Brand New 7290 U-Joint Failure

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blewbyoutobad

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Was having fun with the 69 Dart tonight. Did a launch at 4000 and power shifted to second at 6500 (4 speed). The rear 7290 let go and tore up the flange of the drive shaft. I have 255/60-15 drag radials running on 3:23 gears 489 case. I estimate the mtr is 425 to 450 on the power. Solid lifter Lunati cam and ported X heads, Air Gap and 750 Holley I built. I am having a new pumpkin set up this week a set of 3:91s and will be ordering a new drive shaft. Anyone have any thoughts on what happened and who is good in the drive shaft business. Never had this happen before.
Thanks FABO
 
If the u-joint has a grease fitting in a "corner", in between the u-joint caps, it needs to be in compression as the driveshaft turns. I also had a failure when an OEM yoke began to spread. It happens after a lot of abuse, but just a bit was enough to hammer the u-joint out and break. This was around 15 years ago. Last, but not least, if everything was installed correctly, it could be the quality/metalurgy of the product.

I use billet steel yokes with u-bolts and solid Spicer u-joints. I haven't had a failure since then even though it was "only" a 7260 or 7260/1330 combo joint. I have a best of 1.47 60' times at 3,540+ lbs footbraking a 360. Traction, weight & torque will eventually find the weak link in your drivetrain. The 4 speed doesn't help either with the "shock". Ring & pinion teeth, then the caps are the normal "weak links" in that order, in the driveline chain.
 
User error?
Forgot to grease after install?
Needle bearing got misplaced during install?
Yoke on drive shaft had metal fatigue?
Too much power?
Too much traction?
Not high enough gear ratio?

Post some photos.

BTW not pointing fingers, shirt happens.
 
Well on the street I guess no more power shifting but I think the combination of big tires and the 3:23s with a strap type hold down may have been more than it could take. I havent seen the pinion yoke yet. The drive shaft was built locally without any grease fittings. Had less than 1000 miles. Anyone know anything about Dennys Drive Shafts. Everything going back will be new as well as the 489 case with 3:91s. Dennys has a driveshaft for $450 that will handle up to 700hp, way more than I am making. Uses 1330 joints and 3" tubing.
 
An fyi, some of the spicer non grease joints are made off shore. The ones I have seen have a white sticker over the ‘Made in the USA’ part of the box.
 
If the u-joint has a grease fitting in a "corner", in between the u-joint caps, it needs to be in compression as the driveshaft turns....
@Locomotion How does this stay "in compression" during operation....
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I'm guessing the driveshaft (pictured) would be turning this setup CW (facing the pinion yoke)..and not be correct? Ie drive force is pulling the weakened zerk fitting side apart? This one seems *** backwards!
 
First of all if it has a grease fitting it's no good.
You need a solid cross shaft not one that has a hole in it.
Chromemoly like a lakewood, probably not made any more but someone has to.
 
Probably made in china. Check the box. I need to see pictures.
 
I lost the front prop shaft in my 02 Ram 4x4 a few weeks ago as seen in the pic below. I did not change the U joints like my dad as a kid told me to do when you get a new ride. So I got a new prop shaft to fix the front. I took the drive shaft out and went over to an old man in Vancouver WA that all he does is build drive lines and had him put in new u joints, balanced and painted for 175.

When talking to him, he only sells USA made Spicers that are non serviceable, aka non grease fittings. He saw a grease-able one a few weeks before me that had all four lugs ripped off the center of the U joint and told me to never use them. What he said is that they get over filled with grease, and since the seals under the cap is not as good as the non serviceable (non fitting) the grease is pushed out splitting the seal and then spins out all of the grease and then the needle bearings get ate up..

Last Sping, I had him build me a new drive line for my Duster with 1350 U joints on both ends (same as used on Ram trucks) cost me about 425,which is about the same as Denny’s before shipping. I did have to buy a new 1350 slip yolk and 1350 pinion flange from Diff Dr. which are rated for about 750HP...

