's had a long output shaft/extension housing and the Chevrolet trucks were shorter, making those transmissions more the length we see now. So, use the Chevrolet truck bellhousing, and the flat pan Hydro; I'd stay away from the slant pan due to cornering sloshing trans fluid around, and risking the pickup sucking air. JMO. If you don'y have the correct starter motor for a Chevrolet V-8 flat pan Hydro, prepare to pay some $$$$$ for one; they are hard to find and expensive. I am Butch/56sedandelivery.
Sorry I wasn't too clear, I meant like where the bell housing bolts to the block to the tail shaft, then from where the bell housing bolts to the block to bell housing mount hole on the bell itself. In examining the pictures of the mock up trans and the other one I think we will be fine. I know it is a tough ask for people to have 2 small block Chevy Hydros.
Thanks Butch good info. We have everything for our flat pan, it came out of a working car. Thank goodness. We had some new data plates made up that's about it. Everything else was there. We were just worried about the mounting mainly, because the frame was setup (by someone else) using the slant pan setup, and then we are going to be using the flat pan (which is currently being rebuilt so we cannot confirm the fitment at the moment).
OK, You've got one stock Chevrolet truck trans with the stock bellhousing, and a slant pan with an aftermarket bellhousing adapter. Flat pan or slant pan will bolt to the bellhousings of either, but it's hard to say how your slant pan is mounted, but it looks like the pan will "hang down" on one side. You also have the short truck trans, one with the 54-56 Olds 55-56 Pont slant pan length, but there's still the L-O-N-G Cadillac version. And, you have the hard to find slip yoke also! Do you have a starter motor? If you'll look at your aluminum bellhousing adapter, you'll see a recess where the starter motor would bolt up. You can use the easier to find, and much cheaper, manual trans/cast iron Powerglide starter motor with that bellhousing adapter. Look at the stock truck bell and it's flat; just compare the two. I think I said front band on the slant pan was externally adjustable, but it's obviously the rear band; it's been a long while since I gave all my Hydro stuff away (stupid, stupid, stupid); right after I gave it all away, the nostalgia thing started, and they were in demand. Chevrolet truck Hydros used a smaller 10" drive/driven torus assembly and cover, than all the other Hydros. Good you have that too. Chevrolet used an 18 bolt together cover to flywheel, everything else used a 32 bolt setup. If you don't have the truck starter motor, swap the bellhousings, and use the car starter motor and aluminum adapter. There used to be aftermarket bellhousing adapters that would allow you to use a slant pan, and the adapter would mount the trans correctly, so the pan was "flat". The throttle pressure linkage on a Hydro is critical, without it, you'll burn them up quickly. You do know, there's a Hydro Group here on the HAMB? If not, check it out. Your truck Hydro should measure roughly 28 inches from the front of the bellhousing, to the end of the extension housing, and is the one to use; more or less the same length as most aluminum Powerglides, TH-350's, etc. I am Butch/56sedandelivery.
Seems like you have the information you need. However, who's building yours!? I like to keep my list of knowledgeable builders on these up to date. Lots of useful info over in the Hydro Tech group as well... (You'll have to join to see the content).
Wow thanks for all the info and for making me aware of the Hydro Tech group. Jason Colby is building our Hydro, he used to operate Goodies Speed Shop. We have not gotten it back yet, there was some issue with getting the bands relined, then we had the great 2019 power outages here in California.
Anyone know of one for sale? Would like to put behind a 331 hemi. Thanks!!! Sent from my iPhone using The H.A.M.B. mobile app
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