[andrewb70]

Originally Posted by 6 Grrrs

I am interested in your results. I have been fighting a vibration in my pickup for years. I would be very interested in doing the cv joint setup if it works.

Tod,

I would think that lowered pick-ups have similar driveline issues as a-bodies. As you lower them, the pinion starts to get higher relative to the output shaft of the transmission. The solution is to keep raising the back of the transmission, but there is a limit to how much that can be done.

Just out of curiosity, what kind of driveshaft are you running? Is it one piece? What material and diameter? Do you know the approximate length?

Andrew

[andrewb70]

Last Thursday I finished my last final, so I am officially done with the spring semester. I am ready to relax and get back to my GTO. It's hard to imagine, but it was three years ago that I completed the L92 engine swap. My, how time flies. In the summer of 2008 I put about 6,000 miles on the car. The plans for this summer are more modest, but I would like to attend a couple of events and maybe visit some friends out west. After much deliberation and for a lack of simple options, I have decided to get the Richmond 6 speed rebuilt. Richmond Gear has been working with me and we came to an agreement. They are currently in possession of my transmission and will give it a thorough inspection. All the gears will be magnufluxed and all parts that are damaged will be replaced. I never had any fundamental objections to the Richmond. I always felt that it shifted fine and offered an awesome, close-ratio gear spread for gears 1-5 and a comfortable .62 overdrive. Keeping the same transmissions will also allow me to keep my current crossmember and not worry about an alternate shifter location.

With road trips planned for the summer, I once again turned to a problem that has plagued my car since day one. Despite numerous efforts I have been unable to completely eliminate the high speed vibration that my car exhibits at speeds about 75 mph. It's really frustrating on long highway trips, because the car feels amazing cruising at speeds between 75 and 80 mph.

I have already posted what my thoughts are regarding the rear end position. I will be swapping out the current rear upper control arms for ones made by RideTech. I firmly believe that while the rear end position may not be entirely responsible for my vibration, it is certainly a factor. I will also be doing other driveline upgrades at the same time. What I have planned may be a little overboard, but I believe that it will completely eliminate any driveline alignment and vibration issues in the future. Here is the plan....

The first step is to get a rear pinion yoke that is machined with the kind of tolerances that are required to achieve smooth operation at sustained high speeds. I chose a 1350 billet yoke from Mark Williams:



With the rear taken care of, the next item to tackle is the driveshaft. There are many fine companies that make driveshafts, but given my alignment issues, I wanted to pick a vendor that was able to offer something unique. I have worked with Frank at The DriveShaft Shop (DSS) in the past when I needed custom axles for my RX7. Frank has always been attentive to my needs and has provided a quality product that has met and exceeded my expectations. The DSS is widely known in the sport compact world for making bullet proof CV axles, and recently they have also been doing some innovative work on the many modern muscle cars that use independent rear suspensions. Cars like the new Camaro, Dodge Charger, GTOs, and Cadillac CTS-V are rear drive, high HP, and heavy. That combination is the perfect storm for breaking driveline components, and DSS has stepped up to the plate with upgraded CV shafts, driveshafts, and complete 9" IRS swap packages.

After deliberating with Frank about my GTO and the issues that I am having we came up with a very elegant solution. Frank will make me a custom driveshaft with a CV joint in the front. People in the 4x4 world have used double cardon CV joint driveshafts for a long time to deal with extreme driveline angles. But double cardon joints are bulky and heavy, and just didn't seem appropriate for a car. What will be used in the front is a 6 ball, Porsche 930 style CV. Like this:




CV joints are designed to operate at high speeds and at extreme operating angles. Furthermore, there is no need to match the front and rear angles, as you need with a shaft that uses u-joints on both ends. With the CV joint in the front I will adjust my pinion angle so that the pinion and the driveshaft have almost a zero working angle. A slight angle is required only to make sure that the needles in the u-joint caps get lubricated. The rear working angle will be less than .5 degrees.

Since a new shaft will need to be fabricated, I have also decided to go a little overboard and opt for a carbon fiber tube. This may be a little over kill, but I am not taking any chances. In fact, Frank felt that my problems can be solved by using a driveshaft made from aluminum. However, a CF driveshaft is lighter than aluminum and offers plenty of torque capacity. Using a carbon fiber driveshaft also tends to significantly lessen the noise generated by the driveline. In some ways its like Dynomat for the driveline. I had the opportunity to drive a friends RX7 with a carbon driveshaft and it felt amazing. When cycling the driveline from load to coast the sensation was like there was a piece of plastic between the rear and and the transmission. It was a firm feeling, yet it lacked the sharpness that is felt with metal components. It was quite amazing.