1350 Transmission Slip Yoke

FORGED STEEL 10 spline 1350 U-bolt yoke package

He has the best prices for these that I could find on the net and when you look at the cost differnace vs the smaller 7260/7290/1310/1330 parts it was a no brainer for me as I’m going to be close to 500 HP soon..

Dr diff also has a strange drive line on his page...





3DCC2F65-452A-485C-B5E1-3E772BC267C8.jpeg
 
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I lost the front prop shaft in my 02 Ram 4x4 a few weeks ago as seen in the pic below. I did not change the U joints like my dad as a kid told me to do when you get a new ride. So I got a new prop shaft to fix the front. I took the drive shaft out and went over to an old man in Vancouver WA that all he does is build drive lines and had him put in new u joints, balanced and painted for 175.

When talking to him, he only sells USA made Spicers that are non serviceable, aka non grease fittings. He saw a grease-able one a few weeks before me that had all four lugs ripped off the center of the U joint and told me to never use them. What he said is that they get over filled with grease, and since the seals under the cap is not as good as the non serviceable (non fitting) the grease is pushed out splitting the seal and then spins out all of the grease and then the needle bearings get ate up..

Last Sping, I had him build me a new drive line for my Duster with 1350 U joints on both ends (same as used on Ram trucks) cost me about 425,which is about the same as Denny’s before shipping. I did have to buy a new 1350 slip yolk and 1350 pinion flange from Diff Dr. which are rated for about 750HP...

1350 Transmission Slip Yoke

FORGED STEEL 10 spline 1350 U-bolt yoke package

He has the best prices for these that I could find on the net and when you look at the cost differnace vs the smaller 7260/7290/1310/1330 parts it was a no brainer for me as I’m going to be close to 500 HP soon..

Dr diff also has a strange drive line on his page...





View attachment 1715711853

CV joint, aka constant velocity joint.
 
CV joint, aka constant velocity joint.

It is. Called a Cardan (H-yoke) CV which has 2 u-joints, and a ball joint vs a CV joint which most of the time is a splined ball in a splined hub joint with retainers and a boot covering. It’s recommended to put a cut red spray straw under the boot edge as a breather so the grease has room to expand and not heat the grease and melt out.

Was talking to a fellow Lucky Dog racer last month at Sonoma on Saturday after that days 8 hour race as they were changing out the CV in their car. They could not figure out why they lost the axel. Tore it apart and the grease was gone from the CV. It only had 12 hours on it. Told them to put the straw in the CV boot... My brother builds vintage F1 cars that run CVs to Hewland gear boxes. Every CV boot has a straw...
 
@Locomotion How does this stay "in compression" during operation....
View attachment 1715711847
I'm guessing the driveshaft (pictured) would be turning this setup CW (facing the pinion yoke)..and not be correct? Ie drive force is pulling the weakened zerk fitting side apart? This one seems *** backwards!

Yes, the driveshaft connected cap should be turning towards the grease fitting. But even those with a fitting in the cap should be avoided for performance use/abuse because they are also cross-drilled to permit grease to reach all 4 caps. As has been mentioned, the non-servicable u-joints that are solid inside, factory greased & sealed should be used. I've seen solid u-joints called "Brute Force", or something like that, but you can tell the difference if you have a Spicer solid on hand to compare it to. I don't believe they make a 7290 solid. You might also get into a fitment issue with the yoke ends because Mopar has some driveshaft diameters that don't have aftermarket ends to match. That's why some of my driveshafts have a 7260/1330 combo for the yoke/driveshaft.
 
I lost the front prop shaft in my 02 Ram 4x4 a few weeks ago as seen in the pic below. I did not change the U joints like my dad as a kid told me to do when you get a new ride. So I got a new prop shaft to fix the front. I took the drive shaft out and went over to an old man in Vancouver WA that all he does is build drive lines and had him put in new u joints, balanced and painted for 175.

