Pinion yoke and u-joint problem . . . still

[terrible one]

Today I was ready to mate the transmission to the rear end via my driveshaft but ran into some trouble. The u-joint was too big to sit in the yoke. The driveshaft is correct length and from a '68 383 car, and the cap/retainer pieces I ordered for the car fit the driveshaft's u-joint perfectly. Therefore, to me it seems like the yoke would be too small? The rear is a 741 case with 3.55 gears . . . anything more I don't know. Were there different sizes in yokes? If so, which one do I need, and how can I change it? I'm on a real hustle here to get the car on the road in a few weeks. Setbacks . Sigh.

Thanks!

[y3chargerrt]

Mopar makes a ujoint that should help you out.

http://www.jegs.com/i/Mopar-Performance/312/P5007418/10002/-1

[terrible one]

Thanks man! But before I shout for joy. . .

Is that u-joint symmetrical? I ask because after looking I found that the two sizes were 7260 (smaller) and 7290 (bigger). That page says that u-joint is for the 7260 driveshaft to 7290 yoke, where I'm going from a 7290 driveshaft to 7260 yoke. Wouldn't matter if the cross was symmetrical but if not then this won't work, right?

[Ghoste]

Just rotate it 90 degrees. 

[terrible one]

Just rotate it 90 degrees. 

Are you sure? It doesn't look like it is even.

[Ghoste]

Oh, now I see what you're saying.  I've used one of those things before and it seems to me that they all came that way.

[terrible one]

Oh, now I see what you're saying.  I've used one of those things before and it seems to me that they all came that way.

All came what way? Offset like that? So no good then? 

[Ghoste]

Well no, the bigger diameter u-joint is also larger from cap to cap.  Does that make sense?

[terrible one]

Haha okay, something clicked in my head, and now I get it. Should work just fine then. 

[terrible one]

Alright, I went on and ordered it. Found the 7260 straps too. Hopefully it'll really be this easy of a fix.

[terrible one]

Well, it's a no go . . .

The MP u-joint fit in the driveshaft just fine, but it STILL did not fit my yoke! It seems like it is still not small enough! I have some pictures of it below. It's also too short from end to end on the yoke side . . . so the ends of the caps wouldn't reach of the end of the yoke either.

Another thing that I noticed while I was down there was that the straps I had were threaded bolts with no nuts, but the yoke isn't threaded. I really don't know where to go from here

[Ghoste]

Are you saying that the holes in the yoke that the retaining bolts would screw into are drilled all the way through, as if it should have a longer bolt with a nut on the other side to retain it?

[terrible one]

Are you saying that the holes in the yoke that the retaining bolts would screw into are drilled all the way through, as if it should have a longer bolt with a nut on the other side to retain it?

Yes, the holes are smooth on the inside. It also looked like it was machined on the backside where a nut would go, which made me think it was factory.

[c00nhunterjoe]

the u-joint you got fits the 742 and 489 cases with the large to small adaption. if i recall the 741 "X" housing is smaller then the other two.

[terrible one]

Aghh that would be my luck!

Really though, I think you're on to something. It just so happens that my chunk is a 741 X case . . .

[c00nhunterjoe]

ok, re-read your posts, i may be confusing myself here.

you have a 741 case but the yoke appears to be designed for u-bolts not straps, thats odd.

what part number joint do you currently have? and what are the measurements of your yoke, what are the measurements of your currently installed conversion joint and what is the length of the origonal joint?

[c00nhunterjoe]

alright, just went out and checked my parts, i have a 742/489 yoke in large joint and in small joint.both are the strap style, not the u-bolt style. they appear to be the same diameter cap but different lengths. both are approximatly 1 inch caps, the small yoke is 3 5/8's long and the large yoke is 3 3/4 long


first the small yoke-





and the large yoke-

[terrible one]

Thanks man. Here's some pictures that I got.

1. Measurement of conversion u-joint



2. Measurement of conversion u-joint



3. Measurement of yoke in the car



4. Measurement of yoke in the car



5. Shot of the backside of yoke in the car



6. Old yoke



7. Old yoke



So what's funny is that on the spot where the u-joint caps rest is the same (too small) between my old and current yoke but other than that they are way different, and the one on the car is the u-bolt style and the one that I pulled out uses straps.

