Broken Driveshaft.

Took car out over the weekend and ended up throwing a driveshaft. I have had the car about 8 years, and this is the first time i have had any issues. Here is what i changed this year. I put in a new rearend(9") and thats it. It has all new rubber bushing, and the engine and tranny are in stock location with stock mounts and cross member.The pinion angle was at 1 degree . My old gm rearend had 4. The yoke is still in the tranny, and on the rearend. Just the center of the driveshaft is gone , like someone twisted it in two. The transmission case busted in two and all the ears are broke off almost like something locked up . I will be taking it out today. Any ideas on what to look for. I know it wasnt rubbing on anything.Any idea on how far the yoke should go in the tranny. I bought a longer yoke for this driveshaft. I had about 7/8" before it bottomed out in the tail housing. Is that enough? Not sure how far a yoke should go into the tail housing. Any ideas will be greatly appreciated. Thanks in advance.

Had several people bring in cars the busted trans like that and ALWAYS found a solid trans mount, solid engine mounts and a chassis that flexed. It may not be your problem but something to look at. We NEVER saw a busted trans case running solid engine mounts and a flexible trans mount.

Thanks for the reply Ego. Actually , im running stock mounts on the engine and tranny with a strap on engine. I just got it apart and noticed that with the new yoke i bought, i only have an inch between the end of the tailhousing and the yoke. Thats what i had when i put it in. I think the yoke is almost bottomed out when the driveshaft is installed. Maybe i should use the stock yoke. Would you happen to know how much you want your yoke in the tranny??? Does the yoke move in when you are under power, or pull out???

Check the underside of your car too right above the yoke on the rearend. Had a car do this one time too and there was a floor brace right above thay yoke that the knuckles caught on. Busted the shaft right in two and the transmission as well .

depending on amount of suspension travel to how much yoke you need hanging out of trans,..1 1/2 to 2 1/2 be close,..if you bought a longer than stock yoke an did not machine out put shaft then itll bottom out inside trans on shaft flange an not shaft bottom out in yoke, an depending on type suspension as to how much pinion angle,1 degree not near nuff,..4 degrees seem conservative still,...on leafs 6 degrees is bout normal up to 8-9 degrees extream...had a car keep spittin shafts,turned out yoke nut backed off just enuff to let pinion bottum out against spool an bind up,...good luck

Thanks White boy. Its a stock 4 link with stock rubber bushings. I am only getting about 3" to 3 1/2 " travel on the rear. I didnt machine the the input shaft or yoke. I am thinking maybe i need to use the stock yoke. Will the yoke bottoming out cause the tranny to split in half. I have been running for 8 years , and have never seen this.Fixing it doesnt bother me ,but i dont want to hurt my driver or anyone else. It sure tore things up.

Quote:

---

Originally Posted by dirty white boy

depending on amount of suspension travel to how much yoke you need hanging out of trans,..1 1/2 to 2 1/2 be close,..if you bought a longer than stock yoke an did not machine out put shaft then itll bottom out inside trans on shaft flange an not shaft bottom out in yoke, an depending on type suspension as to how much pinion angle,1 degree not near nuff,..4 degrees seem conservative still,...on leafs 6 degrees is bout normal up to 8-9 degrees extream...had a car keep spittin shafts,turned out yoke nut backed off just enuff to let pinion bottum out against spool an bind up,...good luck

---

1.5 is the MAX you would want sticking out on a stock yoke.

pinion angle, not sure where you get your ideas from, but your wrong. you might want to read about drive shafts, u joints and such and then youll learn what your pinion angle should be at. Its not a guessing game.

Ive seen the ring/pinion lockup and break the PG trans in two.
Verify the length of the driveshaft at ride heigth and with the rearend free hanging.

After putting driveshaft back in, the aftermarket yoke (1.5" longer) is almost bottomed out in the tranny. I thought i had an inch of clearance, as i have an inch between the yoke and the rear seal on the tranny, but thats as far as the yoke will go in before it hits something in the tranny.The stock yoke can go all the way in and hit the seal.I guess i didnt need a longer yoke after all. One more question. If i have the engine /tranny facing down in the back 3 degrees, and my pinion facing down 1 degree towards the ground, does that mean i have 4 degrees pinion angle, or would i have to (subtract the rear from the tranny)??? I ran more with my old rearend( drilled the upper hole an inch shorter on the arms), but never checked it. I appreciate all the help.

By going to the 9" did you change what gear in the transmission you were using?? Did you go from say running in 2nd or 3rd to running in high gear? If so is your drive shaft balanced? I've seen this MANY times. By going to hight gear you are at 1:1 so your driveshaft is now spinning at the same RPM as your engine. IT MUST BE BALANCED or it will cause a very bad vibration and this will break the tranny (been there) and the driveshaft will come apart as you described....

