2007 CTS-V Build Thread..nothing new but new to me.
08-17-2016, 05:05 PM
#162
That's a hard question to answer. Your misalignment angles depend on the height of your motor mounts, trans mount, subframe bushings, and choice of differential. The Getrag, Ford 8.8", and Ford 9" housings place the differential input flange in different places. On the stock driveline with 25,000 miles, sagging support bearing, rubber guibo, and Revshift mounts everywhere else, you'll find:
Note that if you put a laser boresight on this setup, the center of the prop flange will nail the center of the differential CV flange. Therefore, it's the center support bearing that's causing the big misalignment angles. (It's also important to note that the driveline gets longer when you spin it, so the loaded CTS-V misalignment angles are less than the static values above.)
I don't see any reason why you shouldn't be able to improve on that and achieve a misalignment angle of 0.25-0.50° degrees on the transmission end (where the U-joint will be) by shimming your custom mount/crossbrace. That should make the angular acceleration of the universal joint almost indistinguishable from a CV joint, even at high speeds. If you're cautious, a dual CV setup will provide the smoothest possible rotation, but you'll pay more and it'll be 5-8 lbs heavier.
- Transmission Propeller Flange: 2.75 degrees down
- OEM Driveshaft, First Section: 3.30 degrees down
(Δθ1 = -0.55° @ rubber guibo) - OEM Driveshaft, Second Section: 0.30 degrees down
(Δθ2 = +3.00° @ support bearing) - Differential CV Flange Angle: 0.90 degrees up
(Δθ3 = -0.60° @ Getrag CV joint)
Note that if you put a laser boresight on this setup, the center of the prop flange will nail the center of the differential CV flange. Therefore, it's the center support bearing that's causing the big misalignment angles. (It's also important to note that the driveline gets longer when you spin it, so the loaded CTS-V misalignment angles are less than the static values above.)
I don't see any reason why you shouldn't be able to improve on that and achieve a misalignment angle of 0.25-0.50° degrees on the transmission end (where the U-joint will be) by shimming your custom mount/crossbrace. That should make the angular acceleration of the universal joint almost indistinguishable from a CV joint, even at high speeds. If you're cautious, a dual CV setup will provide the smoothest possible rotation, but you'll pay more and it'll be 5-8 lbs heavier.
I spoke to Frank @ DSS as well and it sounds like if I am willing to do some shimming to get things fairly closely aligned that U-joints will be the way to go.
So now it comes down to material -- Al vs. CF. CF is twice the price but I was real interested in the different torsional "wrap-up" characteristics of the CF shaft - sounded like it made the driveline a lot smoother without giving the impression of slack. Also he indicated it would transmit the least harmonics. Who has practical experience with the difference in a one-piece shaft?
He did also make a strong pitch for rubber engine and trans mounts but definitely said rubber trans no matter what I run for engine mounts.
Trans was picked up today and is on the way back to RSG to be put on the stretcher.
Thanks!
08-18-2016, 10:24 AM
#164
Thanks!
See below where I've pasted a response from DSS that Frank says he sends to all folks that ask the "Al vs. CF" question:
Harmonics
You see the rubber bushings in a car are there to remove harmonics from the cabin, harmonics are caused by the engine firing in pulses and the firing turns the crank, but not smooth like an electric motor, it speeds up every time the spark plug ignites the fuel, this is why the engine has a harmonic damper on the front to kind of smooth this action. when you change from rubber to solid or poly mounts it will sometimes re-introduce the harmonic back in the cabin (the reason rubber is used is to make it quiet)i have been asking under scrutiny why a stock 2 piece will not do this as much as a single one and its simple. the center of the driveshaft that is supported but a by a real soft rubber hanger. its hiding this,shaft is still moving around but the rubber is soaking it up. put a solid rubber there and it would change this tremendously. its kind of masking but its still there, when you put a single shaft in there is nothing hiding the center moving around so its transferred to the ends (think of a tuning fork, hit one side and the other moves not because its out of balance but because a sound it being transmitted thru it) Hope this make sense
material and Harmonics
you are standing in front of (3) 48" long pieces of tube, all about 3.5" in diameter but one is steel, the next aluminum and the 3rd Carbon Fiber. You then pick up the steel on with your thumb and your index finger and strike the middle of the tube with a long screwdriver. The steel shaft will ring like a bell and continue until the harmonic being produced by the strike exhausts itself. You do the same with the Aluminum next, you will get a bit of ring but not as loud and will not hold for near as long. You then pick up the Carbon Fiber and strike it the same way as the others, it make a clack and stops almost immediately.