With my current combination of gears and tire size the driveshaft will be spinning 3675 RPM at 80mph. While this doesn't seem like a lot, when you consider that my old driveshaft was made from mild steel and was 3.5" in diameter, the forces that were generated by such a heavy shaft were significant, even with a properly balanced driveshaft. The DSS has recently installed a new balancing machine that has the ability to spin a shaft to 9500RPM. They have been working with some NASCAR teams to solve some of the driveline issues that they face. Keep in mind that NASCAR race cars operate with the driveline spinning anywhere from 7500-9600RPM. Balancing driveshafts at that speed is a whole different ballgame than your typical 1000 RPM balance job at your local driveline shop.

The resulting driveshaft will be very similar to the shaft that they sell for 2010+ Camaros.



Instead of the billet adapters that are seen in the picture, my shaft will be connected to a modified slip yoke. The rest should be very similar. The finished shaft should be about 17 pounds with the slip yoke. Here are pictures of the components that are used in making the driveshaft. The parts on the left are used for carbon shafts, and the parts on the right are for aluminum shafts:



The bars that mate with the CV are 30 spline and are made out of a high tech 4130 alloy. The dimensions are similar to a Viper T56 output shaft. DSS has gone to great lengths to validate all the components that are used in making the CF driveshafts. This includes destructive testing, which few manufacturers ever do:



As you can see, the 1350 u-joint failed before the tube or the aluminum yoke. I feel very confident that this shaft will outlast every other component in my driveline. I can't wait....

Andrew

[6 Grrrs]

Originally Posted by andrewb70

Tod,

I would think that lowered pick-ups have similar driveline issues as a-bodies. As you lower them, the pinion starts to get higher relative to the output shaft of the transmission. The solution is to keep raising the back of the transmission, but there is a limit to how much that can be done.

Just out of curiosity, what kind of driveshaft are you running? Is it one piece? What material and diameter? Do you know the approximate length?

Andrew

I don't remember the length, but it is a one piece driveshaft. The original was one piece as well. Shortbed regular cabs typically do not have a carrier bearing/2 pc driveshaft (at least in the '88-98 2wds).

Short story...I was about 300-400 miles into the 2007 Power Tour (Kalamazoo MI), when I decided I couldn't handle the drivetrain vibrations anymore. Monday Morning at 7am I was at the local driveshaft shop to have them check my driveshaft for balance. I had just installed 4.56 gears (from 3.73s) in the 14bolt with a new Eaton diff, new bearings, etc. I finished it the day before we left and it felt fine the little bit I drove it around town, but I never got up to highway speeds. I also had pulled the driveshaft and had it shortened/rebalanced (only about 1/2" shorter) because ever since I did the T56 swap, the driveshaft was a little long and was always a pain in the a$$ to get out (pickups have the fuel tank inside the framerail and my 3" dual exhaust is on the other side - needless to say there really isn't much room to remove the driveshaft). Whne the straps were unbolted, you had to rotate the yoke & drivewshaft to find the 'sweet spot' to get it out.

So the guy who built the shaft in 1999 or 2000 shortened it and 'rebalanced' it. I installed it and was on my way. So back to Kalamazoo...when I pulled the driveshaft, they set it up in the lathe. It had .040" runout!!! It also had no balance weights on it (which I never noticed), AND the front yoke had spread approx 1/8", so the front ujoint was moving all over the place. Basically the shop in Kalamazoo would not repair it. I spent about $350 for a new custom built shaft with about .003" runout, and balanced to within the desired amount (I dont remember exactly). My old shaft was 4" in diameter, this new one was 3" (Cromoly I think). When I questoined the guy building the shaft (owner of the shop) about the smaller diameter, he told me it is the same basic shaft he builds for 1000 hp drag cars, and he would stand behind it for the life of the truck.

Well we were on our way and the vibration had all but stopped for the most part. I have since made some changes to my rear springs, and I believe I affected my pinion angle. The truck launches great (1.78 60 ft on ET Street Radialls - used to be 2.20s, with a best of 1.97). I have Cal Tracs on it too. With the CTs there is some pinion adjustment, but very little, and I believe only down.

My truck is lowered 5" in the front & 7" in the rear, which is pretty low for a C1500. There is a pretty severe vibration around 70mph, and get worse as I go faster. I would imagine the driveshaft is spinning pretty fast with the 27.2" tire and the 4.56's. With the 3.73's I never had any vibration issues.

I guess it wasn't the short story I thought it was

[andrewb70]

Originally Posted by 6 Grrrs

I don't remember the length, but it is a one piece driveshaft. The original was one piece as well. Shortbed regular cabs typically do not have a carrier bearing/2 pc driveshaft (at least in the '88-98 2wds).

