Lost driveshaft at 65 mph

[gfigms]

Long story short ... running slight downhill at 65 mph heading to Pikes Peak during the T Bucket Nationals and they was a dip at the bottom of the hill. Hit the dip and BANG ... the driveshaft let go, tried to come up through the floorboard under the seat ... left a heck of a hole ... no, I didn't have a driveshaft loop ... will now. Anyway, ruined the driveshaft, which we found in the weeds about quarter of a mile back, cracked the tailshaft of the C4 trans, broke a "locator" tab off of the pinion yoke and took a piece of the trans yoke with it ... also wiped out the Holley fuel pump as it departed from under the car.

Got all the broken stuff replaced ... many dollars later. With the body still off of the frame, I trailered the chassis down to a local performance shop to have them go over all the setup of the pinion angles, hairpins, etc. All during this build, the one thing I was uneasy about was the driveline setup. Anyway, first comment the guy at the shop makes is about the "shortness' of the driveshaft. He had never seen one only 7 1/2 inches center to center of the u-jonts. He also commented about the C4 tailshaft being centered between the frame rails and the Ford 9" rearend offset. With only a 7 1/2 inch driveshaft, it does look odd, but I don't know what to say to him.

I know there are a couple of you guys running C4 trans behind a Ford engine ... are any of you running a Ford 9" with the offset pinion? How long is your driveshaft and have you had any issues with the lateral offset?

Need some help here.

 

[putz]

Long story short ... running slight downhill at 65 mph heading to Pikes Peak during the T Bucket Nationals and they was a dip at the bottom of the hill. Hit the dip and BANG ... the driveshaft let go, tried to come up through the floorboard under the seat ... left a heck of a hole ... no, I didn't have a driveshaft loop ... will now. Anyway, ruined the driveshaft, which we found in the weeds about quarter of a mile back, cracked the tailshaft of the C4 trans, broke a "locator" tab off of the pinion yoke and took a piece of the trans yoke with it ... also wiped out the Holley fuel pump as it departed from under the car.

Got all the broken stuff replaced ... many dollars later. With the body still off of the frame, I trailered the chassis down to a local performance shop to have them go over all the setup of the pinion angles, hairpins, etc. All during this build, the one thing I was uneasy about was the driveline setup. Anyway, first comment the guy at the shop makes is about the "shortness' of the driveshaft. He had never seen one only 7 1/2 inches center to center of the u-jonts. He also commented about the C4 tailshaft being centered between the frame rails and the Ford 9" rearend offset. With only a 7 1/2 inch driveshaft, it does look odd, but I don't know what to say to him.

I know there are a couple of you guys running C4 trans behind a Ford engine ... are any of you running a Ford 9" with the offset pinion? How long is your driveshaft and have you had any issues with the lateral offset?

Need some help here.

That sucks out loud glad it didn't hit a brakeline on pikes peak that would have been ugly.

 

[Rick]

Long story short ... running slight downhill at 65 mph heading to Pikes Peak during the T Bucket Nationals and they was a dip at the bottom of the hill. Hit the dip and BANG ... the driveshaft let go, tried to come up through the floorboard under the seat ... left a heck of a hole ... no, I didn't have a driveshaft loop ... will now. Anyway, ruined the driveshaft, which we found in the weeds about quarter of a mile back, cracked the tailshaft of the C4 trans, broke a "locator" tab off of the pinion yoke and took a piece of the trans yoke with it ... also wiped out the Holley fuel pump as it departed from under the car.

Got all the broken stuff replaced ... many dollars later. With the body still off of the frame, I trailered the chassis down to a local performance shop to have them go over all the setup of the pinion angles, hairpins, etc. All during this build, the one thing I was uneasy about was the driveline setup. Anyway, first comment the guy at the shop makes is about the "shortness' of the driveshaft. He had never seen one only 7 1/2 inches center to center of the u-jonts. He also commented about the C4 tailshaft being centered between the frame rails and the Ford 9" rearend offset. With only a 7 1/2 inch driveshaft, it does look odd, but I don't know what to say to him.

I know there are a couple of you guys running C4 trans behind a Ford engine ... are any of you running a Ford 9" with the offset pinion? How long is your driveshaft and have you had any issues with the lateral offset?

Need some help here.

I have a 351 with a c-4 tranny and an 8" rear this is the set up i have and never a problem.(of course the pic is before i got the real driveshaft.)

 

[gfigms]

I have a 351 with a c-4 tranny and an 8" rear this is the set up i have and never a problem.(of course the pic is before i got the real driveshaft.)

Is the output shaft of the trans offset or in line with the pinion yoke?