This affect is the same thing that happens when the motor if firing and pulsing the power from the explosions in each cylinder(this is what a Harminc damper trys to stop on the engine) This pulse along with the frequency coming out of the trans and the diff all collide in the hollow tube of a driveshaft, the material will either broadcast it or will not allot it to go any further. Think of a Tuning fork, hit one side and the other moves. Its not out of balance its being excited by the frequency being sent to it, the driveshaft does the same thing so balance is not to blame its harmonic, on the 2005+ mustang Ford had such a problem with this on the car they did a 2 piece driveshaft with (1) u-joint, a hanger bearing (2) CV's and a 9lb damper in the back shaft (talk about a
flywheel affect) this shaft weighs 46lbs and was used to stop the issue. other things like solid or poly mounts will make this even worse but thats a story for another day......
Carbon
Carbon is lighter but its not the real prominent thing it does. The carbon shaft would make the car more consistent with the 60ft times. and help lower them you see when the shaft starts to twist the each of the materials will wrap up. Steel/chromoly 5-7 degrees aluminum is about 20 degrees and Carbon 30 degrees, what the difference is the Carbon releases slowly and does not shock the tires, most see between .1 to .3 gain in the 60's.
Guibo/hanger issue with stock shaft
The stock shaft will have to start by putting the torque into the front Guibo and it
gives, then it moves down to the hanger that is very soft and will move up about .750" then back to the
rear guibo and compress that one, so by the time the torque goes thru the shaft its dampened allot to
the point of feeling soft or disconnected, by putting the single shaft in the car will be allot more responsive to
pedal/torque input. It will have a more athletic feel and be quicker due to the lack of the soft parts being
removed.
Dear DSS, I have some questions regarding your drive shafts.
1/ How do carbon fiber drive shafts cope with radiant heat from the exhaust system? Should a product such as this be used on the relevant section of the exhaust pipe?
the bonding of carbon will start to have issues at 300 degrees, if the exhaust is close wrapping it or shielding it will bring the number below this.
2/ How do cf shafts cope with stone chips and abrasions caused by gravel and other road debris?
our Carbon shafts actually have a outer layer of Fiberglass, this is done to ensure the surface of the carbon to be protected, its about .125 thick and
is very good at saving the shaft, if something were do dig thru it the shaft would be bad but also keep in mind if something were to do this to aluminum it would also ruin the shaft.
3/ Do cf drive shafts have a shelf life? That is, should they be replaced after a certain amount of time?
Heat is the only thing that will shorten the life, all shafts will have a fatigue cycle, Carbon is as high if not higher then Steel/Aluminum
4/ What is the advantage of a carbon fiber shaft over an aluminum shaft?
The biggest this is its ability to absorb harmonics and its torsion properties. you see all shafts will twist before a vehicle moves, steel about 7 degrees aluminum about 20 and carbon about 30. the difference is the others will come back like a spring and put reverse torque or time compounded stress on the shaft and the rest of the drivetrain. Carbon releases its energy over time and will help with either 60ft times in a drag car, coming out of a corner with a Drift,road race/rally or time attack car and it will also protect the drive train from harmful shock. The harmonic advantage is the fact that it will not amplify drivetrain drone or motor/trans harmonics like the other materials.
08-19-2016, 10:17 PM
#167
Mercier, while you're waiting on your new transmission to arrive, you might want to consider picking up a QuickTime RM-8020. I've had my transmission out 19 times to work on various things (i.e.: clutch/slave/hydraulic line adjustments, measurements, and replacements, and several pulls to mess with the linkage bushings and internals), and by pull #17, the aluminum was fatigued to hell. I helicoiled it after that, but the aluminum was so fatigued in those areas that it barely held.
That prompted me to look at the price difference between a new OEM aluminum unit (P/N 12453263 - $320) and a SFI-rated steel bellhousing and flywheel shield ($590). The choice was pretty obvious to me--eventually, a SFI-rated bellhousing becomes a safety requirement to race, and the improved strength, size, and isolation from transmission gear rollover noise are welcome bonuses.
