9" differential yoke runout specs?

[cleandan]

Hello all, I am woking out some driveline vibrations and I measured the axial runout of the 9" differential yoke.
I measured a 0.022" difference.....Then it occurred to me I have no idea what are acceptable yoke tolerances.

I assume they are pretty tight based on how precise a U-joint is made, but they are also cast so maybe things are generous in variance.

Does anyone know if 0.022" is something to be concerned with in terms of axial runout on a differential yoke?

Thanks in advance.

[Katz427]

Without beating the subject to death, Spicer specified .010 runout at the front and rear of driveshaft. However the driveshaft company we have used specified .020 max as measured at the center of the length of the shaft. With new parts one can usually stay well within these specs, however, sometimes tolerance stackup, will bite you. I would like to see your runout closer to these specs.

[jayb]

Dan, where are you measuring the runout?  If it is outside on a cast or forged surface, then I think the runout might be OK, given the variations common in castings and forgings.  If it is on the machined surface that the seal rides on, then that runout seems like an awful lot...

[Falcon67]

As Jay said - I'd not use any exterior surface as a check except the machined seal surface.  I'd be looking for an old pinion, cut the gear off and put it between centers with the yoke, then check the seal surface runout. 

[cleandan]

The measurements were taken on a fully assembled center section in the car.

Internal clip style U-joint caps were installed in the yoke, seated, and clamped in place.
Then I used a dial caliper to measure from the clip seating surface to a hard spot marked on the vehicle.
I also used a graduated level to help place the yoke in the same position for all measurements to help with repeatability.
Specific areas to measure from were marked and used for all measurements for repeatability.

I assumed the machined cup area of the yoke, where the U-joint cap seats, is accurate.
I assumed the machined spring retaining clip area of the U-joint cap is accurate.
I assumed the graduated level is accurate.
I know the dial caliper is accurate.

All these used carefully together is how I made my measurements.
Not ideal, but not bad either....at least for initial testing purposes.

[winr1]

Internal clip style U-joint caps ...

The clips go into the yoke after the u-joint caps are pressed into place ??

If so, are both clips flush with the caps ??

Perhaps measure from the top of the caps ??


The u-joint could be off centered a few thousands in the yoke perhaps ??




Ricky.

[cleandan]

I used a single internal clip style cap (of the correct diameter)
The cap was marked in one spot to measure from and the cap was clocked in the yoke to measure from the same spot on both sides.

Doing this allowed me to measure the yoke seating surfaces without any input from the U-joint itself....I'm trying to isolate the issue so removing variables seemed like a good idea.

I was very careful in seating the cap in the yoke to be certain it was properly placed.

In all this I have noticed the two seating tabs on the yoke (external clip style) are different in the machined areas.
One tab is relatively large, with plenty of material and a defined machined seating area.
The other tab looks to be machined down past its half way mark leaving behind a much smaller tab when compared to the other side.

I think the 1310 yoke should be 2.500" side to side width but the yoke measures a bit bigger than that (can't remember the number at this moment but it was wider than 2.500" by enough to take note.

The more I look into this yoke the more it appears it was machined about .022" off to one side.

If the yoke is off by that much, and the driveshaft is off by a bit too, but still in tolerance, the combined errors may be where my vibration resides.

Before I pull the yoke today I will take some measurements from the machined hole in the pinion gear shaft using a centering device as the place to measure from.

I am going to search for a long style yoke, in cast iron, because an original look matters on this car and see if I can find something a bit more accurate.

As much as I enjoy the vibra-chair as I go down the road I don't think this amount of vibration is doing the car any favors.

I hope I am making progress.
Knowing the acceptable tolerances of the involved parts would be nice, but sometimes we don't get that luxury.

As always, thanks for all the helpful input.

[pbf777]

In all this I have noticed the two seating tabs on the yoke (external clip style) are different in the machined areas.
One tab is relatively large, with plenty of material and a defined machined seating area.
The other tab looks to be machined down past its half way mark leaving behind a much smaller tab when compared to the other side.

     If I'm understanding your description correctly; the physical retention "tab" within the yoke's u-joint cap saddle relief radius as machined is not necessarily going to be consistent in width as the outside dimension is controlled by the yokes' as-forged exterior surface profile.  Here, a good quick test is to take a known good or new proper sized u-joint assembly (caps including the cross-trunnion) and just lay/press it into it's intended seated position with the observation of whether the length of the u-joint is tight between the two "tabs", and also fits tightly in the radius.   

     Beyond just poor previous (monkey  ) efforts, and just wrong parts assembly causing damage, with some often not so ingenious fixes, often if the u-joint becomes excessively worn, and particularly if one or both of the retaining u-bolts were not torque adequately at some point in the past, this can lead to the caps in the assembly slipping and causing a hammering effect, which will given time displace material causing excessive resultant distance to be presented between the two tabs, and allowing the entire driveline assembly to be displaced off center.   

