We have finished testing our new carbon fiber driveshaft and are pleased to say this is one of the best mods yet. Driveline harmonics and gear noise are decreased and the "springy feeling" associated with the stock setup is reduced significantly. Their are many benefits to running a carbon fiber driveshaft. In independent tests, they have been proven to release up to 5% in horsepower gains due to lower rotational mass and decreased driveline harmonics. Additionally, their ability to absorb driveline shock reduces stress on the rest of the driveline.

The factory shaft is a two-piece design that uses a rubber joint in the front and a CV joint in the rear. Both of these are rated for roughly 450RWHP (as we found out in our Project GTO test car that uses a similar setup). With the current nitrous, supercharger, and turbo kits being developed for the CTS-V, this will definitely be a necessary safety precaution. Since this is a part that is usually replaced for safety only, the other benefits make it a no brainer mod. :hmm:

Our heavy duty driveshaft is made from 3.25" diameter carbon fiber with heavy duty 1350 series forged u-joints. The supplied rear yoke adaptor converts the CV pinion flange on the differential to a more traditional and stronger 1350 series u-joint. This rear yoke is machined from 4340 billet then hardened and black oxide coated. The front yoke is available with either a Mark Williams billet yoke or a cryogenically treated cast yoke. The whole unit is rated for 800+ RWHP. The only modification required to the car is the elimination of the factory resonators which are too bulky for use with the larger diameter shaft. this can be accomplished by replacing them with sections of tubing or upgrading to an x-pipe.

The driveshafts are sold with the rear pinion adaptor and your choice of front yoke.
- CF driveshaft with billet front yoke - $1459.95
- CF driveshaft with cryogenically treated cast front yoke - $1349.95


Currently we are ready to start taking orders. Due to the cost involved in making these, we will not start production until we have 5 units ordered with 50% down for materials. Turnaround time is 2-3 weeks once we receive 5 orders. If you are interested, just give us a call to place your order.
Sales@bmrfabrication.com
813-986-9302

http://www.bmrfabrication.com/CTS-V/cf.jpg
http://www.bmrfabrication.com/CTS-V/r-yoke.jpg
http://www.bmrfabrication.com/CTS-V/f-yoke.jpg

BMR -

This may not be the appropriate place to pose this question, but since I expect your awaiting responses from here, thread hijack on.

I purchased and installed your Toe Rods for the CTSV. Problem is, once installed there is no way to adjust them as the jamnut on the inboard end cannot be reached. Is this simply an oversight on your part, my part, or is there a special tool/procedure that can be followed to achieve proper alignment specs without removing the wheel and toe rod to make adjustments?

Thanks...and back to the drive shafts.

Will they clear an exhaust such as the BMR exhaust with the BMR resonator?

Wildwhl

Wild,

I wouldn't hold my breathe to see if they respond. I e-mailed them early yesterday morning about using my car in there ad pic and didn't get a response. :( Even sent them a higher reso pic.

I've been giving this whole suspension thing a lot of thought and there has to be a reason why GM did some of the things they did on the drivetrain. My wheel hop has got significantly better as my car has gotten mileage (9000 miles) and the only problem I have is the slight vibration in sixth on the highway. I really think replacing some of the bushings with urethane is going to make a difference. Did you remove the BMR toe rod ends yet??

Shane

BMR couple questions:
Is the rubber bushings / end eliminated completely?
What is the difference between the billet yoke vs. the cast yoke?
How difficult is the install? Can it be done be an "average home mechanic"?
Is there any balancing of the driveshaft required?

wildwhl: The BMR design is typically how aftermarket toe links are setup...
Here's a toe link for a completely different car (same exact design):
http://www.m2performance.com/images/Link2.jpg

And as you found out, with some cars, one of the nuts end up being hidden... maybe BMR will have a better answer, but i think the only way around this is (1) measure the length of the original and adjust the new link as close as possible to this length before installing and (2) get a good alignment guy... he should figure out how much of an adjustment needs to be made, remove and reinstall the rod with it setup like that (and repeat until it's right). :banghead:

FWIW, half the adjustable shocks in the world have their adjustment knob in a place that cant be reach once it's on the car... so you have to remove the shock to adjust it.

Dreamin -

You're probably right. I took great care to make the rods as close to the same length as the stock ones as possible...but must have been off a tad. The alignment guy managed to get everything close, and he said he'd readjust if I'd pull the rods, make some adjustments to them, and bring the car back - and he wouldn't charge me. It just seems like there must be a way to create rods that can be adjusted on the car that would also improve the performance...just my .02

Dont these things have a right and left hand thread? Should be no different than the front tie rods. Rotate the bar to expand or contract.!then lock the nut.