Short story...I was about 300-400 miles into the 2007 Power Tour (Kalamazoo MI), when I decided I couldn't handle the drivetrain vibrations anymore. Monday Morning at 7am I was at the local driveshaft shop to have them check my driveshaft for balance. I had just installed 4.56 gears (from 3.73s) in the 14bolt with a new Eaton diff, new bearings, etc. I finished it the day before we left and it felt fine the little bit I drove it around town, but I never got up to highway speeds. I also had pulled the driveshaft and had it shortened/rebalanced (only about 1/2" shorter) because ever since I did the T56 swap, the driveshaft was a little long and was always a pain in the a$$ to get out (pickups have the fuel tank inside the framerail and my 3" dual exhaust is on the other side - needless to say there really isn't much room to remove the driveshaft). Whne the straps were unbolted, you had to rotate the yoke & drivewshaft to find the 'sweet spot' to get it out.

So the guy who built the shaft in 1999 or 2000 shortened it and 'rebalanced' it. I installed it and was on my way. So back to Kalamazoo...when I pulled the driveshaft, they set it up in the lathe. It had .040" runout!!! It also had no balance weights on it (which I never noticed), AND the front yoke had spread approx 1/8", so the front ujoint was moving all over the place. Basically the shop in Kalamazoo would not repair it. I spent about $350 for a new custom built shaft with about .003" runout, and balanced to within the desired amount (I dont remember exactly). My old shaft was 4" in diameter, this new one was 3" (Cromoly I think). When I questoined the guy building the shaft (owner of the shop) about the smaller diameter, he told me it is the same basic shaft he builds for 1000 hp drag cars, and he would stand behind it for the life of the truck.

Well we were on our way and the vibration had all but stopped for the most part. I have since made some changes to my rear springs, and I believe I affected my pinion angle. The truck launches great (1.78 60 ft on ET Street Radialls - used to be 2.20s, with a best of 1.97). I have Cal Tracs on it too. With the CTs there is some pinion adjustment, but very little, and I believe only down.

My truck is lowered 5" in the front & 7" in the rear, which is pretty low for a C1500. There is a pretty severe vibration around 70mph, and get worse as I go faster. I would imagine the driveshaft is spinning pretty fast with the 27.2" tire and the 4.56's. With the 3.73's I never had any vibration issues.

I guess it wasn't the short story I thought it was

Tod,

Everything you describe point to our common problem. When you installed the 4.56 gears the speed of the driveshaft increased, given the same vehicle speed. So before the gear swap, the vibration might have started at a higher speed, above the normal highway cruising speed. Doing some calculations, with the 3.73 rear end the driveshaft was spinning 3450 RPM, given a 27.2 inch tire, at 75mph. With the 4.56 gear the driveshaft was now spinning 4200 RPM, all other things being equal. With the 3.73 gears, 4200 driveshaft RPM was 95 mph, so you never felt the vibration. On top of that, you were running a very heavy 4" steel driveshaft.

So when the guy made the new shaft out of 3" cromoly, it was significantly lighter. Frank from the DSS believes that driveshaft weight is critical for smooth operation. He has come to this conclusion based on his high speed testing with the NASCAR teams that run a 4" driveshaft. Despite the fact that they use a .063" wall thickness tube, they are still quite heavy, and can become unstable at the very high speeds that they experience.

CF has a very high stiffness to weight ratio, which makes it idea for driveshafts.

Andrew

[gearbanger]

Does nascar require a steel driveshaft? Probably or they would be using aluminum or carbon I'm sure.

This is very very interesting, cant wait for the results. Andrew, any idea what the driveshaft project price tag is going to be?

[andrewb70]

Originally Posted by gearbanger

Does nascar require a steel driveshaft? Probably or they would be using aluminum or carbon I'm sure.

This is very very interesting, cant wait for the results. Andrew, any idea what the driveshaft project price tag is going to be?

NASCAR rules mandate a steel driveshaft. They should really allow CF because of the safety factor. In case of a major crash the driveshaft can become a lethal projectile. A CF driveshaft will splinter and self destruct in case of a crash.

The cost of the driveshaft will be about the cost of a new Camaro CF shaft.

Andrew

[andrewb70]

The first part of the driveline project arrived yesterday. The Mark Williams billet pinion yoke is a work of art. There are numerous machined surfaces taht can be used to measure runout.





Andrew

[andrewb70]

I am once again impressed by Frank at The Driveshaft Shop. He had the yoke done by last Friday and today he was able to have it black oxide coating applied to it and have pictures taken.

Here is the modified Spicer yoke:








The gold colored part is a cap that keeps the grease from leaking out the back of the CV:




This is a detailed shot of the modified yoke with the CV and front of the driveshaft:



Finally, a shot of the complete assembly. Interestingly, Frank was building a shaft just like mine for another project that had similar driveline alignment issues. It's a custom 1961 Corvette that will get a monster twin turbo engine.



Frank will send me the slip yoke so that I can give him the final measurement for the driveshaft.

Andrew

[gearbanger]

Hey Andrew,

I was reading back through this thread and I thought when you replaced the rear pinion yoke that you had this vibration issue fixed? It sounded that way? Did you not ever test it out on the road before you pulled the tranny?

