Someone asked me if all OW torque converters were the same. The put me down the rabbit hole of checking the PIM to see what I could find. It appears that the torque converter (or clutch) was installed on the engine prior to final assembly. I assume then that each torque converter (or clutch) was specific to the engine, not the transmission?

 

I don’t see how that would be possible. The converter must be engaged with the pump gears before tightening the bellhousing bolts, the only way I could see things being assembled like that is it they indexed the converter and pump gears a certain way before assembly. Very little margin for error.

 

I haven't installed an automatic in 40 years so I don't know the first thing about them. I know you install the clutch on the flywheel first

 

This is incorrect. A clutch is put on the engine and is delivered to the assembly shop. The transmission is flown in on a hoist, or slid in on a tray, the input shaft is clocked to the splines on the clutch, and the units are pushed together and bolted on. Then torqued at a later process.

In an automatic transmission, the engine comes with a flex plate, and you can see it there. The transmission comes with the torque converter carefully fully seated, and there is usually a shipping strap shot into one of the bellhousing bolt holes, either a threaded hole, or it's got a nut on the back. This keeps the torque converter in there solidly. One must remove the strap and put on a jig allowing TC rotation. Typically, you put a magnetic ended pointed rod in the 6 oclock torque converter hole. Once you have landed on the final marriage tray, or are going to marry to the engine while flying, you remove the jig, and marry the two units. Trays are level, hoists end effectors are slightly pitched back to keep the TC from falling out. You align the TC's pin with the flex plate hole at 6 oclock, and marry them.

After that, they get all torqued right. After that, a process with a guy on a stool, or a chair on a rail, will pull that alignment pin and shoot a bolt to torque in there. He will put a servo tool on the crank nut, and index the engine usually 60 degrees nowadays, and shoot the next bolt. He'll go the whole way around and recheck the first one. The automatic trans is now fully connected to the engine.

I was an engine line engineer for 13 years of my 19 so far and have designed and implemented all the hoist, end effectors, marriage slide trays, jigs, and rotators for 6 Toyota lines in North America, so all the stuff I mentioned above was done or redone at least once by me in those shops.

 

In GM engineering and assembly protocols, each transmission is specific to an engine. For assembly purposes, the torque converter is is considered a part of the transmission and therefore each torque converter is also specific to an engine. The converter and the transmission are already married before they see the engine. That way the stall speed and other converter calibrations carefully match with the engine performance specs and transmssion calibrations. Converters might look identical on the outside but they have significant calibration differences internally to match the engine and transmission with which they are used. That's why picking a converter out of a pile only based on size and appearance at the junkyard is a crap shoot. If the converter is OEM, always best to see the engine to which it was attached.

 

So then, is the converter for all OW transmissions the same? 455 H/O, 409 W30?

 

For a given year, yes.

 

Hey Matt69olds,maybe you can help me. I have been trying to find out what was specific with the OW transmissions. I have a 68 W-30, column shift but I'm missing the original torque converter. I had the OW rebuilt and a blue converter was added but I have no way of knowing if it is the proper stall. I've come to understand the OW had an extra "clutch" in it but what about the converter was specific to this transmission ? I'm having one heck of a time trying to get the right answer . Thank you for any enlightenment you can offer ! Jim

 

Do you have a converter that you are trying to verify is a OW part? I assume HydraMatic put a sticker or stamped a part number on the converter somewhere.

If you can verify that what you have is in fact a correct OW converter, you can have it rebuilt. Find a reputable rebuilder locally, or send it to a converter shop. Make sure they know it’s not a core , you want that particular converter rebuilt. I’d write all over it in bright colors so it’s hard to miss.


I have no clue what was unique to the OW converter. I have no doubt each stator, turbine and pump has its own part number or identifying mark so the guys on the assembly line knew what went into each converter. And even if you had access to each part, it would still require someone with the machinery to properly assemble and balance the converter.

If you don’t have a OW specific converter, I have no clue where you might find one. Any reputable converter builder could easily duplicate the performance and characteristics. If I remember correctly, the OW converter had a stall speed between 2400-2800. That’s easily obtained with a stock sized 12 inch converter.

 

To add what I recall from memory......the 1968 H/O (W-45) used the same torque convertor as the Pontiac OHC 6 engine. The stall was about 2200. Keep in mind that the 1968 H/O used the 308 degree in the "Non A/C" cars. Any of the TH400's can have another clutch plate added. I question your fact that the 1968 W-30 came from the factory with the extra clutch plate.

 

Not quite correct. The 6 clutch direct drum had the snap ring groove machine a little higher in the drum, that combined with no wave plate and the piston machined a little thinner provided the extra clearance. I have found those special drums in 66-70 Toronados, and 1 ton trucks,, in addition to the high performance cars.

Some people attempt to machine the piston and use thin steels and friction plates to fit 6 clutches in a 5 clutch drum, I prefer not to do it that way. While the thin plates/frictions are ok in a race car, the thin steels don’t tolerate heat nearly as well, resulting in hot spotting and warping. You also have to be careful machining the piston, if you go too thin the bottom plate can get hung up in the “clean out” groove (supposedly they had to machine the drum with that groove) resulting in no apply.

GM got smart, the 4L80 direct drum is a direct swap into a older 400, they all have the smooth sprag style surface for a 34 element sprag, and most are set up for 6 frictions from the factory.

The valve body had no 2-3 accumulator spring, a unique valve body spacer plate, and some unique valve body calibration.