Looks like I'm going to have to get a different yoke for the rear. I don't even know where to start there. Obviously I want a 7460 or whatever so that it will fit the u-joint I just put on the driveshaft, but are there different spline counts, etc.?

[mikepmcs]

Universal Joint Yokes

The 8-3/4" axle was offered with two size cross & roller style universal
joint.  These are referred to as the '7260' (2-1/8" yoke ID) and the '7290'
(2-5/8" yoke ID).  Most Imperials and some C-bodies used a different univer-
sal joint.  The '1330' type joint was used on Imperials and others with a
constant velocity joint.  The '1330' uses outside snap rings instead of the
inside snap rings used by the '7269' and '7290'.  The cap diameter for the
'7260' is 1.078".  The cap diameter for the '7290' is 1.126".  The '1330'
style joint cap diameter is 1.063".

There are four different yokes that have been used with the 8-3/4" axle
for the '7260' and '7290' style universal joints.  The '741'/'742'
assemblies used a coarse spline (10 splines) drive pinion.  Most of the
aftermarket gears also use this coarse spline yoke mount.  There is a
small yoke for the '7260' and a larger one for the '7290'.  The '489'
assembly used a fine spline (29 splines) yoke.  Note: during the phase-in
period of 69-71 for the '489' unit, there were several permutations of pinion
size and yoke availability.  69-70 '489' units may be equipped with
a coarse (10) spline pinion, particularly for the '7290'.  There are two yokes
for the '7260' and '7290' universal joints with fine (29) splines.  Two
additional yokes were used for the '1330' style universal joint in
constant velocity applications, one for 10 splines and one for 29 splines.

Interchange Notes:

7260, 7290, 1330 yokes may be interchanged if the spline count is the same.

Note:  the 9-1/4" axle (73-up) uses the same fine spline yokes as the
8-3/4" fine spline units (29 splines).

[c00nhunterjoe]

do both of your joints, (new and old) fit your old pumpkin yoke?   have you tried tapping the joint into the new yoke?

[terrible one]

Mike, thanks so much dude!

Going by that, I must have the 1330 yoke. the 7260 side of the u-joint is just barely too big, and the information you supplied shows the 1330 being just a tad smaller than the 7260 which would confirm this again. But I don't think this one would use snap rings on the outside because it has little metal stoppers that seem like they would keep the caps from going past them, so I don't know what to think. It's just weird . . . the chunk is a 3.55 suregrip unit. Of course it's my luck that I bought one with this oddball on it.

That being said, either way this yoke isn't going to work. It looks like my plan of attack should be to remove my current yoke so that I can get a spline count, and then replace it with a same spline 7260 yoke so that it will fit with this u-joint I just bought. How big of a job is it to exchange yokes?

[terrible one]

do both of your joints, (new and old) fit your old pumpkin yoke?   have you tried tapping the joint into the new yoke?

The old joint is definitely way too big for the yoke that's in there now . . . I did not try the old joint with the old yoke. (the old u-joint and driveshaft are not from my car . . . they are from another '68 383 charger. I never tried tapping the joint into the yoke . . . it's definitely not going to fit.

[c00nhunterjoe]

ok, just figured i'd ask, it looks close in the pic but pictures dont tell the story of the guy holding it in his hand!

you dont have to remove the yoke to count the splines, just zip the nut off and the washer then you can clearly see the splines. it will be quite obvious which one you have

[terrible one]

Oh yeah I hear you man! you've been such a big help to me. Thanks for the tip on getting the spline count. I suppose I'll do that tomorrow, then I'll know exactly what yoke I need to find. According to the info Mike posted, it should be a 10 spline, but I can't count on anything anymore it seems!

How hard of a job is it to switch yokes?

[c00nhunterjoe]

i cant recall if the 741's are shimmed pinions or crush sleeved. either way its doable, some will tell you that you cant re-use a crush sleeve but i have done it hundreds of times with no problems. if you dont know what you are doing i reccomend having a friend that is familiar with crush sleeves do it for you...... if its a shimmed pinion then you just smack the old yoke off and smack the new one on. hammers are wonderful inventions.