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Shave 25 lbs of rotating mass

Here's a way to drop 25lbs of rotating mass on our cars. A little pricey, but if it elminates the dreaded DS vibration on a one-piece DS it's worth it.

http://www.vmptuning.com/store/index.php?p=product&id=392&parent=121
 
Nice. Any rear wheel hp increase? Have you ordered one yet?
 

ArizonaBOSS

Because racecar.
Moderator
8,571
2,440
Arizona, USA
I've got a Coast 4" aluminum DS on my GT now, it made a difference in acceleration for sure. Supposedly it's worth like 12rwhp but I haven't re-dyoned since installing it. Theoretically it should help braking too, since you don't have the extra 20lbs rotating inertia to fight while slowing, either. I'd say it's a must-do for a regularly-tracked car.

One thing to be cautious of is tunnel clearance--I'm not sure if any changes were made to the tunnel on the 11+ car, but on the 05-10 there were some rub-spots for the 4" shafts that have to be addressed with either a dremel or some heavy "technical taps" during DS install. Nothing impossible to remedy. As far as vibration goes, gotta make sure the rear mounting flange is installed correctly and FLAT, and if you're very sensitive to vibration, install an adjustable UCA so you can verify your pinion angle is where it needs to be when the axle is at ride height.

I'm leery of the carbon ones, I've seen one literally ripped in half by a mildly modded GT during a track day...not sure what brand it was but I'll stick with the aluminum ones.

Does anyone have one for the 2011+ Mustang yet? (Coast, Shaftmasters, Sypdershaft, etc)
 
I'm done with aluminum one-piece DSs on the S197. Way too many vibration issues especially on lowered cars. You definitely need an adj UCA so you can correct pinion angle, but it's still an issue for way too many people. There's a reason Ford puts two piece driveshafts in these cars. I have an aluminum/chromoly 2-piece on my GT500 rated to 800 hp. I had a one piece aluminum that was fine until I installed the Griggs GR40SS rear suspension. I had to go back to a 2-piece.

Most of the CF driveshafts are rated to handle far more hp than you'll ever get out of the Boss. IF one failed they basically disintegrate and don't pose near the danger of an aluminum or steel shaft whipping around or pole vaulting the car with or without loops.

I have not bought one yet. As AZGT says, theoretically you'd have less driveline loss so higher rwhp/rwtq and less weight to slow the car. I'll definitely consider one, but won't be one of the first things I do.
 
1,255
2
GA
Many people on the Bullitt forum swear by this one by Dynotech:

For 2005-2010:
http://www.brenspeed.com/dshaft05gt.html


For 2011+:
http://www.brenspeed.com/dshaft11gt.html
 
The reason Ford uses a 2pc driveshaft is that because of the motor/trans placement you can’t get good “in phase” driveline angles out of a 1pc driveshaft. As delivered the Trans output flange points to a space below the centerline of the rear ends input flange (at stock ride height, it gets worse when you lower it). At a minimum you want the Trans pointed exactly at the centerline of the diff but that is not even ideal with something that has U-joints because they require some angle in them to “work” correctly. I ended up milling 20mm out of my Prothane engine mounts and adding 6mm of shim to the trans mount to achieve “correct” driveline angles. It allowed me to run the DS 1.25deg down out of the Trans and 1.25deg up coming out of the diff.

I went through all the effort because I couldn’t get MULTIPLE “one piece” (which in reality they are 2pc also) driveshafts to not vibrate my molars out over 150mph.

I currently have great driveline angles but I am still running the stock driveshaft. It’s as smooth as glass. I would like to get another 1pc shaft but the only one I would consider is the VMP shaft because it is the only true 1pc shaft out there that I know of. No matter how tight the tolerances the aftermarket “1pc” shafts will always have some slop in the spline'd section and that will be a source of some harmonics/vibration.
 

ArizonaBOSS

Because racecar.
Moderator
8,571
2,440
Arizona, USA
^^^Good post!

Doesn't there need to be a splined slip-yoke to allow the overall length to change when the rear axle moves vertically?

And yeah, the factory shafts are vibration free for sure. Considering how fast this car (should) be in stock form, I'm not sure it is warranted to remove the factory shaft until any serious modding/gutting for track-only use starts.
 