[andrewb70]

After I replaced the pinion yoke the vibration got better but it wasn't totally eliminated. I put about 2000 miles on the car after I swapped pinion yokes.

Andrew

[HWYSTR455]

I'm watching curiously, and impressed with the parts selection. Looking forward to hearing about the results! Know how frustrating stuff like this can be first hand!

.

[gearbanger]

Okay, well, you were saying that it got alot better and still vibrated in 6th a little. I hope the tranny redo will solve it. Any chance you will give it a try with the original driveshaft before swapping to the new CV shaft?

[andrewb70]

Originally Posted by gearbanger

Okay, well, you were saying that it got alot better and still vibrated in 6th a little. I hope the tranny redo will solve it. Any chance you will give it a try with the original driveshaft before swapping to the new CV shaft?

My old yoke had more run out than was desirable. I forget the exact numbers, but they are listed earlier in this thread. I swapped to a different yoke and the runout was better, but the vibration persisted, although at a lower level. I may be able to try the old shaft as a fall back if the new shaft is not ready for my planned road trip. When my transmission failed the slip yoke got damaged as well. So for me to install the old shaft I would have to swap the slip yoke. I would rather not incur that extra expense if I don't have to. I seriously doubt that the transmission was the cause of the vibration. The vibration was there even when the transmission was new.

Andrew

[andrewb70]

Originally Posted by HWYSTR455

I'm watching curiously, and impressed with the parts selection. Looking forward to hearing about the results! Know how frustrating stuff like this can be first hand!

.

Thanks! I am looking forward to the results as well. Frustration can be a very powerful motivator. In my search for answers I ran across the attached PDF from Spicer. It has some very interesting information on page 9 and 10 about compound angles.

http://www.pro-touring.com/%7Eandrew...11-1-HVTSS.pdf

If the rear end in my GTO is offset it may not cause a vibration by itself, but it can certainly contribute to the compound working angle.

Andrew

[6 Grrrs]

Originally Posted by andrewb70

Thanks! I am looking forward to the results as well. Frustration can be a very powerful motivator. In my search for answers I ran across the attached PDF from Spicer. It has some very interesting information on page 9 and 10 about compound angles.

http://www.pro-touring.com/%7Eandrew...11-1-HVTSS.pdf

If the rear end in my GTO is offset it may not cause a vibration by itself, but it can certainly contribute to the compound working angle.

Andrew

Nice find and great read.

[andrewb70]

Bill Howell and I installed the transmission last night without too much fanfare. I also measured for the driveshaft, which came out to be 55 3/4" from the face of the yoke where the CV mounts to the center of the u-joint on the pinion yoke. Speaking of pinion yokes, after much deliberation I decided that it would be wise to reset the preload on the pinion bearings. This is something that I am not comfortable tackling myself, but one of Bill's friends will handle the task. He has set-up several rear ends for Bill and knowing how hard Bill beats on his cars, I am sure he will do a fine job.

Today I am tackling some minor tasks. I need to pick up a new crush sleeve and pinion seal, an 0-ring for the back-up sensor, and ship the slip yoke back to the DSS so the new driveshaft can be balanced as an assembly.

Andrew

[andrewb70]

Here are a few of pictures of the transmission and how the new slip yoke sits in the tunnel. You can see in the pictures where my old, 1350 yoke used to make contact with the body. Since the front driveline angle is of no concern, I can safely lower the back of the transmission slightly and get enough clearance for the CV joint.







Andrew

[andrewb70]

So far, everything is going according to schedule. Since I was replacing the pinion yoke, I chose to have the pinion bearing pre-load reset. That procedure went smoothly, so the rear end is all set.

The DSS made my driveshaft last week and it is on its way to me. The shipping weight on the driveshaft is 25 pounds with the packaging. I suspect the finished weight of the driveshaft is right around 20 pounds with the slip yoke. I would guess that is easily 15 pounds less than my previous driveshaft. While weight saving was a not a primary concern, it is certainly a nice side benefit. The lighter weight will also be gentler on all the bearings in the transmission and rear end. With some luck I should be taking a test drive on Monday evening. Wish me luck!

Andrew

[andrewb70]

The driveshaft arrived this evening and I got right on installing it.



It looks amazing. I will take more pictures tomorrow with a better camera.

Once the shaft was bolted up, I measured my driveline angles. Since the front u-joint has been replaced with a CV joint, the front working angle is not irrelevant. The rear angle needs to be as low as possible without being zero. I adjusted my rear control arms so the rear working angle is .5 degrees with the pinion slightly down. This way, under power the pinion will want to climb and the angle should get less or increase slightly in the other direction.

Test drive tomorrow.

Andrew

[Motornoggin]

That looks pretty dang cool.