oem tranny mount holes

[RICH MUISE]

Having never While piddling with my tranny mount today for a few minutes, I noticed the two oem holes (slots) are off center from the overall length of the crossmember. I'm just doing a tape measure check, so it's nothing super accurate by any means, but I was careful to line up the tape measure the same way on both sides. It appears the holes have an overall difference of about 5/8 total, or 5/16 off center. What would be the reason for this? I don't have my original Ford tranny, so I don't know if the mounting holes in the tranny are off-centered from the output shaft.
I am going to make a huge assumption here...the centerline of the drivetrain is centered on the vehicle..correct?

[Tom S]

I am going to make a huge assumption here...the centerline of the drivetrain is centered on the vehicle..correct?

Measure to the pinion center.

[RICH MUISE]

Tom...I think what you are telling me is....since the pinion is centered, just make sure the engine to tranny centerline is in line with the pinion center. Is that correct?
This is a case where I want to make sure a little bit of knowledge is not going to be dangerous. I know some pinions are not centered, but I'm under the opinion that the oem '57 drivetrain is centered. I am talking left to right here, not the pinion angle as viewed from the side. That statement is why I was questioning why the tranny mounting holes on the oem crossmember is off center.

[Tom S]

Tom...I think what you are telling me is....since the pinion is centered, just make sure the engine to tranny centerline is in line with the pinion center. Is that correct?

Well, sort of, but not really.  I don't know if the pinion is centered.  Like you, I am just assuming that it, & the rest of the drivetrain, is centered.  Maybe it isn't.  I am surprised that holes on the crossmember are off center.  Doesn't really make much sense but it just now occurs to me that maybe the mounting holes on the oem trans were off center for some reason.  Like a clearance issue with the shape of the auto or stick trans.  I doubt that but I don't have one to look at.
In any case, if the trans was off to one side in relation to the pinion by only 5/16" I can't imagine that it would make much difference.  Easy enough to fix anyway.

[Ford Blue blood]

If your drive line is 100% in line you will have a pesky little vibration.  Ford and other makes place the engine centerline off just a touch (or the pinion) to keep the u-joints loaded up ever so slightly.  The up and down travel keeps them loaded in the vertical plain but the horizontal plain needs a little tweek to keep the u-joints from being perfectly aligned.

[RICH MUISE]

Thanks for the input, Bill and Tom..just what I was looking for.
BTW, when I was striiping down the old Mark viii, I had mentioned I was having a problem removing the driveshaft yoke bolts. I've got the same problem with the exhaust bracket that's bolted on to the bottom of the tranny at the mount location. Yesterday I had a 24 " breaker bar on those bolts and no movement at all. I got to thinking I later discovered that tranny had been rebuilt, and the bolts I can't get out were the ones they would have removed and replaced when they rebuilt the tranny..I'm guessing they were loctited in.
I was hoping to leave my engine/tranny mockup in place until after I reworked the crossmember, but now I'm going to have to drop the R & P back out and pull it out so I can get to those bolts with a cut off wheel..of course if they are in fact loctited in, cutting the heads off the bolts isn't going to help. I know..I should have done that before I "installed" it in the car. LOL..

[Tom S]

If your drive line is 100% in line you will have a pesky little vibration.  Ford and other makes place the engine centerline off just a touch (or the pinion) to keep the u-joints loaded up ever so slightly.

I wondered about that too but don't remember ever seeing that info anywhere.  Especially the part about the factory offsetting them.  Where in the world did you find/get that info?

[Ford Blue blood]

Tom I really don't know where the info came from.  There have been numerous articles over the years in magazines that I get/have gotten dealing with building the drive line and problems folks run into and of course the cause and fixes.

The parts that stuck with me were keeping the u-joints phased and the fact that when any u-joint is installed there is no such thing as "zero clearence" with respect to the ends of the cups and the end of the trunion it's self.  There is a little slop in there, the trunion will slid side to side in the cups.  The other part is if the engine is 5 degrees up the pinion needs to be 5 degrees up.

Following those rules over the years has served me well, no complaints from guys I built cars for and many happy folks who's cars got the pesky little vibration done away with.

[RICH MUISE]

Bill..thanks again..question..."The other part is if the engine is 5 degrees up the pinion needs to be 5 degrees up." Probably a matter of how you're looking at it, but is this what you meant to say?
Tom...There is an excellent thread running on the Hamb right now titled "Pinion Angel?"..yes, you'll also have to misspell it to search. I'll try again to post a link, but I just dumped this whole reply trying to do it the first time. It's what Bill is saying I believe with tons of drawings and technical stuff, but well explained. In particular look at the info Gimpyshotrods is posting.
http://www.jalopyjournal.com/forum/showthread.php?t=785703

[62galxe]

If its Loctite a little heat will break it loose.

[Ford Blue blood]

Yup...that's it.  Thanks Rich.