Yoke Sizes

Bruceynz

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Hi Guys,

Ok the 1973 trans I had rebuilt will not take the yoke from my 998 trans, the spline counts seem to be correct but the diameter of the yoke must be different, I measure the yoke at 1.56" The spline match up and the yoke pushes on about an inch and thats it.

trans.jpg


Looking into trans

yoke.jpg


Looking into yoke
 

AJ/FormS

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I have mated an A998 from 1980, to a 60s driveshaft, So IDK but in my case they were compatible.
Looking at the pattern of plowed up grease in your yoke, it seems like
your yoke is crushed oval
To prove it;
Load the yoke up with a little grease, all the way around and only need to go about a half inch deep. Clean the splines on the shaft,index the yoke to the shaft, and push them together until things get tight. Separate them and note where the grease is piled up inside the yoke, in relation to the index. Redistribute the grease,clean the shaft, turn the yoke about 90*in relation to the index mark, and repeat. Note again where the grease piles up. If it's in the same place, then the yoke is likely crushed. If it's in a different place, maybe the shaft is twisted or there may be crushed splines on the shaft.
Nice camera work.
 
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Bruceynz

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found this, is this my problem?

rnt_8935s_p04_ang.jpg


And there are a couple of different sized (O.D.)output seals for the 904 based transmission as well.

Housing bore 2.372 uses National# 2506
Housing bore 2.249-2.25 uses National # 8935S

Both of these are the boot type seal.
 

slant6billy

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I had a similar issue last year, but with a chevy. I was swapping a trans from an S10 Blazer. Real pain of a job too. Got all complete and the driveshaft would not go into the trans. I thought a seal issue too. I removed the input yoke from the drive shaft to make things easier as I tested fitting it. I did find that it only wanted to go in at a certain spot. Also I was not able to just push it with my hand. It required some added leverage. Perhaps I was just too weak to force it on. I did make certain the splines were clean and free of debris. I think the replacement trans had something going on with the splines or tail shaft. Put the drive shaft back together and used a prybar to push it on. Truck never had an issue and the owner was a little abusive since. I agree the seal might be fighting u on this. Can you try a different seal and also I suggest temporarily remove the yoke end from the drive shaft for less frustration
 

Bruceynz

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it will not go in, there is a problem, my friend thought I was talking shit so he had to come over and see this for himself, he said he would not of believed it until he saw it and he has been building mopars for years! He thinks I need to talk to the trans shop and find out if they have a different size seal. The thing goes on the splines on but don't won't go on all the way, something going on its so tight it can't slide and thats not a good idea!
 
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Bruceynz

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Ok it looks like I have got to the bottom of it, I have been screwed over by 4.5 thou! Can you believe it, the 904 lock up trans has a yoke of 1.5625" or 1 9/16th" and the non lock up are at 1.558" yoke diameter, there is a bushings in the back that requires 3 thou clearance and this is where the problem lies!

How would you know, why would you change it by 4.5thou, did the engineer go hey lets change the yoke size today to justify salary, who knows we will never know!


upload_2017-10-24_22-17-10.png


Thanks
Bruce
 
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Bruceynz

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I think if you had a used trans and it has a tail shaft bronze bushing there is a chance the larger 1.562" shaft will fit, but when its all new I think there will be some problems, we are talking 4.5thou and there is 3 thou clearance then if it wears 1.5thou then it will slip in. If the oil tolerances are ok at that I dunno I am no engineer, I have ordered a yoke from USA at 1.558" so when it arrives will see if I can solve the mystery.

I have mated an A998 from 1980, to a 60s driveshaft, So IDK but in my case they were compatible.
Looking at the pattern of plowed up grease in your yoke, it seems like
your yoke is crushed oval
To prove it;
Load the yoke up with a little grease, all the way around and only need to go about a half inch deep. Clean the splines on the shaft,index the yoke to the shaft, and push them together until things get tight. Separate them and note where the grease is piled up inside the yoke, in relation to the index. Redistribute the grease,clean the shaft, turn the yoke about 90*in relation to the index mark, and repeat. Note again where the grease piles up. If it's in the same place, then the yoke is likely crushed. If it's in a different place, maybe the shaft is twisted or there may be crushed splines on the shaft.
Nice camera work.
 