Also for true pinion angle measure the angle of the drive shaft at ride height and the angle of the pinion and add the 2 together, thats your true pinion angle.

Thanks alot for the info Dirt track. I was running a saginawin second gear( 1.89 second gear) and a 3.73 before(7.05) Now i am running the same tranny in high gear with a 7.00. I used the same driveshaft , and i have never had any issues with it before. I did not rebalance it after putting it in though. It was turning around 6600 rpm when it let go.I am going to get a new driveshaft from speedway.I will check my pinion angle like you said.I really appreciate the info.

The Speedway driveshaft still has to be balanced. FYI

Ahh. I did not know that. Thanks Chaps.

Southwest Speed has the best deals on driveshafts. They come balanced and ready to go and even include the yoke and rear universal. I've had several of them and turned in the mid to high 7's with no problems.

Thanks alot for the info Dirt Track.What size would you recommend? Engine is roughly 300 hp, and car weights 3250 with e-mods. Running about 6500 to 6600 rpm.(high gear in tranny)Thanks for all the info.

You should be good with the 2".

Thanks Dirttrack.

We took a long driveshaft we had to a truck parts store/shop and they cut it down, balanced, and put in new u-joints and painted it for $65

Thanks for the info guys. One other question. How do you determine the driveshaft length. Lets say at ride height , my length from center of rear u-joint to the center of front yoke is 53" with the yoke pushed all the way in the tranny. When i raise my car up on the lift, this distance only changes about 3/8" at most and thats when the suspension is hanging way down. How much clearance do i want between the yoke and the tail housing where the seal is ?Is there a set amount. Thats the last thing i need to figure out before trying this again. Thanks for any info.

If your yoke can go in inch and out an inch with no problems you are OK.

Quote:

---

Originally Posted by Living_Truth

Carolina Driveline also specializes in these. That's where I've bought my last two.

:)

---

driveline specialist an stone heavy duty in g'boro can fab up any type of shaft you can imagine!!

Quote:

---

Originally Posted by stock car driver

1.5 is the MAX you would want sticking out on a stock yoke.

pinion angle, not sure where you get your ideas from, but your wrong. you might want to read about drive shafts, u joints and such and then youll learn what your pinion angle should be at. Its not a guessing game.

---

splicer web site,...an lots of post on here! as i said,depending on type of suspension to,..if his suspension moves rearend forward more than 1 1/2 he gotta have more yoke slide,..basic physic's 2 objects of matter cant occupy same space at same time...cant argue with sir isacc newton can ya?

Quote:

---

Originally Posted by dirty white boy

splicer web site,...an lots of post on here! as i said,depending on type of suspension to,..if his suspension moves rearend forward more than 1 1/2 he gotta have more yoke slide,..basic physic's 2 objects of matter cant occupy same space at same time...cant argue with sir isacc newton can ya?

---

Im not sure if you are even using english in the above post?

BUT to clarify with a oem slip yoke the MOST ANYONE should have exposed is 1.5.


As for using posts on here as a reference, thats just laughable based on your own BEING incorrect when it comes to pinion angle by a MILE!

Quote:

---

Originally Posted by stock car driver

Im not sure if you are even using english in the above post?

BUT to clarify with a oem slip yoke the MOST ANYONE should have exposed is 1.5.


As for using posts on here as a reference, thats just laughable based on your own BEING incorrect when it comes to pinion angle by a MILE!

---

he posted he had just installed a longer than stock yoke in his first post,....correct me on pinion angle then,..been tryin to get it straight in my mind as im puttin motor,trans an rear end in miner for first time an need to get it right!,..an had thought i had a good grasp of it all threw posting threads an studing your an ego an others replys to them...

http://www.drivetrain.com/parts_cata..._problems.html

http://www.carcraft.com/howto/91758/index.html

quot...According to Bickel, a ladder-bar suspension normally requires ½ degree of pinion angle, a four-link requires 1-2½ degrees, and a leaf-spring suspension requires up to 6 to 7 degrees.

Quote:

---

Originally Posted by dirty white boy

http://www.drivetrain.com/parts_cata..._problems.html

http://www.carcraft.com/howto/91758/index.html

quot...According to Bickel, a ladder-bar suspension normally requires ½ degree of pinion angle, a four-link requires 1-2½ degrees, and a leaf-spring suspension requires up to 6 to 7 degrees.

---

Nice to see you doing some research and educating yourself. Taking a persons word on a forum is not always the best way to go. Now that you did some looking Ill tell you my opinion.

In my opinion the numbers you quoted above are what they believe the pinion needs to be at in order to make sure it doesnt over center and they are taking into account some extra security... or extra angle a little.

I run NEW rear bushings and maintain them well and run the same pinion angle in my rearend as I have ANGLE in my motor. In other words I match the two u joints angle so as to not lose HP by having a bind in either or both joints!

My motor is mounted LEVEL at ride height all scaled etc. My pinion is ZERO in the car.