Mine came in this week. Will be installing it tomorrow.
That prompted me to look at the price difference between a new OEM aluminum unit (P/N 12453263 - $320) and a SFI-rated steel bellhousing and flywheel shield ($590). The choice was pretty obvious to me--eventually, a SFI-rated bellhousing becomes a safety requirement to race, and the improved strength, size, and isolation from transmission gear rollover noise are welcome bonuses.
Mine came in this week. Will be installing it tomorrow.
Last edited by FuzzyLog1c; 08-20-2016 at 06:21 PM.
08-20-2016, 07:58 AM
#168
I finally got my 1 piece working very well but I honestly don't think you're going to get a 1 piece with 2 u-joints happy because you're limited in what you can do.
You can't really rotate the diff in the cradle because the axles will hit. So about the only thing you can do there is shim the cradle and you can only go so far with it. You can raise an lower the trans a little but ultimately, you'll be shimming the motor mounts to make it work.
I wouldn't go back to a 2 piece driveshaft. I like the direct feel of the one piece.
You can't really rotate the diff in the cradle because the axles will hit. So about the only thing you can do there is shim the cradle and you can only go so far with it. You can raise an lower the trans a little but ultimately, you'll be shimming the motor mounts to make it work.
I wouldn't go back to a 2 piece driveshaft. I like the direct feel of the one piece.
08-20-2016, 08:48 PM
#169
Mercier, while you're waiting on your new transmission to arrive, you might want to consider picking up a QuickTime RM-8020. I've had my transmission out 19 times to work on various things (i.e.: clutch/slave/hydraulic line adjustments, measurements, and replacements, and several pulls to mess with the linkage bushings and internals), and by pull #17, the aluminum was fatigued to hell. I helicoiled it after that, but the aluminum was so fatigued in those areas that it barely held.
That prompted me to look at the price difference between a new OEM aluminum unit (P/N 12453263 - $320) and a SFI-rated steel bellhousing and flywheel shield ($590). The choice was pretty obvious to me--eventually, a SFI-rated bellhousing becomes a safety requirement to race, and the improved strength, size, and isolation from transmission gear rollover noise are welcome bonuses.
Mine came in this week. Will be installing it tomorrow.
That prompted me to look at the price difference between a new OEM aluminum unit (P/N 12453263 - $320) and a SFI-rated steel bellhousing and flywheel shield ($590). The choice was pretty obvious to me--eventually, a SFI-rated bellhousing becomes a safety requirement to race, and the improved strength, size, and isolation from transmission gear rollover noise are welcome bonuses.
Mine came in this week. Will be installing it tomorrow.
Note that Tremec insists that these bells be aligned to keep your warranty on a new trans. I know you are reinstalling with your same unit, but this tells me some of these can be "off" from the mfg and require offset dowel pins. RSG told me they are always dead on. I'm going to check mine when I get things back together. This requires pulling the faceplate off a trans so pretty sure this is one of those things a LOT of folks don't actually do. I'll have he old trans to steal the front plate from.
08-20-2016, 09:00 PM
#170
I finally got my 1 piece working very well but I honestly don't think you're going to get a 1 piece with 2 u-joints happy because you're limited in what you can do.
You can't really rotate the diff in the cradle because the axles will hit. So about the only thing you can do there is shim the cradle and you can only go so far with it. You can raise an lower the trans a little but ultimately, you'll be shimming the motor mounts to make it work.
I wouldn't go back to a 2 piece driveshaft. I like the direct feel of the one piece.
You can't really rotate the diff in the cradle because the axles will hit. So about the only thing you can do there is shim the cradle and you can only go so far with it. You can raise an lower the trans a little but ultimately, you'll be shimming the motor mounts to make it work.
I wouldn't go back to a 2 piece driveshaft. I like the direct feel of the one piece.
FWIW, Frank @ DSS seemed fairly sure two U-joints would work very well. Also said that with modern materials and grease, the min angle to turn a U-joint's bearings isn't important anymore in the context of my project. He said they may only last 80K miles instead of 150K but U-joints themselves are cheap and easy to change so I am less worried about that and more interested in having a light, very straight shaft, if that can be accomplished.
