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Discussion Starter #1
Posted this up in another section and didn’t get any replies so I thought I’d try here...

I got the ford racing aluminum driveshaft and am wondering, before I beat up my trans tunnel with a snapped driveshaft, how long is it going to last? 700hp with a transbrake, I’ve got a driveshaft loop installed, but would rather not test it out. Any other stronger options if it’s not going to hold up?
 

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Discussion Starter #2
Car is a 2004 turbo 2v, weight around 3100lbs with built 4r70, 8.8 rearend, if I’m not snapping the shaft, what’s gonna go first?
 

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When I got a new driveshaft made the shop told me that the ford racing are only rated at 600 he said the u joints are 1330 so I went to 1350 and got a different piece that attaches to the rear
 

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it might last but lot of variables at play... suspension, tires, pressure, 60', stall
are transbrakes easier or harder on driveshafts?
at the very least upgrade to 1350 Ujoints

i got mine from The Drive Shaft Shop after snapping the ford unit although i'm running a T56 6speed
 

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Discussion Starter #7
I would think the transbrake would be harder on it versus clutch car. Is that the front or rear universal that’s the weak link?
 

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A transbrake is in an automatic. The torque converter "absorbs" some shock-thus making it little easier on the driveline(s) as compared to a clutch dump, ESPECIALLY a clutch that doesn't offer much slippage at the "hit". Or worse yet, a clutch that locks and running drag radials, going into wheel hop. That'll destroy stuff quick.

I would not worry so much about the shaft at the hit as I would the rear end, u-joints, and especially the axles. Driveshafts rarely fail in the first 1/2 of the track-usually at the far end where the speed of the shaft gets high, it becomes deflected due to it's speed and bends itself. Then it just wads up for a lack of a better term.
 

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IMO, one of the u-joists will be the part that fails. I snapped FMS aluminum one in Bowling Green last fall and am pushing the same power as the OP. They had the track in perfect shape for the NMRA event and it dead hooked. Hard to say if the front u-joint or the shaft failed first as the u-joint was broken, one ear on the shaft gone, and the other seriously deformed. I am confident it was the front joint as it was a conversion (T56) and are only available locally greasable (hollow).

I disagree with Todd. It will fail on the hit or not at all. I have never seen a driveshaft (or axles) fail beyond 60'. Granted, if your shaft is seriously out-of-balance or a u-joint is not moving freely, something may fail as RPM increases. It is the shock load that kills them.

I also have a conversion u-joint in the rear as it is a 9". I have been running a shortened stock shaft since the breakage, but my plan is to buy a shaft with 1350 joints at both ends and change the pinion yoke on the rear to 1350. I just have to hate to pull the center section to re-set the pinion preload and I can't remember how many splines are on the Currie setup.
 

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I twisted the front slip yoke on my FMS aluminum shaft. Mild 331 Stick / Slicks. Initially I could not figure out why I could not slide the yoke forward to get the shaft out. Spline's were twisted. Replaced it with Forged Chromoly one from Sonnax.
 

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Discussion Starter #11
I’ve got the sonnax unit in mine too, would I be better of running a stock steel driveshaft? I bet I can sell this aluminum one before I break it and recoup some money to buy a better custom one down the road.
 

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I twisted the front slip yoke on my FMS aluminum shaft. Mild 331 Stick / Slicks. Initially I could not figure out why I could not slide the yoke forward to get the shaft out. Spline's were twisted. Replaced it with Forged Chromoly one from Sonnax.
how much power and what sort of ets do you run?
 

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is it always the front Ujoints that go or have some of you had the rear ones fail?

i ask because i have a driveshaft loop on the front side of the driveshaft and my maximum motorsports torque arm crossmember acts like a secondary one if anything was too fail but i've been concerned with a rear failure and planned on building a rear driveshaft loop onto my torque arm just in case although have since gone to a custom aluminum shaft from the drive shaft shop with 1350s that can handle over 1000tq so its on back burner for now
 

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how much power and what sort of ets do you run?
94 Cobra mostly street. 331 9.8:1, ported GT40Y heads, Rawls cam, ported Cobra upper & lower, 65mm TB. 325RWHP @5000 385 RWTQ @3800 Dynojet. 320RWHP from 3850 to 5600. 350 Torque from 3100 to 5000. Full weight 3644 with driver. Best ET 12.19 @ 111.20. on MT 17" street slicks.
 

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IMO, no. Then you will be in the same position I was in; 1350 one way (tranny) and a 1330 (FRPP shaft) the other. You can only purchase that conversion joint at your local part stores greasable (hollow) and it will break. A solid version may be available online from Strange, etc.

I assume you have 1330s in both directions at the rear since it is a FRPP shaft and and 8.8 rear. It is probably solid so much stronger. However, the weakest link will always break.
 

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Discussion Starter #17
Okay, I’ll just keep what I got and fix what I break when I break it. I’ve yet to touch the rear end, so I’ve yet to cross that bridge. Just wanted to see if the ford racing unit would hold up for now. I like the cheap stuff breaking (u-joints) versus the expensive stuff (driveshaft).
 
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