When talking to him, he only sells USA made Spicers that are non serviceable, aka non grease fittings. He saw a grease-able one a few weeks before me that had all four lugs ripped off the center of the U joint and told me to never use them. What he said is that they get over filled with grease, and since the seals under the cap is not as good as the non serviceable (non fitting) the grease is pushed out splitting the seal and then spins out all of the grease and then the needle bearings get ate up..

Last Sping, I had him build me a new drive line for my Duster with 1350 U joints on both ends (same as used on Ram trucks) cost me about 425,which is about the same as Denny’s before shipping. I did have to buy a new 1350 slip yolk and 1350 pinion flange from Diff Dr. which are rated for about 750HP...

1350 Transmission Slip Yoke

FORGED STEEL 10 spline 1350 U-bolt yoke package

He has the best prices for these that I could find on the net and when you look at the cost differnace vs the smaller 7260/7290/1310/1330 parts it was a no brainer for me as I’m going to be close to 500 HP soon..

Dr diff also has a strange drive line on his page...





View attachment 1715711853

Thank you for the info, Good read
 
Anyone have any thoughts on what happened and who is good in the drive shaft business. Never had this happen before.
Check for adequate pinion angle.
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I bet you have a CF-II set-up.
Mine killed a 7260 right quick on the street, with 275/60-15 BFGstreet tires.
Very early on, I swapped out the CF-II disc for a stock 340 disc. They don't last very long, but they also don't break stuff. And I don't do 4000rpm drops any more.And I reduced the clamping force by shimming the PP away from the flywheel.
Eventually I installed 1350 at the front and a hybrid 1350/7290 at the rear.
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As you may know, the CF-II has flyweights that increase the clamping with rpm. So I launch below 3000, then floor it. That gives the clutch a lil slip on take-off but as soon as the Rs go over ~3000, the PP bites and the tires loose grip (295s now, sometimes 325/50-15 BFG-DRs).. This is much more satisfactory on the street.
To take off normally;
I blip the throttle just a lil, then, more or less just dump it and go, letting the heavy stock 340 rebalanced FW, do the work.
My starter gear is 3.55 x 3.09=10.97,
which would be same as 4.10 x2.66=10.91
My 60fts,with street suspension,and this clutch set-up, the only time I ever went to the track, were greater than 2.2
The shims I used were just hardened washers. I cannot recall anymore how thick they were, I'll guess maybe .060. Maybe less.
The 340 discs usually fail by spitting out springs, but occasionally by throwing off the linings. When I drive half-decent , I can get several summers out of them. But it only takes a few full-clamp drops to spit springs.
By it's ET of 93 in the Eighth, at 3457 pounds, this lil 367 is making 433hp; by the Wallace Calculator. Track is at 900ft. Powershifted at up to 7200
 
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Thank you for the info, Good read

Your welcome. On stock drive lines, they were tapered on one end. They can be reconditioned, but youll be suck with stock u joints. With having one made, 3 inch tubing full length is normal and fits no problem, You can have any size yolks welded on... just have to ensure you have the right slip yolk and pinion yolk for what you requested...
 
Now it a good time to upgrade to those 1350 u joints
 
So what failed? Is the ujoint actually broken at the cross? did a yoke fail? Or did a cap come out of its resting place?

no photos?
 
Didn’t read all the posts and Not sure if mentioned but it could have to much rear end rotation (over angled joint)
 
Thanks all, the pinion angle is set up correctly. U joint did not break, just tore up the caps and flange. I will see the car this afternoon and Im betting its those crappy strap clamps that broke. I will change the pinion flange when the pumpkin is rebuilt next week for 1350 and u bolt clamps.
 
Thanks all, the pinion angle is set up correctly. U joint did not break, just tore up the caps and flange. I will see the car this afternoon and Im betting its those crappy strap clamps that broke. I will change the pinion flange when the pumpkin is rebuilt next week for 1350 and u bolt clamps.
Stock springs? They can rotate quite a bit a 4000 hit, I’ve broke straps that way, they can’t take that amount of rise
 
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