Broken Driveshaft.

**turner** · 05-29-2011, 08:38 AM

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.

**Egoracing** · 05-29-2011, 09:24 AM

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.

**turner** · 05-29-2011, 12:01 PM

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???

**C10** · 05-29-2011, 12:37 PM

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 .

**dirty white boy** · 05-29-2011, 01:02 PM

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

**turner** · 05-29-2011, 01:46 PM

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.

**stock car driver** · 05-29-2011, 06:47 PM

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.

**DaveBauerSS6** · 05-29-2011, 11:14 PM

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.

**turner** · 05-31-2011, 12:46 PM

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.

**dirttrackrocker** · 05-31-2011, 03:10 PM

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.

**turner** · 05-31-2011, 03:26 PM

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.

**Chaps46** · 05-31-2011, 04:30 PM

The Speedway driveshaft still has to be balanced. FYI

**turner** · 05-31-2011, 06:36 PM

Ahh. I did not know that. Thanks Chaps.

**dirttrackrocker** · 06-01-2011, 09:42 AM

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.

**turner** · 06-01-2011, 10:22 AM

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.

**dirttrackrocker** · 06-01-2011, 10:35 AM

You should be good with the 2".

**turner** · 06-01-2011, 12:36 PM

Thanks Dirttrack.

**keithbaker** · 06-01-2011, 02:54 PM

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

**turner** · 06-02-2011, 11:40 AM

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.