Driveline help needed

[Bad Moose]

Welper's found this site and with that found a bunch of knowledgeable threads and people here. So I thought I would join and see what your thoughts are.

Help build my roadster with my father. He has always wanted to build a car that scared him and he got the job done! LOL So he decided to pass it to me. Well I finally got it home and took it out on a nice weekend and the driveshaft broke at the weld. 808 miles on the driveshaft. What I will say is that IT IS NOT THE SUPPLIER FOR FFR'S FAULT NOR WILL I OR DO I BLAME THEM. This thread is not to point blame it is to try and provide ideas for the solution. Here are the pics because carnage is always cool:

http://i872.photobucket.com/albums/ab290/badmoose69/Cobra/IMG_1101_zpsgy3pswtk.jpg
http://i872.photobucket.com/albums/ab290/badmoose69/Cobra/IMG_1106_zpsktyspicl.jpg
http://i872.photobucket.com/albums/ab290/badmoose69/Cobra/IMG_1102_zpsynzucxwb.jpg
http://i872.photobucket.com/albums/ab290/badmoose69/Cobra/IMG_1108_zpsbnufn7qd.jpg

Now here are the questions:

Is there a reasonable priced place for e brake cables?

The front hoops that are welded for the e brake to the frame are crushed. What are some good alternatives to welds a new tab on and screwing up the powder coat?

Do you think I can get away with just the two cables or do I need the short e brake cable itself? It does not look damaged but there is a soft kink in it?

Do you see any other problems or cause of failure?

[KDubU]

Holy crap! Now I know why some recommend the driveshaft safety loop. Not sure about the ebrake cable questions but I don't think they are expensive from FF. Is the ebrake the only casualty besides the driveshaft.

[CraigS]

The single cable look fine to me. FFR might be the easiest so you get the same cable you have and don't need to try to adapt others. I would also recommend Forte's Parts
http://www.fortesparts.com/
or Breeze
http://www.breezeautomotive.com/
for cables and a driveshaft.

[edwardb]

Factory Five would have the e-brake cables. Or you could get them many other places. But there are different types and lengths. Best would be to measure the ones you have to make sure to get the right ones. Measure the outer housing and the inner cable. Plus what brakes you have since that affects what ends they have. That short cable, usually called an equalizer, looks like it's probably OK to reuse. I don't know of a way of fix the e-brake mounting without the welding affecting the powder coat. It's in a pretty hidden area. Just touch it up with some matching paint. It will be fine.

Care to tell us more about the build and what was happening when the driveshaft exploded like that? That's a little scary to say the least. But more details please. I'm thinking something more than just an easy Sunday drive.

[Bad Moose]

The car has a Rousch Racing 351w 427r pushing 550hp 535 torque. Independent rear suspension with trimec five speed trans. Painted and body work done by Steve Cook OKC. I can go into detail later on that, but you get the jest.

Believe it or not it was a Sunday drive. With this setup and 60 degrees you don't get on it or blip the throttle as you guys know. The car is planted but will not hold the road at these temps. I was taking off at an intersection rolling into to it and shifting to 2nd and BOOM bang bang ...... Overall the damage was not too bad and the driveshaft is caged quite well. There is a hole in the AL on the passenger wall smaller than a dime, brake cables, and of course the drive shaft.

[2bking]

The break line on the driveshaft is a typical shear line fracture that started sometime in the past and propagated from repeated stress and/or vibration. I don't recall seeing aluminum driveshafts included in the kits so is this an aftermarket part? If it was aftermarket, did it have a horsepower or torque spec?

[Bad Moose]

The drive shaft came through FFR. It was shortened by a shop in OKC, and that is their weld that broke. I know this car was a special order through FFR as they supplied all drivetrain parts. Which is very rare.

[Duke]

What's the angle for the transmission vs. the pumpkin? I'm wondering if they were very far off and may have caused stress on the driveshaft, ultimately leading to the failure. MK1?

[Bad Moose]

MK III I believe. Started in 2006 and finished 2011.

If I remember correctly it is a fairly straight shot. But I will verify when installing the new one. I personally think that when they shortened the drive shaft, they put it on the lathe and trimmed the 1/2 inch off and slapped it back together. The AL was crystallized due to being welded twice. Again this is just my thoughts. I seen it on iron but this is the first time on AL for me.

[Bad Moose]

I'll try and get the numbers by the end of this week end and a better build list for you guys.

[NukeMMC]

I bought parking brake cables for a 95 Mustang (http://www.summitracing.com/parts/dhb-c95240/overview/year/1995/make/ford/model/mustang)and cut the sheath to length and reinstalled the cap/boss and cut the cable to length and installed a 1/8" swage on the cut end.