Dont these things have a right and left hand thread? Should be no different than the front tie rods. Rotate the bar to expand or contract.!then lock the nut.

Seems simple, yes, but in fact YOU CANNOT GET TO THE JAM NUT TO LOCK THE NUT! The jam nut is INSIDE the pocket which the toe rod mounts in - no possible way that I can see to get a wrench or even leverage a screwdriver and spin the toe rod against...

And therein lies the problem :(

Back to the carbon fiber driveshaft. I could not determine if the BMR shaft is one piece or two piece. If it is two piece, does it use the factory hangers and rubber for the center support?
The other question relates to price. Carbon fiber applications remain expensive. Is this because of the labor and time associated with production, or does it have more to do with volume in this case?
Rob Ketcham

Back to the carbon fiber driveshaft. I could not determine if the BMR shaft is one piece or two piece. If it is two piece, does it use the factory hangers and rubber for the center support?
The other question relates to price. Carbon fiber applications remain expensive. Is this because of the labor and time associated with production, or does it have more to do with volume in this case?
Rob Ketcham
Also, the factory shaft is very tight around the connection to the diff. The heat shield is only about 1/2" away. Does it clear?

wildwhl - Unfortunately options are limited in the toe rods design. Spherical rod ends are only manufactured in specific sizes and for strength purposes the threaded shank can only be so long. This is what dictates the jamnut position. It would be easy to weld a nut in the center for adjustment purposes but the jam nuts would still be at the ends. We even tried to use spherical bearings in the ends so we could use a center double adjuster but, after checking with 8 different bearing manufacturers, nobody makes a spherical bearing narrow enough to fit the inner mount. You probably did everything right. Our car was a little over a degree off on the passenger side right of the showroom floor. The simplest way to adjust them is to remove the mount at the wheel and adjust it there. Since it is not a "captured" mount you can get two wrenches in their to tighten it.

ssmith100 - Sorry it took us a few days to return your email, we are about 3-4 days behind at the moment. Your question required a response from our owner who has been busy preparing the shop for this other hurricane. Typically we respond to email within the same day. In fact, we recommend that people either call us of email us for the quickest response. We don't have the manpower to keep up with all the forums we sponsor and a lot of times people misjudge late response times for not caring.

Dreamin -
Is the rubber bushings / end eliminated completely?
Yes, the new driveshaft eliminates the front rubber bushing altogether, the rear is a CV joint.
What is the difference between the billet yoke vs. the cast yoke?
We provide the two yokes just because they are available. The cryogenicly treated yoke is rated to 800RWHP and is plenty sufficient but if you just have to have the best we also offer the billet yoke. This is the same yoke used in cars running 6 and 7 second quarter mile times. Since it was only $110 more, we decided to make it an option.
How difficult is the install? Can it be done be an "average home mechanic"?
It's not too bad however most people will not be able to do this at home. The two most difficult points of the install is removing the resonators which requires fabrication and welding (this could be done at an exhaust shop before the install) and replacing the the rear pinion yoke. The pinion yoke is retained by a larger nut that requires an impact wrench capable of 300 ft/lbs. Once this nut is broken loose, the yoke can be knocked loose from the pinion with a rubber mallet or dead blow hammer. The rest of the install is simply remove and replace.
Is there any balancing of the driveshaft required?
No, the driveshafts ship prebalanced.

Rob Ketchum - The carbon fiber shaft is one piece and eliminates the center carrier. A one piece conversion for this application is only possible with carbon fiber due to the length of the shaft. Steel, chrome moly, and aluminum would require a 4" diameter to keep the "critical speed" at a safe level. With the space limitations of the CTS tunnel 3.25" is maxxed out. As for the expense, it is definitely associated with production because they are used in a surprising amount of applications from monster trucks to conveyors to dump trucks. Believe it or not, the company we are working with on the carbon fiber portion of the shaft turns out over 100 shafts daily for various applications, mostly commercial :eek: Part of the expense is also the billet pinion adaptor. In mass production a mold could be made and these could be forged but for such a limited application they are cut from billet, hardened and coated. This operation is definitely more costly although you have a bulletproof product in the end.

lasstss - The heat shield is close but clears on our test car. The pinion yoke adaptor positions the joint portion of the shaft further forward so it is not actually as close as it would seem.

Wild,

I wouldn't hold my breathe to see if they respond. I e-mailed them early yesterday morning

Shane


I'm sure there is a reason. They responded to me timely on two different occasions.

Their are many benefits to running a carbon fiber driveshaft. In independent tests, they have been proven to release up to 5% in horsepower gains due to lower rotational mass and decreased driveline harmonics. Additionally, their ability to absorb driveline shock reduces stress on the rest of the driveline.



I'd be interested in seeing RWHP dyno results!

