tail shaft slip yoke ..

[John G.]

I'm in the process of rebuilding my Muncie 4-speed with a 'master rebuild' parts kit. While all gears, etc., check out ok one thing I notice is that the driveshaft slip yoke does have some noticable wear in the area that rides inside the trans tailshaft rear bushing. While it doesn't appear too bad, is there a spec or tolerance on how much wear is acceptable. .?.. The wear area on the slip yoke appears smooth, though a bit uneven or wavy along it's length. A new tailshaft bushing comes in the rebuild kit.

Is it possible to recondition the wear area on the slip yoke .. ? .. - 600 grit sandpaper, perhaps .. ? . . Or, is it toast .. ? .. I was wondering what you guys think ..

Thanks ..

John

[Mike M.]

Re: tail shaft slip yoke ..

sanding the yolk, on its outside diameter surface, will only remove imperfections in its surface that interphase with the seal. it won't reduce and slop in the yolk to tailshaft interphase

[Mike M.]

Re: tail shaft slip yoke ..

john; ignore my first post. if you're worried about wear on yolk where it contacts the tailshaft bushing, i'd guess that replacing the bushing would solve the slop problem as the bushing's material makeup is significantly softer that the yolk's material and wera and tear would impact the bushing many miles before it would damage the yolk.mike.

[Joe L.]

Re: tail shaft slip yoke ..

John-----

If there is obvious wear on the transmission yoke, I'd say that the only real solution is to replace it. You may be able to "smooth out" some of the rough surface with fine grit sandpaper----this will help prevent the worn yoke from "taking out" the new bushing you installed.

It's hard to say without seeing it. However, any wear which renders the OD of the slip joint "uneven" really means that the yoke is shot. There are some "rebuilt" yokes on the market which involves the turning down of the OD of the slip joint section of the yoke and pressing on a steel or stainless steel sleeve. This restores the bearing surface. However, in the process the yoke is seriously weakened as the sleeve material restores no torsional strength, whatsoever. I don't recommend "rebuilt" yokes.

Most of these transmission yokes are GM-discontinued and the Corvette yokes are mostly Corvette-only pieces. Some may be available through Spicer dealers. Also, reproduction yokes are or will soon be available in the Corvette marketplace.

[Greg L.]

Re: tail shaft slip yoke ..

Not sure if it's worth it or not for you,but a common O/H process (if the shaft is not too worn) in aviation is to chrome plate the worn area to build it up and then machine it down to the original spec. I've never done this myself but all you might need is a good chrome shop and someone to regrind the shaft. Just a thought.

[Joe L.]

Re: tail shaft slip yoke ..

Greg------

That method would work just fine. However, you would need to find a shop which does hard chrome plating and not just decorative work. The hard chrome platers are much less common than decorative platers, though. Generally, they are either "captive shops" in the aircraft, heavy equipment, or industrial maintenence industries or certain job shops which serve those industries. The overall cost for such a repair would likely be very high and far exceed the cost of a replacement. For an irreplaceable part it would be worth it, though. Also, there would be another benefit: the so-repaired part would be, essentially, "immortal" since the hard-chromed surface would be "wear-proof".

[Greg L.]

Re: tail shaft slip yoke ..

Good point Joe...I just assumed that chrome was chrome. Another option could be to weld-up the worn area and then grind it back to spec. Any competent machine shop should be able do this. I have no idea what this part is worth but all in all you are probably right in that the cost to repair will likely be more than what it's worth.

[Scott Marzahl]

Re: tail shaft slip yoke ..

I've had several parts for my 67 repaired by hard chroming such as my front spindles and the steering shaft where the lower bearing sits. I have found the cost to be expensive but not too bad. I think the steeering shaft was $75 and the spindles about $100 each. I almost had the yoke repaired too but I just sanded and polished it.

[John G.]

Re: tail shaft slip yoke ..

Thanks guys for all your replies - very interesting .. Well, I did the deed this past weekend with the Muncie rebuild. LOTS of tiny parts to replace .. ! .. The rebuild went pretty well though it took a lot longer to do the job than I at first thought it would. I very much enjoyed doing it myself and feel like I learned something along the way too. I feel I gained a real appreciation in how our manual transmissions work as well as the engineering, materials, and machining processes that went into it. One of the trickier parts to doing the rebuild was reinstalling the tailshaft housing while simultaneously aligning the reverse gear shifter selector that engages the reverse gear flange. It took a bit of finagling the works around and getting the reverse gear to slide back on to the mainshaft but finally it went. . .. Patience needed here. .!. .

One thing I found interesting with respect to the wear on the slip yoke was that the original installed tailshaft bushing appeared to be in fair condition. The surface wear area inside the old bushing appeared 'level', or 'flat' - no depressions or unevenness, etc. . I used a digital caliper to measure both the old original tailshaft bushing and the new bushing that was supplied with the parts kit. The new bushing measured 1.525" vs 1.492" for the old original bushing. I thought sure there would be more difference than this .. ! .. The slip yoke is actually worn more than the bushing .. ? ..

The hard chrome process and machining back to size to repair the slip yoke sounds like an interesting way to go for a long lasting fix. .. Then again, maybe the new slip yokes have better metallurgy than those from 40 years ago. ? . .
Thanks ..

John