Not sure If Im in the correct spot or how to get there if Im not.Anyhow, Im getting ready to tune a 2020 Sierra with a 6.2 that just had a cam, headers, supercharger, and an upgraded fuel system installed but my question is with a 10L80 and a 3.23 gear ratio what is the most RPMs I can spin that aluminum driveshaft?
Its just a hair over 4.5" in diameter and like 68.5" in length joint to joint. Im unsure on wall thinkness tho.
I have never heard or read anyone discuss the actual RPM. Just a generic 100 mph'ish limit.
Issue is at 100 mphish in 7th gear which would be the 1:1 gear on the 10L80 is the shaft would spin the same as the 6600 rpm that this would be capable of now. In fourth gear even at 6000 rpms Im gonna be spinning the shaft at almost 3400 rpms and I thought the rumor was 3200 max and thats why GM put the rev limiter on these at 108 m.p.h.?
In my opinion, whatever the vehicles speed limiter is set at, I wouldn't go past it.
Seen some carnage and seen many youtube videos of guys chucking the stock driveshaft over 100mph. A built 3in or 3.5 steel driveshaft is the way to go.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
So a Denali has a tire p275/60r20 approx 35 inch diameter using 7th gear should be 3,100 rpm. Sounds exactly what you said RaceReady. I would have to believe engine torque would also be a factor in its demise. More torque less MPH before failure.
https://www.drive-lines.com/php10/dlrpm.php
http://www.grimmjeeper.com/gears.html
i remember when the lightning came out with a aluminum driveshaft, old school never understood that at the time.
The speed limiter will be tuned out as were gonna be around 700 h.p. with E85. Im already at 630 h.p. at 6100 r.p.m.s on pump gas. This Denali actually has factory 275/50/22s that are 32.8" tall. Right now Im hitting 100 m.p.h. in 4th gear with r.p.m.s to go. Theres no way I can use 7th gear as Ill be around 6600 r.p.m.s as its the 1:1 gear. Im just unsure how much more in 4th I have on the driveshaft side.
What gear you are in has nothing to do with your driveshaft RPM. The reason we were all using 7th gear is because it is straight through 1:1 and makes it mathematically easier to calculate DS RPM. The issue at hand will be...Originally Posted by RaceReady
1. The Torque you apply to the driveshaft. Let's do the twist.
2. The length of the driveshaft. Sets up more harmonics.
3. The RPM of the driveshaft. Centrifugal imbalance causing harmonics.
I understand the gear doesnt really make a difference when your driving on the street. On the dyno doing a pull it makes a difference as I will either be spinning the rear wheels at 100 m.p.h. or 150 m.p.h. When I do a 2000 RPM to 7700 RPM pull I want to be as close to the 1:1 ratio as possible which ideally would have been 7th gear. My torque will prolly be close to 600 and the driveshaft is about 68.5" joint to joint. Thats why I need to know whats the stock driveshaft RPM rating is so I can calculate properly to run full pulls on the dyno in the closest gear to 7th as possible. Just so everyone knows 90 percent of the cars I usually dyno are Camaros.. with Corvettes covering almost the remaining percent.
I think you need to be looking at drive shaft critical speed calculators. But you need more information on the thickness. You might reach out to some of the driveshaft manufactures and see if they know the thickness. http://wallaceracing.com/driveshafts...age%20contains
Stock driveshaft is .0625 wall. I think the way to go is the driveshaft critical speed calculators. I was just hoping to find someone that may know for sure, experienced the same situation, or more familiar with these trucks than I am currently. Thank You guys!
5" OD .125 wall aluminum is the highest critical speed unit anyone is able to make, outside of carbon fiber - but most CF shafts can't be made longer than what's typical for a race car type length, not the typical truck length. Lots of so-called driveshaft shops do not even know what you're talking about if you ask them about critical speed. I do not know how or why they are in the driveshaft business if they can't tell you the safe speed for one of the things they're making and selling to the public.
For these 70" and longer applications, someone out there really REALLY needs to get tooled up to make then in 6" OD aluminum. Huge difference in critical speed between 5" and 6" given the same length.
GM Gen4 Injectors v2.1.xls
"My life has become a single, ongoing revelation that I haven't been cynical enough."
Funny how accounts marked as 'banned' are still able to log in and do stuff on the site, huh?
Is there a reason to not use a center support bearing?
thats what i did in my silverado... went from single to a two piece shaft for this very reason
OK, what do you mount the center bearing to on a platform that never had an option of a 2-piece shaft? No way I can see to add a crossmember of any sort without relocating the stock fuel tank. Mine, the 'problem vehicle', is a LWB 2WD Envoy with a 74.75" long driveshaft.
2WD SWB is at 59", which is almost tolerable. That's 6" shorter than my El Camino.
4WD/AWD SWB is only 45". One of those would go like 190 MPH without asploading.
GM Gen4 Injectors v2.1.xls
"My life has become a single, ongoing revelation that I haven't been cynical enough."
Funny how accounts marked as 'banned' are still able to log in and do stuff on the site, huh?
Is there another way to retrofit a center support bearing into a place there's never been one before? The likeliest spot also happens to be right where the parking brake cables come out of the floorpan.
GM Gen4 Injectors v2.1.xls
"My life has become a single, ongoing revelation that I haven't been cynical enough."
Funny how accounts marked as 'banned' are still able to log in and do stuff on the site, huh?
Start fabricating! The two shafts don't have to be equal lengths. Triangulate it if need be, it doesn't need to be a right angle.
Fabricate a hole through the middle of the fuel tank to get to the frame rail? There's no other access to the driver's side.
GM Gen4 Injectors v2.1.xls
"My life has become a single, ongoing revelation that I haven't been cynical enough."
Funny how accounts marked as 'banned' are still able to log in and do stuff on the site, huh?
Taking rear gear out of it might be an option.
I don't dyno trucks anymore for this specific reason. I've had trucks that had been on my dyno 5 other times.. but that last pull BAM. It's often catastrophic. Like broke transmission/transfer case, exhaust beat flat, brake lines, fuel tank.. etc..
Even short cab/short bed trucks can't be trusted.
Tuner at PCMofnc.com
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^^^ could probably make that out pvc, lol. Get harware and cut down a 2 piece shaft out of a surburban?
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