BMR -

Thank you for the responses to our questions.

I have another for you, and I don't intend to turn this into a "general BMR tech forum"...however, between the various items I've purchased I have three different torque recommendations for the cradle bolts in the V

110 ftlbs (AWH kit)
140 ftlbs (verbal, over the phone)
180 ftlbs (trailing arms)

Which is it? Will achieve the 180 ftlbs torque number eliminate the popping/clanking/banging associated with the wheel hop kit?

Thanks...and I do understand now the reasoning for the design of the toe rods.

Finally, I, too, would like to see some dyno numbers on this carbon driveshaft. Does it add more noise(s) to the car?

If we still have a shop left after this hurricane we will try to get some dyno results next week sometime.

wildwhl - The original 110 ft/lbs was a typo, it was supposed to be 140. Nobody noticed this until we started receiving questions about bolts loosening up. The torque specification was confirmed with a Cadillac dealership. Unfortunately what they didn't tell us was that the cradle has seperate torque specs for the front and rear bolts. :banghead: The front bolts should be 185 ft/lbs. Sorry for the confusion.

As for the clunking, a lot of this can be associated with loose cradle mounts however we have just recently discovered a new source of the noise. When designing our pinion support brace we noticed that the front differential mounting bolt is smaller than the hole in the cradle. As the pinion rises, the slop in this connection allows the bolt to clunk when it contacts the cradle. An easy way to test this is to loosen and retighten this bolt. It is not accessible enough to use a torque wrench but the bolt is the same size as the cradle bolts so you can estimate 140 ft/lbs. We have done this to two seperate cars and noise is significantly reduced. Of course adding a BMR pinion support brace is even better at controlling pinion rise and reducing this noise :sneaky:

If we still have a shop left after this hurricane we will try to get some dyno results next week sometime.

wildwhl - The original 110 ft/lbs was a typo, it was supposed to be 140. Nobody noticed this until we started receiving questions about bolts loosening up. The torque specification was confirmed with a Cadillac dealership. Unfortunately what they didn't tell us was that the cradle has seperate torque specs for the front and rear bolts. :banghead: The front bolts should be 185 ft/lbs. Sorry for the confusion.

As for the clunking, a lot of this can be associated with loose cradle mounts however we have just recently discovered a new source of the noise. When designing our pinion support brace we noticed that the front differential mounting bolt is smaller than the hole in the cradle. As the pinion rises, the slop in this connection allows the bolt to clunk when it contacts the cradle. An easy way to test this is to loosen and retighten this bolt. It is not accessible enough to use a torque wrench but the bolt is the same size as the cradle bolts so you can estimate 140 ft/lbs. We have done this to two seperate cars and noise is significantly reduced. Of course adding a BMR pinion support brace is even better at controlling pinion rise and reducing this noise :sneaky:

And hence the reason I have a pinion support brace sitting on the bench to install tonight or tomorrow morning :D

So, to clarify:

Front cradle bolts (24mm) = 185 ftlbs
Rear cradle bolts (21mm) = 140 ftlbs
Pinion support bolt (21mm?) = 140 ftlbs

How about the AWH bolts, or in other words the bolts at the front trailing arm...serious thread hijack, I know, but I'm good at it :)

As for the clunking, a lot of this can be associated with loose cradle mounts however we have just recently discovered a new source of the noise. When designing our pinion support brace we noticed that the front differential mounting bolt is smaller than the hole in the cradle. As the pinion rises, the slop in this connection allows the bolt to clunk when it contacts the cradle. An easy way to test this is to loosen and retighten this bolt. It is not accessible enough to use a torque wrench but the bolt is the same size as the cradle bolts so you can estimate 140 ft/lbs. We have done this to two seperate cars and noise is significantly reduced. Of course adding a BMR pinion support brace is even better at controlling pinion rise and reducing this noise :sneaky:

Does anyone know where this front differenctial mounting bolt is located? I don't understand how loosening and retightening this bolt will solve the clunking noise if the bolt (head?) is too small for the application. But if this is all it takes to reduce most of the clunking noise it sounds too good to be true. I can't believe GM hasn't figured this out yet.

This is the photo of the BMR pinion support brace installed from the BMR Fab website.

BMR Fab - In reference to my last post could you please note the bolt that you loosened and re-tightened to reduce the "clunk". Hope the hurricane hasn't flooded you out.

Rich H

If we still have a shop left after this hurricane we will try to get some dyno results next week sometime.




were the dyno runs ever completed?

FYI, I milled 1/8" off the back of the pinion support. It now clears the heat shield and is very clear of the gas tank. It stiffened things up a bit. Im happy with this part.
Still not happy with the rattling end links on the lower arms!
These need to have urethane mounts not the rod eyes...