RoadRacer78 said:
The reason Ford uses a 2pc driveshaft is that because of the motor/trans placement you can’t get good “in phase” driveline angles out of a 1pc driveshaft. As delivered the Trans output flange points to a space below the centerline of the rear ends input flange (at stock ride height, it gets worse when you lower it). At a minimum you want the Trans pointed exactly at the centerline of the diff but that is not even ideal with something that has U-joints because they require some angle in them to “work” correctly. I ended up milling 20mm out of my Prothane engine mounts and adding 6mm of shim to the trans mount to achieve “correct” driveline angles. It allowed me to run the DS 1.25deg down out of the Trans and 1.25deg up coming out of the diff.

I went through all the effort because I couldn’t get MULTIPLE “one piece” (which in reality they are 2pc also) driveshafts to not vibrate my molars out over 150mph.

I currently have great driveline angles but I am still running the stock driveshaft. It’s as smooth as glass. I would like to get another 1pc shaft but the only one I would consider is the VMP shaft because it is the only true 1pc shaft out there that I know of. No matter how tight the tolerances the aftermarket “1pc” shafts will always have some slop in the spline'd section and that will be a source of some harmonics/vibration.
Thanks for posting. It sounds like you went through similar issues to what I had gone through with my GT500. I'm not in a hurry to replace the stocker, but it looked to me like the VMP option was the best I've seen. Justin tuned my GT500 after having a few "bad" tunes from other vendors and it runs absolutely perfect. He really puts out quality product.
 
ArizonaGT said:
^^^Good post!

Doesn't there need to be a splined slip-yoke to allow the overall length to change when the rear axle moves vertically?
You are correct that if the shaft has U-joints there has to be a spline'd section at some point to accommodate suspension travel. It would be ideal to have it in the Trans tailshaft ala’ “Old School” setups. Swapping to a T-56 6spd would achieve that but that is certainly the long way around! The nice thing about VMP’s setup is that CV joints have a certain amount of “play” in them so they can accommodate the suspension travel of the rear end. In addition to that a CV joint makes a U-joint look positively Stone Age by comparison.

And yeah, the factory shafts are vibration free for sure.
Which is AMAZING considering how horrible the stock driveline angles are! :eek:


Considering how fast this car (should) be in stock form, I'm not sure it is warranted to remove the factory shaft until any serious modding/gutting for track-only use starts.

Agreed, For track days or roadracing I myself would stick with the stock shaft until the car was modded to the point where you are messing with stuff like motor/trans placement etc like I did. It works great and has proven itself to be plenty durable/strong.

If I were running it down the quarter with some serious traction I would want to switch to a “1pc” though. From what I have seen the stock shaft is good for about mid 11’s which is not too hard to pull off these days. All it takes is a blower or a Nitrous kit and a set of drag radials.

All that being said, I can absolutely tell how much “snappier” the car is when I have a light driveshaft in it. It feels very similar to having light wheels, except for when you are trying to change direction of course. I plan on going with the VMP shaft at some point this season, as soon as I cross a few more things off my list.
 
1,255
2
GA
The only complaint I have about the 2-piece driveshaft is that there is a lot of slop in the drive line. I would clank the u-joints in my Bullitt at low RPM until I figured out how to drive it. The 2011 GT I test drove seemed to be better about that (or may just I was ;D ).
 
PJWANNABE said:
The only complaint I have about the 2-piece driveshaft is that there is a lot of slop in the drive line. I would clank the u-joints in my Bullitt at low RPM until I figured out how to drive it. The 2011 GT I test drove seemed to be better about that (or may just I was ;D ).
I don’t think that “clank” you are hearing is the DS. The liquid filled motor mounts have so much play in them that when engaging the clutch, especially in 1st or reverse the motor will “rock” enough to bounce the tailpipes off of the bumper cover. I had a buddy confirm for me that was what was going on. It doesn’t help I have a Spec Stage III clutch either. It’s a grabby little bastard. When I switched to Prothane engine mounts the “clank” went away.
 
1,255
2
GA
RoadRacer78 said:
PJWANNABE said:
The only complaint I have about the 2-piece driveshaft is that there is a lot of slop in the drive line. I would clank the u-joints in my Bullitt at low RPM until I figured out how to drive it. The 2011 GT I test drove seemed to be better about that (or may just I was ;D ).
I don’t think that “clank” you are hearing is the DS. The liquid filled motor mounts have so much play in them that when engaging the clutch, especially in 1st or reverse the motor will “rock” enough to bounce the tailpipes off of the bumper cover. I had a buddy confirm for me that was what was going on. It doesn’t help I have a Spec Stage III clutch either. It’s a grabby little bastard. When I switched to Prothane engine mounts the “clank” went away.