I've been thinking--if the CF shaft twists 30 degrees, wouldn't the shaft length be changing when that happens? With semi-rigid mounts at each end, could that in itself be causing some issues of its own(or contributing at least)? Might I be afforded a little more leeway because I will have the slip-yoke at the trans end to allow for driveline length changes?
08-21-2016, 12:29 AM
#173
Then you should consider shortening your driveshaft by replacing your OEM T-56 with a longer T-56 XL (or equivalent). The V1's driveshaft is insanely long--it's 10-15" longer than some competing vehicles, which means that any driveshaft you select is going to have a low critical speed. As a result, there isn't a driveshaft available in the V1 length with legitimate 200+ mph capability. Don't believe DSS' 250+ mph claims for their 3.25" carbon fiber driveshafts. They should be taken to court for advertising Mustang critical speeds on their V1 products. Be safe and do the math yourself.
Here's some data you may be interested in: the 4.0" diameter, 61.5" long (54.5" mainshaft) PST CTS-V1 aluminum driveshaft has a critical speed of 7100 RPM. Their 3.75" carbon fiber model has a critical speed of 9000 RPM. Those shaft diameters are at the extreme limit of what you can install in the V1 without hitting the bottom of the shifter. Those critical speeds equate to 151 mph for the aluminum model and 191.5 mph for the carbon fiber model, assuming the V1's OEM 3.73 final drive ratio. Since I'm running a 3.50 ratio, the critical speed of the 3.75" CF driveshaft is a little higher on my car (204 mph). Remember that shortening your driveshaft will increase critical speed exponentially.
Here's some data you may be interested in: the 4.0" diameter, 61.5" long (54.5" mainshaft) PST CTS-V1 aluminum driveshaft has a critical speed of 7100 RPM. Their 3.75" carbon fiber model has a critical speed of 9000 RPM. Those shaft diameters are at the extreme limit of what you can install in the V1 without hitting the bottom of the shifter. Those critical speeds equate to 151 mph for the aluminum model and 191.5 mph for the carbon fiber model, assuming the V1's OEM 3.73 final drive ratio. Since I'm running a 3.50 ratio, the critical speed of the 3.75" CF driveshaft is a little higher on my car (204 mph). Remember that shortening your driveshaft will increase critical speed exponentially.
Last edited by FuzzyLog1c; 08-21-2016 at 01:09 AM.
08-21-2016, 01:01 AM
#175
Then you need to shorten your driveshaft by replacing the transmission with a T-56 XL (or equivalent). The V1's driveshaft is insanely long--it's 10-15" longer than most competing vehicles, which means that any driveshaft you choose is going to have a low critical speed. As a result, there isn't a driveshaft available in the V1 length with a legitimate 200+ mph critical speed. Don't believe DSS' 250+ mph claims for their 3.25" carbon fiber driveshaft--they should be sued for false advertising. Do the math yourself.
Short of walking through the calculation for you tonight, the 4.0" diameter, 61.5" long (54.5" mainshaft) PST CTS-V1 aluminum driveshaft has a critical speed of 7100 RPM. That shaft thickness is right at the extreme limit of what you can install in the V1 without hitting the bottom of the remote shifter linkage. By contrast, the PST 3.75" carbon fiber CTS-V1 driveshaft has a critical speed of 9000 RPM. That equates to 151 mph for the aluminum model and 191.5 mph for the carbon fiber model, assuming the OEM transmission gear ratios and a 3.73 rear end. Since I'm running a 3.50 ratio, my critical speed is a little higher (204 mph). Shortening the driveshaft will increase critical speed exponentially.
Short of walking through the calculation for you tonight, the 4.0" diameter, 61.5" long (54.5" mainshaft) PST CTS-V1 aluminum driveshaft has a critical speed of 7100 RPM. That shaft thickness is right at the extreme limit of what you can install in the V1 without hitting the bottom of the remote shifter linkage. By contrast, the PST 3.75" carbon fiber CTS-V1 driveshaft has a critical speed of 9000 RPM. That equates to 151 mph for the aluminum model and 191.5 mph for the carbon fiber model, assuming the OEM transmission gear ratios and a 3.73 rear end. Since I'm running a 3.50 ratio, my critical speed is a little higher (204 mph). Shortening the driveshaft will increase critical speed exponentially.