 

[clamper]

Milt,
Thank god you are safe! When I was jeeping I had days like you. I'm in the middle of rebuilding my T and I thought with such a short driveshaft (10") that I didn't need a hoop. But know I've changed my mind, I'm researching bolt in hoops as we speak. Aganin I'm glad you all are all right except for a lighter wallet. :jawdrop:

 

[Old Rotor Flap]

My opinion........ is....that the slip joint in the drive shaft reached the end of it's travel too quickly or was extended beyond it's normal dimension, flexed the trans tail shaft and either broke the trans housing first then the drive shaft due to the shaft's ability to move further off it's normal envelope of centerline angularity.

If the drive shaft tube/weld/flange broke first, then the whipping end(s) probably took their revenge on the trans tailshaft housing, floor, fuel pump and associated components. All of this in a matter of a second or two due to the dip at 65.

This might be demonstrated should someone be able to draw this out in Solidworks of some other dynamic program.

Or, you could just count your blessings that no one was hurt, kinda take the guy's comment about the shaft being the shortest he's seen with a grain of salt and remember that I've never seen South America either..... and I've been all over the world......... well, except for foreign countries.

 

[GAB]

I built a couple of drive shaft loops like this and gave them to a couple of people to try. In both cases, they interfered with other things such as the floor and crossmembers. This one is for the TH400. The idea was to keep the shaft spinning instead of oscillating. Oh well, it seemed like a good idea at the time.

 

[Rick]

Is the output shaft of the trans offset or in line with the pinion yoke?

Although you cant see it but the engine is turned just a hair to line up better.You dont have to turn it much since the engine and trans combo are so long.

 

[der Spieler]

He also commented about the C4 tailshaft being centered between the frame rails and the Ford 9" rearend offset.

Why was the rearend offset? The axle tubes on the Ford 9" are of different lengths so that the pinion will be centered.

 

[gfigms]

Why was the rearend offset? The axle tubes on the Ford 9" are of different lengths so that the pinion will be centered.

Huh?

 

[der Spieler]

Huh?

The mechanic wondered why the rear end was offset. To me that means the pinion wasn't centered between the frame rails. Was it centered?

 

[GT63]

The mechanic wondered why the rear end was offset. To me that means the pinion wasn't centered between the frame rails. Was it centered?

The rearend housing was centered, Which made the pinion offset. I have the same thing with my Ford 8 inch but my drive shaft is nearly 24 inches long since I have a TH350 tranny.

 

[HTWOODS]

If you have a ford truck 9"... Mine is out of 1976 F-150...the axle lengths are the same. Thus the pinion is 2" offset to one side. I did not realize this when I welded the brackets on the rear end.

In a ford truck the drive shaft is 50+ inches long, so this is not a problem.

I contacted Spicer. The angles of the arch should not interfere with a 11" driveshaft. This is pushing the envelope; however. Spicer told me I should expect the life to be less, and like 30,000 miles. The 5-7 degree or so spec for u-joints to bind is a rating for big truck u-joints. When you calculate the angles of the arch on a smaller u-joint, they will withstand close to 15 degress without binding. I figured mine to be 11 degrees offset. According to Spicer they will live, but live a shorter life.

I have not run it yet. It should be interesting. I'm not loosing sleep... I do have a safety loop. I have approximately 1 1/8" of slip yolk end play. I don't think this will bottom out into the tranny tail shaft.

 

[HTWOODS]

Thought I would post some pics of my set-up.

 

[blownt]

My Ford 9" came out of a 76 Tbird/Cougar. Normally the pinion is centered and the 9" housing is offset 2". But I have a buggy spring and I wanted the housing centered in the middle of the buggy spring so my pinion is offset 2". I got my axles from Moser and when I first got them one axle was too long so I sent it back and told them my housing is centered. They fixed it and sent it back to me. My driveshaft is 10 5/8" eye to eye.

That picture looks to me the weld holding the rear driveshaft yoke to the shaft tube broke. Appears to me whoever made that weld when they made the shaft did not do a very good job.

 

[gfigms]

The theory is that when I first measured for the driveshaft length two things were wrong. First, I did not have the pinion angle set close enough and second, I did not have enough weight on the rearend like it would be under normal conditions. These two factors could have resulted in a driveshaft about an inch too long and when the car, then loaded, hit the dip at 65 mph, the driveshaft "bottomed" out against the trans tailshaft and when two objects try to occupy the same space at the same time, something is going to give\break.

With the rearend loaded with about 600 pounds, there is only about 1/8" travel before the driveshaft bottoms out.

I have a 5 inch pinion yoke and Currie sells a 4 inch ... if it is the same carrier bearing size and spline count, that will give me another inch of play under full load. Making a 4 inch tube driveshaft an inch shorten would not, in my opinion, be the thing to do. The yoke, if it can be done, is less than half the cost of a new driveshaft. But, at this point, money is not the issue. Making it right is the issue.