MoparFins

Techical Discussions => Tech- - DRIVE TRAIN => Topic started by: Snotty on May 12, 2009, 09:26:51 AM

Title: Different U-Joint Sizes
Post by: Snotty on May 12, 2009, 09:26:51 AM
I did not realize there were three different rear u-joints for Mopar rears! 
 
Perhaps you know that I installed a Mopar A Body 8.75 under the Gremlin.  Jerry and I replaced the axles and brakes with 4.5" bolt axles and all new brake hardware.  We also swapped the 3.55 Open rear with the 3.23 SG I took out of the Newport.  No problem!
 
Well, here's where it got weird.  I picked up an A Body driveshaft at Fall Fling last year.  This past month we took it to a shop to get shortened and have the T-10 AMC-specific front yoke attached.  I told them what case I have on the rear.  With no further questions asked we left and I picked up the new shaft a few days later.
 
BTW, the shaft looks great!!  It cost $123.00 to cut, balance, and fit the u-joints and yoke.  Much better than the $500.00 I was quoted to get one custom-made!
 
OK, I installed the shaft (Jerry was woring on the interior).  It fit like a glove!  BUT, when I went to connect the rear joint to the rear yoke I learned that there are two different size rear yokes!!
 
I guess these are not specific to the case, for I told them it was a 489; I had this third member on my Newport - it was a perfect fit!  I held the u-joint up to the rear I got from Mark - perfect!  I learned then that I will need to make a swap on my u-joint when I install that one on my Newport.
 
Long story getting shorter, I got a correct u-joint last Friday and installed it.  It fits and works great!  It needed to be wide on the shaft, yet short for the third member.
 
MORAL OF THE STORY: Be sure of the sizes of your third memeber and shaft before you buy a u-joint.  Apparently, they are not specific to the type of rear you have.
 
I did not know that.
Title: Different U-Joint Sizes
Post by: Stan Paralikis on May 12, 2009, 11:00:54 AM
Quote from: Snotty
MORAL OF THE STORY: Be sure of the sizes of your third member and shaft before you buy a u-joint.  Apparently, they are not specific to the type of rear you have.
Snotty, Snotty, Snotty. (http://www.moparfins.com/forum/smileys/smiley36.gif)  Always read back to yourself what you write before posting. (http://www.moparfins.com/forum/smileys/smiley2.gif)
Title: Different U-Joint Sizes
Post by: Stan Paralikis on May 12, 2009, 11:02:13 AM
All joking aside.  I did not know that and would have made the exact same mistake.
Great advice.(http://www.moparfins.com/forum/smileys/smiley4.gif)
Title: Different U-Joint Sizes
Post by: Steve on May 12, 2009, 01:33:47 PM
I would have just tried to change the yoke from the other rear and call it a day
Title: Different U-Joint Sizes
Post by: Butch Houghton on May 13, 2009, 06:53:55 AM
Uh,  you can't just change the yoke on 489 case.    It uses a crush sleeve that the yoke is tightened against to a spec.   You pull the yoke & you might just need to install a new crush sleeve,    or  there is a solid spacer available now but it requires setting up the pinion again.

The 741 & 742 cases don't have a crush ( just shims ) so you can change those without issue.

The  U-joints are know as a 7260 ( small joint ) & 7290 ( big Joint ) on most of our cars & then some used a 1350 joint ( usually Dana equipped cars & trucks & maybe Imps ).

The conversion joint for 7260 to 7290 is the easy fix,   available from about 4 different suppliers. 

When it comes to Yoke there's 4 different ones also,  Fine or Coarse splined Pinion & big or small joint so you gotta know what you need.

Butch


Title: Different U-Joint Sizes
Post by: Snotty on May 13, 2009, 01:03:53 PM
Quote from: Commando1
Quote from: Snotty
MORAL OF THE STORY: Be sure of the sizes of your third member and shaft before you buy a u-joint.  Apparently, they are not specific to the type of rear you have.
 
OK, let's get out of the gutter and let Stan float by....
 
(http://www.moparfins.com/forum/smileys/smiley36.gif)  It hit me as I read it in your post!!  D'oh!
 
Now, let's talk about the size of that shaft....   (http://www.moparfins.com/forum/smileys/smiley17.gif)
Title: Different U-Joint Sizes
Post by: Snotty on May 13, 2009, 01:06:45 PM
[/QUOTE]
 
One of the guys in my Car Club said the same, Butch.  I had no idea, because when I swaped the third member in my Newport, and then changed it back, both yokes were the same size.
 
