When I had the driveshaft made I had it measured so the slip yoke was bottomed out and pulled back out 1 inch Posted from the TJJ App for iPhone & iPad
I believe the 904 came out in 1960 and the 727 in 62 or 63. These were both 3 speeds and a big improvement over the earlier automatics. The early 904 had a "6" designation and used for slant six motors. When the 273 and 340 v8 motors came out the 904 lost its 6 designation and was used in all 6 cyl. and small block motors. The HP 340 and 360 motors used a version of the 727 as did all big blocks from then on. The two are very simular in design and if it is true that you have a 904 trans then the motor is not a 400 BB but a small block because I do not believe anyone made an adapter to bolt a 904 up to a BB.
I think the clue is that the longer you drive the vibration gets worse. What is your rear tire psi? As you drive the tire and air gets hotter and hotter, just an idea.
Then it has to be a 727 because I know for a fact it is a 400. Posted from the TJJ App for iPhone & iPad
I have an electronic vibration analyzer that measures vibration and can display the individual vibration "frequency" which is frequently related in some way to rpm of the problem component. http://www.maintenanceworld.com/articles/coxj/vibrationpen/diagram1.jpg It can save a lot of trial and error when troubleshooting vibration problems. If you were close to Eastern Mass we could go for a ride. Here is a link to a reed tachometer. http://www.jackssmallengines.com/Parts-Lookup/19200 /304830/ps?gclid=CKfY6c3OnbcCFUee4AodhTcAbA It could be used to identify the frequency of the vibration(s?) you are feeling at 45 mph. If its about 600 rpm or cpm it is related to tires and wheels. Driveshaft balance or sometimes seized u-joints would likely be more like 1500-1800 rpm. U-joint angle issues, sometimes seized u-joints,or super soft trans mounts or axle mounting usually is twice driveshaft rpm, 3000-3600 in this example.
The combination of the 400 and the 904 still sounds strange to me. Chrysler may have put the two together in some applications but I've not seen it. So my thinking keeps going back to the 400 being externally balanced, as previously mentioned. And then maybe the 904 got added on at a later time. And if the torque converter from the 904 was used and it was from an internally balanced engine, that might be the source of a vibration. The Torquflites used balance weights welded to the converter, not to the flex-plate. Any converter is likely to have at least a small weight attached to it to balance just the converter. For use with an externally balanced engine, there will be maybe two larger weights, possibly a couple inches long. Hard to describe here but a websearch will probably show you the specific difference. This isn't really dependant on the transmission type. Either way, an externally balanced engine will require a specific torque converter, as well as the harmonic balancer, I believe.
All I can give you is my experiance in something close. 440 with 727 trans vibrated like a bitch, knocked out screws vibrated the floor and my feet...turned out it was the wrong torque converter...some need to have balance weights , some not..I changed the TC and all my problems went away...well, the vibration problem on that car went away if it aint that, than keep lookin well , i see claymart has a quicker keyboard
Figured it out today! I ended up putting a 5/16 shim in the tranny mount to raise it up and change the driveshaft angle. All is well now! Well... For as good as it can get with it being 60 years old and mostly original equipment Posted using the Full Custom H.A.M.B. App!
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