Looks like you had an aluminum driveshaft. While it may be ok for a full-length Mustang driveshaft, a short driveshaft combined with higher horsepower is a recipe for disaster. You found out the hard way. Get with Denny's Driveshafts thru Mike Forte.

[Bad Moose]

I don't understand the AL driveshaft comment NukeMMC. If it is rated it should be ok? Please shed some light on this. I'm having a shop here in Wichita do a new driveshaft that was suggested by a race shop that focuses on chassis and suspension for drag racing.

MPE Racing is where the driveshaft originated from, so I was incorrect earlier. Mind you it was modified by someone else.

Not starting an argument here, just trying to get a better understanding.

[Bad Moose]

Another question. I'm going through the receipts and I'll be d@#$ if I can find where the brake cables came from. I found where the E brake handle and front t cable came from was disc brakes r us http://www.discbrakesrus.com/make/ford/cabley.htm. Now I called FFR like you suggested and priced the cables through them which are about $40 cheaper than these http://www.discbrakesrus.com/make/ford/cables.htm. Now I don't want to do this twice and deal with the headaches involved with that. Are the ffr and these the same? What are your thoughts?

[Bad Moose]

Anyone on why not the AL driveshaft?

I'm getting the parking brake cables slowly figured out. Through research I have found this p/n M-2809-A ford racing which updates to LRS-2635D from LMR and was wondering on the how big were the end wire crimp size.

[karlos]

I don't believe it's necessarily the use of aluminum that's a potential problem, but welded aluminum is another matter. Unlike some of the mild steels (like A36) which can be welded without any degradation in parent material properties, aluminum will suffer a strength (and ductility) hit every time it's welded. That is unless it's re-heat treated after welding. Which I'm guessing wasn't done in the case of this driveshaft. You mentioned that the driveshaft was shortened and rewelded. I suspect it was the reweld that led to the problem.

[BEAR-AvHistory]

550HP in a 2300lb car. Would not waste any time or money on a very short aluminum shaft. Best thing is to ty to eliminate any potential points of failure.

[Bad Moose]

I don't believe it's necessarily the use of aluminum that's a potential problem, but welded aluminum is another matter. Unlike some of the mild steels (like A36) which can be welded without any degradation in parent material properties, aluminum will suffer a strength (and ductility) hit every time it's welded. That is unless it's re-heat treated after welding. Which I'm guessing wasn't done in the case of this driveshaft. You mentioned that the driveshaft was shortened and rewelded. I suspect it was the reweld that led to the problem.

I believe you are correct with the reweld causing the failure. But since the car was built with an AL driveshaft I would like to keep it that way, but I also don't like fixing the things I break. I'm planning on visiting with the guys that are build the new driveshaft extensively and figuring out what they suggest. I do have the feeling I will be going back with a steel driveshaft but we will see how confident they are.

I have the e brake handle end together now and a bracket manufactured where the driveshaft screwed it up. Touched up with paint. Will be ordering the cables late this week and hopefully be driving the car again in 2 weeks.

[2bking]

Anyone on why not the AL driveshaft?

I'm not much of a driveshaft expert but as an ME I have an observation. The longer aluminum drive shafts can absorbed shocks and vibration that the shorter ones are forced to transmit thus higher stresses are induced. Combine that with the welding issue karlos pointed out and you have a recipe for failure for the short shaft. Properly designed mechanical components such as bearings, shafts, wheels, etc have infinite life meaning they will not fail during the lifetime of the equipment when being used for the intended purpose. For rotating components, infinite life is no failures within the first million revolutions while being subjected to the design loads. Assuming a rear end ratio of 3.5, your driveshaft has seen a little over 2 million revolutions during the 800 miles driven but only a small fraction of those were close to a design load. A conclusion can be drawn that the shaft has been overloaded or is being subjected to a vibration in addition to the design loads. Because you have the IRS, one source of the vibration could be the alignment of the output shaft of the transmission to the input shaft of the differential. They need to be parallel within less than one degree to keep driveshaft from producing a rotational vibration. The aluminum shaft is a little lighter with less rotating mass but I think a steel driveshaft is a better choice.

[GoDadGo]

A new shaft can be ordered from Factory Five Racing. The cost is minimal.

[NukeMMC]

As has been stated, the problem isn't that the drive shaft was aluminum, but that it was aluminum and modified (shortened, I presume?). When welding aluminum you create an area immediately adjacent to the weld bead that is extremely hard and brittle. Unless you use proper post heat after the weld, or in some cases completely annual the piece, you have lost futility in and around the weld and thus strength. You can see the failure of your piece is at the toe of the weld and moves to the center. It also looks like there was very little plastic deformation (stretching prior to the yield) which indicates a low-strength, highly brittle fracture. A longer drive shaft may have been able to absorb some of the torsional stresses and spread the stresses more evenly on the welds.