Interesting... The '08 Bullitt does have a very grabby clutch.
 
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RoadRacer78 said:
I went through all the effort because I couldn’t get MULTIPLE “one piece” (which in reality they are 2pc also) driveshafts to not vibrate my molars out over 150mph.

I was thinking this was a no brainer mod...I HATE THESE TYPE OF HIGH SPEED VIBRATIONS (might have something to do with once losing a wheel at 90+mph after noticing a funny vibration ;D).
 
Mark said:
I was thinking this was a no brainer mod...I HATE THESE TYPE OF HIGH SPEED VIBRATIONS (might have something to do with once losing a wheel at 90+mph after noticing a funny vibration ;D).
Definitely a pucker factor moment. I lost brakes at 100 heading into a tight S turn....fortunately it was on a very flat track in the middle of several cornfields :eek:
 
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cloud9 said:
I'm done with aluminum one-piece DSs on the S197. Way too many vibration issues especially on lowered cars. You definitely need an adj UCA so you can correct pinion angle, but it's still an issue for way too many people. There's a reason Ford puts two piece driveshafts in these cars. I have an aluminum/chromoly 2-piece on my GT500 rated to 800 hp. I had a one piece aluminum that was fine until I installed the Griggs GR40SS rear suspension. I had to go back to a 2-piece.

Most of the CF driveshafts are rated to handle far more hp than you'll ever get out of the Boss. IF one failed they basically disintegrate and don't pose near the danger of an aluminum or steel shaft whipping around or pole vaulting the car with or without loops.

I have not bought one yet. As AZGT says, theoretically you'd have less driveline loss so higher rwhp/rwtq and less weight to slow the car. I'll definitely consider one, but won't be one of the first things I do.

Gary,
Can you expand on your issues with the 1 pc ds after the griggs went in?
Thanks,
Lee.
 
lbp said:
cloud9 said:
I'm done with aluminum one-piece DSs on the S197. Way too many vibration issues especially on lowered cars. You definitely need an adj UCA so you can correct pinion angle, but it's still an issue for way too many people. There's a reason Ford puts two piece driveshafts in these cars. I have an aluminum/chromoly 2-piece on my GT500 rated to 800 hp. I had a one piece aluminum that was fine until I installed the Griggs GR40SS rear suspension. I had to go back to a 2-piece.

Most of the CF driveshafts are rated to handle far more hp than you'll ever get out of the Boss. IF one failed they basically disintegrate and don't pose near the danger of an aluminum or steel shaft whipping around or pole vaulting the car with or without loops.

I have not bought one yet. As AZGT says, theoretically you'd have less driveline loss so higher rwhp/rwtq and less weight to slow the car. I'll definitely consider one, but won't be one of the first things I do.

Gary,
Can you expand on your issues with the 1 pc ds after the griggs went in?
Thanks,
Lee.
The issue was the lack of pinion angle adjustment in their torque arm. When I had the traditional 3-link setup with an adjustable UCA we could reset the pinion angle to the factory setting and I had no issues with DS vibration on the one-piece aluminum. For some reason there's no PA adjustment on the Griggs torque arm setup. If you lower the car and try to use the factory (non-adjustable) UCA, expect vibration issues. I am guessing you may have swapped yours for a rod end adjustable version with your Cortex setup?
 
144
0
MA
I just installed and removed the Dynotech Aluminum DS from my Boss.

It had some harmonics, not bad, but at around 80+ MPH, I felt a vibration.

Since I had ordered it from Lethal Performance, I asked if they would accept it as a return and give me a credit toward future purchases. They said I would need to send it to Dynotech to have them check the balancing, and we would go from there. Sort of irritated me since I know it vibrated and all I wanted was a credit! Lethal assured me it WOULD NOT vibrate.

If anyone wants it, let me know. Personally, I think the reason it vibrated is that a single piece driveshaft on these cars is not ideal. I know Dynotech will say its "fine", which will cost me more money and time to ship it back and forth.

Its your's for $600 you pay shipping. That is if you feel lucky, lol.
 
so is the shafts balance off? if not ill take it off your hands. are there any dents or scratches in it from shipping ect? noting noticeable about it that would make you think its the cause?

if not tell me how to get ahold of you offline and il do it
 

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