Assumtions, we know what those do to us! 
Title: Different U-Joint Sizes
Post by: Steve on May 13, 2009, 04:03:18 PM
I said "TRY".  Sheeesh (http://www.moparfins.com/forum/smileys/smiley2.gif)
 
But you are right.  I wan't aware of 4 yokes.  Snotty didn't say it was a 489. . .  I've pulled a few stunts in the past and gotten away with it.  I would Imagine Butch has too.
Title: Different U-Joint Sizes
Post by: Butch Houghton on May 14, 2009, 04:46:32 AM
I got yer 3rd member right here!   LOL!

Anyway......yeah it can be confusing.   It's fun to pull a Yoke to swap say for the U-joint sizing only to find out you've got a coarse pinion & no coarse Yokes left in stock!    those things ain't cheap now.   That's why the conversion joint is really the way to go.

And yeah I've tried to swap a 489 yoke.....almost always doesn't work out so good.   Either noisy or you get it all outa spec & kill a pinion bearing.     Sometimes you get away with it if you very carefully watch your torque.    The solid spacer is nice cause you set the pinion up once with it & it's just like a 741/742 then with just shims & changing yoke isn't an issue then.

Seems most of the ones we run into are fine-splined pinions .    The Coarse ones are a bit more rare but still with all of us swapping 3 rd members aroung you just never know untiol you pull a Yoke.

As far as strength between the big & small yoke....Yeah the big one is stronger but the small one can hold up to plenty so I wouldn't sweat it with an Auto car.   The Hemifury Still has the Small joint shaft in it & no problems,  even how I drive!   A buddy ran his 11sec Belvedere with small joints the whole time he raced it & now it's back on the streets with the same 451 stroker & same driveshaft.      Chrysler over-designed most of that stuff anyway.

The only difference between a 741/72/489 is the pinon diameter ,  741 being the smallest......it's still a bigger diameter pinion than the revered 9" ford unit!

Where's the Beef!

Butch




Title: Different U-Joint Sizes
Post by: Steve on May 14, 2009, 05:17:36 AM
[/QUOTE]
 
I swore off meat lately.  Just fish. . .
 
Agreed. . .I've gotten away with it a few times. but not always
Title: Different U-Joint Sizes
Post by: Snotty on May 14, 2009, 03:15:54 PM
Quote from: POLARACO
  Snotty didn't say it was a 489. . .  .
 
Oh, you are wrong, Mopar breath!  Look again, 6th paragraph in my post.   (http://www.moparfins.com/forum/smileys/smiley36.gif)
Title: Different U-Joint Sizes
Post by: Snotty on May 14, 2009, 03:21:21 PM
[/QUOTE]
 
The Gremlin is a built 401 (now 407) with a BW T-10 and 3.23 sure grip.  Seeign as how your Hemi car is doing all right with a small yoke, I'm not going to sweat this one.
 
Or....
 
...should I?
 
To Steve, I did consider swapping the yokes but decided swapping the joint to be an easier, and less time consuming route.  Now, having read Butch's comments, I'm glad I went the way I did.
Title: Different U-Joint Sizes
Post by: Steve on May 14, 2009, 03:36:32 PM
Quote from: Snotty
Quote from: POLARACO
  Snotty didn't say it was a 489. . .  .
 
 
I fall asleep in your sermans too.  (http://www.moparfins.com/forum/smileys/smiley2.gif)  Sorry I missed that
Title: Different U-Joint Sizes
Post by: Butch Houghton on May 15, 2009, 05:54:32 AM
A lot depends on how you're gonna drive the car.    Cruising mostly & occasionally drop the hammer from a start with street tires...sure.

Gonna put slicks on & go racing,  I might be concerned.   

I suspect it's just gonna be a fun car & no strip time so I wouldn't sweat it.

My Dart had a 340, 6bbl & 4 speed with 3.91's for years & I hammered on it regularly & never spit a joint.  Small joint shaft in it.    Course when I built the stroker motor ( 394) with a modified 6bbl & still had the 7/16" studs in the wheels & mini tubbbed with 295/50/15's out back then the issues showed.   The studs all bent!  too much torque for them.    I got high-strength axles with 1/2 X 3" studs to solve that but the joints never gave up.  I did upgrade to a 3" driveshaft with big joints since I was upgrading anyway.

Butch



Title: Different U-Joint Sizes
Post by: Snotty on May 15, 2009, 08:04:19 AM

Quote from: POLARACO
Quote from: Snotty
Quote from: POLARACO
  Snotty didn't say it was a 489. . .  .
 
 

Wait a minute!  How could you, I haven't sent one to yo yet!!!


Oooooppppss!  Sorry Buddy...

Title: Different U-Joint Sizes
Post by: Snotty on May 15, 2009, 08:11:51 AM
Butch, we are going to take it to the strip occasionally, as I have done with my Newport, but we're never going t go full-bore.  We're building this car to be a driver, not a racer.  Thanks Buddy!