Kernel Sanders

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I had a similar issue with a used 727 Big Block trans I picked up a few years back... The PO neglected to mention it was dropped on its tail and tweeked the tail housing. When trying to slide the yoke in it would just stop feeling like it hit something solid. It was, the tail bushing!

I replaced the entire tail housing and all was golden again.
 

BudW

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The PO neglected to mention it was dropped on its tail and tweeked the tail housing.
I suspect this may be more of your problem than anything else might be. I have seen some tight seals before – but seals make contact right away, and not an inch into it.

My guess is the tailhousing is buggered up somehow (shipping, dropped or something). Checking the bushing for roundness is not difficult – unless it is installed (like it is) for the output shaft is in the way.

Without the yoke, the output shaft will be a bit of up/down play on the shaft (which is normal). With a camera (video?) and light – "visually" check for distance between output shaft and bushing. Also check to see if bushing might have a bright spot on it (from contacting the yoke).

If bushing distance looks correct the entire distance – then it might just be the seal (being tight). Put some ATF on the outside of yoke (never install a propeller shaft yoke dry) and take a rubber mallet and tap on end of propeller shaft.

I have seen more than a handful yokes take a forceful bump with palm of hand to get past the seal - for the first time.

Note: the outer part of seal keeps mud and dust off of the yoke, only. The outer boot part can be removed – but I prefer to use them. The yoke moves in and out (of transmission) a lot more than people know (or think) about.

I have only seen 3 different kinds of slip yokes from Chrysler (early ‘60’s to 2000).
The 230/903/904/998/999 (ie: small yoke).
The 727/833 (ie: big yoke)
And the 48RE from diesel pickups (really big slip yoke – and makes the 727 one look tiny).

I have seen fully splined yokes (older ones) and yokes with a key in them (yours has a key) which most are). The key allows air to go towards the transmission when yoke moves inwards/outwards. The fully splined ones has a small hole on outer end to allow for air movement – but they tend to leak out the hole and are not recommended because of that.
That has nothing to do with your problem, though.

If there is a “non-lockup” vs. “lockup” slip yoke differences, then it is news to me – and I have man-handed a thousands of propeller shafts in my life.

They do make oversize bushings and seals for undersize slip yokes (seals for yokes that are grooved/bushings for damaged yokes that were machined down for re-use).
BudW
 

Bruceynz

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The reason the yoke goes in so far is because the yoke has a small taper on the nose. I measured it, there seems to be an undocumented change that has happened. Is 4.5 thou much, no it isn't but in other ways it moose well be 1 inch bigger :)

There are 2 yokes, 1.558" and 1.562" there appears to be only one bush listed, if the bush is bronze the shaft will wear it to size but if its white metal it won't.

Someone here may have played with them, I dunno what is going on, when my 1.558"yoke arrives and if it pops right in we will know what is going on, if not we will know I was barking up the wrong tree!

I have got my fingers crossed my research will pay off other wise I will be standing there with a nice shiny yoke in my hand with the other hand scratching my head. If fact if it doesn't fit I might smash myself over the head with the new yoke!:mad:

Thanks
Bruce
 
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Bruceynz

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If someone can measure the ID of a tail housing bushing I think we can put this one to bed quite quickly :)
 
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BudW

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I have a sizeable box of mixed Torqueflight bushings. On top of my head, I doubt there is the 904 version in that box (but again, maybe there is).

The tail housing is somewhat easy to crush (or flatten the bushing area – making it oval shaped. The same applies to the yoke – but it takes a lot more to make the slip yoke oval shaped.

The Yoke is a lot easier to check for roundness – with a micrometer or caliper. The bushing would be easy to check – except for the output shaft gets in the way to measure it.

I put a note in my pocket to locate and see if I have a 904 tailhousing bushing, when I get home, tonight.
BudW
 
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