Output shaft yokes

[Bainford]

 I'm doing a rear axle overhaul on my Special. During disassembly I found that there were no shims between the output yoke and the output shaft shoulder. As expected, the roll pin is broken into three pieces. The Dave Bean catalogue says this will result in a 'wallowing out' of the yoke splines, creating a loose fit, and that is indeed what has happened. The yoke is now a sloppy fit on the shaft splines. I quick check shows there should have been approximately .030" of shim in there. A close inspection of the shaft splines shows very little wear, but the female splines in the yoke are worn significantly.

I tried to order a new pair of yokes from RD Enterprises last week (they are on the website), but they are on backorder and apparently have been for some time. RD is supposed to get back to me with some idea of delivery time, but I'm losing optimism. I called Dave Bean as well, but no luck. Apparently Banks may have them, but they are pricey little buggers (RD quoted over $450 USD each), and ordering from the UK won't make them any cheaper, but if that's the only source...

Does anyone know of a North American source for these yokes?

[jbcollier]

They are designed to wear that way as the yokes are cast iron and the output stub axle is hardened steel.  Yoke wear is a minor issue compared to potential damage inside the transaxle.  Are the output stub axles still tight with no play in/out, or up/down?

[Bainford]

Up/down has no discernible movement. Axial float measures .005” (spec .002 - .004”). Reasonable, I would think, for a 50,000 mile assembly.

[jbcollier]

That's good news.  Good luck in your search.

[Bainford]

I managed to find a pair of inboard yokes at Banks. Surprisingly, even with overseas shipping and an exorbitant import fee, they were still much cheaper than I could source in North America. These yokes have two sets of pin holes at the yoke hub, one 5 mm and one larger (I assume the larger is for a different application) These are likely the only available replacements for inboard yokes.

However, there is a dimensional difference between the new parts and the originals that have me concerned. The distance between the 5 mm scroll pin bore and the u-joint bore is about .140" greater on the new yokes. This creates a number of potential issues;
- This makes for .140" less spline engagement (which, with the original yokes, is already minimal)
- There is an additional .140" of leverage of the radial torque loads from the u-joints/axle against the end of the shaft splines, aggravating the 'wallowing out' and wearing tendency of the yoke splines.
- And perhaps of most concern, this will result in the axle pushing the center of the wheel outboard by .140", whilst the lower portion of the upright held in place by the lower link. This would result in a not insignificant change in suspension geometry, specifically, adding positive camber. And this, on a stock suspension with no camber adjustment.
- Though a minor issue, but I now have to endure the nuisance of sourcing an additional .140" shims for each side as well.

I am reluctant to use these yokes as they are. I have been considering boring a third set of holes through the hub portion of the yoke, half way between the two existing sets, axially positioned closer to the u-joint bores.

Thoughts?

Has anyone used these replacement yokes as is? Did you incur any issues as a result?

[Triton]

I had the same issue, i bought 2 new yokes of Banks. When i stripped it down i found that the splined spacers and o rings were missing , a previous owner had just put a couple of thick washers in place. Richard at Banks managed to find me a couple of s/h ones. I rebuilt it up with new  o rings and 36x54x8 oil seals. Both sides leaked a little so i stripped it down and used 35mm seals instead i also coated the o rings and the groove in the spacers with with a sealer i find very good which is called ThreeBond.  I shimmed them up tight and have done around 100ml and the drivers side is snuff dry but a slight weep on the other side. I think this may be my fault ,i got the oilseal in a little cocked,will put a new seal in this week.My car is a 73 Special so i used the smaller holes on the yokes with 5mm scroll pins. I also put a coat of ThreeBond around the oilseal.  Stuart....

[Roger]

Are you sure you have the right yoke for your gearbox? I know there are different types.

[jbcollier]

First, double check you measurements (I know they are probably good but just make sure).  Then contact the supplier and see what they say.  Don't modify them until you are sure you want to rather than return them.

[Bainford]

I had the same issue, i bought 2 new yokes of Banks. When i stripped it down i found that the splined spacers and o rings were missing , a previous owner had just put a couple of thick washers in place. Richard at Banks managed to find me a couple of s/h ones. I rebuilt it up with new  o rings and 36x54x8 oil seals. Both sides leaked a little so i stripped it down and used 35mm seals instead i also coated the o rings and the groove in the spacers with with a sealer i find very good which is called ThreeBond.  I shimmed them up tight and have done around 100ml and the drivers side is snuff dry but a slight weep on the other side. I think this may be my fault ,i got the oilseal in a little cocked,will put a new seal in this week.My car is a 73 Special so i used the smaller holes on the yokes with 5mm scroll pins. I also put a coat of ThreeBond around the oilseal.  Stuart....

Thanks Stuart. Interesting comments about the oil seal size. I have noticed that my old oil seal has not been bearing firmly against the shaft spacer. Not sure what size the old seals were, but my new ones are indeed 35 mm. Did you use a sealant on the threads of the diff nuts that hold the seal? Using the new yokes as delivered, have you noticed any change of rear camber after reassembly?

[Bainford]

Roger, JB, I intend to verify that the new yokes are the proper items, though I am reasonably sure that they are. I am giving serious thought to drilling a new hole in a proper location in order to maintain the wheel geometry.

[jbcollier]

The holes only line up in one orientation.  You will need to jig it up very carefully.

[4129R]

The holes only line up in one orientation. 

I think this means that the holes in the diff output shafts are not exactly central, so you cannot line up the holes with the yokes 180' out, they have to be exactly lined up at 0' or 360'.

[Triton]

    I must admit that i never checked for a different measurement on the new yokes. I can't check now because i have machined the old yokes down to make a couple of splined oil seal spacers if i ever need them. My box is a 352 and i had it stripped and rebuilt by a specialist, there is no leak on the finned nut threads so i think he will have put sealer on them.The spacers measure 36mm but i have used 35mm , it's only .5 mm less around.Not checked the camber but the car looks to sit right,will check tomorrow.I have stripped the leaking side down this morning and waiting for a new seal. Will see if i make a better job this time. If you are going to drill another pin hole i would take them to a good engineering shop if you don't have the equipment.  Stuart.......

[jbcollier]

The other solution would be to try it and see what you have.  If your camber is within specs, all's good.  If not, just fit adjustable lower links and revel in the improved handling with the increased rear track.  After that, it's pretty simple way to shorted the half-shafts.  Sounds crazy but any drive shaft shop can easily do the work.

[Bainford]

Cheers JB. I have considered the orientation requirement. This makes boring a hole in the new yoke tricky. Basically it is a need to lay out the new hole relative to the splines. Looking at the current hole, it can be seen that the bore breaks through the female spline of the yoke at the crest of a spline, and then through the valley of a spline on the opposite side of the yoke hub.

Actually, I was surprised to find the hole in the shaft to be the same size as the hole in the yoke (5 mm). For some reason, I was under the impression the hole in the shaft was larger. This made sense, possibly for functional reasons, and certainly to ease the shimming job, but especially to account for production variations. Even back in the day, but especially today, with aftermarket parts, and manufacturing tolerances on this stuff being what it is, I am amazed that the pin holes ever line up suitable to drive a size-for-size 5 mm pin through it all.

As for cutting the drive shaft, that will be Plan C.