08-21-2016, 01:27 AM
#176
Sorry, your response arrived before I finished checking my earlier post. The critical speed of a shaft, supported by bearings on either end, is inversely proportional to length squared. Shaft critical speed is a function of support structure stiffness, Young's Modulus, the second moment of area, and the mass of the shaft. You can balance or even "superbalance" a shaft at any RPM you want to minimize deflection, but that won't eliminate the resonant mode at that RPM.
Last edited by FuzzyLog1c; 08-21-2016 at 01:36 AM.
08-21-2016, 07:45 AM
#177
When I was having so many problems with my first 1 piece, Frank offered to build me a cf 2 peice but I didn't and still don't have time to be their Guinea pig.
DSS has been very good to work with in most regards and I think he'll build you whatever you want but it's going to be up you to make it work. "Should work" are the key words here.
I'd ask Frank why they decided to market the ujoint CV combo.
DSS has been very good to work with in most regards and I think he'll build you whatever you want but it's going to be up you to make it work. "Should work" are the key words here.
I'd ask Frank why they decided to market the ujoint CV combo.
08-21-2016, 07:50 AM
#178
Originally Posted by FuzzyLog1c
Then you should consider shortening your driveshaft by replacing your OEM T-56 with a longer T-56 XL (or equivalent). The V1's driveshaft is insanely long--it's 10-15" longer than some competing vehicles, which means that any driveshaft you select is going to have a low critical speed. As a result, there isn't a driveshaft available in the V1 length with legitimate 200+ mph capability. Don't believe DSS' 250+ mph claims for their 3.25" carbon fiber driveshafts. They should be taken to court for advertising Mustang critical speeds on their V1 products. .
08-21-2016, 11:25 AM
#179
Ok my brain usually doesn't like to do math on weekends but I'll make an attempt to figure out where I need to be for shaft speed. I don't know the weight of DSS' CF shafts(plus fiberglass sleeve, etc.) to figure out deflection but I suppose I can get that from DSS.
27" tire @ 4.56 gears, target 160 MPH(in this build)
2 * 3.14159 * 13.5 = 84.823" tire diameter
63,360(in/mi) / 84.823 = 746.97 wheel turns per mile
746.97 * 4.56 (gears) = 3406.18 shaft revs per mile.
160MPH / 60 mins = 2.667 MPM
3406.18 * 2.667 = 9084.28 RPM shaft speed
I've looked over the formulae and see that it should increase significantly but even if linear and I take out 8" from 61.5 that's a 13% increase in overhead that would give me 9084.28 * 1.13 = 10265.24 shaft RPM.
10265.24 / 3406.18 = 3.014 MPM
3.014 * 60 = 180.82 MPH.
Faster than I want to go...for now.
Next I'll measure for actual shaft length and we can see what my critical speed might be as long as I can get some additional data from DSS.
27" tire @ 4.56 gears, target 160 MPH(in this build)
2 * 3.14159 * 13.5 = 84.823" tire diameter
63,360(in/mi) / 84.823 = 746.97 wheel turns per mile
746.97 * 4.56 (gears) = 3406.18 shaft revs per mile.
160MPH / 60 mins = 2.667 MPM
3406.18 * 2.667 = 9084.28 RPM shaft speed
I've looked over the formulae and see that it should increase significantly but even if linear and I take out 8" from 61.5 that's a 13% increase in overhead that would give me 9084.28 * 1.13 = 10265.24 shaft RPM.
10265.24 / 3406.18 = 3.014 MPM
3.014 * 60 = 180.82 MPH.
Faster than I want to go...for now.
Next I'll measure for actual shaft length and we can see what my critical speed might be as long as I can get some additional data from DSS.
08-21-2016, 11:31 AM
#180
When I was having so many problems with my first 1 piece, Frank offered to build me a cf 2 peice but I didn't and still don't have time to be their Guinea pig.
DSS has been very good to work with in most regards and I think he'll build you whatever you want but it's going to be up you to make it work. "Should work" are the key words here.
I'd ask Frank why they decided to market the ujoint CV combo.
DSS has been very good to work with in most regards and I think he'll build you whatever you want but it's going to be up you to make it work. "Should work" are the key words here.
I'd ask Frank why they decided to market the ujoint CV combo.
So when there is a bearing in the middle in a 2-piece, am I hearing that critical shaft speed is calculated separately for each piece, therefore increasing it significantly?