The more I look into this yoke the more it appears it was machined about .022" off to one side.

If the yoke is off by that much, and the driveshaft is off by a bit too, but still in tolerance, the combined errors may be where my vibration resides.

      These values as you have presented if accurate are way out of acceptable sums; something closer to .003" deviation would be expected, in excess of say .006" begin to expect vibratory effects, .012" or more, your just wasting your time!   

      Acquire a dial-indicator, fixture it to the rear-end housing (not something that can change position in the relationship  ), mount a complete u-joint assembly (one that has proven to 'register' properly as described previously  ) and indicate off the machined stop surface of the cap exposed, rotating the yoke repeatedly until one is confident with the process and the execution with repeatability. 

     Scott.

[cleandan]

Confirmed, this yoke is machined off center.
I removed the yoke yesterday and did some measuring with it mounted in my lathe.
Without question the yoke is machined off center.

The locating tabs are also too wide, and one side is vague in its ability to seat the U-joint cap.

One tab is clearly machined with a defined area for the cap to seat.
The other tab is more like a suggestion about seating in the general area, rather than having any defined spot to seat.

This is allowing the U-joint to have too much side to side motion in the saddles (about .020") while also allowing the seat to be vague and inconsistent each time the U-joint is mounted in the saddles.

The yoke is a cast iron "long" version with 28 spline input, standard (non-daytona) bearing, 1310 spacing (3.219" wide) but using 1.125" diameter caps rather than the 1.062" caps most 1310's use. It also uses U-bolts to retain the U-joint.
I would like to replace this yoke with a proper cast version to keep the original look.

Most places to not offer the 1310 spacing with the larger cap saddles...at least not on the website info I can find.
Many places do list a "special Ford" style that speaks about this different size build, but they don't offer a replacement.

If you have a good yoke you would sell, or you know where I should source a new version, please let me know.
Come Monday I will call a local driveline shop to see what they can find for me.

I know there are different variations on U-joints, but holy smokes, I never knew there were so many variations.

[jayb]

Holy smokes is right LOL!  Whether the yoke is machined off center or not really shouldn't impact it's performance, as long as all the machined surfaces are correct relative to each other.  Variations in casting and forging datum points will lead to these kinds of variations.  You mentioned that one of the u-joint cup machined areas looked precise, have you thought about just reinstalling the yoke, and then installing the driveshaft and tapping the U-joint against the side of the yoke that looks right?  I think once it is clamped in place the U-joint probably won't move from that spot.  If in the vehicle it had been sitting against the other side, it could have left the driveshaft off center.  Just a thought, in case you can't find the right yoke...

[pbf777]

Confirmed, this yoke is machined off center......................Without question the yoke is machined off center.

Not to be at odds, particularly as I'm not the one holding the part in hand, but, I believe your description in your observation is consistent with my explanation previously; that do to the U-joint being permitted to slip in the U-bolt(s) in operation, this causing a hammering effect which led to the material loss; this vs. actually being machined of center by the O.E..   Generally one would expect the side demonstrating the not so defined remaining machine work and narrower tab was the U-bolt that had provided the insufficient clamping force.   

You mentioned that one of the u-joint cup machined areas looked precise, have you thought about just reinstalling the yoke, and then installing the driveshaft and tapping the U-joint against the side of the yoke that looks right?  I think once it is clamped in place the U-joint probably won't move from that spot.   Just a thought, in case you can't find the right yoke...

     This is fine as described for perhaps only a interim fix, but generally in order to provide adequate clamp-load by the U-bolts to resist joint-cap movement in the plane that the register "tabs" function, would require torquing values beyond that as intended by the fasteners, and possibly (particularly but not limited to...... ) distortion of the bearing cap leading to premature failures to the rollers and trunnion in service.   

     Scott.

[cleandan]

Yesterday I called Joe, we talked, and sure enough he had one proper yoke in his stash.
I went out there, we talked for about half an hour and I purchased the yoke.

I has clearly been hammer bashed to remove int at some point, but all looked good enough to give it a try.

Some clean up work, rust removal, grease and grime removal and a bit of paint spruce up (cast iron grey of course) and the important areas measured very good.

Today I installed the refurbed yoke and the new driveshaft I purchased from "Dead Nuts On"....a really good place by the way and...............Wait for it................


Things are greatly improved. My driveshaft and yoke issues are now gone, and so is the vibra-matic drivers seat, but I can live with that.

All the stuff I have been fooling around with was supposedly installed by a well respected shop.
All together the issues I found were.
1) Driveshaft tube oval shaped, not round, by .060"
2) Driveshaft bent in two places....not a lot, but enough to matter over its length.
3) Driveshaft very poorly balanced.
4) Wrong U-joint installed on the differential end.
5) Damaged pinion yoke with at least .022" axial runout.

All together the issues added up and made a real problem.

Thanks for the ideas, hints and other comments.

Now onto figuring out why the clutch/flywheel is not quite balanced either.