Simple material properties of aluminum are that in general (there are dozens of grades of both aluminum and steel) aluminum is about half the strength of steel but 1/3 the weight. This allows you to make an aluminum part that is similar in strength but weighs less than steel. The problem you run into is in the fabrication. Carbon steels lose very little strength when welded without applied pre or post heating. Aluminum is not so fortunate.

As another item to consider - for a 10" drive shaft, how much HP loss to you really think you're saving by using aluminum vs steel?

[Jeff Kleiner]

...As another item to consider - for a 10" drive shaft, how much HP loss to you really think you're saving by using aluminum vs steel?

Thank you! ;)

Moose, you'd do well to listen to Karlos, King and Bruce.

Good luck,
Jeff

[skullandbones]

This reminds me of an application on the first hot rod I had. It was a 55 Chevy with a destroked 409 with lots of torque/hp. I spun the clutch one day to the point it would not even take off without feathering it. Turns out, it had an aluminum fly wheel with no steel friction surface. Yeah! Hard to believe, right? It was a great idea except for the obvious reason not to do it. This is similar situation. Don't use aluminum when there is no particular advantage to the application. You were very lucky to get out of this one with as little damage as you had. I would replace it with the most indestructible steel shaft I could find. The only thing about the e cable is they're such a PITA to work on due to the tight quarters under these cars.

Better luck in the future,

WEK.

[6t8dart]

You are very lucky it broke like it did, it could have done a lot of damage to your leg. I have always done drive shaft safety loops, but in am considering actually adding some steel plating to cover the length of the drive shaft now. I once had a brand new drive shaft break in half and go through the right rear tire sidewall due to a missing retaining clip in the u-joint at the shop I just picked it up from after some trans work. I made it about 1 mile before it let loose.

I'm glad you are alright, and I agree with Karlos, multiple heat events caused it to be brittle. I am definitely going with steel now.

[Bad Moose]

Thanks guys! This is all making sense now. Like stated, I'm lucky no one got hurt, it was me and my son in there when it went. I never thought about the torsional differences on the length causing a different kind of failure and shortening the life. I believe we are in the 1 degree ballpark in alignment.

[TMScrogins]

Not normally on this forum. Usually on the "other" forum. But trying to start putting some presence on this forum. This driveshaft deal is near and dear to me. First off, as others have attested, you are very lucky. I too had a similar incident with my driveshaft letting go on a dyno run at about 6,000 rpm. I too was very lucky that no one was injured. I had a driveshaft safety loop which I am convinced prevented injury to persons. The vehicle was not so fortunate (over $15,000 in damage). I'll never run a high performance car without a safety loop.

I had the IRS with a Tremec TKO and a Coyote. The cause of the failure... An out of balance driveshaft. It completely tore up the underside of the car smashing in the 4" round rear crossmember. The driveshaft took out the transmission (sheared the nose clean off of the transmission), broke the block on the engine and wiped out the rear end in less than a second. Coolant, motor oil, tranny oil and bits and pieces all down on the floor and around the vehicle instantaneously. Pieces of the drivehshaft pierced the trans tunnel side aluminum. The carpet tore but the pieces did not come through. Very violent, very scary.

6T8Dart is bang on. I did what he is contemplating. When I repaired, I plated with steel the inside of the trans tunnel from the trans output shaft rearward as an extra safety precaution.

I'm posting not to suggest you had an out of balance driveshaft but to strongly urge you to make sure you put a safety loop in. Also, make sure the driveshaft shop balances the shaft at higher speeds. Many shops can only spin to about 4,000 RPM which isn't fast enough for my peace of mind.

Trevor


514495145051451

[Bad Moose]

Brake cables arrived today. Took driveshaft down to get built. Was advised to go with steel by the shop, so 3" steel it is. Also looking at the Metco driveline loop. That is going to happen in the near future also. But for now I should be driving the Cobra end of tomorrow or by the weekend at the latest.

[Avalanche325]

There is no need for an aluminum driveshaft on these cars. It doesn't matter what the driveshaft was rated for, as soon as it was modified, the rating is gone. 550HP and no driveshaft loop is asking for a trip to the hospital. Check out Metco Motorsports. The make a really nice loop that just bolts on. They are getting ready to make a run of them according to the other forum. And, yes, you should have one even with a steel shaft.

Edit:
Oh, I see you are already looking at the loop. I guess I didn't read everything.

[Bad Moose]

New driveshaft installed brake lines run. Test drive done. Smiloe on the bouys face, done, Yippeee she back on the road again.