My motor is 1.25 angled down compared to the frame if the frame was dead level. I run the rear of my car a little higher than the front most of the time is the only reason there is any angle.

Quote:

---

Originally Posted by stock car driver

Nice to see you doing some research and educating yourself. Taking a persons word on a forum is not always the best way to go. Now that you did some looking Ill tell you my opinion.

In my opinion the numbers you quoted above are what they believe the pinion needs to be at in order to make sure it doesnt over center and they are taking into account some extra security... or extra angle a little.

I run NEW rear bushings and maintain them well and run the same pinion angle in my rearend as I have ANGLE in my motor. In other words I match the two u joints angle so as to not lose HP by having a bind in either or both joints!

My motor is mounted LEVEL at ride height all scaled etc. My pinion is ZERO in the car.

My motor is 1.25 angled down compared to the frame if the frame was dead level. I run the rear of my car a little higher than the front most of the time is the only reason there is any angle.

---

done researched it till my head hurts,..have no clew what ride hights will be,..got frame level!! all i can find has pointed to 4 to 5 degrees down on motor,...an 6 down on pinion,full camaro clip-tube back, on leafs...with stock type solid motor mounts,...now im confused again!! hell tryin to build a dang car with no experience,no help,an sadest,no money!! all my experiences with drive lines has been in tandem axle big trucks an i know what it takes to get them to live runnin flat out tote'in 80,000lbs! but thats a total defferant world than a dirt car!

leaf cars do require negative pinion angle to prevent going past center, normally 6 degrees to as much as 9 in extreme cases

Quote:

---

Originally Posted by bushracing67

leaf cars do require negative pinion angle to prevent going past center, normally 6 degrees to as much as 9 in extreme cases

---

ALL cars trucks etc should have the pinion angle set so that the rear joint wont ever rotate past zero.

I checked my pinion at ride height, and my pinion is pointing down in the front 1 degree. The driveshaft if pointing down in the rear 3 degrees. I have 1 1/4 " that the yoke can move in. I took the springs out and raised the rearend up as far as it will go, and still have almost the same 1 1/4" clearance. Gonna run it wed if it doesnt rain. Thanks for all the help.

One time I had a slightly bent rear end yoke that shelled out 2 drive shafts before I figured it out.Put a dial indicator on the yoke and turn the yoke.Mine was 10-20 thou. out I think.Put a new yoke on-no more problems.Good luck

Hi Nick. What is acceptible run out of a rear yoke???Runnin 7 to 1 in high gear.Thanks.

I dont know what factory tolerances are but mine was bent enough to really make that needle jump on the dial indicator.It's just something easy to check and rule out.Good luck!

Quote:

---

Originally Posted by stock car driver

Nice to see you doing some research and educating yourself. Taking a persons word on a forum is not always the best way to go. Now that you did some looking Ill tell you my opinion.

In my opinion the numbers you quoted above are what they believe the pinion needs to be at in order to make sure it doesnt over center and they are taking into account some extra security... or extra angle a little.

I run NEW rear bushings and maintain them well and run the same pinion angle in my rearend as I have ANGLE in my motor. In other words I match the two u joints angle so as to not lose HP by having a bind in either or both joints!



My motor is mounted LEVEL at ride height all scaled etc. My pinion is ZERO in the car.

My motor is 1.25 angled down compared to the frame if the frame was dead level. I run the rear of my car a little higher than the front most of the time is the only reason there is any angle.

---

so you have no wrap in your springs??? reason for negative numbers is when on gas the pinion lifts upward thus making driveshaft level from trans to rearend. if rear of trans is downhill when yoke makes upward movement your past zero and now positive. this is also why its beleived that negative will create more drive due to fact that front of rear is lifting upward and fighting thus pushing tires into ground.

ı want new job. good luck. + rep

my car did the same thing this year - spit the driveshaft in two and cracked the case on a powerglide trans - what we have found that we are pretty sure was the problem was a snubber above the rearend and on wrap up it caught the snubber and twisted the end off the driveshaft and i suppose slammed the rest of the driveshaft into the transmission putting a lot of pressure on everything in the tranny busting the case - just make sure you dont have something in the way of your wrap up on acceleration - the rearend moves more than you think even on a leaf car

this is also why its beleived that negative will create more drive due to fact that front of rear is lifting upward ????????? MORE DRIVE ??? How does it give more drive? I put mine at 7 degrees on pinion angle.

Ran last week, and everything worked great. You can see where the yoke has moved in the tranny almost an inch. When i put the longer aftermarket yoke in it, it was almost bottomed out when it was just sitting, wich i did not know. The aftermarket yoke bottomed out on the splines before it hit the tailshaft.Seem to have everything worked out now. I can tell you that if your bushings are in good shape,your pinion will not move up more than a degree or two with a 300 hp engine with a stock 4 link setup from what i have witnessed.